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Table of Content

    25 June 2001, Volume 22 Issue 2
    PROSPECTS FOR CHINA'S OIL INDUSTRY OF THE EARLY 21ST CENTURY
    Zhang Kang
    2001, 22(2):  95-99.  doi:10.11743/ogg20010201
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    China's oil industry has developed into manhood stage. The reserves in East China are characterized by lower annual grouth rate with large absolute meserves, slow decrease of residual recoverable reserves and oil production, but there is still a potential to develop oil production and slow down the decrease. As for Northwest China and China's sea area, petroleum provinces for strategic replacement and strategic reserve regions will be realized within 10 years. This is the decisive facter in determining the tendency of early 21st centoury's oil production. It is important to attract foreign capital and bring in advanced technology so as to improve China's oil industry; to develop and make full use of the broad oil market in order to ensure the demand for oil of China's sustainable econonic growth.

    GENETIC DISCRIMINATION OF MARINE SAPROPELIC TYPE GAS IN TARIM BASIN
    Chen Shijia, Ma Liyu, Fu Xiaowen Lin Feng, Luo Yuhong
    2001, 22(2):  100-101,118.  doi:10.11743/ogg20010202
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    Sapropelic gas could be derived from the cracking of both sapropelic kerogen and sapropelic crude oil. The differences between these two different kinds of genetic gases are: 1 the value of C2/C3 of the gas derived fron kerogen remains constant while that of the gas derived from crude oil increases gradually; the difference of carbon isotope of (δ13C213 C3) is opposite to the above memtioned values. It is considered that the gas in Jilak, Sangtamu and Jiefangqu regions in North Tarim Basin is derived from sapropelic kerogen while the gas in Lunnan, Yinmali regions is derived from crude oil.

    NEW RECOGNITION ON HYDROCARBON GENERATION OF DESMOCOLLINITE
    Wen Zhigang, Zhang Aiyun, Wang Zhengyun, Lin Xiaoyun
    2001, 22(2):  102-104.  doi:10.11743/ogg20010203
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    In coal beds, though hydrocarbon generation potential of liptinite is much higher than that of equal amount of desmocollinite, total amount of hydrocarbon generation of desmocollinite may not be lower than that of liptinite due to its large proportion. The simulation results of Jurassic coal-measures in Yining Basin, Xinjiang show that when simulation temperature is 380~420℃, hyrocarbon generation reaches its peak stage, and hydrocarbon generation stops at the temperature 450~500℃ To compare with liptinite, desmocollinite has longer hydrocarbon generation duration.

    FOSSILS OF SCOLECODONT AND ACRITARCH FROM SHANGXI GROUP IN SOUTHERN ANHUI AND THEIR GEOLOGICAL SIGNIFICANCE
    Chen Guanbao, Yin Leiming, Xu Shutong
    2001, 22(2):  105-107.  doi:10.11743/ogg20010204
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    Whether the distributive province of Shangxi Group metamorphosed strata in southern Anhui is an old land or an orogenic belt is quite controversial by geologists, but the age of the metamorphosed strata is very important to solve this problem. The scolecodonts and acritarchs reported here are new discoveries . They provide a direct evidence to the recognition of their ages and in the meantime some problems about the country rock ages determinated by the isotopic ages of intrusive bodies are presented. This discovery possesses important significance in the study of tectonic evolution of this area.

    TECTONIC EVOLUTION OF WEST MANJIAER REGION
    Zhao Jingzhou, Tian Jun
    2001, 22(2):  108-113.  doi:10.11743/ogg20010205
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    Since Tarim movement at the end of Pre-sinian, the west Manjiaer Depression has experienced about 6 major tectonic evolution stages. Sinian-Ordovician was the formation stage of intra-cratonic depression and Awati-Manjiaer( or A-Man) low ridge,which was a large,wide, low-amplitude one with the high point near Manxi-1 Well. Silurian-Devonian was the formation stage of intra-cratonic compressive bending depression and Lunnan paleo-uplift. Owing to the strong early Hercynian movement at the end of Devonian, Yingmaili-Lunnan paleo-uplift turned into two separate uplifts. At the same time, A-Man low ridge moved westward and was compressed into a narrow one. Carbonifernus-Permina was the formation stage of intracratonic rifting depression and inherited development of the Lunnan paleo-uplift, whereas the Triassic was the formation stage of quasi-foreland depression and deformation of the paleo-uplift. After the strong In-dosinian movement at the end of Triassic, the west Manjiaer region entered a new stage of inland depression and formation of Hadexun Uplift during the Jurassic to Paleogene. The Hadexun is a nose-shaped uplift dipping northeast, which is directly opposite to the trend of Lunnan plaeo-uplift. The Neogene was also an important stage, Manjiaer Depression, together with the North Tarim uplift, were changed into the foreland slope of Kuche foreland basin, and the Hadexun Uplift was finally fixed.

