The paper presents the results of comprehensive studies of filtration and capacitance properties of highly porous reservoir rocks of the aquifer of an underground gas storage facility.The geomechanical part of the res...The paper presents the results of comprehensive studies of filtration and capacitance properties of highly porous reservoir rocks of the aquifer of an underground gas storage facility.The geomechanical part of the research included studying the dependence of rock permeability on the stress-strain state in the vicinity of the wells,and physical modeling of the implementation of the method of increasing the permeability of the wellbore zone-the method of directional unloading of the reservoir.The digital part of the research included computed tomography(CT)-based computer analysis of the internal structure,pore space characteristics,and filtration properties before and after the tests.According to the results of physical modeling of deformation and filtration processes,it is found that the permeability of rocks before fracture depends on the stress-strain state insignificantly,and this influence is reversible.However,when downhole pressure reaches 7-8 MPa,macrocracks in the rock begin to grow,accompanied by irreversible permeability increase.Porosity,geodesic tortuosity and permeability values were obtained based on digital studies and numerical modeling.A weak degree of transversal anisotropy of the filtration properties of rocks was detected.Based on the analysis of pore size distribution,pressure field and flow velocities,high homogeneity and connectivity of the rock pore space is shown.The absence of pronounced changes in pore space characteristics and pore permeability after non-uniform triaxial loading rocks was shown.On the basis of geometrical analysis of pore space,the reasons for weak permeability anisotropy were identified.The filtration-capacitance properties obtained from the digital analysis showed very good agreement with the results of field and laboratory measurements.The physical modeling has confirmed the efficiency of application of the directional unloading method for the reservoir under study.The necessary parameters of its application were calculated:bottomhole geometry,stage of operation,stresses and pressure drawdown value.展开更多
The relationships between permeability and dynamics in hydrocarbon accumulation determine oil- bearing potential (the potential oil charge) of low perme- ability reservoirs. The evolution of porosity and permeabilit...The relationships between permeability and dynamics in hydrocarbon accumulation determine oil- bearing potential (the potential oil charge) of low perme- ability reservoirs. The evolution of porosity and permeability of low permeability turbidite reservoirs of the middle part of the third member of the Shahejie Formation in the Dongying Sag has been investigated by detailed core descriptions, thin section analyses, fluid inclusion analyses, carbon and oxygen isotope analyses, mercury injection, porosity and permeability testing, and basin modeling. The cutoff values for the permeability of the reservoirs in the accumulation period were calculated after detailing the accumulation dynamics and reservoir pore structures, then the distribution pattern of the oil-bearing potential of reservoirs controlled by the matching relationship between dynamics and permeability during the accumulation period were summarized. On the basis of the observed diagenetic features and with regard to the paragenetic sequences, the reservoirs can be subdivided into four types of diagenetic facies. The reservoirs experienced two periods of hydro- carbon accumulation. In the early accumulation period, the reservoirs except for diagenetic facies A had middle to high permeability ranging from 10 × 10-3 gm2 to 4207 × 10-3 lain2. In the later accumulation period, the reservoirs except for diagenetic facies C had low permeability ranging from 0.015 × 10-3 gm2 to 62× 10-3 -3m2. In the early accumulation period, the fluid pressure increased by the hydrocarbon generation was 1.4-11.3 MPa with an average value of 5.1 MPa, and a surplus pressure of 1.8-12.6 MPa with an average value of 6.3 MPa. In the later accumulation period, the fluid pressure increased by the hydrocarbon generation process was 0.7-12.7 MPa with an average value of 5.36 MPa and a surplus pressure of 1.3-16.2 MPa with an average value of 6.5 MPa. Even though different types of reservoirs exist, all can form hydrocarbon accumulations in the early accumulation per- iod. Such types of reservoirs can form hydrocarbon accumulation with high accumulation dynamics; however, reservoirs with diagenetic facies A and diagenetic facies B do not develop accumulation conditions with low accumu- lation dynamics in the late accumulation period for very low permeability. At more than 3000 m burial depth, a larger proportion of turbidite reservoirs are oil charged due to the proximity to the source rock, Also at these depths, lenticular sand bodies can accumulate hydrocarbons. At shallower depths, only the reservoirs with oil-source fault development can accumulate hydrocarbons. For flat surfaces, hydrocarbons have always been accumulated in the reservoirs around the oil-source faults and areas near the center of subsags with high accumulation dynamics.展开更多
