Formation damage mechanism and control strategy of the compound function of drilling fluid and fracturing fluid in shale reservoirs

For the analysis of the formation damage caused by the compound function of drilling fluid and fracturing fluid,the prediction method for dynamic invasion depth of drilling fluid is developed considering the fracture extension due to shale minerals erosion by oil-based drilling fluid.With the evaluation for the damage of natural and hydraulic fractures caused by mechanical properties weakening of shale fracture surface,fracture closure and rock powder blocking,the formation damage pattern is proposed with consideration of the compound effect of drilling fluid and fracturing fluid.The formation damage mechanism during drilling and completion process in shale reservoir is revealed,and the protection measures are raised.The drilling fluid can deeply invade into the shale formation through natural and induced fractures,erode shale minerals and weaken the mechanical properties of shale during the drilling process.In the process of hydraulic fracturing,the compound effect of drilling fluid and fracturing fluid further weakens the mechanical properties of shale,results in fracture closure and rock powder shedding,and thus induces stress-sensitive damage and solid blocking damage of natural/hydraulic fractures.The damage can yield significant conductivity decrease of fractures,and restrict the high and stable production of shale oil and gas wells.The measures of anti-collapse and anti-blocking to accelerate the drilling of reservoir section,forming chemical membrane to prevent the weakening of the mechanical properties of shale fracture surface,strengthening the plugging of shale fracture and reducing the invasion range of drilling fluid,optimizing fracturing fluid system to protect fracture conductivity are put forward for reservoir protection.

Evaluation of the oil and gas preservation conditions, source rocks, and hydrocarbongenerating potential of the Qiangtang Basin: New evidence from the scientific drilling project

The Qiangtang Basin of the Tibetan Plateau,located in the eastern Tethys tectonic domain,is the largest new marine petroliferous region for exploration in China.The scientific drilling project consisting primarily of well QK-1 and its supporting shallow boreholes for geological surveys(also referred to as the Project)completed in recent years contributes to a series of new discoveries and insights into the oil and gas preservation conditions and source rock evaluation of the Qiangtang Basin.These findings differ from previous views that the Qiangtang Basin has poor oil and gas preservation conditions and lacks high-quality source rocks.As revealed by well QK-1 and its supporting shallow boreholes in the Project,the Qiangtang Basin hosts two sets of high-quality regional seals,namely an anhydrite layer in the Quemo Co Formation and the gypsum-bearing mudstones in the Xiali Formation.Moreover,the Qiangtang Basin has favorable oil and gas preservation conditions,as verified by the comprehensive study of the sealing capacity of seals,basin structure,tectonic uplift,magmatic activity,and groundwater motion.Furthermore,the shallow boreholes have also revealed that the Qiangtang Basin has high-quality hydrocarbon source rocks in the Upper Triassic Bagong Formation,which are thick and widely distributed according to the geological and geophysical data.In addition,the petroleum geological conditions,such as the type,abundance,and thermal evolution of organic matter,indicate that the Qiangtang Basin has great hydrocarbon-generating potential.

Sedimentology and Ichnology of Upper Montney Formation Tight Gas Reservoir, Northeastern British Columbia, Western Canada Sedimentary Basin

