Table of Content

25 December 1999, Volume 20 Issue 4

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STUDIES ON GEODYNAMIC SYSTEMS OF SEDIMENTARY BASINS:TAKING WEST LIAONING, NORTH LIAONING AND SOUTH SONLIAO BASIN FOR EXAMPLE

Wang Dongpo, Xu Min, Xue Linfu, Liu li, Wang Deqin

1999, 20(4):  273-278.  doi:10.11743/ogg19990401

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The formation and evolution of a basin is related closely to evolution of the dynamic system in the deep of the earth. The dynamic system mainly consists of the lithosphere, the asthenosphere and the Moho. The thickness of the lithosphere, effective elastic thickness and flowability decide tectonic and thermal artivities and theion, control the depth of detachment, thect thermal texture and architectural types of the basin. The asthenosphere does not only corrode the bottom of the lithosphere, but also affect direcily its thermal property. The Moho is a mobile inteiface. On the whole, it reflects the crustal architecture of different tectonic units; microscopically, it indicats basin-forming model. In North China,a lot of fault-depressed basins formed from Early-Middle Jurassic to early Early Cretaceous and a large depressed basin formed in the late Early Cretaceous in Shongliao Region. These basins are distrituted regularly along Shedao BasinNorth Liaoning-West Liaoning, and hydrocarbons-bearing property changes from gas-bearing fault-depression to depression without oil, until at last fault-depression with no oil and gas at all. This seems to be related to the types of basins, but acturally it is controlled by dymamic systems in the deep of the earth. The main facts are as follows:(1)The lithosphere thickness is about 50～60 km in Shongliao Basin, 25 km thinner than that in West Liaoning. This indicates that the thicker the lithosphere is, the deeper the detachment belts will be, and the bigger the intensity of the lithosphere will be. The intensity of the lithosphere in Shongliso Basin is lower than that in West liaoning. (2)Since there are considerable differences in the basements of the basins, geothermal structure in Shongliao Basin is different from that in West Liaoning. The mantle heat flow Qr=58.1 mW/m² in Shongliao Basin, Qr/Qs=77%,and the mantle heat flow is only 36.8 mWm²,Qr/Qs=59% in West liaoning. The temperabe of crust-mantle boundary in Shogliao Basin(744.4℃)is higher than that in West Liaoning(644C).The geothermal structure is the basic role that caused thermal subsident differences between Shongliao Basin and West Liaoning region.

LOG EVALUATION AND PREDICTION OF GAS RESERVOIR PRODUCTIVITY

Xiao Cixun, Xiao Chongli, Su Yinzi, Hu Huawei, Chen Bixao

1999, 20(4):  279-282,289.  doi:10.11743/ogg19990402

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Probable productive formations are recognized by log data standardization, log curve automativc layering and establishing recognizing models; the parmeters such as effective porosity of The formaions, the absofute and effectivePermeabilities of gas, the index and the coefficient of productivity, and the comprehensive index are calculated. The sedata are used as evaluation porters to detendne pwhctive formations. The standard model of productivity gradecan be obtained by cluster analysis, sublayer productivity grad could be connected to the reservoir productivity(testnonresistance out flow), and then the evaluation and the prediction of reservoir productivity could be realized.

R-FACTOR ANALSIS ASSESSMENT OF OIL-GAS ZONES IN QINGTONG

Liu Deliang, Tan Ying, Yang Xiaoyong, Dai Jinxing

1999, 20(4):  283-289.  doi:10.11743/ogg19990403

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Regional tectonic framework of Qingtong Depression consists of fault-depression and fault-uplift. The faultzones trend mainly NEE and EW. Fourteen secondary structural units are divided as sample points in the depression.Fuzzy mathematical method is used to get the values of qualitative geological conditions of the depression, then the sample point data could be converted into zonal score Values by weigthed mean method, and finally use R-factor analysismethod to assess regional oil-gas reservoirs. In order to estiment those samples with poor parameter relativity, fuzzy comprehensive assessment is made for the main components derived from the factor analysis. The concept of blank-valueand calibrated-value was introduced to stack vertically multi-sequence assessment results.

