OIL&GAS GEOLOGY-2002, Volume 23 Issue 4

FORELAND BASIN AND ITS DEFINITION AND RESEARCH

Liu Chiyang, Zhao Hongge, Yang Xingke, Wang Feng

2002, 23(4): 307-313. doi:10.11743/ogg20020401

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A classical concept of foreland basin can be defined as follows: Formed between the contracted orogen and its neighboring craton,an asymmetrical thrust flexure basin parallels to the orogen and extends in a long and narrow type. This definition includes the main characteristics of distribution location,crustal feature, dynamic mechanism developing stage, planar distribution and profile structures along with corresponding sedimentary formation. However, the basic structures and the location of main units of the foreland basin are variable in various stages of its evolution and also with difference both in its pattern and oil and gas bearing features. The foreland basin, on the basis of its geodynamic environment, can be subdivided into three types of peripheral foreland basin, retro-arc foreland basin and broken foreland basin. The former two types are the fundamental subdivisions. Many compressive basins around orogens in mid-west China generally have the structural features, deformation and deposition of foreland basins. According to dynamic sources, developing stages, and main characters during the development of the foreland basin, the basin could be named in a new type of foreland basin namely, intra-continent foreland basin that can be discriminated from the peripheral foreland basin and retro-arc foreland basin. Therefore they are corresponding to the three different featured convergent stages of ocean subduction, continental collision and intra-continent contraction in the structural evolution of plates. The basis for the definition and the contents for the research of the foreland basin are as follows:(1) tectonic attribute in which kinds the foreland basin belongs to;(2)developing states;(3) basin and orogen coupling;(4) regional bacground;(5) prototype basin topography;(6)evolutional process;(7) sedimentary reaction;(8) vertical distribution. Attention should be paid to the generality of the foreland basin while defining it; Importance should be attached to the individuality of the foreland basin when studying it.

DYNAMIC PREDICTION OF OIL AND GAS POOL FORMATION

Zhao Zhongyuan, Zhang Xiaohui, Ren Zhanli, Jin Jiuqiang

2002, 23(4): 314-320,342. doi:10.11743/ogg20020402

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In accordance with the method of dynamic prediction of oil and gas pool formation, the geological factors related to the process of pool formation and effects can be respectively referred to as two systems of visible system and invisible system. The visible system Framework of system of pool forming elements is composed of source rocks, carrier beds, regional seals and traps. Invisible system hydrocarbon generation, pool formation and its processes, run in and along the framework of the former system, includes the hydrocarbon generation, primary and secondary migration and charge to trap forming the pools. The method of dynamic prediction of oil and gas pool formation is based on the structural map of source rock or the carrier bed near the source rock occurring during the stage of hydrocarbon generation. And then, upon which it is superposed respectively by the maps of pool forming elements and other corresponding maps, using that separately to analyze and predict the possible structural or non structural traps which may be charged by the oil and gas. And at the same time, a predictive map of oil and gas pool formation or a analytic map of the process of pool formation will be drawn up according to whether the changes of primary oil and gas pool formation caused by the successive subsidence and tectonic activity of sedimentary basins in post-pool-forming stage. If great changes really occurred in the primary pools, it is, thereby, necessary to draw up a map of the present structural map of source rock or carrier beds near the source rock to compare with the analytic map to analyze the present occurrences of the primary pools and predict the location of secondary oil and gas formation.

PROBLEMS AND PROGRESS IN SEISMIC TRACE INVERSION

Ma Jinfeng, Xu Shenghui, Wang Guishui, Gao Le

2002, 23(4): 321-325. doi:10.11743/ogg20020403

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Routine post-stack seismic trace inversion techniques are affected by many factors. It is difficult to gain satisfied results in practice. Possible reasons of causing wrong inversion results and interpretation pitfalls were analyzed in terms of main technique details of seismic trace inversion, chiefly concentrating on the aspects of noise, assumed conditions, w(t) extraction, transition of time and depth, low frequency component and restrained conditions etc. The concept of Elastic Impedance put forward by Patric Connolly has improved the reflectivity of normal incidence assumption which combines AVO problems and seismic trace inversion method in a skillful way so as to promote the seismic trace inversion method. Moreover, a model of Generalized Elastic Impedance established on this base suiting the routine post-stack, non-zero offset seismic data was put forward by us. Generalized Elastic Impedance which does not only include acoustic impedance but also include lithologic information of P and S-wave velocity. More accurate P and S-wave velocity and fluid, saturation, penetration information can be got by making a further study on joint P-wave and P-SV elastic impedance inversion. This is the new trend for seismic trace inversion.