In Wangjiatun area of the Northern Songliao Basin, reservoir space can be divided into three types: primary pore, secondary pore and fissure according to their origins,which can be subdivided into eight subtypes: macr...In Wangjiatun area of the Northern Songliao Basin, reservoir space can be divided into three types: primary pore, secondary pore and fissure according to their origins,which can be subdivided into eight subtypes: macro-vesicule, shrank primary vesicule, alteration pore, groundmass corrosive pore, normal structural crack, corrosive structural crack, filled structural crack and groundmass shrank crack according to texture and origin of the pore space. It has characteristic of double pore medium. Volcanic porosities of small diameter samples (with diameter of ca. 2.5 cm) and large diameter samples (with diameter of ca. 21.5 cm) were tested in accordance with the characteristic of volcanic reservoir space. Volcanic porosities for small diameter samples correspond with matrix porosities and those of large diameter samples correspond with total porosities including matrix and fractured porosities. Models of the calculated porosity by acoustic wave or density of volcanic reservoir are established in view of those measured data. Comparison of calculated and measuredporosities shows that precision of calculated porosities is lower for rhyolite and tuffites, and higher for basaltand andesite. Relative errors of calculated porosities by model of large diameter samples are lower than those of small diameter samples, i. e. precision of the former is higher than that of the later.展开更多
Tight sand gas reservoirs are our country’s fairly rich unconventional natural gas resources, and their exploration and development is of prime importance. Sulige Gas Field which located in the northern Ordos Basin i...Tight sand gas reservoirs are our country’s fairly rich unconventional natural gas resources, and their exploration and development is of prime importance. Sulige Gas Field which located in the northern Ordos Basin is tight sand gas reservoirs. It is typically featured by low porosity and low permeability, and the error of porosity calculation by traditional methods is larger. Multicomponent explanation model is built by analyzing the thin slice data, and the objective function is got according to the concept of optimization log interpretation method. This paper puts the Genetic Algorithm and the Complex Algorithm together to form the GA-CM Hybrid Algorithm for searching the optimal solution of the objective function, getting the porosity of tight sandstone gas reservoirs. The deviation got by this method is lesser compared with the core porosity, with a high reliability.展开更多
In these years,the Upper Jurassic andesitic volcanic reservoirs in Erlian basin,the Lower Cretaceous rhyolitic volcanic reservoirs in Songliao Basin,the Cretaceous rhyolitic,and the Paleogene basaltic and trachytic vo...In these years,the Upper Jurassic andesitic volcanic reservoirs in Erlian basin,the Lower Cretaceous rhyolitic volcanic reservoirs in Songliao Basin,the Cretaceous rhyolitic,and the Paleogene basaltic and trachytic volcanic reservoirs in Bohai Bay Basin,and the basaltic volcanic reservoirs in Subei basin were discovered.With more and more volcanic oil and gas fields being discovered and developed,the volcanic rocks demonstrate a great petroleum potential in eastern basins of China.Five volcanic facies were identified in these basins,including volcanic conduit facies,explosive facies,effusive facies。展开更多
The aim of this work was to obtain the physicochemical properties by SEM, XRD, FTIR analyses and the surface characteristics from carbonate outcrops cores such as pore diameter, surface area, porosity and permeability...The aim of this work was to obtain the physicochemical properties by SEM, XRD, FTIR analyses and the surface characteristics from carbonate outcrops cores such as pore diameter, surface area, porosity and permeability. The methods used to characterize them were Scanning Electron Microscopy, SEM;X Ray Diffraction, DRX;Fourier Transform Infrared Spectroscopy, FTIR. The porosity and permeability of natural vuggy fractured porous medium from core samples was determined obtained in the laboratory with conventional procedures. The cores have smooth and rough surfaces with porous with several sizes. Some crystals appear in preferential zones mainly composed by calcium, carbon and oxygen. Apparently into free spaces were found the organic materials, organic residues of crude oil. The cores have smooth and rough surfaces with porous with several sizes. Some crystals appear in preferential zones composed by calcium, carbon and oxygen. Apparently into free spaces were found the organic materials, organic residues of crude oil. The main inorganic compound in cores is calcite, (CaCO3). The porosity was for porous core 26% and for solid core 8.5%. The values obtained show that the cores have permeability where the fluid migrates through the particles at 2.23 × 10-4 cm/s.展开更多
The study or pore characteristics is or great importance in reservoir evaluation,especially in deeply buried s andstone.It controls the storage mechanism and reservoir fluid properties of the permeable horizons.The fi...The study or pore characteristics is or great importance in reservoir evaluation,especially in deeply buried s andstone.It controls the storage mechanism and reservoir fluid properties of the permeable horizons.The first member of Eocene Shahejie Formation(Esl)sandstone is classified as feldspathic litharenite and lithic arkose.The present research investigates the pore characteristics and reservoir features of the deeply buried sandstone reservoir of Esl member of Shahejie Formation.The techniques including thin-section petrography,mercury injection capillary pressure(MICP),scanning electron microscopy and laser scanning confocal microscope images were used to demarcate the pores including primary intergranular pores and secondary intergranular,intragranular,dissolution and fracture pores.Mercury injection test and routine core analysis were led to demarcate the pore network characteristics of the studied reservoir.Pore size and pore throat size distribution are acquired from mercury injection test.Porosity values range from 0.5%to 30%,and permeability ranges 0.006-7000 mD.Pore radii of coarse-grained sandstone and fine-grained sandstone range from 0.2 to>4μm and 1 nm to 1.60μm,respectively,by MICP analysis.The mineral composition also plays an important role in protecting the pores with pressure from failure.Fractured sandstone and coarse-grained sandstone consist of large and interconnected pores that enhance the reservoir porosity and permeability,whereas fine-grained sandstone and siltstone consist of numerous pores but not well interconnected,and so they consist of high porosity with low permeability.展开更多