CO₂/³He RATIO OF MANTLE-DERIVED CO₂ GAS POOLS AND ITS FORMATION MECHANISM IN EAST CHINA

Xu Duo, Zhou Yiaoqi, Zhu Yuelian, Cha Ming

1999, 20(4):  290-294.  doi:10.11743/ogg19990404

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CO₂/³He ratio of the mantle-derived CO₂ gas pools ranges from 10⁷ to 10¹³ in petroliferous basins in East China.This differs greatly from the constant CO₂/³He ratio of 2?10⁹-7?10⁹ of the manile-derived CO₂ gas while Separatng from the basalt magma. The CO₂/³He ratio of Wanjingta CO₂ gas pool formed in Mesozoic in Sogliao Basin ranges from 10⁹-10¹³, but that of the mantle-derived CO₂ gas pools formed since Cenozoic in Huangha, Jiyang, Subei and Shanshui Basins is as low as 10⁷-10⁹. This indicates that CO₂/³He ratio of the mande-derived gas pools is controlled by release mechanism of the gases.The eruption and intrusion of the basalt magma provided a large number of gas sources for the formation of the mantle-derired gas pools; the CO₂ gas in the magma chamber would release directly along fault-passages which cut the chamber deeply. This played an important role in the formaion, the gas source supplies, the CO₂/³He ratio and geochemical properties of the pools. Meantime, characters of CO₂/³He ratio of the inomanic origin CO₂ gas pools provide a new evidence for its mantle-derived origin.

SEISMIC PUMPING MECHANISM OF HYDROCARBON MIGRATION IN DONGYING DEPRESSION

Yan Fuli, Jia Dong, Lu Huafu, Xu Guangwei

1999, 20(4):  295-298.  doi:10.11743/ogg19990405

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Fault activities have important effects on hydrocarbon migration. The evolution process from microfracture→fracture→fault shows vividly the characteristics of periedic and intendttent pulse under the seismic pumping migration mechanism,which were determined by the periodic seismic activities and intermittent pulse of fracture extension of stress field chang in geological history. The unique venical distribution of the complex fault block oilfields in Dongying Depression is the result of altemation of transfusion during tectonic inactivity and seismic pumping during tectionic activity. This phenomenon is common in big oil-gas fields.

DISTINGUISHING CRITERIA OF VALIDITY FOR ARGILLACEOUS GAS SOURCE ROCKS IN TARIM BASIN

Lu Shuangfang, Wang Zhengping, Fong Yali, Zhao Mengjun

1999, 20(4):  299-301.  doi:10.11743/ogg19990406

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According to the principle that generated hydrocarbon minus residual hydrocarbon equals to the amount of expelled hydrocarbon which is expressed by the theory of hydrocarbon expulsion threshold controlling the distribution of oil and gas, and based on the amount of oil and gas calculated by the model of chemical kinetics using the samples of Tarim Basin and the amount of residual oil and gas calculated by the statistical model, the amount of oil and gas expelled from mudstone is calcuulated quantitatively and their relationship with the abundance, types and maturity of organic matter is discussed, The corresponding distinguishing plates are established. The results indicate that the low limit of organic carbon abundance for mud gas source rock is about 0.1%. This is much lower than that of oil sourcemek(TOC=0.4%). This implies that a lot of mudstones which are regarded as non-source rocks according to the distinguishing criteria of oil source rock may be potential gas source rocks.

EVALUATION CRITERION OF MARGINAL RESERVES AND DBD IN MARGINAL RESERVES

Zhang Weimin, Xie Peihua

1999, 20(4):  302-304,315.  doi:10.11743/ogg19990407

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With the development of national economy and increase in demend for petroleum resources, the evaluaion of marginal reserves has become more and more important. Based on the study of the characteristics of marginal reservesand problems encountered in evaluation by conventional criteria, new evaluation criteria are discussed. A new evaluationidea including the basis, the unit, the paramter and methods of evaluation are proposed. According to commercial oilflow standard, a new concept of productivity ratio(DBD) is also proposed. This thus solves the problems of comparabitity of produtivity between wells and of single well that puzzled people for a long time in the marginal reserves evaluation, and could realize the transformation from qualitative to quanitative evaluations.

