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1999 Vol. 21, No. 3

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DISCUSSION ON FORMATION AND EVOLUTION OF JURASSIC BASIN-PROTOTYPE OF QAIDAM BASIN
HU Shou-quan, CAO Yun-jiang, HUANG Ji-xiang, MOU Zhong-hai
1999, 21(3): 189-195. doi: 10.11781/sysydz199903189
Abstract(799) PDF-CN(466)
Abstract:
Qaidam Basin evolution has come down in one continuous line with Qaidam Massif development. Before and in Triassic period, the main part of Qaidam Massif rose stably, but rift zones developed and received marine rift-typed sediments only at southern and northern borderland. At the end of Triassic period, the marine sedimentation on Qaidam Massif (including its surroundings) has ended, and interior basin started to develop in Qaidam area. In the light of the plate-tectonic mechanism to form the nappe structural zones at southern and northern borders of Qaidam Basin, the two continental foreland-basins which developed separately at southern and northern borders of Chaidamu Basin have similar characters and unified formation cause though their scale is different. And the foreland-basins appeared piggyback model and developed gradually towards inside basin. In addition, a series of pull-apart basins have formed at western border of Qaidam Massif. Therefore, Jurassic basin-prototype of Qaidam Massif is a superimposed basin of foreland-basin and full-apart basin. From Cretaceous Period to Paleocene-Eocene, subsidence and sedimentation area migrated gradually towards inside basin because the major thrust belts were piggyback and developed towards inside basin. After Oligocene, the natures of foreland-basin and pull-apart basin were on longer evident due to intensive compression and inside basin flexure caused by collision of Indian plate with Eurasian plate. And the former foreland-basin and pull-apart basin turned into intensive structural deformation zone and local sedimentary area for Neogene and Quaternary.
A STUDY ON THE GEOLOGICAL CHARACTERISTICS AND GEODYNAMIC ORIGIN OF DONGYING MOVEMENT, BOHAI BAY BASIN
SHI Bu-qing, WU Zhi-ping, WANG Ji-xiang, ZHOU Yao-qi, DAI Qi-de
1999, 21(3): 196-200. doi: 10.11781/sysydz199903196
Abstract(584) PDF-CN(372)
Abstract:
Dongying movement in Bohai Bay Basin is an intensely regional tectonic movement occurred during late Paleogene. According to the geological features of Dongying Movement in Bohai Bay Basin and the research results of the former, this paper analyzed the potential geodynamic origins of Dongying movement. One is the effect of quick stretching of lithosphere, upwelling and temperature raising of upper mantle, the other is result of the flexibility discrepancy among upper, lower crust and lithosphere under crust during the lithosphere cooling. Furthermore, this paper illustrated the reason of transition of basin evolution style, i.e. from rifting and extension to uplifting and whole subsidence during Dongying movement of Bohai Bay Basin. Based on isostasy principle, this paper made out a correction method for the calculation of disconformity erosion amount. The possible influences of Dongying movement on the formation and accumulation of petroleum reservoir in Bohai Bay Basin were mentioned.
NEGATIVE INVERSION STRUCTURE IN THE JIYANG DEPRESSION AND ITS PETROLEUM GEOLOGICAL SIGNIFICANCE
CHEN Jie, DONG Dong, QIU Ming-wen
1999, 21(3): 201-206. doi: 10.11781/sysydz199903201
Abstract(651) PDF-CN(343)
Abstract:
The Jiyang Depression is an important Mesozoic-Cenozoic petroliferous basin in East China. In the past, it is always considered as a pure tensional fault basin. However, the latest descovery of negative inversion structure in the basin and its study show that the basin experienced alternate negative inversion and positive inversion stages in the early development period of the Mesozoic, and presents the characteristics of negative inversion structure on the whole. In this paper, the types and characteristics of negative inversion structure are studied, the "thin-based" and "bald-based" two types of negative inversion folds as well as "paranormal fault type" and "upper-normal and lower-reversed mixed type" two categories and four subcategories of negative inversion faults are identified, and the formation and evolution of the basin and the negative inversion structure are discussed. It is pointed out that the negative inversion structure has important significance to basin genesis, tectonic belt evolution, complex hydrocarbon accumulation-belt patterns, pool formation and prediction, etc.