The present work has been accomplished to carry out a detailed study of the characteristics of the Early Jurassic Datta Formation of Trans-Indus Ranges, Pakistan. The discovery of Saib well-1 (Gas and condensate disco...The present work has been accomplished to carry out a detailed study of the characteristics of the Early Jurassic Datta Formation of Trans-Indus Ranges, Pakistan. The discovery of Saib well-1 (Gas and condensate discovery from Jurassic limestone) in the study basin takes an active interest in carrying out extensive exploration activities in the same basin. Jurassic rocks especially Datta Sandstone and Samana Suk Limestone are acting as good reservoirs. The study unit consists of variegated sandstone interbedded with siltstone, carbonaceous clay, and shale and coal stringer. For the current work, two stratigraphic sections (Pezu and Abbo Wanda) have been measured. To examine its sedimentology, depositional environment, diagenetic settings, and reservoir characteristics, a detailed study was conducted and various laboratory techniques have been utilized. About 95 rock samples from the bottom to the top of both sections were collected, and 50 rock samples have been selected for thin section analysis and were examined under a polarizing microscope to show their mineralogical composition, diagenesis, and their reservoir characteristics. XRD (X-ray diffraction), Cathodoluminescence (CL), SEM (Scanning electron microscope) with EDS (Energy-dispersive spectroscope), and Core plug porosity and permeability analysis have been used to interpret its chemical and mineralogical composition and its reservoir characteristics, respectively. Based on field observations and thin section analysis, four depositional facies and six lithofacies have been established. The sedimentary structures, depositional facies, and lithofacies indicate that Datta Formation was deposited in a deltaic environment. Compactions, cementation, fracturing and dissolution can greatly affect the quality of reservoir rock. Based on thin section and SEM analysis, large numbers of primary pores, fracture and secondary pores were observed and connectivity between the pores is good, and at some places, these pores were filled through the authigenic clay minerals like kaolinite, mixed layers illite/smectite and chlorite that influences the reservoir characteristics. Primary pores (thin section) and secondary pores (dissolution pores) and core plug porosity and permeability data (porosity 13.23%-26.89% and permeability 0.12 to 149 mD) shows that Datta Formation has a good reservoir quality.展开更多
Theoretical equations for computing sensitivity coefficients of wellbore pressures to estimate the reservoir parameters in low-permeability reservoirs conditioning to non-Darcy flow data at low velocity were obtained....Theoretical equations for computing sensitivity coefficients of wellbore pressures to estimate the reservoir parameters in low-permeability reservoirs conditioning to non-Darcy flow data at low velocity were obtained. It is shown by a lot of numerical calculations that the wellbore pressures are much more sensitive to permeability very near the well than to permeability a few gridblocks away from the well. When an initial pressure gradient existent sensitivity coefficients in the region are closer to the active well than to the observation well. Sensitivity coefficients of observation well at the line between the active well and the observation well are influenced greatly by the initial pressure gradient.展开更多
In mature reservoirs,the success of preformed particle gel(PPG) treatment rests primarily on the ability of the PPG to reduce and/or plug the high permeable formations,but not damage the low permeable formations.Sta...In mature reservoirs,the success of preformed particle gel(PPG) treatment rests primarily on the ability of the PPG to reduce and/or plug the high permeable formations,but not damage the low permeable formations.Static test models(filtration test model and pressure test model)were used to determine the effect of PPG on low permeable formations.This work used a strong preformed particle gel,Daqing(DQ) gel made by a Chinese company.The particle gel sizes were ranged from 30 to 120 mesh for this work.PPGs are sized in a millimeter or micrometer,which can absorb over a hundred times their weight in liquids.The gel strength was approximately 6500 Pa for a completely swollen PPG with 1 %(weight percentage) NaCl solution(brine).0.05 %,1 %,and 10 % NaCl solutions were used in experiments.Sandstone core permeability was measured before and after PPG treatments.The relationship between cumulative filtration volumes versus filtration times was determined.The results indicate that DQ gels of a particle size of 30–80 mesh did not damage the cores of a low permeability of 3–25 m D.The DQ gels of a smaller particle size ranging from 100 to 120 mesh damaged the core and a cake was formed on the core surface.The results also indicate that more damage occurred when a high load pressure(400 psi) was applied on the high permeability cores(290–310 m D).The penetration of the particle gelsinto the low permeable formations can be decreased by the best selection of gel types,particle sizes,and brine concentrations.展开更多