OIL AND GAS PROSPECTS OF ORDOVICIAN KARST RESERVOIRING IN TARIM BASIN

Wang Jinqi

1999, 20(4):  305-310.  doi:10.11743/ogg19990408

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Ordovician karst reservoiring of Tarim Basin is charaterized by multi-hydrocarbon sources, deep burial reformation and overlap pool forming. The overlapping pools may be the main targets for discovering giant oil and gas fields.Development of Akekule paleo-uplift bears colse relation to its oil and gas accumulation. Large-scale of oil and gas accumulation happened in Cambrian-Ordovician Periods; tectonic movements of Eerly Herctnian laid a foundation for the network of carbonate rock solution; tectonic movements of Late Hercynian founded a structural base for huge oil and gas accumulation; and the overall sealing-caping of the paleo-uplift was perfected in Mesozoic-Miocene Periods. This Period was also the peak stage for oil and gas accumulation and pool-forming. It is suggested that Yakela fault-uplift, Shaxi area,Tazhong uplift, Early Hercynian Mazhatake paleo-uplift and West Bachu regions have fine reservoiring conditionsres pectively. They all have splendid prospects for oil and gas exploration.

FORMATION CONDITIONS OF IMMATURE OIL IN CONTINENTAL BASINS

Cai Xiyuan, Feng Zihui

1999, 20(4):  311-315.  doi:10.11743/ogg19990409

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The immature source rocks of oil in China's continental basins mainly formed in big lake basins influenced By transgression, small fault-subsided lake and gypsum lake basins. Corresponding source materials were algae, desMonollinite related to terrigenous plant, the soluble asphaltene and non-hydrocarbon organic matter preserved in gypSolyte environment. Bacterial action was favourable for organic matter to be inverted into immature oil, and thermal effect was an important condition for the formation of immature oil.

RELATION BETWEEN EXTENSIONAL MOVEMENT AND FORMATION OF OIL-GAS POOLS IN LISHUI-JIAOJIANG SAG

Wang Yi

1999, 20(4):  316-320.  doi:10.11743/ogg19990410

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The basic structural style of lishui-Jiaojiang Say is extensional structure. The extensional movement happened in Late Cretaceous-Paleocene was charaterized by episodic progrssive extension. Different parts of extensional structures in the study area have different characters:the extensional rates change for small in the North to big in the south, and the period largest extension of in the south part was earler than that in the North part. Since Late Cretaceous, the evolution of extensional structural style could be classified into two orders:the evolution of domino-style normal faults to the listric or ramp-flat normal fault system in Lishui Sag; the evolution of groben-horst system controlled by nonrotational planar normal faults to listric or ramp flat normal fault in Jiaojiang Sag. The extensional movement controlled the distribution of sedimentary sequences and systems, and the spatial distribution of source-reservoir-cap rock assemblage. The fault basin architecture can be divided into three-layers structure, and also, oil and gas are distributed in three lagers. The oil-gas pools of Lishui-Jiaojiang Sag are distributed mainly in the rift-depressed sequence. The oilgas pools of self-generation and self-reservoiring should be the main target of exploration in Lishui-Jiaojiang Sag.

TECTONIC EVOLUTION AND OIL-GAS POTENTIAL OF BASINS IN CENTRAL ASIA AND NORTHWESTERN CHINA

Wang Suhua, Qian Xianglin

1999, 20(4):  321-325.  doi:10.11743/ogg19990411

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Both Central Asia and Northwestern China were located in the south margin of Eurasian Continent in Mesozoic. Since Jurassic, they both have experienced similar tectonic evolution, i. e. the extension tectonics in JurassicPaleogene and compressive tectonics in Neogene-Quaternary. The collision of Indian Plate with Paleo-Eurasian Plate resulted in present style of mountain-intercalated basins. The basins possess rich oil and gas resources, favourable poolforming conditions and different post-reformtion. Foreland thrust belts are common structural features in piedmonts of the basins, but their internal structures are varied greatly. Neotectonisms influence strongly on oil-gas accumulation.