    DISCOVERY OF DENGYLNG FORMATION FOSSIL POOL IN CILI, HUNAN AND ITS SIGNIFICANCE
    Zhao Zhongju, Feng Jialiang, Chen Xueshi, Zhou Jingao
    2001, 22(2):  114-118.  doi:10.11743/ogg20010206
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    The Dengying Formation fossil oil pool of Upper Sinian in Nanshanping, Cili County, Hunan Province was formed in Late Silurian-Early Devonian Period. The reservoir spaces were corroded pores,holes and fractures in Dengying Formation dolomite . The Late Jurassic-Early Cretaceous Yenshan movement caused the uplift and erosion of the covery bed of the fossil pool, thus resulting in complete damage of the pool. The discovery of the fossil pool suggests that West Hunan-Hubei Depression had similar hydrocarbon generation and pool-forming process as Weiyuan Gasfield, in Sichuan Province. The difference is that Yenshan movement had little influence on Weiyuan Gasfield, but the Cili fossil oil pool was seriously damaged by the movement. So it is considered that fovourable oil and gas pools could be found in Western Hunan-Hubei Region if favourable covety beds and traps could be found in the area.

    CHARACTERS OF DEEP-BURIED CLASTIC RESERVOIR ROCKS IN HEXIWU STRUCTURAL BELT OF LANGGU DEPRESSION
    Wang Yongxin, Zhao Chenglin
    2001, 22(2):  119-122.  doi:10.11743/ogg20010207
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    Deep-buried clastic rock reservoirs in Hexiwu structureal belt of Langgu Depression mainly consist of feldspathic sandstone with low compositional maturity and middle textural maturity. The deep elastic rocks are in late diage-. nesis stage( A-A ), the physical property of the reservoirs become much more worse. A secondary pore belt developed in the section. From 3 450 m to 3 550 m, intragranular and intergranular solution pores developed well, thus forming available reservoirs, fluid solution caused by decarboxylation of organic acid was the major formation mechanism of secondary pores at the deep section. Pore structure is mainly characterized by small pore-low permeability-fine throat. The content of carbonate, sedimentary fades and diagenesis are the principal factors offecting the physical property of the reservoirs. The porosity of reservoirs in Langfang, Hancun and Beiwang is the highest in Hexiwu structural belt. These places are favourable for the development of the reservoirs.

    EFFECT OF BURIAL HISTORY ON PHYSICAL PROPERTY OF SANDSTONE RESERVOIRS: TAKE YANCHANG OIL REGION IN NORTH SHAANXI AS AN ECAMPLE
    Luo Jinglan, Zhang Chengli, Yan Shike, Wu Fuli, Li Yuhong
    2001, 22(2):  123-127,136.  doi:10.11743/ogg20010208
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    Yanchang Oildom has undergone two uplift-erosion, one hiatus and three subsidence processes since Late Tri-assic. The first subsedence stage(225~208 Ma)were mainly tectonic subsidence under comression; the second and the third subsedence stages(203~157 Ma and 138~97 Ma respectively) were mainly sedimentary loading subsidence in-tension environment. Simulation results show that the physicd property of Middle-Lower Jurassic Yanchang Formation resenoir is much better than that of the underlying Upper Triassic Yanchang Formation. Burial compaction was the primary cause resulting in 1500 porosity decrease of the sandstone of Jurassic sandstone and 200o that of of Triassic sandstone Mechamical compaction of overlying sedimentary loading formed in the second and the third subsidences resulted in worse physical property of the reservoir in the west part than that in the east part of the study area. It is suggested that the 4 +5 members of the Yanchang Formation have favourable trap function and could be regional caprock of Chang-6 member