Polymer injectivity is an important factor for evaluating the project economics of chemical flood,which is highly related to the polymer viscosity.Because the flow rate varies rapidly near injectors and significantly ...Polymer injectivity is an important factor for evaluating the project economics of chemical flood,which is highly related to the polymer viscosity.Because the flow rate varies rapidly near injectors and significantly changes the polymer viscosity due to the non-Newtonian rheological behavior,the polymer viscosity near the wellbore is difficult to estimate accurately with the practical gridblock size in reservoir simulation.To reduce the impact of polymer rheology upon chemical EOR simulations,we used an efficient multilevel local grid refinement(LGR)method that provides a higher resolution of the flows in the near-wellbore region.An efficient numerical scheme was proposed to accurately solve the pressure equation and concentration equations on the multilevel grid for both homogeneous and heterogeneous reservoir cases.The block list and connections of the multilevel grid are generated via an efficient and extensible algorithm.Field case simulation results indicate that the proposed LGR is consistent with the analytical injectivity model and achieves the closest results to the full grid refinement,which considerably improves the accuracy of solutions compared with the original grid.In addition,the method was validated by comparing it with the LGR module of CMG_STARS.Besides polymer injectivity calculations,the LGR method is applicable for other problems in need of near-wellbore treatment,such as fractures near wells.展开更多
Survey and novel research data are used in the present study to classify/identify the lithological type of Verey age reservoirs’rocks.It is shown how the use of X-ray tomography can clarify the degree of heterogeneit...Survey and novel research data are used in the present study to classify/identify the lithological type of Verey age reservoirs’rocks.It is shown how the use of X-ray tomography can clarify the degree of heterogeneity,porosity and permeability of these rocks.These data are then used to elaborate a model of hydraulic fracturing.The resulting software can take into account the properties of proppant and breakdown fluid,thermal reservoir conditions,oil properties,well design data and even the filtration and elastic-mechanical properties of the rocks.Calculations of hydraulic fracturing crack formation are carried out and the results are compared with the data on hydraulic fracturing crack at standard conditions.Significant differences in crack formation in standard and lithotype models are determined.It is shown that the average width of the crack development for the lithotype model is 2.3 times higher than that for the standard model.Moreover,the coverage of crack development in height for the lithotype model is almost 2 times less than that for the standard model.The estimated fracture half-length for the lithotype model is 13.3%less than that of for the standard model.A higher dimensionless fracture conductivity is also obtained for the lithotype model.It is concluded that the proposed approach can increase the reliability of hydraulic fracturing crack models.展开更多
Deep coalbed methane exists in high-temperature and high-pressure reservoirs. To elucidate the dynamic-change laws of the deep coal reservoir porosity and permeability characteristics in the process of coalbed methane...Deep coalbed methane exists in high-temperature and high-pressure reservoirs. To elucidate the dynamic-change laws of the deep coal reservoir porosity and permeability characteristics in the process of coalbed methane production, based on three pieces of low- to medium-rank coal samples in the eastern Junggar Basin, Xinjiang, we analyse their mercury-injection pore structures. We measured the porosity and permeability of the coal samples at various temperatures and confining pressures by high-temperature and confining pressure testing. The results show that the porosity of a coal sample decreases exponentially with increasing effective stress. With increasing temperature, the initial porosity increases for two pieces of relatively low-rank coal samples. The increased rate of porosity decreases with increasing confining pressure. With increasing temperature, the initial porosity of a relatively high-rank coal sample decreases, and the rate of change of the porosity become faster. An exponential relationship exists between the porosity and permeability. With increasing coal rank, the initial porosity and permeability decrease. The change rate of the permeability decreases with increasing porosity.展开更多
Based on detailed studies, this paper proposesthat in the Tarim Basin, hydrocarbon reservoirs widespreadeither in vertical sequences or in plane and high-porosity andhigh-permeability reservoirs are developed all over...Based on detailed studies, this paper proposesthat in the Tarim Basin, hydrocarbon reservoirs widespreadeither in vertical sequences or in plane and high-porosity andhigh-permeability reservoirs are developed all over the basin.However, obvious difference and heterogeneity exist amongdifferent kinds of reservoirs. The lithologic characteristics,reservoir space types and reservoir properties in variousstrata have been probed. The result indicates that althoughthe Paleozoic carbonates have been deeply buried for a longperiod, high-quality reservoirs with the porosity of up to 5%-8% (12% as the maximum) and the permeability of10×10<sup>-3</sup>-100×10<sup>-3</sup> μm<sup>2</sup> (1000×10<sup>-3</sup>μm<sup>2</sup> as the maximum)can be found in certain areas. These include the area withthe development of reefs and carbonate beaches, the weath-ered-crust buried-hill belts that have undergone thelong-term exposure, weathering and leaching, the area withthe development of dolomitization, and those areas that haveexperienced the resolution of carbonic acid and organic acidgenerated by the maturity of the organic matter. Finally, thegenesis of the high-porosity and high-permeability reservoirsin deep-buried conditions (with the depth more than 3500 m)have been investigated thoroughly.展开更多
基金supported by the Russian Science Foundation(Grant No.22-11-00273).