PETROLEUM ACCUMULATON SYSTEMS IN GUNAN SAG,JIYANG DEPRESSION

Wu Tao, Chen Jianyu, Tian Shicheng

1999, 20(4):  326-329.  doi:10.11743/ogg19990412

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Gunan Say is located in Jiyang Depression, Bohai Bay Basin. Based on the characteristics of its source rocks,pool-forming evolution and distribution, the sag can be divided into two pool-forming systems, i. e. petroleum accumulation system I and the system Ⅱ. The main source rock of the system I is the third member of Shahejie Formation, hydrocarbon generation threshold was in the end of Oligocene, and now it is highly matured. The reservoir rocks of the system I are distributed from Mesozoic basement to Neogene clastic rocks. The source rock of the system Ⅱ is the first member of Shahejie Formation, its hydrocarbon generation threshold was in the end of Miocene, and now is lowly matured;the reservoir rocks are mainly distributed in the first and second members of Shahejie Formation and Dongying Formation. Although the source provinces of the two systems are generally superposed, the distribution and propenies of hydrocarbon are different. System I stretches bo the intrasag to surrounding uplifts,while system Ⅱ streches to the intrasag only. Besides their migration and accumulation ways are different.

IN-SITU STRESS, FRACTURE SYSTEM AND OIL-FIELD DEVELOPMENT SHANSHAN OILFIELD

Zhang Li, Yue Leping, Yang Yajuan

1999, 20(4):  330-332.  doi:10.11743/ogg19990413

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Taking Shanshan Oilfields in Turpan-Hami Basin as an example, the control of earth stress over fractures was analyzed, and the effect of earth stress on well-net arrangement and waterflooding was studied in low-permeability sondstone oilfield. It is considered that paleo-tectonic stress field was related to the origin, distribution and development of natural fractures; present stress field affects not only the occurrence and validity of natural fractures, but also controls the configuration and extensional direction of artificial fractures. For the reasonable development of low-permeability Sandstone oilfield, the effect of both natural and artificial fractures of present stress field should be considered. In waterflooling, injection pressure should be lower than the formaion forture pressure. The production and injection wells should not he arranged along the directions of natural fractures and the maximum horizontal principal stress.

EFFECTIVE FACTORS OF OIL DISPLACEMENT EFFICENCY IN CHANG-6 AND CHANG-2 RESERVOIRS, JING'AN OILFIELD

Zhu Yushuang, Qiu Zhihao, Kong Lingrong, Chen Rong, Li Jinfeng

1999, 20(4):  333-335.  doi:10.11743/ogg19990414

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Displacement experiments of oil by water of Chang-6 and Chang-2 reservoir models in Jing'an Oilfields were made. The results indicate that their final oil displacement efficiency differ very little though they have differences in physical properties, and there is greater increase in oil displacement efficiency of Chang-6 reservoir (25.79%) than that of Chang-2 reservoir (4.32%) after water-free period. The major factors affecting their oil displacement efficiencyare the pore structure, the wettability, and pressure increasing way of injected water of the reservoirs.

SEQUENCE STRATIGRAPHY AND RESERVOIR PREDICTION OF UPPER PALEOZOIC IN ORDOS BASIN

Zhai Aijun, Deng Hongwen, Deng Zuyou

1999, 20(4):  336-340.  doi:10.11743/ogg19990415

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Upper Paleozoic strata of Ordos Basin can be divided into three medium-term cycles and eleven short-termcycles based on base-level cycle. The three medium-term cycles, namely MSC1, MSC2, and MSC3 from top to bottom,correspond respectively with Shihezi, Shanxi, Benxi and Taiyuan Formations-Fan-delta, epicontinental sea, delta,allavial fan and river channel deposit systems are identified in the target sections of the study regions. The earier stratawere epicontinetal sea deposits formed on peneplain, when the seawater receded in Permian, nonmarin basin began to form. It is predicted that the reservoirs are distribute widely within the three cycles of MSC1, MSC2 and MSC3. Yi24-E9-Yil4, Yi22-Yi6-Yil3 and Yil5-Zhaotan 1 and Yi9 well areas are favourable regions for reservoir development,While QijihLang-Tabamiao-Shan 196 well areas are the most favorable regions for oil and gas prospecting.

