Three-dimensional unmanned aerial vehicle(UAV)oblique photogrammetric data were used to infer mountainous gravel braided river lithofacies,lithofacies associations and architectural elements.Hierarchical architecture ...Three-dimensional unmanned aerial vehicle(UAV)oblique photogrammetric data were used to infer mountainous gravel braided river lithofacies,lithofacies associations and architectural elements.Hierarchical architecture and lithofacies associations with detailed lithofacies characterizations were comprehensively described to document the architectural model,architectural element scale and gravel particle scale.(1)Nine lithofacies(i.e.,Gmm,Gcm,Gcc,Gci,Gcl,Ss,Sm,Fsm and Fl)were identified and classified as gravel,sand and fine matrix deposits.These are typical depositional features of a mountainous dryland gravel-braided river.(2)Three architectural elements were identified,including channel(CH),gravel bar(GB)and overbank(OB).CH can be further divided into flow channel and abandoned channel,while GB consists of Central Gravel bar(CGB)and Margin Gravel bar(MGB).(3)The gravel bar is the key architectural element of the gravel braided river,with its geological attributes.The dimensions of GBs and their particles are various,but exhibit good relationships with each other.The grain size of GB decreases downstream,but the dimensions of GB do not.The bank erosion affects the GB dimensions,whereas channel incision and water flow velocity influence the grain size of GB.The conclusions can be applied to the dryland gravel braided river studies in tectonically active areas.展开更多
Based on the global basement reservoir database and the dissection of basement reservoirs in China,the characteristics of hydrocarbon accumulation in basement reservoirs are analyzed,and the favorable conditions for h...Based on the global basement reservoir database and the dissection of basement reservoirs in China,the characteristics of hydrocarbon accumulation in basement reservoirs are analyzed,and the favorable conditions for hydrocarbon accumulation in deep basement reservoirs are investigated to highlight the exploration targets.The discovered basement reservoirs worldwide are mainly buried in the Archean and Precambrian granitic and metamorphic formations with depths less than 4500 m,and the relatively large reservoirs have been found in rift,back-arc and foreland basins in tectonic active zones of the Meso-Cenozoic plates.The hydrocarbon accumulation in basement reservoirs exhibits the characteristics in three aspects.First,the porous-fractured reservoirs with low porosity and ultra-low permeability are dominant,where extensive hydrocarbon accumulation occurred during the weathering denudation and later tectonic reworking of the basin basement.High resistance to compaction allows the physical properties of these highly heterogeneous reservoirs to be independent of the buried depth.Second,the hydrocarbons were sourced from the formations outside the basement.The source-reservoir assemblages are divided into contacted source rock-basement and separated source rock-basement patterns.Third,the abnormal high pressure in the source rock and the normal–low pressure in the basement reservoirs cause a large pressure difference between the source rock and the reservoirs,which is conducive to the pumping effect of hydrocarbons in the deep basement.The deep basement prospects are mainly evaluated by the factors such as tectonic activity of basement,source-reservoir combination,development of large deep faults(especially strike-slip faults),and regional seals.The Precambrian crystalline basements at the margin of the intracontinental rifts in cratonic basins,as well as the Paleozoic folded basements and the Meso-Cenozoic fault-block basements adjacent to the hydrocarbon generation depressions,have favorable conditions for hydrocarbon accumulation,and thus they are considered as the main targets for future exploration of deep basement reservoirs.展开更多
Taking the Lower Permian Fengcheng Formation shale in Mahu Sag of Junggar Basin,NW China,as an example,core observation,test analysis,geological analysis and numerical simulation were applied to identify the shale oil...Taking the Lower Permian Fengcheng Formation shale in Mahu Sag of Junggar Basin,NW China,as an example,core observation,test analysis,geological analysis and numerical simulation were applied to identify the shale oil micro-migration phenomenon.The hydrocarbon micro-migration in shale oil was quantitatively evaluated and verified by a self-created hydrocarbon expulsion potential method,and the petroleum geological significance of shale oil micro-migration evaluation was determined.Results show that significant micro-migration can be recognized between the organic-rich lamina and organic-poor lamina.The organic-rich lamina has strong hydrocarbon generation ability.The heavy components of hydrocarbon preferentially retained by kerogen swelling or adsorption,while the light components of hydrocarbon were migrated and accumulated to the interbedded felsic or carbonate organic-poor laminae as free oil.About 69% of the Fengcheng Formation shale samples in Well MY1 exhibit hydrocarbon charging phenomenon,while 31% of those exhibit hydrocarbon expulsion phenomenon.The reliability of the micro-migration evaluation results was verified by combining the group components based on the geochromatography effect,two-dimension nuclear magnetic resonance analysis,and the geochemical behavior of inorganic manganese elements in the process of hydrocarbon migration.Micro-migration is a bridge connecting the hydrocarbon accumulation elements in shale formations,which reflects the whole process of shale oil generation,expulsion and accumulation,and controls the content and composition of shale oil.The identification and evaluation of shale oil micro-migration will provide new perspectives for dynamically differential enrichment mechanism of shale oil and establishing a“multi-peak model in oil generation”of shale.展开更多
A series of theoretical explorations and field tests have been carried out to efficiently develop the Mahu tight conglomerate oilfield in the Junggar Basin.Concepts of steered-by-edge fracturing and proactive fracturi...A series of theoretical explorations and field tests have been carried out to efficiently develop the Mahu tight conglomerate oilfield in the Junggar Basin.Concepts of steered-by-edge fracturing and proactive fracturing interference were proposed.A series of innovative technologies were developed and implemented including optimization of 3-D staggered well pattern,proactive control and utilization of spatial stress field,and synergetic integration of multiple elements.Different from shale,the unique rock fabric and strong heterogeneities of tight conglomerate formation are favorable factors for forming complex fractures,small space well pattern can proactively control and make use of interwell interference to increase the complexity of fracture network,and the"optimum-size and distribution"hydraulic fracturing can be achieved through synergetic optimization.During pilot phase of this field,both depletion with hydraulically fractured vertical wells and volume fracturing in horizontal wells were tested after water injection through vertical wells,then the multi-stage fracturing with horizontal well was taken as the primary development technology.A series of engineering methods were tested,and key development parameters were evaluated such as well spacing,lateral length,fractures spacing,fracturing size,and fracturing operation process.According to geoengineering approach,the 100 m/150 m tridimensional tight-spacing staggered development method was established with systematic integration of big well clusters,multiple stacked pay zones,small well spacing,long lateral length,fine perforation clustering,zipper fracturing and factory operation.According to half-year production performance,100 m/150 m small spacing wells outperformed 500 m/400 m/300 m spacing wells.Its average estimated ultimate recovery(EUR)of wells was identical with those best wells from large-spacing area.Compared with the overall performance of Mahu oilfield,the drainage efficiency and estimated recovery factor of this pilot were significantly boosted with improved economics.展开更多
The exploration and development of oilfield results in damages to land resources. Along with the further development of petroleum in the Gurbantunggut Desert, the fragile ecological environment and land resource was s...The exploration and development of oilfield results in damages to land resources. Along with the further development of petroleum in the Gurbantunggut Desert, the fragile ecological environment and land resource was suffering much more damage. Vegetation degradation and desertification become more prominent. In response to the damage to the fragile ecological environment and oilfield in the Gurbantunggut Desert, limit condition method was used to evaluate the suitability of land reclamation suitability. Results suggested that the main restraining factors for land reclamation were soil condition and water resources. Based on the effect and shortage of oilfield in the Gurbantunggut Desert Oilfield, the reclamation of oilfield in the Gurbantunggut desert was discussed.展开更多
