鄂尔多斯盆地近40多年来的油气勘探工作,因主观认识和客观(地形)上的原因,在早期经历了一段曲折的历史,队伍一度撤出该盆地而转战渭河地堑.1968年底,李四光部长根据他一贯的新华夏构造系找油的思想,坚持油气普查队伍应从渭河撤出并回到盆地中来,即"打回老家去".接踵而来地质部门在庆参井、华参2井以及石油工业部在庆阳以北以马岭油田为代表的中下侏罗统的突破,迎来了上世纪70年代的长庆油田大会战.再伴随其后吴旗、志丹地区的出油气,一个当时为人称道的"庆、华、吴""油气系统"概念在当地流行起来.伴随近10多年来,石油工业部门对上三叠统延长组三角洲和庆阳油田的发现,使这个古老的鄂尔多斯盆地真正恢复了它的青春.
In this paper, the authors discussed the gas generating characteristics of marine shale and marl by hydropyrolysis. At the mature stage of organic matter, the total gas yield of marl was above that of shale, and their total gaseous hydrocarbon yield was approximately the same. The difference between their total gas yield increased with temperature, and the gaseous hydrocarbon yield of marl was above that of shale at higher temperature. The gas drying coefficient of marl was above that of shale and was below 0.55, and their gas drying coefficient tended to be the same at higher temperature. The normal alkane abundance was higher in shale than in marl, and was stronger than the isonormal alkane ,s. Dioxide carbon, nitrogen and hydrogen were major, and oxide carbon was little among nonhydrocarbons.Dioxide carbon content in shale was above that in marl, and hydrogen content in shale was below that in marl. Nitrogen yield was higher at the early and middle mature stage, and was more in marl than in shale.
Orogenesiscoupled/decoupled development was represented as a new thinking for study on oil and gasbearing basins. The soul of the new thinking was a tectonic outlook of mobilism on study, which called for two newemerging academic branches: orogenstratigraphy and orogenpaleogeography. Two methods should be emphasized: the mechanical and historical synthetic analysis of geological structures and the analysis of geodynamics. Because of the complexity and multiplicity of relations between basin and orogen, the prerequisite of analysis was to give a time restriction, namely, a unified kinematic process and geodynamic mechanics between orogenesis and development would be discussed within a relatively short interval. The kinematics of basinorogen coupling could be explored from four aspects. 1)Compression and tension should be interdependent spatially, and the attention be paid to some large or superlarge basins related to collision and postorogenic basins. 2)There were two kinds of strikeslip faults: one was a part of the global shearing net, whose importance in tectonics of China Continent was once neglected; another was what was in the same kinematic system with tensile or compressional faults. 3) The contrains of deep seated courses resulted in tectonic overfly, the basin (or orogen) of shallow structural layers being coexisted with the orogen (or basin) of deeper structural layers. 4)Tectonic escape might be regarded as a combination of the transformation of strikeslip faulting and the affection of deepseated courses, but the extension and strikeslipping in escaping areas should have some distinct characters. The key to understanding the inheritance or decoupling of the Indosinian basinorogen relation was a tectonic differentiation between the west and east parts of the ChinaSE Asia Subcontinent occurred from the Jurassic. The east part became a wide Yanshanides, where the Indosinian basinorogen relation was decoupled. A subductiontype orogeny occurred in the west part in the Early Cretaceous, which did not decouple the Indosinian basinorogen relation. Sandwiched in between the both Yanshanides, there existed a relatively stable zone not involved in the Yanshanian orogeny, where the reformation of the Himalayan movement was the crux if basins were reserved and oilgas accumulation was formed.
There are extensive information on the nuclei, propagation and linkage of faults recorded by the displacements of faults. By utilizing the model of fault displacements, a method to study the history of faults based on observed data of fault displacement was proposed. Taking the Zhangdong normal fault in the inshore of the Dagang Oil Field as an example, the results showed that the restored fault displacement in different sedimentary stages tended to increase, decrease and then increase less with time. It reached the minimum of displacement during sedimentation of the Oligocene Dongying formation, and representd the relatively quiet epoch in regional extension. The parameter of fault propagation is larger in the Eocene than in the Neogene, the latter ca.1.0. This indicated the tendency of decrease in the fault activity with time, corresponding with the evolution of the basin which experienced intense riftsubsidence in the Eocene to depression in the Neogene. It was during the deposition of the Oligocene Dognying formation that the fault activity had generated both the maximum displacement and the maximum lateral variation in displacement.
