OIL&GAS GEOLOGY-2000, Volume 21 Issue 1

STRONG ACTIVITY AND ACTIVE DEEP ACTION: TWO IMPORTANT FEATURES OF CHINESE SEDIMENTARY BASINS

Liu Chiyang, Zhao Zhongyuan, Yang Xingke

2000, 21(1): 1-6,23. doi:10.11743/ogg20000101

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Strong activity and active deep action are two important features of Chinese sedimentary basins, especially for Meso-Cenozoic basins.These features were determined by texture,dynamic evolution of Chinese continent itself and its special tectonic location.The above two important features were proved by a series of geological phenomenas took place in many basins and the neighboring areas.The features directly determined the basic nature,the total appearance,the evolution process and characteristics of the late stage reformation of Chinese sedimentary basins; deeply affected and restricted oil-gas preservation setting,the characteristics of hydrocarbon pool-forming, distribution regularity and resources scale of China's Meso-Cenozoic continental basins and two types of Paleozoic(Including Mesozoic and Mid-Late Proterozoic)marine basins, thus forming distinct characteristics of abundant oil and gas resources in continental basins but complication in marine basin, which are completely in contradiction with the total characteristics of other areas of the world.

POST-REFORMATION AND GEOLOGICAL FEATURES OF CHINA'S PETROLIFEROUS BASINS

Zhao Zhongyuan, Zhou Lifa

2000, 21(1): 7-10. doi:10.11743/ogg20000102

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Post-reformation is one of the most typical characters of the petroliferous basins of China compared with those of the world.It strongly affects hydrocarbon generation,pool-forming and the preservation of oil and gas resources.In turn,the post-reformation is closely related to the inherent geological features of the petroliferous basins of China.The formation of petroliferous basins relied mainly on the broken landmasses or micro-continents.In the global tectonic evolution,they were placed in between the surrounding macro-oceanic plates in Palaeozoic,and in between the Siberian and Indian continental plates and several oceanic plates in Pacific since Mesozoic.Their multi-separation and aggregation as well as formation and evolution were always controlled by the stress accumulation and dissiplation of the geodynamic systems of the surrounding plates,thus resulting in the unique features of multi-stage basin-formation and multi-superposition of different stage basins,the multicyclic tecto-sedimentary evolution and multiple post reformation of the basins.

THINKING FOR RESEARCHES AND OIL-GAS ASSESSMENT OF REFORMED BASINS

Liu Chiyang, Yang Xingke

2000, 21(1): 11-14. doi:10.11743/ogg20000103

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Reformed basins that are widely and numerously found in China are the main replacing areas for China's oil and gas exploration.Oil and gas generation,accumulation,migration,pool-forming and distribution in the reformed basins were controlled by both the tectonic framework of pre-basin stage and the tectonic movements and structural forms of post-basin stage.So oil and gas pool-forming processes were complicated and oil-gas distribution regularity was varied.The process or thinking for the researches and oil-gas assessment of the reformed basins includes:1.collating the attribution of the basin and analysing its dynamic circumstances;2.reverting to the original basin;3.revealing the reformation process of the basin;4.determining the reformation degree and classifying the basin's retention units;5.approaching the characteristics of oil and gas accumulation and dispersion,assessing resources amount;6.taking multi-source hydrocarbon into account;7.paying more attention to late-stage pool-forming;8.paying attention to differential reformation.

STRUCTURAL ANALYSIS AND PETROLEUM GEOLOGY ASSESSMENT OF RELICT BASINS

Yuan Jianying, Zhou Yanru, Li Xiangbo, Zhang Zhengang

2000, 21(1): 15-18. doi:10.11743/ogg20000104

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The structural characteristics such as vertically stratigraphical sequence hiatus,planar sedimentary system and facies incompleteness,delimitation of a basin by erosion or fault,and the structural feature of outcrop in peripheral and near arears could be taken as marks in recognizing relict basins.Most the relict basins underwent multi-tectonic superposition.According to the theory of system and information,the multi-tectonic superposition could be abstracted as the processes of construction,structure and the information record.Then use antitone structural analysis method to recognize and reconstruct the primary tectonic structure and sedimentary feature of a basin in certain geological history.The method includes mainly several key technologies such as tectonic imaging,the determination of deformation age and deformation reversion.Usually one should adopt two steps to assess the petroleum geological conditions in relict basins:(1)use inversion technology to reconstruct the structural framework of the prototype basin,the deposition feature and the primary oil and gas geological feature of the prototype basin;(2)use forward solution to theoretically analyze the prototype basin,then compare the analysis results with actural basin,and correct the effect of subjective factors.On this basis,the space structural hierarchy,the time order and time-space coupling relationship of hydrocarbon generation,pool-forming events could be found,and then oil and gas generation and accumulation regularity could be further understood.