PetroChina Xinjiang Oilfield Company comprehensively promoted the special action to improve quality and efficiency.Through the in-depth interpretation of the balance sheet,income statement,cas h f low statement,we dee...PetroChina Xinjiang Oilfield Company comprehensively promoted the special action to improve quality and efficiency.Through the in-depth interpretation of the balance sheet,income statement,cas h f low statement,we deepened the analysis of the investment and cost structure,collated the corresponding relationship between financial data and key indicators in these sheets,and defined the directions of control one by one.展开更多
The failure of cement sheath integrity can be easily caused by alternating pressure during large-scale multistage hydraulic fracturing in shale-gas well.An elastic-plastic mechanical model of casing-cement sheath-form...The failure of cement sheath integrity can be easily caused by alternating pressure during large-scale multistage hydraulic fracturing in shale-gas well.An elastic-plastic mechanical model of casing-cement sheath-formation(CSF)system under alternating pressure is established based on the Mohr-Coulomb criterion and thick-walled cylinder theory,and it has been solved by MATLAB programming combining global optimization algorithm with Global Search.The failure mechanism of cement sheath integrity is investigated,by which it can be seen that the formation of interface debonding is mainly related to the plastic strain accumulation,and there is a risk of interface debonding under alternating pressure,once the cement sheath enters plasticity whether in shallow or deep well sections.The matching relationship between the mechanical parameters(elastic modulus and Poisson's ratio)of cement sheath and its integrity failure under alternating pressure in whole well sections is studied,by which it has been found there is a“critical range”in the Poisson's ratio of cement sheath.When the Poisson's ratio is below the“critical range”,there is a positive correlation between the yield internal pressure of cement sheath(SYP)and its elastic modulus.However,when the Poisson's ratio is above the“critical range”,there is a negative correlation.The elastic modulus of cement sheath is closely related to its Poisson's ratio,and restricts each other.Scientific and reasonable matching between mechanical parameters of cement sheath and CSF system under different working conditions can not only reduce the cost,but also protect the cement sheath integrity.展开更多
Using the data of drilling, logging, core, experiments and production, the heterogeneity and differential hydrocarbon accumulation model of deep reservoirs in Cretaceous Qingshuihe Formation(K1q) in the western sectio...Using the data of drilling, logging, core, experiments and production, the heterogeneity and differential hydrocarbon accumulation model of deep reservoirs in Cretaceous Qingshuihe Formation(K1q) in the western section of the foreland thrust belt in southern Junggar Basin are investigated. The target reservoirs are characterized by superimposition of conglomerates, sandy conglomerates and sandstones, with high content of plastic clasts. The reservoir space is mainly composed of intergranular pores. The reservoirs are overall tight, and the sandy conglomerate has the best physical properties. The coupling of short deep burial period with low paleotemperature gradient and formation overpressure led to the relatively weak diagenetic strength of the reservoirs. Specifically, the sandy conglomerates show relatively low carbonate cementation, low compaction rate and high dissolution porosity. The special stress-strain mechanism of the anticline makes the reservoirs at the top of the anticline turning point more reformed by fractures than those at the limbs, and the formation overpressure makes the fractures in open state. Moreover, the sandy conglomerates have the highest oil saturation. Typical anticline reservoirs are developed in deep part of the thrust belt, but characterized by "big trap with small reservoir". Significantly, the sandy conglomerates at the top of anticline turning point have better quality, lower in-situ stress and higher structural position than those at the limbs,with the internal hydrocarbons most enriched, making them high-yield oil/gas layers. The exponential decline of fractures makes hydrocarbon accumulation difficult in the reservoirs at the limbs. Nonetheless, plane hydrocarbon distribution is more extensive at the gentle limb than the steep limb.展开更多
The lacustrine organic-rich shale in the Permian Lucaogou(LCG)Formation of the Jimsar Sag,Junggar Basin,is one of the main shale oil plays in China.In this paper,geological and geochemical research techniques were emp...The lacustrine organic-rich shale in the Permian Lucaogou(LCG)Formation of the Jimsar Sag,Junggar Basin,is one of the main shale oil plays in China.In this paper,geological and geochemical research techniques were employed to evaluate the geochemical variability of the lacustrine shale and the pro-duction of organic matter and its preservation conditions.The LcG Formation is characterized by its complex mineral compositions and a wide range of organic matter richness and quality.The presence of high proportions ofβ-carotane and C2g steranes,indicates that the organic matter mainly originated from phytoplankton and aquatic algal-bacterial organisms,especially cyanobacteria.This study found that the productivity of the Lower LCG Member(P2li)was highest,and the Middle LCG Member(P_(2)l_(2))was the lowest.During the deposition of the Lower LCG Member,the lake's bottom water was predominantly a reducing environment,and the degradation of organic matter was largely a result of bacterial sulfate reduction.During the deposition of the Middle and Upper LCG members,the lake's bottom water was mainly oxidizing,and the degradation of organic matter was likely to be caused by aerobic processes.Based on a comprehensive analysis of the origin and production of organic matter,as well as its depo-sitional environment and preservation conditions,two organic matter accumulation models were pro-posed to explain the distribution of the organic-rich shale.In model A,the high influx of volcanic ash released nutrients and brought abundant sulfate into the water,the accumulation of organic matter was mainly controlled by the preservation of organic matter,which was mainly controlled by BsR.In the model B,the influx of volcanic ash was small,organic matter was mainly degraded by oxygen and the accumulation of organic matter is mainly determined by the production of organic matter.展开更多
Large-scale sand fracturing is a necessary means in the efficient exploitation of shale gas/oil.However,in the process of fracturing operation,the sand carrying fluid and proppant easily causes scouring and wear to pr...Large-scale sand fracturing is a necessary means in the efficient exploitation of shale gas/oil.However,in the process of fracturing operation,the sand carrying fluid and proppant easily causes scouring and wear to production strings,especially the casing perforation system,which damage the wellbore integrity and deformation to affect the subsequent fracturing.For this problem,taking the actual construction conditions and perforation technology of an oilfield in western China as an example,the structural parameters of the downhole string were measured and the wall thickness reduction model of casing perforation suitable for large-displacement sand fracturing in horizontal well section was established.With software ANSYS-FLUENT,the casing perforation erosion under the conditions of different displacements,sand content and perforation sand-passing quantity in the process of sand fracturing was simulated and calculated.The influences of three parameters on perforation erosion and expansion were analyzed and the prediction chart of the influences of three main control factors on perforation erosion and expansion was established.The perforation erosion images after fracturing construction were obtained with the downhole eagle perforation logging technology.The logging chart results were compared with the downhole eagle perforation data.The error between the established numerical simulation calculation charts and the real logging data was about 5%,indicating that the simulation charts were the valuable reference.展开更多
Deep-water gravity depositional processes and evolution in arc systems have become topics of intense research focus in recent years.This study discusses the co-evolution of volcanism and deep-water gravity flow deposi...Deep-water gravity depositional processes and evolution in arc systems have become topics of intense research focus in recent years.This study discusses the co-evolution of volcanism and deep-water gravity flow deposits at the southern margin of the Junggar Basin,based on petrology,geochronology and geochemical analyses.The results show that a massive collapse of unstable sediments from the slope was triggered by volcanism,resulting in the formation of slumping gravity flows.The occurrence of volcanic beds in the slump deposits confirm that synchronous volcanism likely affected sediment instability,triggering gravity flows.The Th/Yb,Ta/Yb and Th/Ta elemental ratios,U-Pb ages of detrital zircons and paleocurrent directions indicate that the North Tianshan(NTS)island arc represents the provenance of the Qianxia Formation.Moreover,statistical data on the pyroclastic components in the gravity flow deposits reveal an intensity index of volcanism,indicating that volcanism is strongly related to gravity flow deposits,especially in terms of the type and distribution of the deposits.A model for volcanically-triggered deep-water gravity flow deposits is established,in order to provide a more in-depth understanding of the co-evolution of volcanism and gravity flow deposits within the depositional setting of the late Paleozoic NTS oceanic subduction margin in the Junggar Basin.展开更多