    CHARACTERISTICS OF FLUID DYNAMICAL FIELD IN DAMINTUN DEPRESSION, LIAOHE BASIN
    Ye Jiaren, Hao Fang, Chen Jianyu
    2001, 22(2):  128-132.  doi:10.11743/ogg20010209
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    Fluid dynamical fields in Damintun Depression, Liaohe Basin show that: the paleogeothermal gradient in the study area is greater than present one; the mudstone compaction could be classified into three types such as normal compaction-normal pressure, uncompaction-low overpressure in single interval, and uncompaction-high overpressure in double intervals. The present profile pressure system consists of normal pressure, slight overpressure and intense over-pressure from top to bottom. The fault systems, unconformity surfaces, interconnecting pore systems and diapir structures constitute the complex network system of vertical and horizontal transportation within the depression. Pressure evolution can be divided into two stages of initial overpressure accumulation and overpressure expulsion, and faults had an important controlling role to the formation, evoltution and distribution of the pressures. The fluid potential energy in profiles present a "double-layer" structure, and the depocenter was the fluid supply area whereas the slope was the main fluid dischareg area.

    CHARACTERISTICS OF JURASSIC GAS POOLS IN JUNGGAR BASIN
    Wang Zhengliang, Chen Heli, Song Yan
    2001, 22(2):  133-136.  doi:10.11743/ogg20010210
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    Middle-Lower Jurassic coal measures are the main source rocks of gas pools in Junggar Basin; sand bodies, faults and uncomfomities are migration pathways; the upper parts of Sangonghe and Badaohe Formations are regional cover rocks. Several hydrocarbon migration-accumulation systems could be divided within the basin such as Mosowan-Shixi migration-accumulation system containing gas pools of middle-lower abundance; Shihezi-Hutubi migration-accumulation system in which important hydrocarbon discovery might be found; Dixi-Fukang system in which Saogonghe Formation Gasfield was discovered and northeast Fukang region may be another favourable area; Xiaoguai-Chepaizi and Mahe systems which are less favourable for gas accumulation. In summary, two types of primary and residual secondary gas pools including 4 subtypes were found in Jurassic System in Jurassic Basin.

    GEODYNAMIC BACKGROUND ON FORMATION OF ERLIAN BASIN
    Xiao Ancheng, Yang Shufeng, Chen Hanlin
    2001, 22(2):  137-140,145.  doi:10.11743/ogg20010211
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    The basin group in the east part of Nei Monggol are Middle Cenozoic fault-depressed basins developed on Hercynian basement. The landform of the basins is the result of multiple superimposition of structures. The basin's structural evolution underwent five different evolution stages such as stretch-depressed stage in Early-Middle Jurassic and Early Cretaceous Periods, the reversion stage in late Early Jurassic and late Early Cretaceous and the complete uplift stage since Late Cretaceous. The formation of the Early-Mildle Jurassic fault-depressed basin was related to the differential movement of the East Asian Plate; the reversion of the structures was the result of the close of Monggol-Okhotsk Ocean and the structures of oceanic plate, the Early Cretaceous fault-depressed basin was derived from back-arc deep-seated action caused by the subduction of the Pacific tectonic tract; the late Early Cretaccous basin reversion might beresulted from sinistral strike-slip of East China.

    DISTRIBUTION CHARACTERS OF RESERVOIR SPACE IN NANPU 35-2 OILFIELD
    Wang Hui, Zhao Jianhui, Tong Lianxtng
    2001, 22(2):  141-145.  doi:10.11743/ogg20010212
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    Seisnic inversion and geostatistic methods are two important methods for demonstrating reservoir space distribution. The seismic inversion method can properly describe the lateral distribution regularity of thick sand bodies; the geostatistic method can describe vertical changes of thin sand bodies. The combination of these two methods was used to study the reservoir space distribution of Nanpu 35-2 Oilfield, the results suggest that three kinds of contact relations could be found within fluvial facies sand bodies in the study area such as direct connection, superimposition and cut; the space distribution models include a thick sand body with continueous and extensive plane distribution and a thin sand body with banded vertical distribution. The first distribution model reflects the feature of river channel lateral shift and the superimposition and the second distribution model is the result of meandering stream cutoff.