Several decades of conventional oil and gas production in Western Canada Sedimentary Basin (WCSB) have resulted in maturity of the basin, and attention is shifting to alternative hydrocarbon reservoir system, such as tight gas reservoir of the Montney Formation, which consists of siltstone with subordinate interlaminated very fine-grained sandstone. The Montney Formation resource play is one of Canada’s prime unconventional hydrocarbon reservoir, with reserve estimate in British Columbia (Natural Gas reserve = 271 TCF), Liquefied Natural Gas (LNG = 12,647 million barrels), and oil reserve (29 million barrels). Based on sedimentological and ichnological criteria, five lithofacies associations were identified in the study interval: Lithofacies F-1 (organic rich, wavy to parallel laminated, black colored siltstone);Lithofacies F-2 (very fine-grained sandstone interbedded with siltstone);Lithofacies F-3A (bioturbated silty-sandstone attributed to the Skolithos ichnofacies);Lithofacies F-3B (bioturbated siltstone attributed to Cruziana ichnofacies);Lithofacies F-4 (dolomitic, very fine-grained sandstone);and Lithofacies F-5 (massive siltstone). The depositional environments interpreted for the Montney Formation in the study area are lower shoreface through proximal offshore to distal offshore settings. Rock-Eval data (hydrogen Index and Oxygen Index) shows that Montney sediments contains mostly gas prone Type III/IV with subordinate Type II kerogen, TOC ranges from 0.39 - 3.54 wt% with a rare spike of 10.9 wt% TOC along the Montney/Doig boundary. Vitrinite reflectance data and Tmax show that thermal maturity of the Montney Formation is in the realm of “peak gas” generation window. Despite the economic significance of the Montney unconventional “resource-play”, however, the location and predictability of the best reservoir interval remain conjectural in part because the lithologic variability of the optimum reservoir lithologies has not been adequately characterized. This study presents lithofacies and ichnofacies analyses of the Montney Formation coupled with Rock-Eval geochemistry to interpret the sedimentology, ichnology, and reservoir potential of the Montney Formation tight gas reservoir in Fort St. John study area (T86N, R23W and T74N, R13W), northeastern British Columbia, western Canada.

Geological characteristics of unconventional tight oil reservoir (10^(9) t): A case study of Upper Cretaceous Qingshankou Formation, northern Songliao Basin, NE China

The Daqing exploration area in the northern Songliao Basin has great potential for unconventional oil and gas resources,among which the total resources of tight oil alone exceed 109 t and is regarded as an important resource base of Daqing oilfield.After years of exploration in the Qijia area,Songliao Basin,NE China,tight oil has been found in the Upper Cretaceous Qingshankou Formation.To work out tight oil’s geological characteristics,taking tight oil in Gaotaizi oil layers of the Upper Cretaceous Qingshankou Formation in northern Songliao Basin as an example,this paper systematically analyzed the geological characteristics of unconventional tight oil in Gao3 and Gao4 layers of the Qijia area,based on the data of the geological survey,well drilling journey,well logging,and test.It is that three sets of hydrocarbon source rocks(K2qn1,K2qn2+3,and K2n1)develop in the examined area,and exhibit excellent type I and II kerogens,high organic matter abundance,and moderate maturity.The reservoir is generally composed of thin-bedded mudstone,siltstone,and sandstone,and presents poor porosity(average 8.5 vol.%)and air permeability(average 4 mD).The main reservoir space primarily includes intergranular pores,secondary soluble pores,and intergranular soluble pores.Three types of orifice throats were identified,namely fine throat,extra-fine throat,and micro-fine throat.The siltstone is generally oil-bearing,the reservoirs with slime and calcium become worse oil-bearing,and the mudstone has no obvious oil-bearing characteristics.The brittleness indices of the sandstone in the tight oil reservoir range from 40%to 60%,and those of the mudstone range from 40%to 45%,indicating a better brittleness of the tight oil reservoir.Based on the study of typical core hole data,this paper gives a comprehensive evaluation of the properties of the tight oil and establishes a tight oil single well composite bar chart as well as the initial evaluation system with the core of properties in the tight oil reservoir.This study has theoretical guiding significance and practical application value for tight oil exploration and evaluation in the Qijia area.

Discussion of the Mode and Mechanism of Oil and Gas Accumulation in the Nanbaxian Pool in the North of the Qaidam Basin

Because of the difference ofoil and gas accumulation condition between the hanging wall and the footwall of a fault, there is a peculiar accumulation mechanism that oil and gas mainly exists in the hanging wall of the basement fault, but in the footwall of the shallow detachment fault in the Nanbaxian pool. The oil and gas of the Nanbaxian pool came from the mature Jurassic hydrocarbon source rock of the Yibei depression located at the south of the Nanbaxian pool. Firstly, the oil and gas accumulated in the traps of the hanging wall of the basement fault by way of the unconformity and the basement faults, and turned into some primary deep pools; and then, the shallow detachment fault that formed in the later tectonic movement broke into the deep primary pools, which caused the oil and gas migration upwards along the basement faults and the shallow detachment faults and the evolvement into some secondary oil and gas pools later. The history of the Nanbaxian oil and gas accumulation can be summarized successively as the syndepositional upheaval controlled by faults; single hydrocarbon source rock; unconformities and faults as migration channels; buoyancy, overpressure and tectonic stress as dynamic forces; multistage migration and accumulation of oil and gas; and finally an overlapped double-floor pattern of oil and gas accumulation. The most important explorative targets in the north of the Qaidam Basin are traps connected with the primary pools in the footwall by shallow detachment faults.