It is a hot topic if the Jurassic coal can generate oil in the Ordos Basin. The adsorbed hydrocarbons amount in the Jurassic coal is 5080 kg/t but the productivity of coal is only 6.0270.7kg/t based on the experimental result. If produced oil is less than adsorbed oil in coal, the coal cannot be an effective source rock of oil. On the other hand, comparing to the coal of large and medium sized oilfields in the world, the Jurassic coal in the Ordos Basin is characterized by lower abundance, unfavorable type and lower maturity, which indicates uneffective source rocks. In terms of characteristics of biomarker, the Jurassic oil is not generated by coal in the Ordos Basin. Therefore, the Jurassic coal in the basin can not generate sufficient oil to form a commercial oilfield.
WT5BZ]According to the ordered superimposed styles of high frequency cyclic sequences within long period cyclic sequences,three Ⅲ order cyclic sequences and two Ⅱ order cyclic sequenes were divided in the Carboniferous of the study area. Among them, Ⅲ 1 and Ⅲ 3 cyclic sequences belong to the transgressive tract system, and Ⅲ 2 belongs to the highstand tract system. They constitute together the sequence stratigraphic framework of the study area and control the space time distributive characteristics of sedimentary facies and source rock reservoir cap rock assemblages. As affected by the differences of diagenetic history and different diagenetic environments, the diagenetic characteristics and storage peformances of the Carboniferous clastic and carbonate reservoir rocks have obvious differences between the Bachu Uplifting area and the Maigaiti Slope area. Besides, the reservoirs distributing in the slope area have obviously better physical properties than those in the same formations of the uplifting area, and are the favorable exploration targets in the near future. [WT5HZ]
Based on dynamic and static information of conglomerate reservoirs in Menggulin area of the Erlian basin, a fine description of heterogeneity of the conglomerate reservoirs has been given. The conglomerate belonged to sediments of a braided river delta. The sedimentation and diagenesis controlled macrodistribution of the reservoir, intrabed rhythm, the distribution of interbeds and change of porosity and permeability. The conglomerate was massive structured in the northwest and showed bedded structure in southwest area. It is showed that distribution of residual oil is controlled by sedimentary microfacies, structural condition, relationship of injection and production. Residual oil is concentrated in the high part of local structure, the oil zone of masive reservoirs and the upper part of bedded reservoirs between injection wells in higher watercut stage. The reservoirs of subaqueous channel microfacies with middle to low permeability showed low water driving efficiency, are the rich area of residual oil distribution.
The Permian system which includes the Chuanshanian, the Yangsingian and the Lopingian series can be divided into three series in Guizhou and Guangxi areas of South China. There are two obvious unconformities in the sequence, the one refers to the main episode of the Qiangui epeirogeny in the transitional period at the turn between Chuanshanian epoch and Yangsingian epoch, and another refers to the main episode of Dongwu movement in the transitional period at the turn between Yangsingian epoch and Lopingian epoch, both of which not only forms the evident sequence boundaries of type I but also represents the important changing surfaces of sedimentary facies and paleogeography. Obvious differentiation of depositional facies leads to the formation of a special pattern of paleogeography marked by platformbasinhilltrough, especially for Lopingian epoch, which is reflected by lots of sedimentary features. For examples, coal measures are developed on the widespread platform, and sponge reefs are developed on the margin of the widespread platform as well as the isolated carbonate platform, furthermore, the period of the evident facies differentiation is corresponding to the development period of reefs, etc. The first episode of Dongwu movement in the transitional period at the turn between Yangsingian epoch and Lopingian epoch results in the great change of the paleogeographic pattern. Seven third order sequences can be discerned in the Permian of the study areas, i. e. ,the top part of Carboniferous and the Chuanshanian series form one sequence (SQ19), four sequences which are from SQ20 to SQ23 are discerned in the Yangsingian series, and two sequences which are SQ24 and SQ25 are divided in Lopingian series. The typical drowned event of the carbonate platforms in the transitional period at the turn between Permian and Triassic shows that the top boundary of SQ25 is a obvious drowned unconformity. Therefore, the complex but regular facies changes in time and in space can clearly be illustrated in the series of the maps of sedimentary facies and paleogeography as well as the panel diagrams of sequence stratigraphic framework.