文摘The paper presents the results of comprehensive studies of filtration and capacitance properties of highly porous reservoir rocks of the aquifer of an underground gas storage facility.The geomechanical part of the research included studying the dependence of rock permeability on the stress-strain state in the vicinity of the wells,and physical modeling of the implementation of the method of increasing the permeability of the wellbore zone-the method of directional unloading of the reservoir.The digital part of the research included computed tomography(CT)-based computer analysis of the internal structure,pore space characteristics,and filtration properties before and after the tests.According to the results of physical modeling of deformation and filtration processes,it is found that the permeability of rocks before fracture depends on the stress-strain state insignificantly,and this influence is reversible.However,when downhole pressure reaches 7-8 MPa,macrocracks in the rock begin to grow,accompanied by irreversible permeability increase.Porosity,geodesic tortuosity and permeability values were obtained based on digital studies and numerical modeling.A weak degree of transversal anisotropy of the filtration properties of rocks was detected.Based on the analysis of pore size distribution,pressure field and flow velocities,high homogeneity and connectivity of the rock pore space is shown.The absence of pronounced changes in pore space characteristics and pore permeability after non-uniform triaxial loading rocks was shown.On the basis of geometrical analysis of pore space,the reasons for weak permeability anisotropy were identified.The filtration-capacitance properties obtained from the digital analysis showed very good agreement with the results of field and laboratory measurements.The physical modeling has confirmed the efficiency of application of the directional unloading method for the reservoir under study.The necessary parameters of its application were calculated:bottomhole geometry,stage of operation,stresses and pressure drawdown value.
基金supported by the National Natural Science Foundation of China(Grant No.U1262203)the National Science and Technology Special Grant(No.2011ZX05006-003)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.14CX06070A)the Chinese Scholarship Council(No.201506450029)
文摘The relationships between permeability and dynamics in hydrocarbon accumulation determine oil- bearing potential (the potential oil charge) of low perme- ability reservoirs. The evolution of porosity and permeability of low permeability turbidite reservoirs of the middle part of the third member of the Shahejie Formation in the Dongying Sag has been investigated by detailed core descriptions, thin section analyses, fluid inclusion analyses, carbon and oxygen isotope analyses, mercury injection, porosity and permeability testing, and basin modeling. The cutoff values for the permeability of the reservoirs in the accumulation period were calculated after detailing the accumulation dynamics and reservoir pore structures, then the distribution pattern of the oil-bearing potential of reservoirs controlled by the matching relationship between dynamics and permeability during the accumulation period were summarized. On the basis of the observed diagenetic features and with regard to the paragenetic sequences, the reservoirs can be subdivided into four types of diagenetic facies. The reservoirs experienced two periods of hydro- carbon accumulation. In the early accumulation period, the reservoirs except for diagenetic facies A had middle to high permeability ranging from 10 × 10-3 gm2 to 4207 × 10-3 lain2. In the later accumulation period, the reservoirs except for diagenetic facies C had low permeability ranging from 0.015 × 10-3 gm2 to 62× 10-3 -3m2. In the early accumulation period, the fluid pressure increased by the hydrocarbon generation was 1.4-11.3 MPa with an average value of 5.1 MPa, and a surplus pressure of 1.8-12.6 MPa with an average value of 6.3 MPa. In the later accumulation period, the fluid pressure increased by the hydrocarbon generation process was 0.7-12.7 MPa with an average value of 5.36 MPa and a surplus pressure of 1.3-16.2 MPa with an average value of 6.5 MPa. Even though different types of reservoirs exist, all can form hydrocarbon accumulations in the early accumulation per- iod. Such types of reservoirs can form hydrocarbon accumulation with high accumulation dynamics; however, reservoirs with diagenetic facies A and diagenetic facies B do not develop accumulation conditions with low accumu- lation dynamics in the late accumulation period for very low permeability. At more than 3000 m burial depth, a larger proportion of turbidite reservoirs are oil charged due to the proximity to the source rock, Also at these depths, lenticular sand bodies can accumulate hydrocarbons. At shallower depths, only the reservoirs with oil-source fault development can accumulate hydrocarbons. For flat surfaces, hydrocarbons have always been accumulated in the reservoirs around the oil-source faults and areas near the center of subsags with high accumulation dynamics.
