1999 Vol. 21, No. 4

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STRUCTURAL CHARACTERISTICS OF THE MESO-CENOZOIC BASIN AND RANGE PROVINCE IN SOUTHEAST CHINA
XU Han-lin, SHEN Yang, DING Xiao, XU Jia-wei
1999, 21(4): 285-290. doi: 10.11781/sysydz199904285
Abstract:
Basin and range structure developed during the Meso-Cenozoic period in Southeast China was controlled by those pre-existed fault systems.There are three fault systems in the area with NNE-NE, nearly E-W, NW strikes.Based on the characteristics of the basins, there are three types of basins in the area: graben, listric faults and transform-extension.The characteristics of the basin and range province in Southeast China is shown by longitudinal blocks in S-N and cross zones in E-W.Formation of basin and range province in Southeast China was mainly resulted from geodynamic evolution of west marginal-Pacific tectonic domain, and from collision and squeezing of Indian plate with Euro-Asian continent.
THE DIAGENETIC EVOLUTIVE LAW OF DEEP BURIAL STRATA AT SHAHEJIE FORMATION IN EASTERN AND WESTERN DEPRESSIONS OF LIAOHE OIL FIELD
YU Xing-he, ZHANG Dao-jian, LI Sheng-li, LEI Ming, GAO Jian-jun, SUN Hong-bin, MENG Wei-gong
1999, 21(4): 291-296. doi: 10.11781/sysydz199904291
Abstract:
The development of secondary porosity of sandstones has evidence law at deep burial strata of Shahejie Formation in eastern and western depressions of Liaohe oil field. The eastern depression has three secondary porosity zones in vertical, but western only two. The secondary porosity zone of the second member lower to the third member top of Shahejie Formation, viz the upper secondary porosity, is the result of leached by surface fresh water and integrated process along unconformity interface later period by inorganic acid in open water circulation. The mechanism of lower two zones of secondary porosity is similar to two secondary porosity in western depression which silicate mineral had been made solution by organic acid in seal water circulation. The geological conditions of these two zones forming are following as:temperature is about 100 to 130 Celsius, pressure coefficient is 1.2 to 1.3 around, the phase and depth are during source rock had made abundant expulsion hydrocarbon.
PETROLEUM GEOLOGY AND EXPLORATION PROSPECT OF LEIDONG DEPRESSION IN SOUTH CHINA SEA
YANG Mu-zhuang
1999, 21(4): 297-301. doi: 10.11781/sysydz199904297
Abstract:
Leidong depression is situated in the stable, isolated, close and high geothermal geological setting, with fairly good source rocks, reservoirs, traps and cap rocks. The hydrocarbon was in favor of generation, gathering and preservation. The total hydrocarbon producted is *-**×108t, the total gathering is ****×104t. In addition, the exploration and development condition is favorable due to it is near shore, with shallow and smooth bottom. So, the oil and gas exploration is worth making progress in this area.
TRAP TYPES AND THEIR GENESIS ANALYSES OF WAN’AN BASIN IN SOUTH CHINA SEA
LIU Bao-ming
1999, 21(4): 302-306. doi: 10.11781/sysydz199904302
Abstract:
Five types of traps, including compressional, extensional, shearing, gravitative and strata-litholoical types, were divided on studying the feature of different tectonic movements, seismic sequences and depositional property in Wan'an Basin. The author have simulatesd their evolution relationship based on two sections in the north and south of the basin respectively. Furthermore, the genesis of traps was analyzed. It will provide some evidence for studying petroleum geology in the basin.
ANALYSIS ON THE POOL-FORMING CONDITIONS OF NATURAL GAS ACCUMULATIONS IN THE KUQA DEPRESSION
ZHAO Lin, QIN Sheng-fei
1999, 21(4): 307-310. doi: 10.11781/sysydz199904307
Abstract:
By comprehensive analysis on the characteristics of petroleum geology in the Kuqa Depression in this paper, it is pointed out that the Kuqa Depression has good pool-forming conditions for natural gas. The Kuqa Depression is rich in gas sources, and has favorable gas-source conditions to form giant gas fields. Fractures play an important controlling role in the formation of gas accumulations. They link deep gas sources to shallow reservoirs, and are main pathways for the vertical migration of natural gas. Late pool-forming periods and the Tertiary undercompacted mudstone forming large area of pressure sealings are advantageous to the preservation of natural gas. The generation, migration, accumulation, trap formation and other essential factors of natural gas in the Kuqa Depression are well disposed. This is advantageous to the formation of large-medium scale gas fields. Therefore, it is the favorable area in the Tarim Basin for prospecting large-medium scale gas fields.