Several problems in the study of oil and gas preservation and their commercial potential in marine sequences of South China should include as follows: (1) Areas near the ancient petroleum pools, the large and high anticlines at the edge of basins and the uplifted blocks between sags are not ideal locations for discovery of large oilfield in South China; (2) Conditions of petroleum preservation were very complicated; (3) The properties of hydrogeology could be used to evaluate the preservation condition; and (4) The sedimentation, burial history and geothermal evolution should be studied in detail, and the hydrocarbon generation, migration and accumulation should be analyzed in accordance with its geological settings. On basis of study of regional tectonics, special concerns should be put in the two foreland basins located in the north and south respectively.
Environmental Scanning Electron Microscope (ESEM) as a new tool has been used in oil and gas research fields. The main advantage of ESEM is to operate under reduced pressure and to allow the observation of samples containing liquid or at high temperature in the microdynamic process. Samples used in this paper were different types of source rocks such as mudstone, carbonate and coal or different organic matter from source rocks such as kerogen and alga. Some samples producing hydrocarbon can be observed. The results indicated that the ESEM test at high temperature was helpful to simulate the process of hydrocarbon producing.
Based on the developing characteristics of fluvial facies and each sequence stratigrahic unit in the Quantou Formation of Buhaihelong area, the Songliao Basin, which was observed in outcrop, core and seismic data, the differences among the formation mechanism of three stream types were analysed from the angles of allogenic cycles and authigenic cycles. According to the controlling factor of allogenic cycles, that is, the changes of the base level, the sequence stratigraphic framework of the study area was divided, and the sequence stratigraphic model of fluvial facies was established. The lowstand system tract (LST) is dominated by lateral accretion and characterized by developing braided streams; the transgressive system tract (TST) is dominated by vertical accretion and characterized by developing reticulated streams; the highstand system tract (HST) is dominated by lateral accretion and characterized by developing lowenergy meandering streams; and the regressive system tract (RST) is dominated by lateral accretion and characterized by developing highenergy meandering streams .
The Laiyang Depression is a secondary structural unit of the residual basin developed in the Cretaceous period. There are obvious differences in terms of different periods of the Cretaceous deposition, an angled unconformity surface existing between the Upper and the Lower Cretaceous, and well developed folds and faults in the depression. The structural evolution history may be divided into five stages including pull apart faulted depression during the Laiyang period, the extensional faulted depression during the Qingshan period, compressed folding at the end of the Qingshan period, repull apart faulted depression during the Wangshi period and uplifted erosion during the Cenozoic. The tectonic activity during the Early Cretaceous provided conditions of deposition of hydrocarbon source rocks, and tectonic movement occurred in the Late Cretaceous and the Cenozoic resulted in formation and adjustment of oil and gas pools.
In the light of the complexity of nature fracture networks, it is extremely difficult to do the numerical calculation of fluid flowing and the design optimization of developing wellpatterns . A series of electric analogy experiments were conducted based on the similarity theory in this paper to model the fracture networks and horizontal wellupright well patterns. The relations between fracture networks and horizontal well patterns were studied, and the properties of fracture networks to effect the rate of horizontal wells, such as discreteness, connectivity, density and orientation, were emphasized. As a result, the valuable parameters to optimize horizontalwell designing and pressure fracturing for such complicated reservoirs were presented.
According to the observed and measured data of fluid inclusions in the Qiangtang Basin in this paper, the main types and characteristics of fluid inclusions were studied comprehensively. Based on the study of diagenesis, the authors emphatically discussed the application of the fluid inclusion technology to the study of reservoir diagenesis. The succession of the TriassicJurassic diagenetic evolution in the Qiangtang Basin was established, and the relationship of diagenesis to hydrocarbon migration was analysed. This made a preliminary approach to the application of the fluid inclusion technology to reservoir research.