Based on the geological and geochemical analysis of potential source rocks in different formations and the classification of crude oil types,combined with the hydrocarbon generation thermal simulation experiments,the ...Based on the geological and geochemical analysis of potential source rocks in different formations and the classification of crude oil types,combined with the hydrocarbon generation thermal simulation experiments,the source,genesis,and distribution of different types of oils in the Mahu large oil province of the Junggar Basin are investigated.Four sets of potential source rocks are developed in the Mahu Sag.Specifically,the source rocks of the Permian Fengcheng Formation have the highest hydrocarbon generation potential and contain mainly TypesⅡandⅠorganic matters,with a high oil generation capacity.In contrast,the source rocks in other formations exhibit lower hydrocarbon generation potential and contain mainly TypeⅢorganic matter,with dominant gas generation.Oils in the Mahu Sag can be classified as three types:A,B and C,which display ascending,mountainous and descending C_(20)-C_(21)-C_(23)tricyclic terpenes abundance patterns in sequence,and gradually increasing relative content of tricyclic terpenes and sterane isomerization parameters,indicating an increasing oil maturity.Different types of oils are distributed spatially in an obviously orderly manner:Type A oil is close to the edge of the sag,Type C oil is concentrated in the center of the sag,and Type B oil lies in the slope area between Type A and Type C.The results of oil-source correlation and thermal simulation experiments show that the three types of oils come from the source rocks of the Fengcheng Formation at different thermal evolution stages.This new understanding of the differential genesis of oils in the Mahu Sag reasonably explains the source,distribution,and genetic mechanism of the three types of oils.The study results are of important guidance for the comprehensive and three-dimensional oil exploration,the identification of oil distribution in the total petroleum system,and the prediction of favorable exploration areas in the Mahu Sag.展开更多
With the help of digital image processing technology, an automatic measurement method for the three-phase contact angles in the pore throats of the microfluidic model was established using the microfluidic water flood...With the help of digital image processing technology, an automatic measurement method for the three-phase contact angles in the pore throats of the microfluidic model was established using the microfluidic water flooding experiment videos as the data source. The results of the new method were verified through comparing with the manual measurement data.On this basis, the dynamic changes of the three-phase contact angles under flow conditions were clarified by the contact angles probability density curve and mean value change curve. The results show that, for water-wetting rocks, the mean value of the contact angles is acute angle during the early stage of the water flooding process, and it increases with the displacement time and becomes obtuse angle in the middle-late stage of displacement as the dominant force of oil phase gradually changes from viscous force to capillary force. The droplet flow in the remaining oil occurs in the central part of the pore throats, without three-phase contact angle. The contact angles for the porous flow and the columnar flow change slightly during the displacement and present as obtuse angles in view of mean values, which makes the remaining oil poorly movable and thus hard to be recovered. The mean value of the contact angle for the cluster flow tends to increase in the flooding process, which makes the remaining oil more difficult to be recovered. The contact angles for the membrane flow are mainly obtuse angles and reach the highest mean value in the late stage of displacement, which makes the remaining oil most difficult to be recovered. After displacement, the remaining oils under different flow regimes are just subjected to capillary force, with obtuse contact angles, and the wettability of the pore throat walls in the microfluidic model tends to be oil-wet under the action of crude oil.展开更多
This paper establishes a 3D multi-well pad fracturing numerical model coupled with fracture propagation and proppant migration based on the displacement discontinuity method and Eulerian-Eulerian frameworks,and the fr...This paper establishes a 3D multi-well pad fracturing numerical model coupled with fracture propagation and proppant migration based on the displacement discontinuity method and Eulerian-Eulerian frameworks,and the fracture propagation and proppant distribution during multi-well fracturing are investigated by taking the actual multi-well pad parameters as an example.Fracture initiation and propagation during multi-well pad fracturing are jointly affected by a variety of stress interference mechanisms such as inter-cluster,inter-stage,and inter-well,and the fracture extension is unbalanced among clusters,asymmetric on both wings,and dipping at heels.Due to the significant influence of fracture morphology and width on the migration capacity of proppant in the fracture,proppant is mainly placed in the area near the wellbore with large fracture width,while a high-concentration sandwash may easily occur in the area with narrow fracture width as a result of quick bridging.On the whole,the proppant placement range is limited.Increasing the well-spacing can reduce the stress interference of adjacent wells and promote the uniform distribution of fractures and proppant on both wings.The maximum stimulated reservoir volume or multi-fracture uniform propagation can be achieved by optimizing the well spacing.Although reducing the perforation-cluster spacing also can improve the stimulated reservoir area,a too low cluster spacing is not conducive to effectively increasing the propped fracture area.Since increasing the stage time lag is beneficial to reduce inter-stage stress interference,zipper fracturing produces more uniform fracture propagation and proppant distribution.展开更多
The Middle Permian Lucaogou Formation in Northwestern China mainly contains typical saline lacustrine oil shale.To study the differences in geochemistry and hydrocarbon generation of source-rock samples in Lucaogou Fo...The Middle Permian Lucaogou Formation in Northwestern China mainly contains typical saline lacustrine oil shale.To study the differences in geochemistry and hydrocarbon generation of source-rock samples in Lucaogou Formation in Jimusaer Sag,57 core samples from two boreholes were analyzed herein by performing total organic carbon(TOC)analysis,RockeEval pyrolysis,and gas chromatographicemass spectrometry experiments on saturated hydrocarbons.The kinetics of oil generation were studied using two samples comprising typical maceral components.The results showed that the hydrocarbons produced by telalginite are relatively rich in pristane(Pr),phytane(Ph),b-carotane,high-carbon normal alkanes,and C29 regular steranes.Hydrocarbons produced by lamalginite contain a significantly higher content of C20 tricyclic terpanes(TT),C21TT,C24 tetracyclic terpanes(TeT),C29 norhopane,and C28 regular sterane.Based on the pyrolysis and biomarker compound parameters,telalginite has a higher conversion rate for hydrocarbons than lamalginite in the low-mature to mature stage,which is consistent with their kinetic analysis.Lamalginite source rock displays a much narrower distribution of activation energies than telalginite source rocks.Such narrower activation energy distribution effectively narrows the main stage of hydrocarbon generation.In addition,the activation energy distribution of lamalginite concentrated in the high-value interval,indicating the characteristics of the relatively lagging hydrocarbon generation of lamalginite.展开更多
Origin of authigenic dolomites in the dolomitic reservoir of the Permian Fengcheng Formation in the Mahu Sag of Junggar Basin is unclear.Occurrence and genetic evolution of the authigenic dolomites in dolomitic rock r...Origin of authigenic dolomites in the dolomitic reservoir of the Permian Fengcheng Formation in the Mahu Sag of Junggar Basin is unclear.Occurrence and genetic evolution of the authigenic dolomites in dolomitic rock reservoir of the Fengcheng Formation in the Mahu Sag were analyzed by polarized and fluorescence thin sections,scanning electron microscope(SEM),electron microprobe(EMP),C,O and Sr isotopes analysis,and other techniques.(1)Dolomites were mainly precipitated in three stages:penecontemporaneous-shallow burial stage(early stage of the Middle Permian),middle burial stage(middle stage of the Middle Permian),and middle-deep burial stage,with the former two stages in dominance.(2)Dolomitization fluid was high-salinity brine originating from alkaline lake.In the penecontemporaneous-shallow burial stage,Mg^(2+)was mainly supplied by alkaline-lake fluid and devitrification of volcanic glass.In the middle burial stage,Mg^(2+)mainly came from the transformation of clay minerals,devitrification of volcanic glass and dissolution of aluminosilicates such as feldspar.(3)Regular changes of Mg,Mn,Fe,Sr,Si and other elements during the growth of dolomite were mainly related to the alkaline-lake fluid,and to different influences of devitrification and diagenetic alteration of volcanic materials during the burial.(4)In the penecontemporaneous stage,induced by alkaline-lake microorganisms,the micritic-microcrystalline dolomites were formed by primary precipitation,replacement of aragonite and high-Mg calcite,and other processes;in the shallow burial stage,the silt-sized dolomites were formed by continuous growth of micritic-microcrystalline dolomite and replacement of calcites,tuffs and other substances;in the middle burial stage,the dolomites,mainly silt-and fine-sized,were formed by replacement of volcanic materials.The research results are referential for investigating the formation mechanism and distribution patterns of tight dolomitic reservoirs in the Mahu Sag and other similar oil and gas bearing areas.展开更多