EFFECT OF BIODEGRADATION ON CARBAZOLE COMPOUNDS IN CRUDE OILS

Zhang Chunmin, Zhao Hongjing, Mei Bowen, Chen Mei, Xiao Qianhua, Wu Tiesheng

1999, 20(4):  341-343,348.  doi:10.11743/ogg19990416

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Geochemical analysis of different degrees of biodegradated crude oils show that a slight biodegration affects little to the pyrrolic nitrogen compounds in the oils. The concentrations of cathazole, methylcarbazole and C₂-carbazole decrease with the increasing of the biodegradation for mid-degree biodegraded oils, the concentrations of pyrrolic nitrogen compounds sharply decrease in the heavily biodegraded oils. The relative concentrations of carbazole, methylcarbazole and C₂ carbazole do not show any apparent changes in the non-heavly biodegraded oils; in the heavilybiedegraded oils, the concentrations of carbazole and methylcarbazole decrease, but that of the C₂-carbazole increases.As the C₂-carbazole isomers, the relative Percentage contents of the pyrolic N-H shielded, the prplic N-H semishielded and the pyrolic N-H-exposed carbazoles do not display any obvious variation in the non-heavily biodegraded crude oils, but that of the pyrrolic N-H-exposed carbazoles increase and that of the pyrrolic N-H semi-shielded carbazoles decrease in the heavily biodgraded oils.

TECTONIC FEATURES OF HUINMIN-DONGYING BASIN AND ITS CONTROL OVER OIL

Chen Shuping, Dai Junsheng, Li Li

1999, 20(4):  344-348.  doi:10.11743/ogg19990417

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Kongdian Formation and the fourth member of Shahejie Formation are important oil-gas-0bearing formations in Huimin-Dongying Depression.Their tectonie evolution can be divided into four stages, e. i. the filling of extensional Half-graben, strong fault-block movement, the complication of fault-block movemenmt and deep buried stages.Accordingly, the fault evolution series is plate→listic→Ramp and flat patterns in Kongdian Formation and the fourth Member of Shahejie Formation. The evolution series of Huimin-Dongying Depression was the rotational half-graben→Rolling half-graben→complex half-graben. The fourth member of Shahejie Formation was favourable source rock due to The effect of teotonic movement, Kondian Formation and the fourth member of Shahejie Formation developed into two Sets of normal source-reservoir-cap rock assemblage. The faults in the basin are the main migration paths, and the main Traps are fault-blacks and fault-noses. The uplifts in the depression and marginal slopes are the most favourable sites for oil-gas accumulation.

SOURCE ROCK EVALUATION AND CHARACTERISTICS OF HYDROCARBON GENERATION FROM LOWER PALEOZOIC CARBONATE IN ORDOS BASIN

Li Yanjun, Chen Yicai, Yang Yuancong, Lu Qiang, Zhang Jun, Shi Xiaoying

1999, 20(4):  349-353.  doi:10.11743/ogg19990418

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Based on primary lithology, thermolysis parameter of Lower Paleozoic carbonate source rocks in Ordos Basin,the abundane,types and nature of organic matter in the source rocks are used to determine the maturity and evolution stages of organic matter and estimate hydrocarbon generation ability of the study area. It is considered the kerogen wasⅠ-Ⅱ₁ types with middle-intensity hydrocarbon generation. It is emphasized that hydrocarbon generation of Lower Paleozoic carbonate source rocks can be divided into three phases including four stages, that is, low-maturation phase with R₀=0.65%;maturation phase with R₀=1.50% and high-maturation phase with R₀=2.25%, and the fourth stage of over-maturated pyrolysis gas stage. In this stage, residual kerogen was pyrolyzed and dry gas of high-temprature methan was generated. The source rocks of middle-lower parts of Majiagou Formation and the Cambrian System in the study area are of this stage.

DISCUSSION ON QUANTITATIVE EVALUATION CRITERION FOR HIGH-MATURED CARBONATE GAS SOURCE ROCKS

Li Jian, Jiang Zhusheng, Luo Xia, Li Zhisheng, Zhang Ying

1999, 20(4):  354-356.  doi:10.11743/ogg19990419

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As commercial risk of oil and gas exploration of the world increases, commercial evaluation on source rocks has become more and more important. Till now there isn't a good method to evaluate high matured carbonate source rocks, especially of gas source rocks. Quantitative evaluation criterioa for gas source rocks is introduced in this paper.According to the conception of effective gas source rock, rock isothermal absorber is used to abtain maximum of absorptive gas, then use thermal analogy analyzer to measure the pyrolytic gas amount of the rock. If the pyrolytic gas amountis greater than the maximum of absorptive gas of the rock, the rock then could be considered as available gas source rock. The criterion of high-matured carbonate rocks is established as effective gas source rocks by a lot of experiments.Gas generation rate of l5 l/t is considered to be the lower liwit of the carbonate. source rocks. This criterion is applied to evaluate the available carbonate source rocks in Tarim, Ordos and Sichuan basins, and is proved to be effective.