RESEARCH THINKING AND TYPES OF REFORMED PETROLIFEROUS BASINS

Wang Dingyi

2000, 21(1): 19-23. doi:10.11743/ogg20000105

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Reformed petroliferous basins are those that the feature of the prototype basins have changed greatly under inner and outer geological dynamics.According to different geological dynamics,the reformed basins could be divided into three types:(1)uplift-reformationtype;(2)fault-block reformationtype,and(3)thrust-fold reformationtype.The thinking and method for the exploration of reformed basins should not always use the principle of “determining depression and selecting zone”,but establish a new research thinking of “late pool-forming,pool-forming unit and integral continuous sealing”,and divide the pool-forming units of the basins into reformation-destroying,reformation-preserving and reformation-building types.The last two kinds of pool-forming units are favourable for hydrocarbon exploration.

DEVELOPMENT CHARACTERISTICS OF FLUID DYNAMICS IN REFORMED BASINS

Wang Zhenliang

2000, 21(1): 24-27,37. doi:10.11743/ogg20000106

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The migration nature of fluid and post-reformation of petroliferous basins resulted in multi-period of migration,accumulation,pool-forming and destruction of oil and gas in geological history.On the basis of the researches made on fluid dynamics in Junggar and Ordos Basins,three major characteristics of fluid dynamics of reformed basins were summaried:1.plannar fluid dynamic field could usually be divided into several relatively independent systems;2.the distribution and evolution of fluid dynamics could be divided into different stages in geological history;3.the distribution patterns of fluid dynamics of different strata were not always coincided in space.

GEOLOGICAL CHARACTERS AND EXPLORATION PROSPECTS OF REFORMED-RESIDUAL BASINS

Wang Yingmin

2000, 21(1): 28-32. doi:10.11743/ogg20000107

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Pre-Cenozoic marine strata widely developed in China.These strata have rich potential hydrocarbon reserves but their exploration degree and success ratio are low since they underwent multi-stage reformation and have the feature of residul basin.The reformation includes erosion,structural deformation and deep burial etc.However,the ways of reformation,such as being superposed by foreland basin or rift basin,being uplifted as a plateau or highland,being transformed from thrust folds into fault-fold belt or even orogenic zone,etc.Marine residual basins have complex hydrocarbon pool-forming dynamics.The most important hydrocarbon pool-forming properties are:(1)multi-stage hydrocarbon accumulation resulted in the formation of complex oil and gas systems with dispersed oil and gas pools;(2)late-stage pool-forming controlled by Himalayan movement.Therefor,the key problem of petroleum exploration in residual basins is to understand and describe their heterogeneity of geological characters,graps the dynamic process of hydrocarbon generation,migration,dispersion and accumulation,study the evolution history of various geological factors.In short,marine reformed residual basins bear bright prospects in oil and gas exploration,amd they bound to be the main targets of China's oil and gas exploration in the 21st century.

COMPARISON OF THERMAL EVOLUTION HISTORY IN SEDIMENTARY BASINS,NORTH CHINA

Ren Zhanli

2000, 21(1): 33-37. doi:10.11743/ogg20000108

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Most sedimentary basins in China belong to superimposed basins,their palaeogeothermal fields were generally reformed or changed.According to different reformation types of palaeogeothermal fields,the reformations can been classified into deep buried reformation,thermal event reformation and stress reformation.Because of differences in regional geology background and evolution history,there were greater differences in palaeogeothermal fields of the basins in North China.North China Basin and Tarim Basin were located in stable craton in Paleozoic,and characterized by stable sedimentary structures,and low geothermal gradients;Turpan-Harmi Basin and Junggar Basin were located in Hasakestain Plate,underwent fault subsidence and strong tectonic activities,and their geothermal gradients were high.Geothermal gradients of the basins in the eastern of Algin Rift were higher than those of the basins in western of Algin Rift in Late Mesozoic,and tectonic activities were stronger,indicating a strong regional tectonic thermal event.The basins on the western of Algin Rift were all compressive depressions,their geothermal gradients were lower.Sine Cenozoic,the eastern region of China has been in stretching background,geothermal gradient and heat flow are high in the basins;the west part of China has been in the crust compression and thickening background,geothermal gradient and heat flow are lower in the basins.