文摘In Wangjiatun area of the Northern Songliao Basin, reservoir space can be divided into three types: primary pore, secondary pore and fissure according to their origins,which can be subdivided into eight subtypes: macro-vesicule, shrank primary vesicule, alteration pore, groundmass corrosive pore, normal structural crack, corrosive structural crack, filled structural crack and groundmass shrank crack according to texture and origin of the pore space. It has characteristic of double pore medium. Volcanic porosities of small diameter samples (with diameter of ca. 2.5 cm) and large diameter samples (with diameter of ca. 21.5 cm) were tested in accordance with the characteristic of volcanic reservoir space. Volcanic porosities for small diameter samples correspond with matrix porosities and those of large diameter samples correspond with total porosities including matrix and fractured porosities. Models of the calculated porosity by acoustic wave or density of volcanic reservoir are established in view of those measured data. Comparison of calculated and measuredporosities shows that precision of calculated porosities is lower for rhyolite and tuffites, and higher for basaltand andesite. Relative errors of calculated porosities by model of large diameter samples are lower than those of small diameter samples, i. e. precision of the former is higher than that of the later.
文摘Tight sand gas reservoirs are our country’s fairly rich unconventional natural gas resources, and their exploration and development is of prime importance. Sulige Gas Field which located in the northern Ordos Basin is tight sand gas reservoirs. It is typically featured by low porosity and low permeability, and the error of porosity calculation by traditional methods is larger. Multicomponent explanation model is built by analyzing the thin slice data, and the objective function is got according to the concept of optimization log interpretation method. This paper puts the Genetic Algorithm and the Complex Algorithm together to form the GA-CM Hybrid Algorithm for searching the optimal solution of the objective function, getting the porosity of tight sandstone gas reservoirs. The deviation got by this method is lesser compared with the core porosity, with a high reliability.
文摘In these years,the Upper Jurassic andesitic volcanic reservoirs in Erlian basin,the Lower Cretaceous rhyolitic volcanic reservoirs in Songliao Basin,the Cretaceous rhyolitic,and the Paleogene basaltic and trachytic volcanic reservoirs in Bohai Bay Basin,and the basaltic volcanic reservoirs in Subei basin were discovered.With more and more volcanic oil and gas fields being discovered and developed,the volcanic rocks demonstrate a great petroleum potential in eastern basins of China.Five volcanic facies were identified in these basins,including volcanic conduit facies,explosive facies,effusive facies。
文摘The aim of this work was to obtain the physicochemical properties by SEM, XRD, FTIR analyses and the surface characteristics from carbonate outcrops cores such as pore diameter, surface area, porosity and permeability. The methods used to characterize them were Scanning Electron Microscopy, SEM;X Ray Diffraction, DRX;Fourier Transform Infrared Spectroscopy, FTIR. The porosity and permeability of natural vuggy fractured porous medium from core samples was determined obtained in the laboratory with conventional procedures. The cores have smooth and rough surfaces with porous with several sizes. Some crystals appear in preferential zones mainly composed by calcium, carbon and oxygen. Apparently into free spaces were found the organic materials, organic residues of crude oil. The cores have smooth and rough surfaces with porous with several sizes. Some crystals appear in preferential zones composed by calcium, carbon and oxygen. Apparently into free spaces were found the organic materials, organic residues of crude oil. The main inorganic compound in cores is calcite, (CaCO3). The porosity was for porous core 26% and for solid core 8.5%. The values obtained show that the cores have permeability where the fluid migrates through the particles at 2.23 × 10-4 cm/s.
基金funded by the Natural Science Foundation of China Project(No.41602138)National Science and Technology Special Grant(No.2016ZX05006007)+1 种基金China Postdoctoral Science Foundation-funded Project(2015M580617,2017T100524)the Fundamental Research Funds for the Central Universities(15CX08001A)
文摘The study or pore characteristics is or great importance in reservoir evaluation,especially in deeply buried s andstone.It controls the storage mechanism and reservoir fluid properties of the permeable horizons.The first member of Eocene Shahejie Formation(Esl)sandstone is classified as feldspathic litharenite and lithic arkose.The present research investigates the pore characteristics and reservoir features of the deeply buried sandstone reservoir of Esl member of Shahejie Formation.The techniques including thin-section petrography,mercury injection capillary pressure(MICP),scanning electron microscopy and laser scanning confocal microscope images were used to demarcate the pores including primary intergranular pores and secondary intergranular,intragranular,dissolution and fracture pores.Mercury injection test and routine core analysis were led to demarcate the pore network characteristics of the studied reservoir.Pore size and pore throat size distribution are acquired from mercury injection test.Porosity values range from 0.5%to 30%,and permeability ranges 0.006-7000 mD.Pore radii of coarse-grained sandstone and fine-grained sandstone range from 0.2 to>4μm and 1 nm to 1.60μm,respectively,by MICP analysis.The mineral composition also plays an important role in protecting the pores with pressure from failure.Fractured sandstone and coarse-grained sandstone consist of large and interconnected pores that enhance the reservoir porosity and permeability,whereas fine-grained sandstone and siltstone consist of numerous pores but not well interconnected,and so they consist of high porosity with low permeability.