RESERVIOR CHARACTERISTICS OF YAKELA BLOCK IN THE NORTHERN TARIM BASIN
WANG Mei-ling, ZHAO Ao-shan, LU Yuan-e
1999, 21(4): 311-315. doi: 10.11781/sysydz199904311
Abstract:
There are two kinds of reserviors consisting of clastics and carbonates in Yakela Black. Reser-viors in the Lower Paleozoic are dominated by carbonate rocks with fracture as storing space, which are favorable for hydrocarbon accumulation. Clastic reserviors were developed in the Lower Carboniferous, Mesozoic and Cenozoic. Donghe sandstones in the Lower Carboniferous was fair reservior worsening east-toward. Quality of reserviors in the Mesozoic and Cenozoic was controlled by their sedimentary environments.
RULES OF TRAP TYPES AND SPACE ASSEMBLAGES IN THE AIXIEKE-SANGTAMU HYDROCARBON ZONE OF THE TARIM BASIN, XINJIANG
YUE Jian-hua, KANG Zhi-hong, HAN Yan-ying
1999, 21(4): 316-319. doi: 10.11781/sysydz199904316
Abstract:
In the Ai-Sang zone, traps of various types are well developed. Main trap types include fault anticlines, block buried hills, salt diapirism anticlines, low-extent compressive anticlines and nontectonic traps. Among them, the traps related to rock body occupy an important position. The Late Hercynian, the Indosinian-Yanshanian and the Himalayan tectonic movements formed a series of traps in the zone. And significant breakthroughs in petroleum have obtained in the Ordovician, the Carboniferous and the Triassic traps.
GENESIS AND SIGNIFICANCE OF LOW-RESISTIVITY RESERVOIRS IN THE TRIASSIC OIL AND GAS ACCUMULATIONS OF TAHE OIL FIELD IN THE TARIM BASIN
LI Guo-zheng
1999, 21(4): 320-323. doi: 10.11781/sysydz199904320
Abstract:
The Triassic productive intervals of oil and gas in Tahe oil field belong to low-resistivity reservoirs.According to the study of logging,geological,testing and analytical data,it is considered that lithology,mineralization degree,pore structure,bound water content,conductive mineral,interstitial (colloform) structure,mudstone interbeds and mud performance are important factors directly affecting the formation of low-resistivity reservoirs. Also, the practical significance of studying and distinguishing low-resistivity reservoirs is suggested.
A PRELIMINARY APPROACH TO THE CLASSIFICATION OF OIL AND GAS RESERVOIRS IN IGNEOUS ROCKS
XIAO Shang-bin, JIANG Zai-xing, CAO Ying-chang, QIU Long-wei
1999, 21(4): 324-327. doi: 10.11781/sysydz199904324
Abstract:
Based on the study of characteristics for the Cenozoic igneous rock distribution and discovered oil and gas reservoirs in igneous rocks in the Bohaiwan Basin and according to the analysis of features for tectonic evolution, igneous rock distribution and magmatic activity in this paper, the history of the Cenozoic magmatic activity in the basin is divided into two cycles, and the oil and gas reservoirs in igneous rocks are classified as uplifting-leaching, burying-dissolution, tectonic fracture, pyroclastic rock, igneous rock body lateral-screening, contact-metamorphic and overlapping-draping seven types. On this basis, the location in stratigraphic sections, lithological features and physical property characteristics of each type oil and gas reservoirs are discussed in detail combined with examples.