DISCUSSION ON OIL DERIVED COAL IN THE JURASSIC OIL POOL IN TURFAN-HAMI BASIN

Liu Yiqun, Feng Qiao, Hao Jianrong

2002, 23(4): 326-331. doi:10.11743/ogg20020404

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The Jurassic oil accumulation is considered as oil derived coal because it occurred on coal bearing strata. Luacustrine mudstone and sapropel coal in the middle Permian and the low Jurassic as well as cannel boghead in the middle and upper Triassic have abundant exinoid group and saprepel group, they have highest hydrocarbon-generating potentiality in the basin, while humic coal distributed in the middle and lower Jurassic has abundant vitrinite and inertrinite which has poor liquid hydrocarbon generating potentiality. The hydrocarbon generating assemblage can be divided into two types of cannel boghead deep lake mudstone and humic coal cannel coal shallow lake mudstone in this basin. The Jurassic crude oil is rich in hopane and poor in terpane with type of " V" of sterane indicated by the biomarkers shows that the bacterial and biota in water are mainly liquid hydrocarbon producing matter. Theses features are much like those of lacustrine mudstone and cannel boghead in the Permian. With characteristics of rich in terpane, poor in light hydrocarbon and type of "reversed L Shaped" of sterane shows that the hydrocarbon generating potentiality in humic coal is very low and higher plants are mainly plants for hydrocarbon generation. The Jurassic oil accumulation is a mixed oil sourced accumulation characterized by lacustrine mudstone, cannel boghead in the Permian, Triassic and the lower Jurassic.

EXPERIMENT ON PLUGGING MECHANISM OF POLYACRYLAMIDE WATER PLUGGING AGENT

Sun Wei, Yang Shengzhu

2002, 23(4): 332-335. doi:10.11743/ogg20020405

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The result of visual displacement experiment of the sandstone pore micro model indicates that polyacrylamide chemical plugging agent should have priority to be selected as a chief agent for plugging wide channels in reservoirs. The viscosity variations of the plugging agent after entering the channel can be classified as follows: big slug with low viscosity; big slug with high viscosity and small slug with high viscosity. The process that formed plugging mechanism and plugging result can be described as: absorbed water film produced by pore channel surface-dynastic entrapment of gel network floc-unit-physical plugging- viscoelastic plugging effect. In addition, under the same water plugging condition, PHMP and clay composite plugging agents are more suitable for plugging wide channel and fractured reservoirs, whereas PHMP and TP-920 swelled-grain composite plugging agents are fit for plugging wide channels and fractures, the chemical plugging agent above shows that plugging result in double pore medium has more significance than that in single pore medium.

FORMATION AND POTENTIAL OF FRACTURED MUDSTONE RESERVOIRS

Zhang Jinggong, Yuan Zhengwen

2002, 23(4): 336-338,347. doi:10.11743/ogg20020406

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Almost all fractured mudstone reservoirs found both in and outside China are distributed in source rocks which are mainly composed of mudstones and shales, abundant in organic matter, calcareous and siliceous minerals. The abundance of organic carbon is 1.0%～20% in common with various types and their vitrinite reflectance is 0.5%～1.3%.There are three main genetic types of fractures which are structural,overpressured and diagenetic contraction ones in the source rocks. The mudstone reservoir caprocks are made up of non fractured mudstones, gypsum and halite rocks. Anticline and monocline are major trap types. The fractured mudstone reservoirs are believed to have great source potential due to a great deal of hydrocarbon remained in the source rocks.

A NEW METHOD IN ASSAYING GAS ISOTOPES IN FLUID INCLUSION AND THE WAY OF APPLICATION

Chen Mengjin, Hu Guoyi

2002, 23(4): 339-342. doi:10.11743/ogg20020407

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The methods of pyrolysis and vaccum ball grinding are used to obtain carbon dioxide, methane and other gasses. Then, the carbon isotope values of theses gases can be assayed by a higher sensitive apparatus(Delta S). CO resulting from the pyrolysis can affect the assaying of isotope value whereas the method of vacuum application can't change nature of gasses, therefore, gases extracted by the vacuum ball grinding can reflect the nature of true ancient current and it's more reliable for assaying isotopic value. This method has been used to isotopic assay hydrocarbon gas in inclusions from the Ordovician reservoir calcite veins in central gas field of Ordos basin. The results show that the values of δ¹³C₁ distribute between -2.673% and -4.360%. The values of δ¹³C₂ are from -2.253%～2.580%. The values of δ¹³C₃ are from -2.253%～2.580%. The characteristics of gas from the fluid inclusion show that the gas generated from coal is very different from the gas in gas fields. It is speculated by the author that there would have been at least two stages for the formation of the low Paleozoic natural reservoirs in central gas field of Ordos basin, coal type gas was probably dominant at the earliest stage.