文摘The present work has been accomplished to carry out a detailed study of the characteristics of the Early Jurassic Datta Formation of Trans-Indus Ranges, Pakistan. The discovery of Saib well-1 (Gas and condensate discovery from Jurassic limestone) in the study basin takes an active interest in carrying out extensive exploration activities in the same basin. Jurassic rocks especially Datta Sandstone and Samana Suk Limestone are acting as good reservoirs. The study unit consists of variegated sandstone interbedded with siltstone, carbonaceous clay, and shale and coal stringer. For the current work, two stratigraphic sections (Pezu and Abbo Wanda) have been measured. To examine its sedimentology, depositional environment, diagenetic settings, and reservoir characteristics, a detailed study was conducted and various laboratory techniques have been utilized. About 95 rock samples from the bottom to the top of both sections were collected, and 50 rock samples have been selected for thin section analysis and were examined under a polarizing microscope to show their mineralogical composition, diagenesis, and their reservoir characteristics. XRD (X-ray diffraction), Cathodoluminescence (CL), SEM (Scanning electron microscope) with EDS (Energy-dispersive spectroscope), and Core plug porosity and permeability analysis have been used to interpret its chemical and mineralogical composition and its reservoir characteristics, respectively. Based on field observations and thin section analysis, four depositional facies and six lithofacies have been established. The sedimentary structures, depositional facies, and lithofacies indicate that Datta Formation was deposited in a deltaic environment. Compactions, cementation, fracturing and dissolution can greatly affect the quality of reservoir rock. Based on thin section and SEM analysis, large numbers of primary pores, fracture and secondary pores were observed and connectivity between the pores is good, and at some places, these pores were filled through the authigenic clay minerals like kaolinite, mixed layers illite/smectite and chlorite that influences the reservoir characteristics. Primary pores (thin section) and secondary pores (dissolution pores) and core plug porosity and permeability data (porosity 13.23%-26.89% and permeability 0.12 to 149 mD) shows that Datta Formation has a good reservoir quality.
文摘Theoretical equations for computing sensitivity coefficients of wellbore pressures to estimate the reservoir parameters in low-permeability reservoirs conditioning to non-Darcy flow data at low velocity were obtained. It is shown by a lot of numerical calculations that the wellbore pressures are much more sensitive to permeability very near the well than to permeability a few gridblocks away from the well. When an initial pressure gradient existent sensitivity coefficients in the region are closer to the active well than to the observation well. Sensitivity coefficients of observation well at the line between the active well and the observation well are influenced greatly by the initial pressure gradient.
基金the Research Partnership to Secure Energy for America (RPSEA) for its financial support for this work
文摘In mature reservoirs,the success of preformed particle gel(PPG) treatment rests primarily on the ability of the PPG to reduce and/or plug the high permeable formations,but not damage the low permeable formations.Static test models(filtration test model and pressure test model)were used to determine the effect of PPG on low permeable formations.This work used a strong preformed particle gel,Daqing(DQ) gel made by a Chinese company.The particle gel sizes were ranged from 30 to 120 mesh for this work.PPGs are sized in a millimeter or micrometer,which can absorb over a hundred times their weight in liquids.The gel strength was approximately 6500 Pa for a completely swollen PPG with 1 %(weight percentage) NaCl solution(brine).0.05 %,1 %,and 10 % NaCl solutions were used in experiments.Sandstone core permeability was measured before and after PPG treatments.The relationship between cumulative filtration volumes versus filtration times was determined.The results indicate that DQ gels of a particle size of 30–80 mesh did not damage the cores of a low permeability of 3–25 m D.The DQ gels of a smaller particle size ranging from 100 to 120 mesh damaged the core and a cake was formed on the core surface.The results also indicate that more damage occurred when a high load pressure(400 psi) was applied on the high permeability cores(290–310 m D).The penetration of the particle gelsinto the low permeable formations can be decreased by the best selection of gel types,particle sizes,and brine concentrations.