KINETIC CHARACTERISTICS OF HYDROCARBON GENERATION ON THE PALEOZOIC COAL IN THE EAST MARGIN OF THE ORDOS BASIN
TANG Da-zhen, LIN Shan-yuan, WANG Ji-liu, LIU Da-meng
1999, 21(4): 328-335. doi: 10.11781/sysydz199904328
Abstract:
Based on the variation of kinetic parameters such as average apparent kinetic energy, maximum ratio of hydrocarbon generation and its corresponding main kinetic energy, main interval of hydrocarbon generation,combined with analysis of coal metamorphic process, several evident stages during a pyrogenic hydrocarbon generation of the Paleozoic coal in the east margin of the Ordos Basin has been elaborated here, i.e. early pyrolysis (0.5%<Ro,m<0.8%), metaphase pyrolysis (0.80%<Ro,m<1.65%)and terminal pyrolysis(Ro,m>1.65%). In the study area, the secondary hydrocarbon generation would be more beneficial to formation, accumulation and conservation of coalbed methane when the superimposed metamorphism of the Yanshan Period exerts the coals under the rank of 0.95%Ro,m.
SYNTHETIC EVALUATION OF SOURCE ROCKS IN SOUTHWEST DEPRESSION OF THE TARIM BASIN
DING Yong, GONG Ji-ping, WANG Hui
1999, 21(4): 336-339. doi: 10.11781/sysydz199904336
Abstract:
There mainly are 5 series of source rocks, including horizons in Upper Tertiary, Upper Cretaceous-Lower Tertiary, Middle-Lower Jurassic, Permo-Carboniferous and Cambrian-Ordovician, in Southwest Depression of the Tarim Basin. The depocenter of Cambrian-Ordovician lay in Awati sag and Tanggubasi sag, in which source rocks with high abundance of organic matter, good types and high maturity were developed. They formed the main source rocks in the depression. Source rocks in Permo-Carboniferous are characterized by wide distribution, varying in abundance and type of organic matter, middle to high maturity. The Jurassic and Lower Tertiary source rocks were mainly distributed in Kasi sag and the southwest margin of the depression, and the Upper Tertiary ones in the mountain front of Yecheng sag.
CHARACTERISTICS OF SOURCE ROCKS AND RESOURCE PROSPECT IN THE LUNPOLA BASIN, TIBET
GU Yi, SHAO Zhi-bing, YE De-liao, ZHANG Xiao-ying, LU Ya-ping
1999, 21(4): 340-345. doi: 10.11781/sysydz199904340
Abstract:
The source rocks of the Lunpola Basin were developed in the Tertiary Niubao formation and mainly in N-2 and lower N-3 members and some in upper N-3 member of the formation. Distribution of source rocks was controlled by sedimentary facies with deep- and subdeep-lake facies were their major developing area. The thickest source rocks were in Jiangri-Acuo depression. Source rocks were characterized by medium abundance of organic matter, good parent type and relative high maturity. Since the end of Eocene, there has been favorable source condition for hydrocarbon accumulation, and the early hydrocarbon came from N-2 member and the late one from lower N-3 member. In a word, there is good resource prospect in the Lunpola Basin.
PRINCIPLE AND APPLICATION OF ESTIMATION ON THE DISTRIBUTION OF A SET OF SUBSURFACE FRACTURES BY CORE DATA
YIN Zhong-min, SHAN Ye-hua
1999, 21(4): 346-351. doi: 10.11781/sysydz199904346
Abstract:
A new method to estimate the distribution of a set of subsurface fractures by core data is suggested in this paper.In order to find out optimum distribution of fractures with a given distributive pattern,the pattern must be known in advance.When estimating the distribution of generally undetermined subsurface fractures,the method mentioned above can be used repeatedly selecting different distributive patterns in turn. Then,the respective minimum target function values are compared. Among them, the one with minimum can be considered as the best approximation to practical fracture distribution. Case applications show that if fracture patterns are selected properly, the estimated results from the above-mentioned method are close to measured values;the best estimates for practical fracture distribution can be obtained theredy.
AN APPROACH TO THE SIMULATION EXPERIMENT OF HYDROCARBON GENERATION AND MIGRATION
CHEN Qiang-lu, LIU Yi, ZHU Mei-qian
1999, 21(4): 352-356. doi: 10.11781/sysydz199904352
Abstract:
In this paper, the process of hydrocarbon generation and evolution in the four thermal evolutionary stages (low-mature, mature, high-mature, overmature) of geohistory is simulated by selecting low-mature hydrocarbon source rocks and using the method in which hydrocarbons are generated from artificial pyrolysis and petroleum migration is controlled properly. In the experiment, the hydrocarbons generated from pyrolysis are appropriately classified as drained and occluded hydrocarbons which correspond to the amount of hydrocarbons in geologic body entering reservoirs by primary migration and the amount occluded in parent rocks and evolving continuously together with parent rocks, respectively. The generation of hydrocarbons can be divided into four stages with continuous evolution, from unmature to overmature stages, and the migration into three concentrated stages; that is, the geological process of geologic body during which hydrocarbons generate and migrate simultaneously is simulated as multistage generation and concentrated migration, Thus, the possible distribution of hydrocarbons in reservoirs in different evolutionary stages and under different migration efficiency can be obtained.