    SEDIMENTARY CHARACTERISTICS AND OIL-CONTROLLING FACTORS OF LOW PERMEABLE SANDSTONE RESERVOIRS IN SHUNNING OILFIELD
    Wang Jianmin, Zhou Zhuoming
    2001, 22(2):  146-149,164.  doi:10.11743/ogg20010213
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    Chang-2 oil-horizons of the Yanchang Formation is the main pay bed of Shunning Oilfield The main oil horizon-chang-1 oil horizon is a typical low permeable sandstone reservoir consisted of distributary channel and distrihutary hay sediments. The distributary channel consists of main body, side part and marginal hank. The main body poss eases favourable physical property and is the major place for hydrocarbon accumnlation. Chang 21-1 oil horizon is exten-sively distributed with thick oil-bearing bed; Chang 21-2 oil horizon is restricted with thin oil-bearing bed. They are-placed in the same oil-water system. The distribution of oil and water is mainly controlled by sedimentary facies, structures and the thickness of sand bodies.

    CRUDE TYPES AND MAIN SOURCE ROCKS IN WEST PART OF NORTH SLOPE, CENTRAL TARIM
    Lin Qing, Lin Renzi, Wang Peirong, Zhu Yangniing
    2001, 22(2):  150-153.  doi:10.11743/ogg20010214
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    The oil in the west part of northern slope in Central Tarim Basin can be classified into two types (Ⅰ,Ⅱ) based on the distribution and composition of sterane and terpane. Type-I oil is characterized by relative tow ratio of tricyclic terpanes to hopanes, pregnanes to regular sterane and rearranged steranes to regular sterane, and by relative high ratio of Ts to Tm, C28 to C29 sterane and C30 hopane to C31 homohopanes. Type-Ⅱ oil has opposite biomarker characters to the type-I oil. The difference implies that there may be at least two oil sources in the study area The correlation between the oils and source rocks indicates that the oil of type-Ⅰ was derived from the Cambrian carbonate source rock,and the oil of type-Ⅱ was derived from the Middle-Upper Ordovician marl source rock.

    DIAGENETIC TRAPS IN FAULT-DEPRESSED LACUS BASIN: Take Eh3 Member in Biyang Depression as an Example
    Zhao Zhui, Zhao Quanmin, Sun Chong, Wang Jiying Gu Zhe
    2001, 22(2):  154-157.  doi:10.11743/ogg20010215
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    Biyang Depression is a typical continental fault-depressed lacustrine basin. The Eh3 member in the depression is in the A~B substages of late diagenesis, the cementation and solution of the diagensis bear close relation with the formation of diagenetic traps. Carbonate is the main cement; deep burial solution in the late diagenetic stage is the major solution types. The existence of shielding bed is the key factor of forming the diagenetic traps. According to their characteristics, the diagenetic traps could he divided into three types such as the traps relating to lithologic pinch out, fault and lenticular types. These traps could be further divided into 9 subtypes. The factors that effected the formation of the traps include sedimentary facies, diagenesis, the features of fluid, solution, faulting and expulsive pressure. Among them, sedimentary facies, diagencsis and the feature of fluid are the main factors.

    CHARACTERISTICS OF MICRO-FRACTURES AND THEIR INFLUENCE ON WATERFLOODING IN AERSHAN RESERVOIR, HANAN OILFIELD
    Zhang Li, Yang Yajuan, Yue Leping, Miao Kun, Song Shemin, Zhang Manku
    2001, 22(2):  158-160,193.  doi:10.11743/ogg20010216
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    Structural fractures developed well in Aershan reservoir, Hanan Oilfield. The width of the micro-fractures is 10~30 pin, the length is 1~3 mm and surface density is 0.025 mm2. The micro-fracture porosity and permeability have been calculated, and the distribution is analyzed. Micro-fractures are preface of macrn-fractures and the macro-fracture developed areas are also micro-fracture developed areas. A sandstone micro-model experiment has been done to investigate the process of displacement between fractures and matrix. Based on the above studies, micro-fractures play two different roles on waterflooding. On one hand, they may improve the permeability of the reservoirs; on the other hand, the together with macro-fractures and faults may improve network, which have bad effect on waterflooding. According to the characteristics of,micro-fractures in Aershan reservoir, some suggestions such as periodic injection are put forward to improve the effect of waterflodding in fracture-developed areas.