Distribution characteristics, exploration and development, geological theories research progress and exploration directions of shale gas in China

The shale gas resources in China have great potential and the geological resources of shale gas is over 100×10^(12)m^(3),which includes about 20×10^(12)m^(3) of recoverable resources.Organic-rich shales can be divided into three types according to their sedimentary environments,namely marine,marine-continental transitional,and continental shales,which are distributed in 13 stratigraphic systems from the Mesoproterozoic to the Cenozoic.The Sichuan Basin and its surrounding areas have the highest geological resources of shale gas,and the commercial development of shale gas has been achieved in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in these areas,with a shale gas production of up to 20×10^(9)m^(3) in 2020.China has seen rapid shale gas exploration and development over the last five years,successively achieving breakthroughs and important findings in many areas and strata.The details are as follows.(1)Large-scale development of middle-shallow shale gas(burial depth:less than 3500 m)has been realized,with the productivity having rapidly increased;(2)breakthroughs have been constantly made in the development of deep shale gas(burial depth:3500-4500 m),and the ultradeep shale gas(burial depth:greater than 4500 m)is under testing;(3)breakthroughs have been made in the development of normal-pressure shale gas,and the assessment of the shale gas in complex tectonic areas is being accelerated;(4)shale gas has been frequently discovered in new areas and new strata,exhibiting a great prospect.Based on the exploration and development practice,three aspects of consensus have been gradually reached on the research progress in the geological theories of shale gas achieved in China.(1)in terms of deep-water fine-grained sediments,organic-rich shales are the base for the formation of shale gas;(2)in terms of high-quality reservoirs,the development of micro-nano organic matter-hosted pores serves as the core of shale gas accumulation;(3)in terms of preservation conditions,weak structural transformation,a moderate degree of thermal evolution,and a high pressure coefficient are the key to shale gas enrichment.As a type of important low-carbon fossil energy,shale gas will play an increasingly important role in achieving the strategic goals of peak carbon dioxide emissions and carbon neutrality.Based on the in-depth study of shale gas geological conditions and current exploration progress,three important directions for shale gas exploration in China in the next five years are put forward.

Geological characteristics and co-exploration and co-production methods of Upper Permian Longtan coal measure gas in Yangmeishu Syncline, Western Guizhou Province, China

Coal measure gas(also known as coal-bearing unconventional gas)is the key field and development direction of unconventional natural gas in recent years.The exploration and evaluation of coal measure gas(coalbed methane,coal shale gas and coal measure tight sandstone gas)from single coalbed methane has greatly expanded the field and space of resource evaluation,which is of positive significance for realizing the comprehensive utilization of coal resources,maximizing the benefits and promoting the innovation of oil and gas geological theory and technological advances in exploration and development.For the first time,in Yangmeishu Syncline of Western Guizhou Province,the public welfare coalbed methane geological survey project of China Geological Survey has been carried out a systematic geological survey of coal measure gas for the Upper Permian Longtan Formation,identified the geological conditions of coal measure gas and found high quality resources.The total geological resource quantity of coalbed methane and coal shale gas is 51.423×109 m3 and the geological resource abundance is up to 566×106 m3/km2.In this area,the coal measures are characterized by many layers of minable coal seams,large total thickness,thin to the medium thickness of the single layer,good gas-bearing property of coal seams and coal measure mudstone and sandstone,good reservoir physical property and high-pressure coefficient.According to the principle of combination of high quality and similarity of key parameters of the coal reservoir,the most favorable intervals are No.5-2,No.7 and No.13-2 coal seam in Well YMC1.And the pilot tests are carried out on coal seams and roof silty mudstone,such as staged perforation,increasing hydraulic fracturing scale and"three gas"production.The high and stable industrial gas flow with a daily gas output of more than 4000 m3 has been obtained,which has realized the breakthrough in the geological survey of coal measure gas in Southwest China.Based on the above investigation results,the geological characteristics of coal measure gas in the multi-thin-coal-seam-developed area and the coexploration and co-production methods,such as the optimization method of favorable intervals,the highefficiency fracturing and reservoir reconstruction method of coal measures,and the"three gas"drainage and production system,are systematically summarized in this paper.It will provide a reference for efficient exploration and development of coal measure gas in similar geological conditions in China.