STUDYING ON THE SIMULATION MODEL OF STAGE-BY-STAGE HYDROCARBON EXPULSION
ZHANG Wei-hua, CHEN Rong-shu, CHEN Xi-feng, TANG Jin-liang
1999, 21(4): 357-363. doi: 10.11781/sysydz199904357
Abstract:
A new-type practical hydrocarbon-expulsion model is suggested in this paper. According to this model, hydrocarbon expulsion can be divided into monofactor and bifactor two stages. During the monofactor hydrocarbon-expulsion stage, oil saturation is the only controling factor to the expulsion of hydrocarbons, and the driving force of hydrocarbon expulsion is compaction; in the difactor hydrocarbon-expulsion stage, the expulsion of hydrocarbons is doubly controlled by critical oil saturation and critical fracturing pressure, and the driving force of hydrocarbon expulsion is fluid overpressure. This breaks through the limitations to monostage or monofactor hydrocarbon-expulsion simulation before, refrains from studying on complex facies during hydrocarbon expulsion, and avoids the accumulation of errors. The key of the model is dividing standards of the two stages, the determination of critical oil saturation (Sc) and critical fracturing pressure (pc), and the acquirement of fluid overpressure. This model has obtained good application effects during the quantitative evaluation on the hydrocabon source rocks of the Jiazhangsi Sag in the eastern depression of the Liaohe Basin.
ESTIMATION OF LIGHT COMPONENT LOSSES DURING THE FORMATION OF HEAVY CRUDE OIL IN THE TARIM BASIN
RAO Dan, LIU Yi
1999, 21(4): 364-368. doi: 10.11781/sysydz199904364
Abstract:
Various kinds of heavy crude oil is widespread in the Tarim Basin, especially in marine oxidized residual oceans where its distribution is to a considerable scale. In this paper,geochemical indexes are used to estimate the percentage of crude oil losses so as to find out about the accumulation scales of paleo-pools and to provide reliable data for the hydrocarbon reserve calculation of the basin. Heavy crude oil plays an active role in searching other types of accompanying pools or useful mineral resources together with its forming reasons and periods.
A NEW FORMULA FOR FORMATION GRAIN DENSITY
LI Shao-hu, WU Chong-long, MAO Xiao-ping, ZHANG Qiong-yan
1999, 21(4): 369-371. doi: 10.11781/sysydz199904369
Abstract(1009) PDF-CN(368)
Abstract:
Based on the compaction model of sandstone-mudstone alternating beds, we advance a new formula for formation grain density, which conforms to grain volume and mass balance law. Based on the porosity-depth function and the density-depth function, we can use the new formula to calculate the grain density of formation upon the basement. The calculating result can be used to replace the paleo-formation grain density to calculate the paleo-formation average density (ρs) which is very important to tectonic subsidence.The traditional formula indicated that sandstone percent is the only affecting factor to the formation grain density. The new formula hints that formation grain density is affected by sandstone percent, average sandstone porosity and average mudstone porosity. Further, the decisive factors to the formation grain density are average density and average porosity of the formation.
A NEW METHOD FOR DETERMINING FRACTAL DIMENSION OF PORE STRUCTURE
HE Yan, WU Nian-sheng
1999, 21(4): 372-375. doi: 10.11781/sysydz199904372
Abstract(1111) PDF-CN(498)
Abstract:
There is fractal property in reservior rocks. According to the principle of the fractal geometry, the pore structure can be studied, and the fractal model of the capillary pressure curve and the relative permeability and the pore throat distribution can be set up. But the pore structure can be predicted when the fractal dimension D has been acquired. At present, the fractal dimension is acquired by the scanning electron microscopy. But it is not easy to use it to calculate D. Based on proposed fractal capillary pressure model, the fractal dimension D is predicted by capillary pressure data. The practical data verifies the validity of this method and the method is simpler than scanning electron microscopy.