Bent-housing motor is the most widely used directional drilling tool,but it often encounters the problem of high friction when sliding drilling in horizontal wells.In this paper,a mathematical model is proposed to sim...Bent-housing motor is the most widely used directional drilling tool,but it often encounters the problem of high friction when sliding drilling in horizontal wells.In this paper,a mathematical model is proposed to simulate slide drilling with a friction reduction tool of axial vibration.A term called dynamic effective tractoring force(DETF)is defined and used to evaluate friction reduction effectiveness.The factors influencing the DETF are studied,and the tool placement optimization problem is investigated.The studyfinds that the drilling rate of penetration(ROP)can lower the DETF but does not change the trend of the DETF curve.To effectively work,the shock tool stiffness must be greater than some critical value.For the case study,the best oscillating frequency is within 15∼20 Hz.The reflection of the vibration at the bit boundary can intensify or weaken the friction reduction effec-tiveness,depending on the distance between the hydraulic oscillator and the bit.The optimal placement position corresponds to the plateau stage of the DETF curve.The reliability of the method is verified by thefield tests.The proposed method can provide a design and use guide to hydraulic oscillators and improve friction reduction effectiveness in horizontal wells.展开更多
Based on the combination of core observation,experimental analysis and testingand geological analysis,the main controlling factors of shale oil enrichment in the Lower Permian Fengcheng Formation in the Mahu Sag of th...Based on the combination of core observation,experimental analysis and testingand geological analysis,the main controlling factors of shale oil enrichment in the Lower Permian Fengcheng Formation in the Mahu Sag of the Junggar Basin are clarified,and a shale oil enrichment model is established.The results show that the enrichment of shale oil in the Fengcheng Formation in the Mahu Sag is controlled by the organic abundance,organic type,reservoir capacity and the amount of migration hydrocarbon in shale.The abundance of organic matter provides the material basis for shale oil enrichment,and the shales containing typesⅠandⅡorganic matters have good oil content.The reservoir capacity controls shale oil enrichment.Macropores are the main space for shale oil enrichment in the Fengcheng Formation,and pore size and fracture scale directly control the degree of shale oil enrichment.The migration of hydrocarbons in shale affects shale oil enrichment.The shale that has expelled hydrocarbons has poor oil content,while the shale that has received hydrocarbons migrated from other strata has good oil content.Lithofacies reflect the hydrocarbon generation and storage capacity comprehensively.The laminated felsic shale,laminated lime-dolomitic shale and thick-layered felsic shale have good oil content,and they are favorable lithofacies for shale oil enrichment.Under the control of these factors,relative migration of hydrocarbons occurred within the Fengcheng shale,which leads to the the difference in the enrichment process of shale oil.Accordingly,the enrichment mode of shale oil in Fengcheng Formation is established as"in-situ enrichment"and"migration enrichment".By superimposing favorable lithofacies and main controlling factors of enrichment,the sweet spot of shale oil in the Fengcheng Formation can be selected which has great significance for the exploration and development of shale oil.展开更多
Low-temperature oxidation(LTO)is the main reaction that affects fuel formation in the in-situ combustion process,which has important significance for the subsequent combustion propulsion and the successful extraction ...Low-temperature oxidation(LTO)is the main reaction that affects fuel formation in the in-situ combustion process,which has important significance for the subsequent combustion propulsion and the successful extraction of crude oil.In this study,heavy oil was subjected to LTO reactions at different temperatures.Three types of reaction products with varying oxidation depths were characterized in terms of the number of oxygen atoms and the polarity of the molecule to reveal the low-temperature oxidation process of the heavy oil.Ketone compounds and acid polyoxides in the oil phase and deep oxidation products with a higher number of oxygen atoms in the coke were identified with increasing oxidation depth.The experimental results showed that the oxidation reaction of the heavy oil changed from kinetic-controlled to diffusion-controlled in the open oxidation system of the heavy oil as the oxidation depth increased.The oxidation reaction of the oil phase reached a maximum and stable value in oxygen content.The molecular compositions of the ketone compound and acid polyoxide did not change significantly with further increase in reaction temperature.The molecular compositions of the deep oxidation products with a higher number of oxygen atoms in the coke phase changed significantly.The coke precursor molecules with a lower oxygen content and condensation degree participated in the coke formation,and the oxidation reaction pathway and the complexity of the oxidation product component also increased.展开更多
An uncertainty analysis method is proposed for the assessment of the residual strength of a casing subjected to wear and non-uniform load in a deep well.The influence of casing residual stress,out-of-roundness and non...An uncertainty analysis method is proposed for the assessment of the residual strength of a casing subjected to wear and non-uniform load in a deep well.The influence of casing residual stress,out-of-roundness and non-uniform load is considered.The distribution of multi-source parameters related to the residual anti extrusion strength and residual anti internal pressure strength of the casing after wear are determined using the probability theory.Considering the technical casing of X101 well in Xinjiang Oilfield as an example,it is shown that the randomness of casing wear depth,formation elastic modulus and formation Poisson’s ratio are the main factors that affect the uncertainty of residual strength.The wider the confidence interval is,the greater the uncertainty range is.Compared with the calculations resulting from the proposed uncertainty analysis method,the residual strength obtained by means of traditional single value calculation method is either larger or smaller,which leads to the conclusion that the residual strength should be considered in terms of a range of probabilities rather than a single value.展开更多
基金supported by the National Science and Technology Major Project(Grant No.2017ZX05008-006004-002)the National Natural Science Foundation of China(Grant Nos.41502126 and 41902155)the Open Foundation of Top Disciplines in Yangtze University(Grant No.2019KFJJ0818022)。
文摘Three-dimensional unmanned aerial vehicle(UAV)oblique photogrammetric data were used to infer mountainous gravel braided river lithofacies,lithofacies associations and architectural elements.Hierarchical architecture and lithofacies associations with detailed lithofacies characterizations were comprehensively described to document the architectural model,architectural element scale and gravel particle scale.(1)Nine lithofacies(i.e.,Gmm,Gcm,Gcc,Gci,Gcl,Ss,Sm,Fsm and Fl)were identified and classified as gravel,sand and fine matrix deposits.These are typical depositional features of a mountainous dryland gravel-braided river.(2)Three architectural elements were identified,including channel(CH),gravel bar(GB)and overbank(OB).CH can be further divided into flow channel and abandoned channel,while GB consists of Central Gravel bar(CGB)and Margin Gravel bar(MGB).(3)The gravel bar is the key architectural element of the gravel braided river,with its geological attributes.The dimensions of GBs and their particles are various,but exhibit good relationships with each other.The grain size of GB decreases downstream,but the dimensions of GB do not.The bank erosion affects the GB dimensions,whereas channel incision and water flow velocity influence the grain size of GB.The conclusions can be applied to the dryland gravel braided river studies in tectonically active areas.