Theories and practices of carbonate reservoirs development in China

Carbonate reservoirs in China have the characteristics of diversified accumulation pattern, complex structure and varying reservoir conditions. Concerning these characteristics, this article tracks the technical breakthroughs and related practices since the 1950 s, summarizes the developed theory and technologies of carbonate reservoir development, analyzes their adaptability and problems, and proposes their development trend. The following theory and technologies have come into being:(1) carbonate reservoir formation mechanisms and compound flow mechanisms in complex medium;(2) reservoir identification and description technologies based on geophysics and discrete fracture-vuggy modeling method;(3) well testing analysis technology and numerical simulation method of coupling free flow and porous media flow;(4) enhanced oil recovery techniques for nitrogen single well huff and puff, and water flooding development techniques with well pattern design in spatial structure, changed intensity water injection, water plugging and channel blocking as the core;(5) drilling and completion techniques, acid fracturing techniques and its production increasing techniques. To realize the efficient development of carbonate oil and gas reservoirs, researches in four aspects need to be done:(1) complex reservoir description technology with higher accuracy;(2) various enhanced oil recovery techniques;(3) improving the drilling method and acid fracturing method for ultra-deep carbonate reservoir and significantly cutting engineering cost;(4) strengthening the technological integration of information, big data, cloud computation, and artificial intelligence in oilfield development to realize the smart development of oilfield.

Petroleum Source-Rock Evaluation and Hydrocarbon Potential in Montney Formation Unconventional Reservoir, Northeastern British Columbia, Canada

Source-rock characteristics of Lower Triassic Montney Formation presented in this study shows the total organic carbon (TOC) richness, thermal maturity, hydrocarbon generation, geographical distribution of TOC and thermal maturity (Tmax) in Fort St. John study area (T86N, R23W and T74N, R13W) and its environs in northeastern British Columbia, Western Canada Sedimentary Basin (WCSB). TOC richness in Montney Formation within the study area is grouped into three categories: low TOC ( 3.5 wt%), and high TOC (>3.5 wt% %). Thermal maturity of the Montney Formation source-rock indicates that >90% of the analyzed samples are thermally mature, and mainly within gas generating window (wet gas, condensate gas, and dry gas), and comprises mixed Type II/III (oil/gas prone kerogen), and Type IV kerogen (gas prone). Analyses of Rock-Eval parameters (TOC, S2, Tmax, HI, OI and PI) obtained from 81 samples in 11 wells that penetrated the Montney Formation in the subsurface of northeastern British Columbia were used to map source rock quality across the study area. Based on total organic carbon (TOC) content mapping, geographical distribution of thermal maturity (Tmax) data mapping, including evaluation and interpretation of Rock-Eval parameters in the study area, the Montney Formation kerogen is indicative of a pervasively matured petroleum system in the study area.

Forming mechanism of hydrocarbon reservoirs in Yingshan Formation of Yuqi block in Akekule arch,Tarim Basin

The reservoir conditions,oil and gas charge history and accumulation phases were studied for Yingshan Formation of Yuqi block,and an oil and gas accumulation model was established by using the techniques of reservoir prediction,fluorescence thin section and fluid inclusion analysis under the guidance of the theories of oil and gas accumulation.The results indicate that the main rock types in Yingshan Formation are micrite and calcarenite.The carbonate reservoirs are of cave,fracture-pore and fracture types,and their physical properties are intermediate;there are at least four oil/gas charges,i.e.late Hercynian,Yanshanian,early Himalayan and middle Himalayan(Cenozoic).The most important charge periods are late Hercynian,early Himalayan and middle Himalayan;the oil and gas accumulation model is self source-lateral expulsion of hydrocarbon-multistage accumulation,or hydrocarbon sourced from and preserved in the same old rocks-long term expulsion of hydrocarbon-multistage accumulation.