STUDYING ON THE EVALUATION METHOD OF TRAP ACCUMULATION RELIABILITY
LUO Qun
1999, 21(3): 207-214. doi: 10.11781/sysydz199903207
Abstract(667) PDF-CN(266)
Abstract:
Reducing exploration risks to the lowest limit and raising the successful probability of exploration are always the aims which geological explorers long for day and night. As the direct targets of hydrocarbon exploration, the correctness of evaluation results for traps will be derectly related to the success or failure of hydrocarbon exploration. Reliable evaluation can effectively reduce exploration risks and raise exploration benefits. By summing up the evaluation methods of conventional traps and according to the theory of hydrocarbon accumulation systems, the theory of reliability is introduced into trap evaluation in this paper, and "the reliability of trap accumulation" and its evaluation train of thought are advanced for the first time. Based on the analysis of subjective and objective factors which affect the reliability of trap accumulation, the geological conceptive model, the mathematical model and the evaluation system for the evaluation of trap accumulation reliability are established. This makes an attempt to further approach the application of the reliability theory to hydrocarbon exploration.
SEDIMENTARY FACIES ANALYSIS ON THE LOWER PERMIAN ANGJIE FORMATION OF THE CUOQIN BASIN IN TIBET AREA
WANG Shao-lan, WANG Guan-min, CHEN Qing-hua
1999, 21(3): 215-218. doi: 10.11781/sysydz199903215
Abstract(652) PDF-CN(232)
Abstract:
The research of sedimentary facies is an important foundational work for the exploration and evaluation of petroliferous basins. According to data obtained from measured sections in Lajiadang, Juncang town, Nima county, Tibet, the lithological features, the types of sedimentary facies, the vertical sedimentary evolution of sections and the regional sedimentary characteristics of the Lower Permian Angjie Formation are analyzed in this paper. This formation is dominated by a set of sandstone-mudstone dark clastic rock series which belongs to marginal marine deposit at the end of the Gondwana Carboniferous-Permian glacier period. Its sedimentary type has the characteristics of both the stable deposit of Gondwana continent and the low energy deposit under coastal conditions, and mainly consists of a set of tidal-flat sedimentary assemblage whose sedimentary environment is related to short-period and small-scale inshore glacier activities.
SHATTERED BRECCIA OF THE UPPER SINIAN DENGYING FORMATION IN DAYONG, WEST HUNAN PROVINCE
GUO Jian-hun, WANG Fang-ping, LIU Gui, WANG Zheng-yong, GAO Zhen-zhong
1999, 21(3): 219-224. doi: 10.11781/sysydz199903219
Abstract(515) PDF-CN(332)
Abstract:
The vertical succession of carbonate rock's shattered breccia in the Upper Sinian Dengying Formation of Dayong, West Hunan province consists of five layers, from bottom to top including the underlying unshocked layer, the fissure layer, the microfold layer, the breccia layer and overlying unshocked layer. A vertical succession represents a seismic catastrophic event. It lacks liquefied homogeneous layers compared with the preexisting normal succession. This may reflects the fracturing mechanism of the more rigid rock body with higher solidification degree. Shattered breccia is a kind of better reservoir rock body. Centered on the fracture systems where earthquake took place, it forms a lithologic trap type thinning out towards bilateral reservoir rock body.
ANALYSIS ON THE UPPER DEVONIAN-TRIASSIC SEQUENCE STRATIGRAPHY IN THE TARIM BASIN AND ITS CONTROLLING FACTORS
WANG Yi
1999, 21(3): 225-231. doi: 10.11781/sysydz199903225
Abstract(671) PDF-CN(289)
Abstract:
The Devonian-Triassic stratigraphic sequences in the Tarim Basin can be divided into two megasequences, five supersequences and twelve sequences. The Late Devonian-Triassic regional geotectonic evolution underwent the local splitting and rematching of "the paleo-Xinjiang plate", and the Tarim Basin involved the Late Devonian-Early Permian back-arc rift and the Late Permian-Triassic foreland basin two stages. The megasequence Ⅰ is the product of the back-arc rift evolutionary stage, in which the supersequence ⅠA represents the deposit of downwarped basins in the craton and the supersequence ⅠB represents the basin-filling deposit of rift in the bacd-arc craton. The megasequence Ⅱ is the deposit of the foreland basin evolutionary stage, in which the supersequence ⅡA represents the filled deposit of peripheral foreland basins and the supersequence ⅡB adn ⅡC are the deposit of inland downwarped basins. Research reveals that tectonic process played a decisive role in the formation of most Ⅲ-order sequences. Only in the evolutionary period of the Late Devonian-Carboniferous passive continental marginal and craton basins, during which tectonics are relatively stable, did the global eustacy act a greater part in the formation of the sequences.