R_o INVERSION OF THERMAL HISTORY RECONSTRUCTION IN SEDIMENTARY BASIN AND ITS RELATED PROBLEMS

Chen Gang, Zhao Zhongyuan, Li Pilong, Ren Zhanli, Yan Hanjie, Liu Aiyong

2002, 23(4): 343-347. doi:10.11743/ogg20020408

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Vitrinite reflectance, also abbreviated to R_o, in various depth of same sedimentary basin is a reflector of thermal current density changes experienced by the basin. Therefore, the evolutional history of a basin can be reflected by reconstructing ancient thermal current, paleo-ground temperature and a R_o model in the basin. However, R_o can be explained in several ways for multi-cycle basins and with inconvertibility, the reconstruction of a prototype basin would be started at the first and try your best to get as much reliable information about R_o as possible when you conduct basin inversion with R_o. In order to overcome inconvertible and coverable feature of R_o, LgR_o-H section can be explained segment by segment to gain average value of R_o as that segment R_o value in terms of the sedimentary stratum separated by unconformity. As for abrupt change LgR_o-H curve, attention should be paid to effects of local volcanic activities and abnormal value should be picked out. Moreover R_o. Information about basin outcrops and shallow buried areas is mainly applied to explain features of paleo-ground temperature in the early stage of the basin evolution.

DISTRIBUTION CHARACTERISTICS OF PRESENT HYDRO-DYNAMICS IN NW MARGIN OF JUNGGAR BASIN

Wang Zhenliang, Zhu Yushuang, Geng Peng, Gao Shengli, Sun Mingliang

2002, 23(4): 348-352. doi:10.11743/ogg20020409

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NW margin of Junggar basin with relatively complicated structures is composed of western uplift and west part of Mahu depression. The development characteristics of present hydro dynamics fields have been studied by means of analyzing parameters of fluid physics and fluid chemistry, measuring pressure data in reservoirs, compaction and overpressure in mudstones and distribution of fluid potential. Fluid physicochemical features from various layers show different hydro dynamics distribution distinctions of its own, so as to recognize easily where gravity flow is strong and where frequent replacement of water between deep layer and shallow layer, namely; districts from Hongshanzui to Wuerhe in the Carboniferous System, Kelamay and adjacent Xia No. 40 well in the Permian, Ke No.114 wells and Feng No.1, Wuerhe in the Triassic, Baijiantan Baikouquan in the Jurassic. It is believed by measuring pressure in situ in sandstones that hydrostatic pressure is basically preserved in the Jurassic and Carboniferous, and overpressure to a certain extent would appear at some depth in the Triassic and Permian, where development of overpressure in plane occurs in Mabei and Xiazijie areas.It is indicated by calculating abnormal pressure in mudstones from compaction curves that the beginning depth of overpressure is between 1800～2300 m while the beginning corresponding layer is quite different,moreover thick layers of under compaction mudstone contribute markedly to abnormal pressure. It is believed by studying distribution of hydraulic head in the Permian and Triassic that hydrodynamic fields are present mainly as compaction flow, whereas in some high positions of structures or fractures around northwest margin of Junggar basin the fields are developed and present as gravity flow or meteoric ground water flow.

DISCOVERY AND SIGNIFICANCE OF THRUST STRUCTURES OF XUYANGQIAO-HEILONGCUN BURIED HILL BELT OF HUANGHUA DEPRESSION

Chen Qinghua, Liu Chiyang, Li Qin, Wang Shuxian

2002, 23(4): 353-356. doi:10.11743/ogg20020410

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The paper discusses mainly the distribution, geometric features and genesis of thrust structures in Xuyangqiao-Heilongcun buried hill belt in Huanghua depression and the significance in discovering them. Several thrust faults are interpreted with high quality geologic data and well-logging data collected in our research work in the study area. These thrust faults are found in the study to be characterized with deep dissection, big separation and major width of the section. It is believed that above mentioned thrust faults were formed in the early Yanshanian due to the chief motive force of left strike-slip of Tanlu rift. The discovery of the thrust structures in Xuyangqiao-Heilongcun buried hill belt in Huanghua depression is of great guiding significance in oil and gas exploring in Dagang oilfield.