    DEPOSITIONAL SYSTEM AND SEQUENCE STRATIGRAPHY OF S33-4 SUBMEMBER IN DONGPU DPERESSION
    Li Jian, Wang Deren, Bai Xingying
    2001, 22(2):  161-164.  doi:10.11743/ogg20010217
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    S33-4 submember of Dongpu Depression can be divided into two Ⅲ-grade sequences. Each of them consists of lowstand system tract, highstand system tract and lacustrine transgression-regression system tract. Low stand delta depositional system, lowstand fan depositional system and dry brine lake depositional system are mainly developed in the lowstand system tract. In the highstand system tract, highstand delta depositional system, highstand sublacustrine fanturbidite sand depositional system arid braided river depositional system-turdidite sand depositional system developed well. In the lacustrine transgression-regression system tract, lacustrine fan-delta depositional system, braided river depositional system, lacustrine transgression-regression delta depositional system and beach bar depositional system developed well. Low stand delta sand body and lowstand fan sand body are the most favorable ones for oil and gas exploration, and highstand delta sand body, highstand sublacustrine fan sand body, braided river sand body and fan-delta sand body are secondary.

    SEQUENCE STRATIGRAPHY OF JURASSIC IN WEST JUNGGAR BASIN
    Gao XinSheng, Zhao Xiafei, Li Tianming, Tang Zhonghua
    2001, 22(2):  165-168.  doi:10.11743/ogg20010218
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    The high-resolution seguence stratigraphy of the Jurassic System in west Junggar Basin was studied and six unconformity surfaces (or sequence boundaries) were recognized-The Jurassic System could be divided into five sequences according to the surfaces, and an isochronic formation skeleton was set up which coincides with Junggar Basin. The long-term base level rising cycle of sequence-I is composed of braided river alluvial fan; the long-term base level falling cycle of sequen-1 consists of shore-shallow lake→delta front→delta plain . The long-term base-level rising cycle of sequence-2 is composed of basal braided channel sandstone-conglomerate→meandering stream→delta; its falling semi-cycle mainly consists of shore-shallow lake→delta front. The long-term base-level rising semicycle of sequence-3 is composed of braided river→meandering stream→delta; its falling semi-cycle consists of shore-hallow lake→deta front.

    POOL-FORMING CONDITION AND ACCUMULATION REGULARITY OF OILS AND GASES IN BIYANG DEPRESSION,NANXIANG BASIN
    Wang Min, Qin Weijun, Zhao Zhui, Yu Peixiang
    2001, 22(2):  169-172.  doi:10.11743/ogg20010219
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    Biyang Depression is a secondary structural unit in Nanxiang Basin. The depression is in half-graben shape which faulted in the south part and overlapped in the north part. The depositional stage of Hetaoyuan Formation was the major fault-subsided stage of the depression, source-reservoir-cap rock assemblage with great thickness and three types and nine subtypes of oil-gas pods formed in the deep depressed area. The discovered oil and gas pools are distributed in circularity around the depression. From shallow to deep of the depression, the oil pools change from dense oil gas to normal and then condensed oil pools. The inherited depression in the north part of the slope is the major oil-gas enriching area, the two sets of fractures within the area are favourable for the formation of fault-noze and fault-block oil pools. The thick mudstone of the third member of Hetaoyuan Formation is regional cap rock of the pools.

    FEATURES OF VOLCANIC ROCK RESERVOIR SPACES IN OULITUOZI REGION, LIAOHE BASIN
    Gao Shanlin, Li Xuewan, Song Bairong
    2001, 22(2):  173-177.  doi:10.11743/ogg20010220
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    Reservoir spaces of the Tertiary volcanic rocks in Oulituozi region, Liaohe Basin are generally developed in trachyte, tufflava, lava, trachydacite, brecciated trachyte, proclastic rocks, brecciated lava and can be divided into two main types. Primary pores include vesicles, inter-crystal pores, inter-breccia pores, cooling joint; the secondary porosity includes solution fissures, voids and structureal fissures. Vesicles and solution pores are the most important pore types in this area which occupy 65%~70% of the total amount of the porosity. Based on the statistics of mercury method and image plane scanning associated with the ratio curves of porosity and permeability, the reservoirs could be divided into four types. Type-Ⅰ and types-Ⅱ are favorable reservoirs. Four evolution stages of the reservoir spaces have been identified in Oulituozi region. Favorable reservoir spaces were mainly formed in the first and second stages.