文摘Polymer injectivity is an important factor for evaluating the project economics of chemical flood,which is highly related to the polymer viscosity.Because the flow rate varies rapidly near injectors and significantly changes the polymer viscosity due to the non-Newtonian rheological behavior,the polymer viscosity near the wellbore is difficult to estimate accurately with the practical gridblock size in reservoir simulation.To reduce the impact of polymer rheology upon chemical EOR simulations,we used an efficient multilevel local grid refinement(LGR)method that provides a higher resolution of the flows in the near-wellbore region.An efficient numerical scheme was proposed to accurately solve the pressure equation and concentration equations on the multilevel grid for both homogeneous and heterogeneous reservoir cases.The block list and connections of the multilevel grid are generated via an efficient and extensible algorithm.Field case simulation results indicate that the proposed LGR is consistent with the analytical injectivity model and achieves the closest results to the full grid refinement,which considerably improves the accuracy of solutions compared with the original grid.In addition,the method was validated by comparing it with the LGR module of CMG_STARS.Besides polymer injectivity calculations,the LGR method is applicable for other problems in need of near-wellbore treatment,such as fractures near wells.
基金The research was carried out within the framework of the grant for state support of leading scientific schools of the Russian Federation(Grant No.NSh-1010.2022.1.5).
文摘Survey and novel research data are used in the present study to classify/identify the lithological type of Verey age reservoirs’rocks.It is shown how the use of X-ray tomography can clarify the degree of heterogeneity,porosity and permeability of these rocks.These data are then used to elaborate a model of hydraulic fracturing.The resulting software can take into account the properties of proppant and breakdown fluid,thermal reservoir conditions,oil properties,well design data and even the filtration and elastic-mechanical properties of the rocks.Calculations of hydraulic fracturing crack formation are carried out and the results are compared with the data on hydraulic fracturing crack at standard conditions.Significant differences in crack formation in standard and lithotype models are determined.It is shown that the average width of the crack development for the lithotype model is 2.3 times higher than that for the standard model.Moreover,the coverage of crack development in height for the lithotype model is almost 2 times less than that for the standard model.The estimated fracture half-length for the lithotype model is 13.3%less than that of for the standard model.A higher dimensionless fracture conductivity is also obtained for the lithotype model.It is concluded that the proposed approach can increase the reliability of hydraulic fracturing crack models.
基金funded by the National Natural Science Fundation of China(Nos.41672149,41302131,41362009)the Key Project of the National Natural Science Foundation of China(No.41530314)+2 种基金the Scientific Research Foundation of the Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process of the Ministry of Education,China University of Mining and Technology,(No.2017-001)the National Science and Technology Major Project of the Ministry of Science and Technology of China(Nos.2016ZX05044-002,2011ZX05033,2011ZX05034)the Fundamental Research Funds for the Central Universities(No.2012QNB32)
文摘Deep coalbed methane exists in high-temperature and high-pressure reservoirs. To elucidate the dynamic-change laws of the deep coal reservoir porosity and permeability characteristics in the process of coalbed methane production, based on three pieces of low- to medium-rank coal samples in the eastern Junggar Basin, Xinjiang, we analyse their mercury-injection pore structures. We measured the porosity and permeability of the coal samples at various temperatures and confining pressures by high-temperature and confining pressure testing. The results show that the porosity of a coal sample decreases exponentially with increasing effective stress. With increasing temperature, the initial porosity increases for two pieces of relatively low-rank coal samples. The increased rate of porosity decreases with increasing confining pressure. With increasing temperature, the initial porosity of a relatively high-rank coal sample decreases, and the rate of change of the porosity become faster. An exponential relationship exists between the porosity and permeability. With increasing coal rank, the initial porosity and permeability decrease. The change rate of the permeability decreases with increasing porosity.
文摘Based on detailed studies, this paper proposesthat in the Tarim Basin, hydrocarbon reservoirs widespreadeither in vertical sequences or in plane and high-porosity andhigh-permeability reservoirs are developed all over the basin.However, obvious difference and heterogeneity exist amongdifferent kinds of reservoirs. The lithologic characteristics,reservoir space types and reservoir properties in variousstrata have been probed. The result indicates that althoughthe Paleozoic carbonates have been deeply buried for a longperiod, high-quality reservoirs with the porosity of up to 5%-8% (12% as the maximum) and the permeability of10×10<sup>-3</sup>-100×10<sup>-3</sup> μm<sup>2</sup> (1000×10<sup>-3</sup>μm<sup>2</sup> as the maximum)can be found in certain areas. These include the area withthe development of reefs and carbonate beaches, the weath-ered-crust buried-hill belts that have undergone thelong-term exposure, weathering and leaching, the area withthe development of dolomitization, and those areas that haveexperienced the resolution of carbonic acid and organic acidgenerated by the maturity of the organic matter. Finally, thegenesis of the high-porosity and high-permeability reservoirsin deep-buried conditions (with the depth more than 3500 m)have been investigated thoroughly.