Mechanisms of abnormal overpressure generation in Kuqa foreland thrust belt and their impacts on oil and gas reservoir formation

Based on overview for mechanism of abnormaloverpressure generation in sedimentary basins, an insightdiscussion is made by the authors for the distribution, fea-tures and generation mechanisms of abnormal overpressurein the Kuqa foreland thrust belt. The abnormal overpressurein the Kelasu structure zone west to the Kuqa forelandthrust belt was primarily distributed in Eogene to lowerCretaceous formations; structural compression and struc-tural emplacement as well as the containment of Eogenegyps-salt formation constituted the main mechanisms for thegeneration of abnormal overpressure. The abnormal over-pressure zone in the eastern Yiqikelike structure zone wasdistributed primarily in lower Jurassic Ahe Group, resultingfrom hydrocarbon generation as well as structural stressother than from under-compaction. Various distributionsand generating mechanisms have different impacts upon theformation of oil and gas reservoirs. K-E reservoir in the Ke-lasu zone is an allochthonous abnormal overpressure system.One of the conditions for reservoir accumulation is the mi-gration of hydrocarbon (T-J hydrocarbon source rock) alongthe fault up to K-E reservoir and accumulated into reservoir.And this migration process was controlled by the abnormaloverpressure system in K-E reservoir. The confined abnor-mal overpressure system in the Yiqikelike structure zoneconstituted the main cause for the poor developing of dis-solved porosity in T-J reservoir, resulting in poor physicalproperty of reservoir. The poor physical property of T-J res-ervoir of Yinan 2 structure was the main cause for the ab-sence of oil accumulation, but the presence of natural gasreservoir in the structure.

Dolomite reservoir formation and diagenesis evolution of the Upper Ediacaran Qigebrak Formation in the Tabei area,Tarim Basin

Ancient dolomite reservoirs play an increasingly important role in deep oil and gas exploration.The mechanism of formation and preservation of dolomite reservoirs is complex,which is always the key issue.With the discovery of deep oil and gas in the Ediacaran dolomites of the world,the upper Ediacaran Qigebrak Formation in the Tabei area has begun to attract attention,but its reservoir space difference and formation mechanism have yet to be clarified.Based on ultra-deep drilling cores and field outcrops in the Tabei area,the lithofacies,reservoir space,and formation mechanism are systematically analyzed by macro to micro,and qualitative to quantitative petrology:(1)The types of dolomite can be divided into five major categories,including microbial dolomite,granular dolomite,residual granular dolomite,crystalline dolomite and karst breccias.(2)The main types of reservoir space are microbial-framework pores,microbial-mold pores,and non-fabric selective dissolution pores.Spongiomicrobialite,karst breccias,and fine-grained dolomite are the dominant reservoir rock types.(3)High-frequency sedimentary cycles and meteoric dissolution are the key factors of reservoir formation.Two sets of large-scale reservoirs are present:the first set is mainly controlled by the supergene karst of the Keping movement,and the second set is mainly controlled by high-frequency sedimentary cycles in the penecontemporaneous period.The reservoirs formed at the shallow burial stage and were preserved until the deep burial stage.(4)The quality of a deep reservoir depends on the geological events that affect the processes of pore reduction and increase.Cementation,compaction and pressure solution are the main destructive diagenetic processes;however,the reservoir space can still be effectively preserved under the influence of constructive diagenetic processes,such as meteoric dissolution and early dolomitization.This research has important theoretical and practical significance for revealing the formation mechanism of upper Ediacaran deep dolomite reservoirs in the Tarim Basin.