WT5BZ]The Leshan Longnusi, Qianzhong and Jiangnan Uplifts mainly controlled the development of the Upper Sinian and the Lower Paleozoic primary oil and gas pools, while the Luzhou and Kaijiang Uplifts and the Late Paleozoic Triassic (isolated) anteclises in Nanpanjiang Shiwandashan area controlled the distribution of the Upper Paleozoic and the Triassic primary oil and gas pools. As the paleouplifts in the south of China have been reconstructed in different degrees, the intact uplifting faces do not exist already. There are few the Meso Paleozoic primary oil and gas pools existing presently in the south of China. The most early primary oil and gas pools in the Sichuan Basin were reconstructed to secondary gas pools, and the primary oil and gas pools in Yangtze and South China areas were mainly destoryed to fossil oil pools. It was suggested that the Meso Paleozoic hydrocarbon exploration in the south of China should mainly consider secondary oil and gas pools and regenerated hydrocarbon pools, that is, the secondary gas pools in the Upper Yangtze area and the regenerated hydrocarbon pools in the Middle Lower Yangtze area. Also, the specific favorable hydrocarbon exploration districts were pointed out, which were confirmed by the discovery of Zhujiadun gasfield in the Yancheng Depression of the North Jiangsu Basin and the West Kaixiantai oil bearing Structure in the South Chenhu area of the Jianghan Basin. [WT5HZ]
The integral geological study and petroleum exploration indicated that Tahe oilfield formed on the basis of longdeveloped paleouplift was a large scale one which consisted of karstfracture reservoirs of the Lower Ordovician carbonate rocks. Karst holes, cracks and pores developed in the Lower Ordovician carbonate rock constitute four types of oil and gas reservoirs, including crack type, porecrack type, crackpore type and reef type. Long lasting generation of hydrocarbon, multiphase tectonic movement and multistage karstification resulted in quite different oil characteristics in different part of the oilfield. Petroleum accumulation and pool forming were controlled by the Akekule Uplift, development level of karstfracture in carbonate rocks and distribution of mudstones of the Carboniferous Bachu Formation.
Based on 3D seismic data and well information and combining with regional tectonic background, the structural feature and its evolution were analyzed and formation history of hydrocarbon accumulation was restored in Xiaermen oilfield. Xiaermen structure is an anticline complicated by the later faults. The tectonic activity at the end of Paleogene was characterized by compression and uplift, and folds were developed in Biyang depression. The faults in the depression were formed in the end of Neogene. The structural evolution and formation of hydrocarbon accumulations passed through 3 stages, i.e.(1) subsidence and deposition with development of reverse drag anticline in Early Paleogene, early migration and accumulation of hydrocarbon; (2) regional compression and uplift in the end of Paleogene, formation of anticline lithology reservoirs; and (3) extension and fault movement in the end of Neogene, complicated anticline, destruction of reservoir, and formation of secondary fault lithology reservoirs.
The uniform porositydepth function drawing up on observed data does not express the history of because different clastic are different in lithology and process in a well or an identical region. The original porosity lied on clastic size and lithofacies so that the original porosity of a sort clastic can be considered as the same, but the process could be different from each other. For the sake of reliability of decompaction correction, this paper provides a method of delaminated decompaction correction. First, in a well or an identical region are delaminated into some compaction unit beds based on their lithology, age, process and so on. Then, the respective porositydepth function which expresses each delaminated compaction unit bed needs to be found. The original porosity in the porositydepth function could be determined by modeling sediments. The compaction model of delaminated compaction unit bed in a well or an identical region could be different or same but it should be reasonable to express their process. And last, using the backstrip method computes the paleaothickness and original thickness based on conversation law of solid thickness of beds.
On basis of Xray diffraction of clay minerals, analysis of resincast thin sections of cores and SEM observation of samples in twelve wells, the clay mineral types and their distribution in four oil groups of the third member of Fuling Group in Taixin oilfield, the northern Jiangsu Basin were described. The relationship between clay mineral types and porosity or pore structure of reservoirs was discussed. The influence of transform of clay minerals with geological evolution on reservoir character was analyzed. The results showed that kaolinite was positive correlation with porosity, but chlorite and illite were negative correlation with that. The chlorite showed obvious negative influence on preservation of porosity. Occurrence of secondary pores was accordance with the first rapid transform zonation of clay minerals in burial depth of 2 350-2 750m. The most favourable position for development of secondary pores was forecasted.