REFORM IN BASIN AND ITS SIGNIFICANCE IN PETROLEUM GEOLOGY

Zhang Kang

2000, 21(1): 38-41,45. doi:10.11743/ogg20000109

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The reformed basins were the prototype basins which were evidently reformed during post-stage structural movements;those underwent weak erosion and reformation are still prototype basins.As for oil and gas exploration,basin means connectedly distributed sedimentary rock mass;as for the reserves,about 50% of oil reserves and 70% of gas reserves are in reformed basins.Those basins are the main targets of hydrocarbon exploration in the 21st century since their exploration degree is low.In the research of basin reformation,regional uncomformity is an important factor in influencing the oil and gas distribution of the basins,thus the uncomformity and the strata above and below it should be taken as a special geological body.The multicycle opening-closing movement of the crust is the key to understand the basin reformation and its hydrocarbon evolution.One should investigate the oil and gas pools by means of the positive and opposite thinkings of the prototype and present basins.

OXIDATION AND ORGANIC MATTER EVOLUTION IN SOUTHEAST UPLIFT OF SONGLIAO BASIN

Wang Yongchun, Miao Hongbo, Liu Changwei, Jing Chengjie, Wang Yabo, Yu Shumei

2000, 21(1): 42-45. doi:10.11743/ogg20000110

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When organic matter undergo oxidation,the compositive proportion of elements,the highest pyrolysis peak temperature,the rate of hydrocarbon conversion and vitrinite reflectance would change distinctly,the conventional distinguishing index of organic matter evolution would lose its significance.The study results of the southeast uplift in Songliao Basin show that after the oxidation of organic matter,the O/C ratio of kerogen decreases with the increasing of evolution degree,thus reulting in the reflected evolution degree higher than the actural one and increasing in T^amx.The oxidated organic matter usually has higher conversion ratio under the same thermal condition.The reflectance of the vitrinite formed in strong oxidation condition is higher than in normal circumstance,and that in strong reduction condition reduces.Therefore,to study the evolution of organic matter in the southeast uplift,especially in Yingcheng Formation of the uplift in Songliao Basin,one could not make a conclusion according to a certain index.

CHARACTERS OF QUASI-FORELAND BASINS IN WESTERN-CENTRAL CHINA AND THEIR OIL AND GAS POTENTIAL

Yang Minghui, Liu Chiyang

2000, 21(1): 46-49. doi:10.11743/ogg20000111

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Quasi-foreland basins is a kind of complex reformed basins in Western and Central China which are actually superimposition of prototype basins formed in different stage.The basins were effected by different tectonic settings and controlled by stress fields during basin evolution,thus forming different sedimentary systems and sequences.Hence,tectonism and sedimentation were main factors controlling multiphase hydrocarbon generation and multiphase pool-forming of the basins.The development processes of the basins consiste of two stages of hydrocarbon generation and pool-forming conditons,and the sedimentary sequences themselves also possessed source-reservoir-cap rock complex conditions.To explor oil in this kind of basins,one should pay attention to hydrocarbon generation conditions,study the conditions of pool-forming and late preservation of the pools.

MULTI-MECHANISM OF HYDROCARBON GENERATION OF CHINA'S PETROLIFEROUS BASINS

Guo Zhanqian, Yang Xingke

2000, 21(1): 50-52,64. doi:10.11743/ogg20000112

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The hydrocarbon generation mechanism of China's petroliferous basins could be divided into organic mechanism,inorganic mechanism and synthetic mechamism due to their sources.Excepting zonal hydrocarbon generation model,kitchen and catalytic models of organic hydrocarbon generation mechanism should be taken into considerable account.The kitchen model means that the eruption and intrusion of igneous magma resulted in the acceleration of maturation of organic matter in sediments.Calalytic model means that elements such as Pd,Fe,Mn,Zn,Cu etc.could improve the combination of carbon and hydrogen and produce more hydrocarbon.This calalytic model might exist in Songliao Basin,Dagang and Xinjiang Oilfields.The important indication of inorganic hydrocarbon generation mechanism is the antitone of carbon isotopic ratio in methan homologue,this has been proved in Tarim and Songliao Basins.Experiment results indicate that CO₂ and H₂ could be synthesized into methane hydrocarbon with melten iron as medium.Basalt,olivine basalt and peridotite buried in deep strata may act just as the melten iron in laboratory.Therefore,there should be the case of synthetic hydrocarbon generation mechanism in deep of the earth.