CHARACTERISTICS AND OIL SOURCE FOR MESOZOIC VOLCANIC POOLS IN FENGHUADIAN REGION

Luo Jinglan, Zhang Chengli

2002, 23(4): 357-360. doi:10.11743/ogg20020411

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The Mesozoic volcanic rocks in Fenghuadian, Huanghua depression,mainly consist of rhyolites,trachydacites, trachytes and minor trachyandesites and dacites. Two lithofacies, volcanic explosion(including explosion and effusion subfacies) and volcaniclastic lithofacies can be distinguished. Reservoir in different lithofacies are characterized with different reservoirs physical properties, the volcanic explosion subfacies are the most favorable reservoirs. Different locations of volcanic rock in terms of palaeo-geomorphology have a great impact on the reservoir quality. Upper portion of the lava of the volcanic effusion subfacies in the highland of palaeo-geomorphology and in the hinge area are believed to be ideal oil and gas reservoirs. It is indicated by organic geo-chemical researches that source rock samples gathered from the volcanic rocks are quite similar to TIC chromatograph of mudstone extracts and saturated hydrocarbon chromatograph from Member Ⅱ,Ⅲ of Kongdian Formation, sterane and hopane of crude oil also have similarities with mudstone from Member Ⅱ of Kongdian Formation, therefore, the Eocene Member Ⅱ(E_K₂)of Kongdian Formation overlain the Suite and in Cangdong depression is the principal source rocks for generation of hydrocarbons reserved in Fenghuadian suite.The faults in the suite may have acted as conduits for hydrocarbon migration.

FRACTURE FEATURES OF REVERSED BASIN:TAKING SANZHAO AREA OF SONGLIAO BASIN FOR EXAMPLE

Zhang Li, Yue Leping, Yang Yajuan, Wang Xiujuan

2002, 23(4): 361-363,367. doi:10.11743/ogg20020412

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Songliao basin has principally experienced extensional and reverse stages. A set of near NW tension fractures and two sets of oblique shear fractures were chiefly formed in the stage of extensional structure, whereas two sets of near NE and NW shear fractures and one set of EW spreading fractures were developed in the stage of reverse structure. Fault growth activities could not cease basically until the late Qingshankou Formation. Structural fractures were not well developed due to sediments in plasticity in the Third Forth Member of Quantou Formation and Qingshankou Formation in particular. Most of fractures formed in the stage of extensional structure are discovered to be filled with calcite and in inefficient due to prolonged process of diagenesis. During the reverse stage, structural fractures were extensively formed by compressional process because the reservoir in the basin was already in deep diagenesis. Therefore, fractures in Sanzhao area were mainly formed in the reverse stage.

RELATIONS BETWEEN ARCHIE'S FORMULA AND RESERVOIR PORE STRUCTURE

Li Qiushi, Zhou Rongan, Zhang Jingong, Wu Hannin, Li Xuesen

2002, 23(4): 364-367. doi:10.11743/ogg20020413

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It is discovered by the experimental study on Shan-2 Paleozoic reservoir of Shan-141 well area that the resistivity factor F in Archie's Formula is not only related with the porosity and tortuousity of the pore but also related with the throat of the pore as well. When the throat rate =1, the minimum of n is 1, when the throat becomes larger, n becomes larger accordingly. It is concluded that the smaller the ratio of the pore throat,the lower the Value F is. The size of Value n of the reservoir resistivity index is chiefly effected by the ratio of the pore throat.The theory is that when the pore is full of oil, the layer of the conductor decreases and the length of it increases.

RESEARCH ON THE SEGMENTATION OF DAXING FAULT

Zhao Hongge, Liu Chiyang

2002, 23(4): 368-371. doi:10.11743/ogg20020414

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Daxing fault in Jizhong sag is characterized with segmentation and variations for each segment. The fault, according to its extending trends, can be divided into four segments namely; north segment(NNE trend), mid-north segment(NE trend), mid-south segment(near EW trend) and south segment(near NS trend).Each segment has a distinctive difference of its own in fault geometry, associated structures, active age and the sedimentation control etc. Especially, the NE trend segment controls the structural characteristics of the whole Langgu sag. The structural character varies in the hinge area between two segments. As a boundary fault controlling the sag, the evolution of Daxing fault has intrinsic correlations with each segment due to the same effects of extensional stress field in the early Tertiary.