基金Supported by the Science and Technology Project of China National Petroleum Corporation(2021DJ02).
文摘Based on the global basement reservoir database and the dissection of basement reservoirs in China,the characteristics of hydrocarbon accumulation in basement reservoirs are analyzed,and the favorable conditions for hydrocarbon accumulation in deep basement reservoirs are investigated to highlight the exploration targets.The discovered basement reservoirs worldwide are mainly buried in the Archean and Precambrian granitic and metamorphic formations with depths less than 4500 m,and the relatively large reservoirs have been found in rift,back-arc and foreland basins in tectonic active zones of the Meso-Cenozoic plates.The hydrocarbon accumulation in basement reservoirs exhibits the characteristics in three aspects.First,the porous-fractured reservoirs with low porosity and ultra-low permeability are dominant,where extensive hydrocarbon accumulation occurred during the weathering denudation and later tectonic reworking of the basin basement.High resistance to compaction allows the physical properties of these highly heterogeneous reservoirs to be independent of the buried depth.Second,the hydrocarbons were sourced from the formations outside the basement.The source-reservoir assemblages are divided into contacted source rock-basement and separated source rock-basement patterns.Third,the abnormal high pressure in the source rock and the normal–low pressure in the basement reservoirs cause a large pressure difference between the source rock and the reservoirs,which is conducive to the pumping effect of hydrocarbons in the deep basement.The deep basement prospects are mainly evaluated by the factors such as tectonic activity of basement,source-reservoir combination,development of large deep faults(especially strike-slip faults),and regional seals.The Precambrian crystalline basements at the margin of the intracontinental rifts in cratonic basins,as well as the Paleozoic folded basements and the Meso-Cenozoic fault-block basements adjacent to the hydrocarbon generation depressions,have favorable conditions for hydrocarbon accumulation,and thus they are considered as the main targets for future exploration of deep basement reservoirs.
基金Supported by the National Natural Science Foundation(42202133,42072174,42130803,41872148)PetroChina Science and Technology Innovation Fund(2023DQ02-0106)PetroChina Basic Technology Project(2021DJ0101).
文摘Taking the Lower Permian Fengcheng Formation shale in Mahu Sag of Junggar Basin,NW China,as an example,core observation,test analysis,geological analysis and numerical simulation were applied to identify the shale oil micro-migration phenomenon.The hydrocarbon micro-migration in shale oil was quantitatively evaluated and verified by a self-created hydrocarbon expulsion potential method,and the petroleum geological significance of shale oil micro-migration evaluation was determined.Results show that significant micro-migration can be recognized between the organic-rich lamina and organic-poor lamina.The organic-rich lamina has strong hydrocarbon generation ability.The heavy components of hydrocarbon preferentially retained by kerogen swelling or adsorption,while the light components of hydrocarbon were migrated and accumulated to the interbedded felsic or carbonate organic-poor laminae as free oil.About 69% of the Fengcheng Formation shale samples in Well MY1 exhibit hydrocarbon charging phenomenon,while 31% of those exhibit hydrocarbon expulsion phenomenon.The reliability of the micro-migration evaluation results was verified by combining the group components based on the geochromatography effect,two-dimension nuclear magnetic resonance analysis,and the geochemical behavior of inorganic manganese elements in the process of hydrocarbon migration.Micro-migration is a bridge connecting the hydrocarbon accumulation elements in shale formations,which reflects the whole process of shale oil generation,expulsion and accumulation,and controls the content and composition of shale oil.The identification and evaluation of shale oil micro-migration will provide new perspectives for dynamically differential enrichment mechanism of shale oil and establishing a“multi-peak model in oil generation”of shale.
基金Supported by the China National Science and Technology Major Project(2017ZX05070)PetroChina Science and Technology Major Project(2017E-04)PetroChina–China University of Petroleum(Beijing)Strategic Cooperation Project(ZLZX2020-01)
文摘A series of theoretical explorations and field tests have been carried out to efficiently develop the Mahu tight conglomerate oilfield in the Junggar Basin.Concepts of steered-by-edge fracturing and proactive fracturing interference were proposed.A series of innovative technologies were developed and implemented including optimization of 3-D staggered well pattern,proactive control and utilization of spatial stress field,and synergetic integration of multiple elements.Different from shale,the unique rock fabric and strong heterogeneities of tight conglomerate formation are favorable factors for forming complex fractures,small space well pattern can proactively control and make use of interwell interference to increase the complexity of fracture network,and the"optimum-size and distribution"hydraulic fracturing can be achieved through synergetic optimization.During pilot phase of this field,both depletion with hydraulically fractured vertical wells and volume fracturing in horizontal wells were tested after water injection through vertical wells,then the multi-stage fracturing with horizontal well was taken as the primary development technology.A series of engineering methods were tested,and key development parameters were evaluated such as well spacing,lateral length,fractures spacing,fracturing size,and fracturing operation process.According to geoengineering approach,the 100 m/150 m tridimensional tight-spacing staggered development method was established with systematic integration of big well clusters,multiple stacked pay zones,small well spacing,long lateral length,fine perforation clustering,zipper fracturing and factory operation.According to half-year production performance,100 m/150 m small spacing wells outperformed 500 m/400 m/300 m spacing wells.Its average estimated ultimate recovery(EUR)of wells was identical with those best wells from large-spacing area.Compared with the overall performance of Mahu oilfield,the drainage efficiency and estimated recovery factor of this pilot were significantly boosted with improved economics.