Geologic characteristics, controlling factors and hydrocarbon accumulation mechanisms of China’s Large Gas Provinces of low porosity and permeability

Based on the analysis of the geological characteristics and controlling factors, we analyzed the formation mechanism of different types of gas reservoirs. The main characteristics of gas provinces with low porosity and permeability are mainly as follows: large area, low abundance, small gas pools and large gas provinces; widely distributed excellent hydrocarbon source rocks with closely contacted source-reservoir-cap association; development mainly in large continental depressions or in paralic shallow-river delta systems; many kinds of traps coexisting in large areas, dominantly para-layered lithologic, digenetic and capillary pressure traps; double fluid flow mechanisms of Darcy flow and non-Darcy flow; complicated gas and water relations; and having the resource distribution of highly productive "sweet spots", banding concentration, and macroscopically large areas integrated. The main controlling factors of large sandstone gas provinces with low porosity and permeability are stable dynamic backgrounds and gentle structural frameworks which control the extensive distribution of alternate (interbedded) sandstones and mudstones; weak hydropower of large gentle lake basins controlling the formation of discontinuous, low porosity and permeability reservoirs in shallow-water deltas; regionally differential diagenesis and no homogeneous digenetic facies controlling the development of favorable reservoirs and digenetic traps; and weak and dispersive reservoir-forming dynamic forces leading to the widely distributed small traps with low abundance. Low porosity and permeability gas provinces with different trap types have different formation mechanisms which include fluid diversion pressure difference interactive mechanism of lithologic-trap gas accumulations, separated differential collection mechanism of digenetic-trap gas accumulations, and the Non-Darcy flow mechanism of capillary-pressure gas accumulations.

Data driven prediction of oil reservoir fluid properties

Accuracy of the fluid property data plays an absolutely pivotal role in the reservoir computational processes.Reliable data can be obtained through various experimental methods,but these methods are very expensive and time consuming.Alternative methods are numerical models.These methods used measured experimental data to develop a representative model for predicting desired parameters.In this study,to predict saturation pressure,oil formation volume factor,and solution gas oil ratio,several Artificial Intelligent(AI)models were developed.582 reported data sets were used as data bank that covers a wide range of fluid properties.Accuracy and reliability of the model was examined by some statistical parameters such as correlation coefficient(R2),average absolute relative deviation(AARD),and root mean square error(RMSE).The results illustrated good accordance between predicted data and target values.The model was also compared with previous works and developed empirical correlations which indicated that it is more reliable than all compared models and correlations.At the end,relevancy factor was calculated for each input parameters to illustrate the impact of different parameters on the predicted values.Relevancy factor showed that in these models,solution gas oil ratio has greatest impact on both saturation pressure and oil formation volume factor.In the other hand,saturation pressure has greatest effect on solution gas oil ratio.

中国海相油气勘探若干重大科学问题

中国覆盖区海相地层（以古生界为主）勘探多年，勘探发现与预期结果差距甚大，认为主要原因是我国石油地质家对海相油气富集及分布规律的认识甚少。我国海相盆地与国外富油气海相盆地差异显著：①时代老；②有机质丰度低；③有机质热演化程度高；④勘探目的层埋藏深；⑤油气藏保存条件差。必须开展多学科联合研究，从新的角度加快研究３个基础理论问题：①成盆理论，要进行地球动力学和盆地沉积建造类型、地层样式及地层成岩事件研究；②成烃理论，要进行古生物学、古海洋学、古环境化学、沉积学、有机岩石学、有机地球化学和物理化学研究，研究不能受干酪根热降解成烃学说的束缚，有可能提出更适于我国古生代海相盆地的新成烃理论；③成藏理论，要揭示以碳酸盐岩为主的地质体中的油气运移问题，建立油气充注成藏过程的物理化学场模型，并以动态平衡观点建立油气藏调整模型。（王孝陵摘）

深层海相碳酸盐岩优质储层的形成、保存和破坏机制——以四川盆地震旦系—志留系为例

四川盆地震旦系—志留系碳酸盐岩普遍埋藏深度超过3500 m,属深层碳酸盐岩储层范畴。宽广的潮坪相和陆棚相沉积环境从根本上决定了盆内下组合碳酸盐岩储层岩石类型主要为颗粒碳酸盐岩、晶粒结构白云岩及裂缝性灰岩。多期次的构造运动导致下组合岩溶储层发育,特别是志留纪末期的加里东运动导致从乐山—龙女寺古隆起核部由西向东依次发育震旦系、寒武系和奥陶系古岩溶带。现今下组合储层中广泛分布的沥青表明下组合曾有过广泛的油气成藏过程,形成古油藏或古气藏,亦表明下组合在油气充注时曾普遍发育优质储层。岩石学和地球化学研究表明,复杂多变、期次繁多的成岩演化和流体充注与下组合优质储层的形成、保存和破坏密切相关,总体上,对四川盆地深层海相碳酸盐岩储层而言:1)原位沉积体系、白云岩化对震旦系和寒武系优质储层发育控制作用弱、仅对奥陶系和志留系具有较强的控制作用;2)古隆起是优质储层发育的先决条件,表生岩溶与破裂作用为必备条件;3)烃类流体充注和热裂解作用早期优质储层保存的主要机制,此外,适度的重结晶作用是形成优质储层的持久动力,埋藏过程中外源侵蚀性流体溶蚀作用的储层效应有限;4)压实压溶作用、胶结充填作用是储层致密的最主要的因素。