DEPOSITIONAL SEQUENCES OF YITONG GRABEN (EASTERN CHINA) AND ITS RESPONSE TO TRANSFORM-EXTENSIONAL PROCESSES
LU Yong-chao, REN Jian-ye, LI Si-tian, YE Hong-po
1999, 21(3): 232-236. doi: 10.11781/sysydz199903232
Abstract(683) PDF-CN(331)
Abstract:
The Yitong Graben is located in the north eastern segment of the Tertiary rift system in East China.The graben is bounded by a steep dipping transform fault on the northwestern side and subparallel normal faults on the southeastern side, with very thick marginal fan complexes indicating syntectonic sedimentation. The graben is infilled with Tertiary sediments up to 6000 m thick, in which a series of different scaled hiatuses and tectonic inversion events have been discerned during hydrocarbon exploration. According to regional and local conformities, the basin infill may be divided into three tectonic sequences, among which the major sequence TS2 is further subdivided into three sequences sets and fourteen subsequences. Based on the sequence stratigraphic framework, depositional system tracts are reconstructed. Integrative analysis of the depositional structural features showed that the regional tectonic stress system experienced a transformation from dextral transfersional-shear through thermal subsidence to sinistral compressional-shear with a general extensional setting. Extension and wrenching dominated the graben evolution and affected the depositional style in different evolutionary stages and the spatial configuration of depositional system. The conclusions have been applied with some success to prospection of reservoir and hydrocarbon source-rock distribution and lithologic-stratigraphic traps in this basin.
HISTORICAL ANALYSIS OF RESERVOIR FLUID AND STUDY OF HYDROCARBON ACCUMULATION PROCESS IN TUYUKE OIL FIELD
HUANG Zhi-long, DONG Xue-mei, LIU Guang-di
1999, 21(3): 237-241. doi: 10.11781/sysydz199903237
Abstract(581) PDF-CN(311)
Abstract:
The diagenetic fluid inclusion of reservoirs can reflect the physical and chemical conditions when fluid was trapped and provide important information about hydrocarbon inflow. By studying on fluid inclusion combined with the generation and expulsion history of source rocks, the inflow periods and accumulation process of hydrocarbon in Tuyuke oil field are analyzed in this paper. Research reveals that there are mainly two periods of hydrocarbon inflow process in the field. In which, the Lae Triassic-Early Jurassic is the key accumulation period.
PRESSURE STRUCTURE AND PETROLEUM DISTRIBUTION IN TAZHONG AREA
WANG Hong-jun, HUANG Xiao-ming
1999, 21(3): 242-245. doi: 10.11781/sysydz199903242
Abstract(575) PDF-CN(313)
Abstract:
Pressure separation is usually controlled by the following factors, such as subsidence rate, sediment types and diagenesis during the diagenetic evolution, as a result the pressure gradient is uncontinuous. According to the variation of gradient pressure structure can be divided. Pressure separation controlled the petroleum accumulation and distribution to a certain degree. This paper illustrated the viewpoint by example of petroleum reservoirs in Tazhong uplift, Tarim Basin.
ASSESSMENT OF GAS RESOURCES IN SHIWU-DEHUI AREA OF SONGLIAO BASIN
LONG Sheng-xiang
1999, 21(3): 246-250. doi: 10.11781/sysydz199903246
Abstract(542) PDF-CN(282)
Abstract:
Shiwu-Dehui area of Songliao Basin has favorable geological condition of forming gas pools, so it is one of most important areas for exploring and exploiting gas in China.Author identified the structure play of Quandou Formation and the structure play of Dengluku Formation and used FASPUM, a play assessment software, to assess gas resources of these plays. The result suggested that Quandou Formation and Dengluku Formation of the area were very rich in gas resource and had a very brilliant exploration prospect.