文摘The exploration and development of oilfield results in damages to land resources. Along with the further development of petroleum in the Gurbantunggut Desert, the fragile ecological environment and land resource was suffering much more damage. Vegetation degradation and desertification become more prominent. In response to the damage to the fragile ecological environment and oilfield in the Gurbantunggut Desert, limit condition method was used to evaluate the suitability of land reclamation suitability. Results suggested that the main restraining factors for land reclamation were soil condition and water resources. Based on the effect and shortage of oilfield in the Gurbantunggut Desert Oilfield, the reclamation of oilfield in the Gurbantunggut desert was discussed.
文摘PetroChina Xinjiang Oilfield Company comprehensively promoted the special action to improve quality and efficiency.Through the in-depth interpretation of the balance sheet,income statement,cas h f low statement,we deepened the analysis of the investment and cost structure,collated the corresponding relationship between financial data and key indicators in these sheets,and defined the directions of control one by one.
基金Research work was financed by the National Natural Science Foundation of China(No.52074232)Sichuan Science and Technology Program(No.2022NSFSC0028,No.2022NSFSC0994).Without their support,this work would not have been possible.
文摘The failure of cement sheath integrity can be easily caused by alternating pressure during large-scale multistage hydraulic fracturing in shale-gas well.An elastic-plastic mechanical model of casing-cement sheath-formation(CSF)system under alternating pressure is established based on the Mohr-Coulomb criterion and thick-walled cylinder theory,and it has been solved by MATLAB programming combining global optimization algorithm with Global Search.The failure mechanism of cement sheath integrity is investigated,by which it can be seen that the formation of interface debonding is mainly related to the plastic strain accumulation,and there is a risk of interface debonding under alternating pressure,once the cement sheath enters plasticity whether in shallow or deep well sections.The matching relationship between the mechanical parameters(elastic modulus and Poisson's ratio)of cement sheath and its integrity failure under alternating pressure in whole well sections is studied,by which it has been found there is a“critical range”in the Poisson's ratio of cement sheath.When the Poisson's ratio is below the“critical range”,there is a positive correlation between the yield internal pressure of cement sheath(SYP)and its elastic modulus.However,when the Poisson's ratio is above the“critical range”,there is a negative correlation.The elastic modulus of cement sheath is closely related to its Poisson's ratio,and restricts each other.Scientific and reasonable matching between mechanical parameters of cement sheath and CSF system under different working conditions can not only reduce the cost,but also protect the cement sheath integrity.
基金Supported by the National Natural Science Foundation of China (41902118)Natural Science Foundation of Xinjiang Uygur Autonomous Region (2022D01B141)+1 种基金Natural Science Foundation of Heilongjiang Province (LH2021D003)Heilongjiang Postdoctoral Fund (No.LBH-Z20045)。
文摘Using the data of drilling, logging, core, experiments and production, the heterogeneity and differential hydrocarbon accumulation model of deep reservoirs in Cretaceous Qingshuihe Formation(K1q) in the western section of the foreland thrust belt in southern Junggar Basin are investigated. The target reservoirs are characterized by superimposition of conglomerates, sandy conglomerates and sandstones, with high content of plastic clasts. The reservoir space is mainly composed of intergranular pores. The reservoirs are overall tight, and the sandy conglomerate has the best physical properties. The coupling of short deep burial period with low paleotemperature gradient and formation overpressure led to the relatively weak diagenetic strength of the reservoirs. Specifically, the sandy conglomerates show relatively low carbonate cementation, low compaction rate and high dissolution porosity. The special stress-strain mechanism of the anticline makes the reservoirs at the top of the anticline turning point more reformed by fractures than those at the limbs, and the formation overpressure makes the fractures in open state. Moreover, the sandy conglomerates have the highest oil saturation. Typical anticline reservoirs are developed in deep part of the thrust belt, but characterized by "big trap with small reservoir". Significantly, the sandy conglomerates at the top of anticline turning point have better quality, lower in-situ stress and higher structural position than those at the limbs,with the internal hydrocarbons most enriched, making them high-yield oil/gas layers. The exponential decline of fractures makes hydrocarbon accumulation difficult in the reservoirs at the limbs. Nonetheless, plane hydrocarbon distribution is more extensive at the gentle limb than the steep limb.
基金supported by National Science Foundation for Young Scientists of China(Grant 41702143)Major basic science and technology projects of CNPC(2021DJ0206-03)。
文摘The lacustrine organic-rich shale in the Permian Lucaogou(LCG)Formation of the Jimsar Sag,Junggar Basin,is one of the main shale oil plays in China.In this paper,geological and geochemical research techniques were employed to evaluate the geochemical variability of the lacustrine shale and the pro-duction of organic matter and its preservation conditions.The LcG Formation is characterized by its complex mineral compositions and a wide range of organic matter richness and quality.The presence of high proportions ofβ-carotane and C2g steranes,indicates that the organic matter mainly originated from phytoplankton and aquatic algal-bacterial organisms,especially cyanobacteria.This study found that the productivity of the Lower LCG Member(P2li)was highest,and the Middle LCG Member(P_(2)l_(2))was the lowest.During the deposition of the Lower LCG Member,the lake's bottom water was predominantly a reducing environment,and the degradation of organic matter was largely a result of bacterial sulfate reduction.During the deposition of the Middle and Upper LCG members,the lake's bottom water was mainly oxidizing,and the degradation of organic matter was likely to be caused by aerobic processes.Based on a comprehensive analysis of the origin and production of organic matter,as well as its depo-sitional environment and preservation conditions,two organic matter accumulation models were pro-posed to explain the distribution of the organic-rich shale.In model A,the high influx of volcanic ash released nutrients and brought abundant sulfate into the water,the accumulation of organic matter was mainly controlled by the preservation of organic matter,which was mainly controlled by BsR.In the model B,the influx of volcanic ash was small,organic matter was mainly degraded by oxygen and the accumulation of organic matter is mainly determined by the production of organic matter.
基金support from Sichuan Science and Technology Program(21JCQN0066)supported by National Natural Science Foundation of China(No.51774249).
文摘Large-scale sand fracturing is a necessary means in the efficient exploitation of shale gas/oil.However,in the process of fracturing operation,the sand carrying fluid and proppant easily causes scouring and wear to production strings,especially the casing perforation system,which damage the wellbore integrity and deformation to affect the subsequent fracturing.For this problem,taking the actual construction conditions and perforation technology of an oilfield in western China as an example,the structural parameters of the downhole string were measured and the wall thickness reduction model of casing perforation suitable for large-displacement sand fracturing in horizontal well section was established.With software ANSYS-FLUENT,the casing perforation erosion under the conditions of different displacements,sand content and perforation sand-passing quantity in the process of sand fracturing was simulated and calculated.The influences of three parameters on perforation erosion and expansion were analyzed and the prediction chart of the influences of three main control factors on perforation erosion and expansion was established.The perforation erosion images after fracturing construction were obtained with the downhole eagle perforation logging technology.The logging chart results were compared with the downhole eagle perforation data.The error between the established numerical simulation calculation charts and the real logging data was about 5%,indicating that the simulation charts were the valuable reference.