DEFINITION OF MILANKOVITCH CYCLES FOR YANGCHANG FORMATION OF THE UPPER TRIASSIC IN ORDOS BASIN

Zhang Xiaohui, Zhao Zhongyuan

2002, 23(4): 372-375. doi:10.11743/ogg20020415

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Climate changes caused by orbital are widely recorded in sedimentary record and reflected by Gamma-ray logging data. The thickness range of stratigraphic cycles in Yangchang Formation is obtained through analyzing the Gamma-ray logging data of Shaan NO.15 in Ordos basin. The thickness range caused by eccentricity is 9.6-18.75m and the thickness range caused by obliquity of the earth's axis and climate precession is 1.18-6.82m.The sedimentation rate of various oil layers in Yangchang Formation ranges from 7.8 to 14.2cm/ka.

FORMATION STAGES OF NATURAL GAS RESERVOIRS IN DUQIAOBAI AREA OF DONGPU DEPRESSION

Ren Zhanli, Feng Jianhui, Cui Junping, Ren Laiyi

2002, 23(4): 376-381. doi:10.11743/ogg20020416

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The results of isotope dating of illite in hydrocarbon reservoirs and testing results of saturation pressure and homogenization temperature of fluid inclusion indicate that natural gas reservoirs in Duoqiaobai area of Dongpu depression can be mainly divided into two mega-stages;The first stage is about 30.4-18.4Ma corresponding to the early sedimentary stage of Dongying-Guantao Formation, the chief formation stage of natural gas reservoirs. The most of this stage is in correspondence with the erosion stage of 27-17Ma which is favorable for the formation of natural gas reservoirs due to the reduction of erosion stratum pressure. The second stage is equivalent to the Quaternary(since 2Ma),this stage is on one hand for adjustment of the formed natural gas reservoirs, on the other hand for continuously injection of the secondary crop gas. The characteristics of formation of natural gas reservoirs in Duqiaobai area of Dongpu depression is in general with the newer of layer, the later of gas reservoirs forming and the older of layer, the earlier of gas reservoirs forming. The formation stage of natural gas reservoirs in Duqiaobai area is earlier in comparison with that in Qiaokou and Baimiao area.

RESERVOIR HETEROGENEITY OF XINGLONGTAI OIL LAYER IN DU-NO.84 BLOCK OF SHUGUANG-1 AREA, LIAOHE OILFIELD

Dang Ben, Zhao Hong, Zhou Lifa, Wei Heming, Dun Tiejun

2002, 23(4): 382-386. doi:10.11743/ogg20020417

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Xinglongtai oil reservoir is characterized, in terms of micro heterogeneity, by obvious distinctions on component and structure of rock between underlayer series and upper one. Rock assemblage in upperlayer series mostly consists of sandstones without gravel which are mainly feldspar rock-fragment ones, whereas rock assemblage in underlayer series is chiefly composed of sandstone with gravel which are mainly feldspar rock fragments. The sorting of sandstone grains is poorer in underlayer series than that in upper one. The particle size in underlayer series is thicker than that in upper one. Macro heterogeneity shows uneven growth of sand body and obvious variations of porosity and permeability.Vertically,the thickness of single sand body and the frequency of sand body as well as the density of sand rock are all smaller in upperlayer series than that in under one.Horizontally, the sand body in the upperlayer series is divided into two parts locating in the east and west which gradually join together upwards. The distribution of sand bodies in the underlayer series is wide. Whereas the distribuition area gradually decreases upwards. Inter-layer, internal and plane heterogeneity of porosity and permeability is obvious, moreover the inter-layer heterogeneity is intense than internal heterogeneity which gradually gather head from bottom to top.Primary reasons leading to reservoir heterogeneity are sedimentary environment and tectonism.