AUTOMATIC RECOGNIZING TECHNIQUE OF LOG HIGH-RESOLUTION SEQUENCE STRATIGRAPHY AND ITS APPLICATION

Zheng Xiaowu, Deng Hongwen, Xu Huaida, Lin Jincheng, Chen Mengjin

1999, 20(4):  357-360.  doi:10.11743/ogg19990420

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The formating sedimentation model is controlled by the accommodating space to sediment sapply ratio. For river-delta sedimentary system, shale to sand ratio can be used to describe quantitatively the ratio of accommodation space to sediment supply rate. The key techniques used include:automatic recognizing log-facies, quantitative calculation of shale/sand ratio curves and log curve filtering. The techniques could considerably improve the efficiency and accuracy of the recognition of high-resolution Sequence stratigraphy.

4-D SEISM AND ITS BASIC REQUIREMENTS

Zhuang Donghai, Xu Yun, Wu Dabala

1999, 20(4):  361-364.  doi:10.11743/ogg19990421

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4-D seism, also known as time-delay 3-D seism, is a new technique for reservoir development and management. Its main task is to study the differences between time-delay 3-D seismic data caused by fluid changes in reservoirs. So time-delay seismic data must have repeatability or identity. Be combined with well and development history data,4-D seismic data can provide more accurate reflection cocfficient, temperature, pressure, productivity capacity and fluid changes of reservoirs. This technique can also improve recovery rate and well-drilling success ratio. But it must be pointed out that this technique is not suitable for all reservoirs. It only suitable for the reservoirs whose pore fluid, rock compaction and pressure change considerably, the net-overload pressure is small and reservoirs are buried shallower,and there are seismic differentiae in given range of seismic resolution of reservoirs, synthetic effect. In order to gain its proper economic benefit, the operation of 4-D seism will be carried out into three stages:1. feasible study, 2. forerunning test in site, and 3. oilfield application on a large scale. At present, all successful examples of 4-D seism focus on forerunning test.

RESEARCH METHOD OF IDEALIZATION

He Zi'ai

1999, 20(4):  365-368.  doi:10.11743/ogg19990422

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Idealized research method is an approach of knowledge transforming and deepening, which has two forms:mode method and ideal experiment method. The common features of both methods are:a ideal state; a simplified form of abandonment and abstract; a high degree of abstract and predictive function. These features differ greatly from actural section. Replacing the mode by actural section is incorrect and harmful, and also a depreciation to the mode method.Though idealized method is an logical one, it is the combination of thinking in image and abstract thinking. The conception stage is dominated by diverging thinking and analogy thinking; the construction stage is dominated by criticizing thinking, stereoscopic and abstract thinking.

CHARACTERISTICS AND RESEARCH STATUS OF DEEP-WATER TRACTIVE CURRENT DEPOSITS

Liu Lijun

1999, 20(4):  369-374.  doi:10.11743/ogg19990423

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Since 1960's, the study of deep-water tractive current deposits has become a new research field in sedimentology. The present studies on deep-water tiactive current deposits are mainly focused on contourits current deposit, internal-tide and internal-wave deposits. Considerable progress has been made in the study of contourite corrent depositssince mid-1960's, especially in the study of modern contourite deposits. Now deep understanding has made on the formation mechenism, the characteristics of texture and structure, the vertical sequences, the rock facies and recognition marks of contourite deposits. The discovery of contourite-dome is the most important and distinctve achievement in this field. Numerous large-scale modern contourite-dome, which can be compared with deep-water turbidite fans, were discovered in deep-water oceanic areas and in stratigraphic record. The study on internal-tide and internal-wave deposits began in the early 1990's and developed rapidly, and has made considerable progress in the formation mechanism, the characteristics of texture and structure, the vertical sequences, the rock facies and arcognition marks. The Ordovician internal-tide and internal-wave deposits in West Zhejiang and Tarim Basin are typical cases in this field. Compared withturibidities, the deep-water tractive current deposits are more favourible in the reservoir characteristics, and have veryimportant oil-gas-bearing potential.