BEDROCK HYDROCARBON-BEARING CHARACTERISTICS AND POOL-FORMING CONDITIONS OF MAMUWUSU SAG IN BADAIN JARAN BASIN
LU Chong-ning, DUAN Chun-jie, KANG Xing-wen, LI Bao-lin
1999, 21(3): 251-255. doi: 10.11781/sysydz199903251
Abstract(659) PDF-CN(289)
Abstract:
There are several Paleozoic sags in Badain Joran Basin.The first two wells drilled in Mamuwusu sag of the northwestern part of the basin were all found good oil/gas show,which indicated the possibility of forming bedrock oil/gas pools.The source rocks is Jurassic,the unconformity surfaces and faults are the dominant migration pathway,and the bedrock shows relative good storage ability.There are a series of block traps of buried hills in the area and distribution of oil and gas is different in different parts.The bedrock oil-gas pools may be the important exploration targets in the basin.
ANALYSIS ON THE WATER-DRIVE MECHANISM AND DEVELOPMENT RESULTS OF ANSAI SUPERTIGHT OIL FIELD FTER WATER-OCCURRENCE
SUN Wei, QU Zhi-hao, LI Jing-feng
1999, 21(3): 256-260. doi: 10.11781/sysydz199903256
Abstract(727) PDF-CN(378)
Abstract:
On the basis of water-drive experiments with the micromodel of true sandstone,the water-drive mechanism and characteristics of the Ansai Chang-6 supertight reservoir after water-occurrence is observed and analyzed.It is considered that the Jiamin Effect exert a notable influence on the water-drive efficiency after water-occurrence,and is characterized by the increase of injection resistance and pressure.With the rising of injection pressure,the water-flow pathway formed before is "deadlocked" after injected water forms new seepage pathways,the oil drops left in pore throats only deform and are difficult to migrate under the impact of additional capillary resistance.Affected by the anisotropy of reservoir pore structure,the seepages of fluid in the Chang-6 reservoir only have effects on part well-interconnected macro-pores.When injected water is 0.5-0.8 times of pore volume,water occurs in all oil wells.the continuous jaming-colesing-rejaming process of the oil drops left in water-flushing pathways under hydrodynamic action is one of the ways to raise the oil-expulsive efficiency after water-occurrence.The water-drive patterns in fissure-developing zones mainly depend on whether pore permeability,fissure permeability and displacement pressure are high or low.
RESERVOIR GEOLOGICAL AND DEVELOPMENT CHARACTERISTICS OF TIGHT AND SUPERTIGHT MARGINAL OIL FIELDS——A CASE STUDY OF CONTINENTAL OIL FIELDS IN THE MESOZOIC BASINS OF NORTH LIAONING PROVINCE
YAO Guang-qing, PAN Lin, GUAN Zhen-liang
1999, 21(3): 261-265. doi: 10.11781/sysydz199903261
Abstract(651) PDF-CN(222)
Abstract:
The marginal oil field is a common type of oil fields in continental strata.As there are small reserves,low accumulation energy and poor reservoir quality in oil fields,many defficulties emerge when developing this kind of oil fields.Recent years,a lot of continental tight and supertight marginal oil fields were discovered in the Mesozoic (Upper Jurassic) basins of North Liaoning and Nei Monggol,among which Majiapu,Liao-1 district and Bai 3-4 district are three typical tight and supertight oil fields.In this paper,the reservoir characteristics of this kind of marginal oil fields are emphatically discussed,the reason why reservoirs have low permeability is analyzed,and the reservoir dynamic characteristics of tight oil fields are summarized.On this basis,strategies for reasonable development of marginal oil fields are suggested.