基金jointly funded by the National Natural Science Foundation of China(Grant Nos.41972120,42172129)the State Key Laboratory of Paleobiology and Stratigraphy(Nanjing Institute of Geology and Paleontology,CAS)(Grant No.173131)+1 种基金the Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(Grant No.2020CX050103)the China Postdoctoral Science Foundation(Grant No.2021M702720)。
文摘Deep-water gravity depositional processes and evolution in arc systems have become topics of intense research focus in recent years.This study discusses the co-evolution of volcanism and deep-water gravity flow deposits at the southern margin of the Junggar Basin,based on petrology,geochronology and geochemical analyses.The results show that a massive collapse of unstable sediments from the slope was triggered by volcanism,resulting in the formation of slumping gravity flows.The occurrence of volcanic beds in the slump deposits confirm that synchronous volcanism likely affected sediment instability,triggering gravity flows.The Th/Yb,Ta/Yb and Th/Ta elemental ratios,U-Pb ages of detrital zircons and paleocurrent directions indicate that the North Tianshan(NTS)island arc represents the provenance of the Qianxia Formation.Moreover,statistical data on the pyroclastic components in the gravity flow deposits reveal an intensity index of volcanism,indicating that volcanism is strongly related to gravity flow deposits,especially in terms of the type and distribution of the deposits.A model for volcanically-triggered deep-water gravity flow deposits is established,in order to provide a more in-depth understanding of the co-evolution of volcanism and gravity flow deposits within the depositional setting of the late Paleozoic NTS oceanic subduction margin in the Junggar Basin.
文摘Based on the geological and geochemical analysis of potential source rocks in different formations and the classification of crude oil types,combined with the hydrocarbon generation thermal simulation experiments,the source,genesis,and distribution of different types of oils in the Mahu large oil province of the Junggar Basin are investigated.Four sets of potential source rocks are developed in the Mahu Sag.Specifically,the source rocks of the Permian Fengcheng Formation have the highest hydrocarbon generation potential and contain mainly TypesⅡandⅠorganic matters,with a high oil generation capacity.In contrast,the source rocks in other formations exhibit lower hydrocarbon generation potential and contain mainly TypeⅢorganic matter,with dominant gas generation.Oils in the Mahu Sag can be classified as three types:A,B and C,which display ascending,mountainous and descending C_(20)-C_(21)-C_(23)tricyclic terpenes abundance patterns in sequence,and gradually increasing relative content of tricyclic terpenes and sterane isomerization parameters,indicating an increasing oil maturity.Different types of oils are distributed spatially in an obviously orderly manner:Type A oil is close to the edge of the sag,Type C oil is concentrated in the center of the sag,and Type B oil lies in the slope area between Type A and Type C.The results of oil-source correlation and thermal simulation experiments show that the three types of oils come from the source rocks of the Fengcheng Formation at different thermal evolution stages.This new understanding of the differential genesis of oils in the Mahu Sag reasonably explains the source,distribution,and genetic mechanism of the three types of oils.The study results are of important guidance for the comprehensive and three-dimensional oil exploration,the identification of oil distribution in the total petroleum system,and the prediction of favorable exploration areas in the Mahu Sag.
基金Supported by National Science and Technology Major Project of China (51674271)Major Technical Field Test of PetroChina (2019F-33)。
文摘With the help of digital image processing technology, an automatic measurement method for the three-phase contact angles in the pore throats of the microfluidic model was established using the microfluidic water flooding experiment videos as the data source. The results of the new method were verified through comparing with the manual measurement data.On this basis, the dynamic changes of the three-phase contact angles under flow conditions were clarified by the contact angles probability density curve and mean value change curve. The results show that, for water-wetting rocks, the mean value of the contact angles is acute angle during the early stage of the water flooding process, and it increases with the displacement time and becomes obtuse angle in the middle-late stage of displacement as the dominant force of oil phase gradually changes from viscous force to capillary force. The droplet flow in the remaining oil occurs in the central part of the pore throats, without three-phase contact angle. The contact angles for the porous flow and the columnar flow change slightly during the displacement and present as obtuse angles in view of mean values, which makes the remaining oil poorly movable and thus hard to be recovered. The mean value of the contact angle for the cluster flow tends to increase in the flooding process, which makes the remaining oil more difficult to be recovered. The contact angles for the membrane flow are mainly obtuse angles and reach the highest mean value in the late stage of displacement, which makes the remaining oil most difficult to be recovered. After displacement, the remaining oils under different flow regimes are just subjected to capillary force, with obtuse contact angles, and the wettability of the pore throat walls in the microfluidic model tends to be oil-wet under the action of crude oil.
基金Supported by National Natural Science Foundation of China(51974332)Strategic Cooperation Project Between PetroChina and China University of Petroleum(Beijing)(ZLZX2020-07).
文摘This paper establishes a 3D multi-well pad fracturing numerical model coupled with fracture propagation and proppant migration based on the displacement discontinuity method and Eulerian-Eulerian frameworks,and the fracture propagation and proppant distribution during multi-well fracturing are investigated by taking the actual multi-well pad parameters as an example.Fracture initiation and propagation during multi-well pad fracturing are jointly affected by a variety of stress interference mechanisms such as inter-cluster,inter-stage,and inter-well,and the fracture extension is unbalanced among clusters,asymmetric on both wings,and dipping at heels.Due to the significant influence of fracture morphology and width on the migration capacity of proppant in the fracture,proppant is mainly placed in the area near the wellbore with large fracture width,while a high-concentration sandwash may easily occur in the area with narrow fracture width as a result of quick bridging.On the whole,the proppant placement range is limited.Increasing the well-spacing can reduce the stress interference of adjacent wells and promote the uniform distribution of fractures and proppant on both wings.The maximum stimulated reservoir volume or multi-fracture uniform propagation can be achieved by optimizing the well spacing.Although reducing the perforation-cluster spacing also can improve the stimulated reservoir area,a too low cluster spacing is not conducive to effectively increasing the propped fracture area.Since increasing the stage time lag is beneficial to reduce inter-stage stress interference,zipper fracturing produces more uniform fracture propagation and proppant distribution.
文摘The Middle Permian Lucaogou Formation in Northwestern China mainly contains typical saline lacustrine oil shale.To study the differences in geochemistry and hydrocarbon generation of source-rock samples in Lucaogou Formation in Jimusaer Sag,57 core samples from two boreholes were analyzed herein by performing total organic carbon(TOC)analysis,RockeEval pyrolysis,and gas chromatographicemass spectrometry experiments on saturated hydrocarbons.The kinetics of oil generation were studied using two samples comprising typical maceral components.The results showed that the hydrocarbons produced by telalginite are relatively rich in pristane(Pr),phytane(Ph),b-carotane,high-carbon normal alkanes,and C29 regular steranes.Hydrocarbons produced by lamalginite contain a significantly higher content of C20 tricyclic terpanes(TT),C21TT,C24 tetracyclic terpanes(TeT),C29 norhopane,and C28 regular sterane.Based on the pyrolysis and biomarker compound parameters,telalginite has a higher conversion rate for hydrocarbons than lamalginite in the low-mature to mature stage,which is consistent with their kinetic analysis.Lamalginite source rock displays a much narrower distribution of activation energies than telalginite source rocks.Such narrower activation energy distribution effectively narrows the main stage of hydrocarbon generation.In addition,the activation energy distribution of lamalginite concentrated in the high-value interval,indicating the characteristics of the relatively lagging hydrocarbon generation of lamalginite.