TECTONIC EVOLUTION AND POOL-FORMING REGULARITY IN TAINAN SAG

Li Zhijun, Li Bin, Chen Hui

2000, 21(1): 53-56. doi:10.11743/ogg20000113

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Tainan Sag underwent Jratak and Bogda foreland two depression stages.The sag has been a secondary sag on the north dip slop of Turpan-Harmi Basin since Late Permian.The study area underwent three big transformation:(1)the northward transformation from Jratak foreland basin to Bogda foreland basin in Early Permian;(2)uplifting and denudation in the end of Taodonggou Group sedimentation;(3)tectonic inversion,denudation,fault-block dip and disintegration in Late Indosinian-Early Yenshan Period.The above mentioned transformations determined the characteristics of the source rocks in Tainan Sag such as restricted distribution,lower thermal evolution degree,small source potential and predominant with lower maturity of thick crude oil.Therefore,the oil of huge thick oil pools of Lukqin structure belt should be mainly drived from Taibei Sag.Lukqin trap was formed in late Indosinian epoch and the oil pools were formed in the end of Indosinian-Early Yenshan Period.Then the oil was further thickenen,remigrated and destoried,thus causing Lukqin structural belt to be separated into many fault-blook thick oil pools and asphalt-plugged reservoirs.

STRUCTURAL EVOLUTION AND HYDROCARBON EXPLORATION OF LANLIAO FAULT BELT IN DONGPU DEPRESSION

Zhang Yamin, L? Yancang, Xu Linli, Wang Shikun Zhou Senlin, Song Jing, Wang Jingyun

2000, 21(1): 57-60. doi:10.11743/ogg20000114

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The formation and evolution of Lanliao fault belt in Dongpu Depression may be divided into two periods and five stages such as Mesozoic and Cenozoic Periods,and compression,iniital fracture,strong fracture,shrinkage and after vibration stages.Hydrocarbon trap types in Lanliao fault belt are various.According to oil and gas geological feature,the location of traps,the screening condition and the occurrence,the trap types could be divided into eight kinds,i.e.the nose structure,half-anticline,the upwarping lithologic trap,buried-hill trap,stratigraphic unconformity trap,the reef trap,the paleochannellithological trap and the nappe structural trap.Rich oil and gas source,favourable hydrocarbon migration conditions,the multi-passage,the subaqueous fan sandbodies and structure-controlling are the major factors of hydrocarbon accumulation.

ANALYSIS OF OIL-GAS POOL CHARACTERISTICS IN BAIYINCHAGAN DEPRESSION

Zhang Xinjian, Fang Jianming, Tang Wenzhong

2000, 21(1): 61-64. doi:10.11743/ogg20000115

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Oil-gas pools of Baiyinchagan Depression are principally distributed in the Middle and Upper parts of Tenggar Formation of Bayanhua Group,Lower Cretaceous.The reservoirs of thick oil is above the oil generation threshold,thin oil is below that.There main oil-gas pool types of the depression are:(1)the reverse drag-anticlin oil pools;(2)drape-anticlin oil pools;(3)fault-block and fault-nose oil pools.The pool types and scales are controlled by oil source sag,regional source-reservoir-cap rock complex,anticlinal structures or fault-blocks and sedimentary facies or sandbody types.

CHARACTERS OF LOWER CRETACEOUS RESERVOIRS AND OIL-GAS DISTRIBUTION IN CHAGAN REFORMED DEPRESSION

Wang Xinmin, Li Tianshun

2000, 21(1): 65-70. doi:10.11743/ogg20000116

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Lower Cretaceous in Chagan Depression developed mainly volcanic and clasticrock reservoirs.The clasticrock reservoirs are characterized by low maturities of composition and texture,high contents of rock debris and filling materials,multi-compositon of filling materials and multi-type cemention.The selective soultion of carbonate cement and compacting of volcanic rocks resulted in the development of secondary pores,thus forming available reservoirs in some sections of low porous and low permeable clastic rocks.Volcanic rock reservoirs are mainly formed by overflow basalt,incompletely filled pores,fractures and holes in it and they are favourable reservoir spaces.The distribution of oil layers in the reservoirs is controlled by the sandbody distribution of favourable facies zones and the sections where secondary pore developed.At the same time,high quality oil is an important reason for oil accumulation in reservoirs with poor reservoir physical properties.

CONTROLLING THE CHANGES OF DEPOSITIONAL SYSTEM TO HYDROCARBON DISTRIBUTION IN TAIBEI SAG, TURPAN-HARMI BASIN

Zhang Daisheng, Li Chengming

2000, 21(1): 71-75. doi:10.11743/ogg20000117

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Taibei Say was the depositional center of Turpan-Harmi Basin after Jurassic.Coal measures hydrocarbon source rocks were deposited in the early stage;the northern material source progressed southward continuously in a period of great prosperity while the southern material source retreated,thus forming a huge thickness regional mudstone caprock.The northern material source depositional system is above the cap rock and the southern material depasitional source is below it.They construct a good reservoir-cap rock complex.The changes in depositional systems controlled hydrocarbon distribution.Most of the hydrocarbon is distributed in the southern material source depositional system,while some small scale of secondary oil and gas pools are in the northern material source depostional system.The center of lake basin of decline stage controlled directly the distribution of shallow hydrocarbon pools.The tectonic activities of the late stage of the depression development could effect the regulation and reconstitution of hydrocarbon pools.