FRACTURES IN THE MUDSTONE OF TIGHT RESERVOIRS
ZENG Lian-bo, XIAO Su-rong
1999, 21(3): 266-269. doi: 10.11781/sysydz199903266
Abstract(832) PDF-CN(384)
Abstract:
In tight reservoirs,lime,mica,calcareous and other brittle mineral often exist because the composition of mudstone interbeds is impure.This greatly heightens the brittle degree of mudstone,and makes it liable to form fractures under tectonic stress.So tectonic fractures are relatively developed in mudstone.Different series and different dips of tectonic fractures in mudstone interbeds are interconnected with nontectonic fractures often to form the 3-D network ststem of fractures.This makes the permeability of mudstone interbeds greatly increased and the fractures in mudstone commonly have better oil-bearing features.Thus,the mudstone in tight reservoirs generally cannot perform a true sealing function and can be classified as quasireservoirs or fractures reservoirs of mudstone.Their accumulation patterns are massive.
REE GEOCHEMICAL CHARACTERISTICS OF THREE TYPES OF COALS IN THE EARLY PALAEOZOIC IN SOUTHERN CHINA
GAO Chang-lin, YE De-liao
1999, 21(3): 270-272. doi: 10.11781/sysydz199903270
Abstract(644) PDF-CN(297)
Abstract:
There are lots of bone coal,sapropelite and shungite in the Early Palaeozoic Erathem in southern China.There are different geochemical characteristics in major,micro and REE elements in the bone coal,sapropelite and shungite.The bone coal,sapropelite are rich in Al,Fe,Ca,Mg K,Na,P,Sr,Cu,Zn,Co,Cr and REE,and the shungite is poor in the above elements. There are an abvious positive-Eu anomaly in the shungite and a negative-Eu anomalies in the bone coal and sapropelite.The sapropelite and bone coal are sedimentary origin and the shungite is the product of petroleum evolution.
PRELIMINARY EXPERIMENTAL STUDY ABOUT EFFECT OF DEFORMATION ON ORGANIC MATURITY
ZHOU Jian-xun
1999, 21(3): 273-277. doi: 10.11781/sysydz199903273
Abstract(637) PDF-CN(296)
Abstract:
Three kinds of coal samples were coaxially deformed with Griggs-type rock experiment apparatus under high temperature and confining pressure. The vitrinie reflectance of original samples is 4.90% (coal sample L), 3.41% (coal sample X) and 0.67% (coal sample J) respectively. Phyrophyllite was used as confining pressure medium. Strain rates were kept constant during each experiment. The temperature condition is 350～700℃ and the confining pressure range is 400～600MPa. The shape of samples is column with 19mm in diameter and 40mm in length. Samples were kept open to outside during experiment so that produced gas can be vented out continually. In this paper some questions about effects of structural deformation on organic maturity are discussed by analysis to the changes of vitrinite reflectance in the samples which are of different strain and stress but of same temperature and confining pressure and near deformation time. It is indicated that increase of vitrinite reflectance is of positive relationship to stain. This result is similar to that of Mastalerzs (1993) study (although there are some differences in sample and condition of apparatus between these two studies) and further proved that structural deformation can promote the level of organic maturity. Deformation, as compared with time and temperature, is a subsidiary factor to organic maturity. Deformation alone can not cause the increase of organic maturity. Although the effects of hydrostatic pressure are more complicated, it appears to impede the increase of organic maturity in this experimental study. Strain seems to be more important than stress although it is still hard to respectively distinguish their effects on organic maturity by experiment. Although mechanisms of coaxial deformation promoting coalification are not clear yet, flattening of existing pores and mechanical rotation of aromatic lamellae are not likely to be the principal mechanisms. The possible origin may be that coaxial deformation promotes balance reaction equation of coalification to its positive direction.
SEPARATION METHODS OF PYRROLIC COMPOUNDS IN CRUDE OIL
LI Su-mei, ZHANG Ai-yun, WANG Tie-guang, GU Sao-hui, SHI Quan
1999, 21(3): 278-282. doi: 10.11781/sysydz199903278
Abstract(657) PDF-CN(392)
Abstract:
Two isolution methods of pyrrolic nitrogen fractions in crude oils are introduced and evaluated.The emphasis is emplaced on the experimental result of the method of column liqulid chromatgraphy using native and foreign solvent.The result showed that it was practicable to use native solvents instead of foreign ones to separate pyrrolic nitrogen fractions.

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