    CLASSIFICATION AND ESTIMATION OF ORGANIC FACIES IN JURASSIC SOURCE ROCKS FROM NORTH MARGIN, CHAIDAMU BASIN
    Peng Licai, Yang Huizhu, Liu Langui Lu Zonglun, Bao Jicheng
    2001, 22(2):  178-181.  doi:10.11743/ogg20010221
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    The Jurassic hydrocarbon source rocks on the north margin of Qaidam Basin could be divided into highstand marsh peat organic facies, forest marsh peat organic fades, shore-shallow lake organic facies and semideep-deep lake organic facies. The first facies contains high inertinite contents, its organic matter is mainly Ⅲ2-type, its hydrocarbon-generation capacity is the lowest and gas is the main product; the second facies contains high viitrinite and Ⅲ1-type organic matter, It hydrocarbon generation capacity is relatively low with gas is the main product; the third facies is primarily coal measures with lower sapropelinite. Its organic' matter is mainly Ⅱ-and Ⅲ1-types with lower to poor hydrocarbon generation capacity; the last facies has the highest sapropelinite, the organic matter is Ⅰ2-or Ⅰ1 types with the best oil generation capacity

    GREY ASSOCIATIVE ESTIMATION OF TRAPS IN SOUTHWEST MARGIN OF JIANGHAN BASIN
    Zhu Ling, Zhu Wei, Lu Jing, Peng Changzi
    2001, 22(2):  182-184.  doi:10.11743/ogg20010222
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    Grey associative analysis in trap assessment is to study the simularity between actural traps and ideal traps; give pool-forming factors different weights through correlation analysis so as to quantitatively evaluate trap's pool-forming condition. The assessment results of the traps on southwest margin of Jianghan Basin indicate that, Xiefengqiao structure is most favourable for hydrocarbon exploration; Nangang 1~3 and Caixue fault-noses and Dingjiahu fault-block are secondary. Caixue and Dingjiahu structures should be major exploration targets in future.

    DELTA DEPOSITS OF BRAIDED RIVER FROM SHAHEJIE FORMATION, LOWER TERTIARY IN BONAN SAG
    Li Donghai, kang Renhua, Li Weifeng, Peng Detang
    2001, 22(2):  185-186.  doi:10.11743/ogg20010223
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    Plenty of braided river delta front deposits and prodelta deposits were discovered in Lower Tertiary Shahejie Formation in Bonan Sag, Shengli Oilfields. They differ greatly from other types of delta deposits. The main body of the delta front consists of subaqueous distributary channel sandbars composed of pebbled sandstone and midium-coarse sandstone. Cross-bedding developed well in the delta, especially lateral accretion cross-bedding formed by lateral displacement and accretion of river channel sandbars.

    A DYNAMIC SIMULATION METHOD FOR MATURITY OF ORGANIC MATTER IN SUPERPOSED ROCKS OF MULTIPLE THERMAL SOURCES
    Wu Chonglong, Li Xing
    2001, 22(2):  187-189.  doi:10.11743/ogg20010224
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    The experimential expressions of T-t-Ro,m ( Wu Chonglong, 1991), which were established with double regression method, can not only predigest the Bostick(1979) chart,but also can be taken as statistic expressoin of Arrhenius equation on coal metamorphism. Both the experimential expressions and the Bostick chart can't directly describe multiple them-tat source and multiple stage superimposed metamorphism of organic matter and coal. In order to solve this problem, a new dynamic simulation method for organic matter maturity is proposed in this paper by taking the experimential formulation as a base and using differential method of integral calculus. This method can be used to simulate dynamic coupling organic matter maturation and coal metamorphism under different thermal conditions and its development process.

    SIMULATING METHOD OF PARETO TRUNCATED DISTRIBUTION: A New Approach to Predicting the Number,Size and Distribution of Gasfields
    Zhang Jiliang
    2001, 22(2):  190-193.  doi:10.11743/ogg20010225
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    Gas resources assessment methods could be divided into two kinds: genetic method and statistical simutation method. The assessment results of these two methods obtained from the same geologic unit may differ differently, and usually the result of the genetic method is greater than that of the later. But combine these two methods together, use Pareto truncated distribution as numerical model, use iterative algorithm to obtain uniform results, the size,the number and the distribution of the gas fields and also gas resources enrichment which in a very important parameter for regional estimation analysis.