STRUCTURAL FEATURE OF M BASIN AND ITS RELATION TO OIL AND GAS

Wang Xiulin, Wang Wangquan, Li Suzhen, Zhang Yamin, Fang Jianming

2000, 21(1): 76-79. doi:10.11743/ogg20000118

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M Basin located in African Plate is a intracontinental fault-depressed basin developed on Pre-Cambrian basement during Meso-Cenozoic.The basin mainly consists of EW and NW directional tectonic systems.According to fault scales,their control over the basin and their formation and faulting times,the faults of the basin can be divided into five grades,which correspond to the three major evolution stages of the basin.The long-term inherited developed structural belts are favourable for oil and gas accumulation;the faults developed in late period did destruction to the pools formed in early period,and the traps formed in late period didn't possess pool-forming condition.Since faults developed well in the basin,oil and gas migrated vertically.The faults developed earlier(before AM Formation deposition)have sealing function.

CONTROLLING FACTORS OF SINIAN GAS POOLS IN CALEDONIAN PALEOUPLIFT,SICHUAN BASIN

Li Guohui, Li Xiang, Yang Xinan

2000, 21(1): 80-83. doi:10.11743/ogg20000119

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The formation and evolution of Caledonian paleo-uplift in Sichuan Basin possessed long-term and complicacy.This resulted in different pool-forming stages of Sinian natural gas of the uplift.The early stage of pool-forming occured in Indo-Chinese Epoch;the late stage was in Himalayan Epoch.Each pool-forming stage could be divided into three types i.e.high entrapment with high resistance,high entrapment with low resistance and low entrapment.The main controlling factors of Sinian gas pools in Caledonian paleo-uplift are high sealling capability,high position of the structure;strong tectonic deformation and a close interconnection between the late-stage formed traps and the paleo-reservoirs.

SELECTION OF FAVOURABLE BLOCKS FOR CARBONIFEROUS HYDROCARBON EXPLORATION IN QILIAN-ZOULANG-HELAN DEPRESSION

Sun Dongsheng, Bai Yubao, Yu Yuanjiang

2000, 21(1): 84-87. doi:10.11743/ogg20000120

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Qilian-Zoulang-Helan Region developed into a large depressed basin in Carboniferous Period.The main sedimentary facies were delta,shore and shoal sea facies.The basin underwent considerable reformation in the late stage of Carboniferous,it shrank in the end of Variscan Period,but its tectonic framework didn't change much;in Indo- Chinese Epoch,the basin was denuded seriously,Permian System was completely denuded due to strong fold,and Carboniferous System was also denuded in different degrees;in Yenshen Period,the basin began to disintegrate,but the Mesozoic distribution areas were favourable for preservation of Carboniferous System.The residual basins were deeply buried in Himalayan Period,and the Carboniferous System was piecemeal distributed in the depressed belts of orogenic zone.In eastern and southern depressions of Bayanhott Basin,the remained Carboniferous System is larger and thicker,and has more types of hydrocarbon source rocks with higher hydrocarbon generation potential,it should be taken as target area for oil exploration.

A NEW CALCULATING METHOD OF DENUDED AMOUNT FOR PROTOTYPE BASIN—WAVE ANALYSIS

Zhang Yiwei, Li Jingchang, Jing Zhijun, Liu Guochen

2000, 21(1): 88-91. doi:10.11743/ogg20000121

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There are plenty of traditional methods to calculate denuded amount of Prototype Basin,but the results of these methods can hardly reflect the real reason of lacuna.The wave analysis method is based on the principle from knowing to unknowing to establish the wave equation by sedimentary rate histogram of residual stratum in geological time profile,and then find out the periodic wave of stratum deposited in different stages,judge the reason and the amount of sedimentary lacuna.To use this new method,one have to select the study areas as evenly as possible first,then change the lithologic-thickness sections into lithologic-time sections according to original data analysis,and finally plot sedimentary rate curves,restore stratigraphic denudation amount.The method was used to analyse the Huayong Formation in Sanshui Basin.The results suggest that there had been sediments of Late Oligocene and Neogene,but all were denuded.The present boundary of the Sanshui Basin was acturally formed after 39 Ma

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