基金Supported the Major National Oil and Gas Projects of China(2016ZX05046-006).
文摘Origin of authigenic dolomites in the dolomitic reservoir of the Permian Fengcheng Formation in the Mahu Sag of Junggar Basin is unclear.Occurrence and genetic evolution of the authigenic dolomites in dolomitic rock reservoir of the Fengcheng Formation in the Mahu Sag were analyzed by polarized and fluorescence thin sections,scanning electron microscope(SEM),electron microprobe(EMP),C,O and Sr isotopes analysis,and other techniques.(1)Dolomites were mainly precipitated in three stages:penecontemporaneous-shallow burial stage(early stage of the Middle Permian),middle burial stage(middle stage of the Middle Permian),and middle-deep burial stage,with the former two stages in dominance.(2)Dolomitization fluid was high-salinity brine originating from alkaline lake.In the penecontemporaneous-shallow burial stage,Mg^(2+)was mainly supplied by alkaline-lake fluid and devitrification of volcanic glass.In the middle burial stage,Mg^(2+)mainly came from the transformation of clay minerals,devitrification of volcanic glass and dissolution of aluminosilicates such as feldspar.(3)Regular changes of Mg,Mn,Fe,Sr,Si and other elements during the growth of dolomite were mainly related to the alkaline-lake fluid,and to different influences of devitrification and diagenetic alteration of volcanic materials during the burial.(4)In the penecontemporaneous stage,induced by alkaline-lake microorganisms,the micritic-microcrystalline dolomites were formed by primary precipitation,replacement of aragonite and high-Mg calcite,and other processes;in the shallow burial stage,the silt-sized dolomites were formed by continuous growth of micritic-microcrystalline dolomite and replacement of calcites,tuffs and other substances;in the middle burial stage,the dolomites,mainly silt-and fine-sized,were formed by replacement of volcanic materials.The research results are referential for investigating the formation mechanism and distribution patterns of tight dolomitic reservoirs in the Mahu Sag and other similar oil and gas bearing areas.
文摘Bent-housing motor is the most widely used directional drilling tool,but it often encounters the problem of high friction when sliding drilling in horizontal wells.In this paper,a mathematical model is proposed to simulate slide drilling with a friction reduction tool of axial vibration.A term called dynamic effective tractoring force(DETF)is defined and used to evaluate friction reduction effectiveness.The factors influencing the DETF are studied,and the tool placement optimization problem is investigated.The studyfinds that the drilling rate of penetration(ROP)can lower the DETF but does not change the trend of the DETF curve.To effectively work,the shock tool stiffness must be greater than some critical value.For the case study,the best oscillating frequency is within 15∼20 Hz.The reflection of the vibration at the bit boundary can intensify or weaken the friction reduction effec-tiveness,depending on the distance between the hydraulic oscillator and the bit.The optimal placement position corresponds to the plateau stage of the DETF curve.The reliability of the method is verified by thefield tests.The proposed method can provide a design and use guide to hydraulic oscillators and improve friction reduction effectiveness in horizontal wells.
文摘Based on the combination of core observation,experimental analysis and testingand geological analysis,the main controlling factors of shale oil enrichment in the Lower Permian Fengcheng Formation in the Mahu Sag of the Junggar Basin are clarified,and a shale oil enrichment model is established.The results show that the enrichment of shale oil in the Fengcheng Formation in the Mahu Sag is controlled by the organic abundance,organic type,reservoir capacity and the amount of migration hydrocarbon in shale.The abundance of organic matter provides the material basis for shale oil enrichment,and the shales containing typesⅠandⅡorganic matters have good oil content.The reservoir capacity controls shale oil enrichment.Macropores are the main space for shale oil enrichment in the Fengcheng Formation,and pore size and fracture scale directly control the degree of shale oil enrichment.The migration of hydrocarbons in shale affects shale oil enrichment.The shale that has expelled hydrocarbons has poor oil content,while the shale that has received hydrocarbons migrated from other strata has good oil content.Lithofacies reflect the hydrocarbon generation and storage capacity comprehensively.The laminated felsic shale,laminated lime-dolomitic shale and thick-layered felsic shale have good oil content,and they are favorable lithofacies for shale oil enrichment.Under the control of these factors,relative migration of hydrocarbons occurred within the Fengcheng shale,which leads to the the difference in the enrichment process of shale oil.Accordingly,the enrichment mode of shale oil in Fengcheng Formation is established as"in-situ enrichment"and"migration enrichment".By superimposing favorable lithofacies and main controlling factors of enrichment,the sweet spot of shale oil in the Fengcheng Formation can be selected which has great significance for the exploration and development of shale oil.
基金supported by the National Key R&D Program of China(2018YFA0702400)the PetroChina Exploration&Production Company(KS2020-01-05).
文摘Low-temperature oxidation(LTO)is the main reaction that affects fuel formation in the in-situ combustion process,which has important significance for the subsequent combustion propulsion and the successful extraction of crude oil.In this study,heavy oil was subjected to LTO reactions at different temperatures.Three types of reaction products with varying oxidation depths were characterized in terms of the number of oxygen atoms and the polarity of the molecule to reveal the low-temperature oxidation process of the heavy oil.Ketone compounds and acid polyoxides in the oil phase and deep oxidation products with a higher number of oxygen atoms in the coke were identified with increasing oxidation depth.The experimental results showed that the oxidation reaction of the heavy oil changed from kinetic-controlled to diffusion-controlled in the open oxidation system of the heavy oil as the oxidation depth increased.The oxidation reaction of the oil phase reached a maximum and stable value in oxygen content.The molecular compositions of the ketone compound and acid polyoxide did not change significantly with further increase in reaction temperature.The molecular compositions of the deep oxidation products with a higher number of oxygen atoms in the coke phase changed significantly.The coke precursor molecules with a lower oxygen content and condensation degree participated in the coke formation,and the oxidation reaction pathway and the complexity of the oxidation product component also increased.
基金supported by the National Natural Science Foundation of China[51804061,51974052,51774063]the Academician Led Special Project of Chongqing Science and Technology Commission[cstc2017zdcy-yszxX0009]+1 种基金the Chongqing Research Program of Basic Research and Frontier Technology[cstc2019jcyj-msxmX0199,cstc2018jcyjAX0417]the Chongqing Education Committee foundation[KJQN201901544,KJZD-K201801501].
文摘An uncertainty analysis method is proposed for the assessment of the residual strength of a casing subjected to wear and non-uniform load in a deep well.The influence of casing residual stress,out-of-roundness and non-uniform load is considered.The distribution of multi-source parameters related to the residual anti extrusion strength and residual anti internal pressure strength of the casing after wear are determined using the probability theory.Considering the technical casing of X101 well in Xinjiang Oilfield as an example,it is shown that the randomness of casing wear depth,formation elastic modulus and formation Poisson’s ratio are the main factors that affect the uncertainty of residual strength.The wider the confidence interval is,the greater the uncertainty range is.Compared with the calculations resulting from the proposed uncertainty analysis method,the residual strength obtained by means of traditional single value calculation method is either larger or smaller,which leads to the conclusion that the residual strength should be considered in terms of a range of probabilities rather than a single value.