CHARACTERISTICS OF DETRITAL RESERVOIRS AND REGULARITY OF GAS CONCENTRATION IN SULIGEMIAO GAS FIELD

Li Wenhou, Wei Honghong, Ma Zhenfang, Qu Hongjun, Liu Ruie, Chen Quanhong

2002, 23(4): 387-391,396. doi:10.11743/ogg20020418

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Quartz sandstone, lithic quartz sandstone and lithic sandstone are main types of reservoir rock in Shan Member-Ⅰ,Ⅱ of Shanxi Formation and He Member-Ⅷ of Shihezi Formation in the Permian in Suligemiao region. Those rocks, with good maturation in composition and moderate maturation in texture, have experienced diagenesis of compaction, cementation and dissolution and have formed secondary solution pore, primary residual inter-granular pore space and intercrystalline pore. Reservoir in the region can be divided into four types on the basis of its physical property, capillary pressure curves and relations of pore combination. It is discovered by studying that braided and meandering stream channel sand bars, delta plain branch channels and underwater branch channels in braided and meandering stream delta front are favorite reservoir belts in this region, which control the distribution of highly permeable reservoir. The well graded quartz sandstone with high content of quartz and coarse quartz is the foundation for forming good reservoir. The development of secondary pore is the key for forming highly permeable reservoir.

LATE PERMIAN SPOROPOLLEN ASSEMBLAGE FROM LUCAOGOU FORMATION IN SANTANGHU BASIN

Yin Fengjuan, Liu Hongfu, Hua Hong

2002, 23(4): 392-396. doi:10.11743/ogg20020419

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Lucaogou Formation in Santanghu basin consists of a set of shallow lacustrine-semi lacustrine deposits mainly in gray mudstone. Abundant spores and pollen grains including 28 species of 26 genera are recognized in the mudstone. It is indicated by studying that Lucaogou Formation sporopollen assemblage is characterized by the dominance of Gymnospermous Polle grains and a small amount of Pteridophyte spores. Cordaitina, Hamiapollenites, Protohaploxypinus,Striatopdocarpites, Striatoabieites and Alisporites are dominant in the mudstone. It is believed that Lucaogou Formation belongs to the early late Permian in age based on its feature of sporopollen assemblage and comparison. Sporopollen colors may reflect then ancient temperature between 60℃～110℃ and evolution of organic material in low maturation stage.

PALEOMAGNETIC RESEARCH OF DRILLING CORES IN NANIWAN OIL FIELD

Yang Binyi, Wu Hanning, Li Xuesen, Lu Jianjun

2002, 23(4): 397-401. doi:10.11743/ogg20020420

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Secondary viscous remanence(low-temperature component) and primary remanence(high-temperature component) can be effectively separated by thermal-demagnetizing process. The orientation of the viscous remanence should be correspondent with that of available magnetic field, and the primary remanence should be consistent with the magnetic field orientation of then deposition of rocks. The original direction of drilling cores can be determined by vector compounds in line with above principle. The anisotropy of rock magnetic susceptibility, caused by the oriented arrangement of magnetic minerals effected by then magnetic field,reflects the feature of the rock magnetic fabric. The magnetic fabric shows mainly as the rock depositional fabric, therefore, environmental information of rock deposition can be gained and pale-current orientation and extension direction of sand body can be defined by studying the magnetic fabric. A research on the paleomagnetic orientation and magnetic fabric from recent drilling cores in Nanniwan oil field indicates that the extension direction of reservoir sand body in the area(namely, water flow direction) is near EW.

SEDIMENTATION AND DIAGENESIS OF DELTA IN TAIBEI SAG OF TURFAN-HAMI BASIN

Liu Linyu, Liu Yiqun, Li Wenhou, Di Shixing

2002, 23(4): 402-405,414. doi:10.11743/ogg20020421

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During sedimentation of the Jurrasic Sanjianfang Formation in Taibei sag of Tuha basin, northern part of the sag developed into a fan-delta due to its steeper topography whereas southern part of the sag evolved into a braided channel delta owing to its gentle topography. Clastic rock compounds as a main sedimentation body deposited by means of distributary channel sediments are well developed in the sedimentation of the fan delta and braided channel delta. Mechanical compaction, cementation and solution effects are chief diagenesis of Sanjianfang Formation. Clastic rock body in front of the fan delta in northern part of the sag is manly characterized by mechanical compaction effort and weaker solution effect. Most of primary interparticle pores would disappear in the reformation of intense mechanical compaction of clastic rock body and become a reservoir body of low porosity and permeability with the main feature of cementation of autogenic minerals and solution effect of unstable compositions. Whereas the braided channel delta in southern part of the sag has not experienced mechanical compaction because of its higher content of rigid material, preserved with a large amount of remaining interparticle pores which become a reservoir of good physical property with the reformation of solution effect.

RELATIONSHIP BETWEEN OIL FIELD WATER AND OIL & GAS POOL IN YANQI BASIN

Yuan Zhengwen, Quan Shujin, Qiao Guilin

2002, 23(4): 406-409. doi:10.11743/ogg20020422

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