大巴山前陆冲断带古水动力演化阶段及其对油气藏形成和保存的影响

针对传统古水动力阶段划分存在的问题,结合大巴山前陆冲断带特殊构造特征,以油气成藏组合为单元,将大巴山前陆冲断带古水动力演化阶段划分为沉积水动力阶段、渗入水动力阶段、构造作用水动力阶段和埋藏水动力阶段。其中下部油气成藏组合主要经历了1个沉积水动力阶段、4个渗入水动力阶段、4个埋藏水动力阶段和3个构造作用水动力阶段,中部油气成藏组合主要经历了1个沉积水动力阶段、3个渗入水动力阶段、2个埋藏水动力阶段和3个构造作用水动力阶段,而上部油气成藏组合主要经历了渗入水动力阶段。二叠纪至早白垩世的埋藏水动力阶段有利于下部油气成藏组合油气的生成和运聚成藏,但是构造作用水动力阶段,对油气藏的调整和改造作用影响很大,晚白垩世之后的渗入水动力阶段,导致下部成藏组合的油气藏进一步遭到调整和破坏。在晚三叠世末至晚白垩世的埋藏水动力和构造作用水动力阶段,中部成藏组合的原油发生大量裂解,同时形成了许多调整-改造型油气藏,晚白垩世之后的渗入水动力和构造作用水动力阶段,大巴山前陆坳陷带中部成藏组合的油气藏发生了大量的调整和改造作用,而大巴山前陆基底拆离构造带和前陆盖层滑脱构造带中部成藏组合的油气藏则主要表现为改造和破坏作用。

松辽盆地北部异常高压在油气成藏与保存中的作用

通过松辽盆地北部青山口组和嫩一段、嫩二段泥岩异常高压及其在油气运聚成藏与保存中的作用研究 ,认为异常高压不仅是其烃源岩油气向外排出的动力 ,还是油气穿层运移和倒贯运移的动力。异常高压极值点的位置控制了油气在纵向上的分配量。异常高压增强了该区泥岩盖层毛细管封闭能力 ,使其具有抑制浓度封闭作用 ;使T2 、T1 断层具封闭性 ,阻止地下水及氧和细菌对油气藏的破坏。异常高压导致了青山口组泥岩内构造裂缝开启 ,有利于形成泥岩裂缝油气藏。

港西油田浅层气成藏条件

为寻找中国石油大港油田公司的接替资源,分析了港西油田浅层气藏储层条件、气源条件、运移条件以及浅层气得以保存的有利条件,结果表明:①储集层主要由馆陶组辫状河沉积砂体和明化镇组曲流河沉积砂体组成,砂体横向分布不稳定、浅层速度变化快,为研究区主要含气层系,储层物性好,为新近系油气提供了良好的储集空间;②港西地区断层发育,新近系和古近系又是不整合接触,为港西油田凸起的浅层气从深层往上运移创造了良好的条件,浅层区孔渗性好,烃源岩丰度高,因此砂层也成为有效的输导系统;③馆陶组、明化镇组均发育较好盖层,成藏和保存条件优越。结论认为:港西油田浅层天然气具有良好的油气勘探前景。

江汉盆地东部白垩系多源次生成藏条件分析

从叙述江汉盆地东部白垩系沉积特征、储集条件、构造特征入手,分析了区内白垩系上、下层系的烃源条件和三维输导系统及多源次生成藏的地质条件;认为江汉盆地东部白垩系油藏具多重油源条件,是一个次生多源油藏。在此基础上,进一步预测了有利的油气勘探区。