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2004 Vol. 26, No. 5

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COALBED METHANE EXPLORATION THEORY AND PRACTICE IN THE HIGH COAL RANK AREAS OF CHINA
LIU Hong-lin, ZHAO Guo-liang, WANG Hong-yan
2004, 26(5): 411-414. doi: 10.11781/sysydz200405411
Abstract(821) PDF-CN(479)
Abstract:
There is obvious difference between the distribution of coalbed methane in the U.S. and in China, based on the comparison between origination condition. Large amount of coalbed methane resource is distributed in the high coal rank area of China, especially in the North and South China. Postsedimentary tectonic activities may lead to high permeability and high gas content. These potential sweet points could be found through detailed geologic study. Guided by this theory, the first coalbed methane gas field in China located in the high coal rank area was discovered in the 1990s, which has edriched the theory and expanded the exploration scope of coalbed methane.
COMPLEXITY CAUSES EXPLANATION AND CHARACTERISTICS ANALYSIS OF OIL AND GAS DISTRIBUTION IN THE SEDIMENTARY BASINS OF CHINA
TONG Heng-mao, CAO Dai-yong
2004, 26(5): 415-421. doi: 10.11781/sysydz200405415
Abstract(756) PDF-CN(350)
Abstract:
From 9 aspects, the complexities of Chinese sedimentary basins are discussed, including: 1)large quantity, small size, wide distribution; 2)multiplicity in basin types, with geodynamic setting widely changed; 3)poly-stage basin superimposition and basin composition; 4)terrestrial sedimentary basin being dominant; 5)large quantity and intense activity of faults; 6)strong post-stage rebuilding; 7)frequent magmatic activity; 8)high speed sedimentary, with deposition center migrating with time; 9)asymmetry in geothermal fields. The complexity causes of Chinese sedimentary basin are analyzed, and it is pointed out that, complicated plate tectonic situation and evolution history are the fundamental reasons. Finally, the unusual characteristics of oil and gas distribution in Chinese sedimentary basins are briefly discussed.
CAUSES OF SUBNORMAL PRESSURE IN THE SEDIMENTARY BASINS
ZHANG Li-kuan, WANG Zhen-liang, YU Zai-ping
2004, 26(5): 422-426. doi: 10.11781/sysydz200405422
Abstract(2031) PDF-CN(607)
Abstract:
The forming mechanisms of subnormal pressure can be divided into 4 types: 1)increase in pore volume caused by tectonic uplift and formation erosion, or chemical effects of pore water; 2)fluid flowing out due to the release of overpressure in seal formation, unhomogeneous flow, osmosis across semipermeable shale membranes and diffusion of light hydrocarbon; 3)deep burial of saturated gas reservoir; 4)piezometric surface lower than ground surface. In some sedimentary basins in which large-scale tectonic uplift has taken place, the main cause of low pressure may be the removal of overburden, which results in dilation of pore volume with the consequent reduction in stress and temperature. Subnormal pressure in the small-scale uplift area is mostly related to the diffusion of light hydrocarbon and the burial of saturated gas reservoir. The release of overpressure seems to be a probable mechanism; however, it is a question how low pressure can be preserved. The chemical effect and osmosis effect of pore water are self-limited, which may not be the major factors in subnormal pressure system. Aside from unhomogeneous flow, other mechanisms require good seal, otherwise pressure will be equalized to normal hydrostatic. The low pressure is not a true meaning subnormal pressure, because that the piezometric surface is lower than the ground surface, but people give a wrong assumption in the course of showing the relative size of pressure.
CHARACTERISTICS OF THE CENOZOIC STRUCTURAL EVOLUTION IN THE NORTH OF THE DONGYING SAG, THE BOHAIWAN BASIN
XIE Rui-jie, QI Jia-fu, WANG Yong-shi, YANG Qiao
2004, 26(5): 427-431. doi: 10.11781/sysydz200405427
Abstract(882) PDF-CN(459)
Abstract:
Based on the equilibrium section principle and by decompaction correction, the profiles of the Cenozoic structural evolution in the north of the Dongying Sag, the Bohaiwan Basin and the paleostructural maps of the subface of the Sha-3 Member before the sedimentation of the Sha-1 Member and the Guantao Formation were compiled. Starting with the evolution profiles and the plane paleostructures, the characteristics of the Cenozoic structural evolution in the study area were summarized systematically. The study showed that the present subface structural configuration of the Sha-3 Member was formed before the sedimentation of the Sha-1 Member, and decollement faults were developed in the caprocks of the study area. The results were of good reference values for the studying of structural evolution process of the similar areas.
BACKGROUND AND PROTOTYPE OF THE MESO-CENOZOIC BASINS IN HEXI CORRIDOR REGION
LUO Kai-ping, FAN Xiao-ling
2004, 26(5): 432-436. doi: 10.11781/sysydz200405432
Abstract(786) PDF-CN(471)
Abstract:
Many different types (prototype) of Meso-Cenozoic basins have been formed in Hexi Corridor region on Qilian Caledonian folded basement in a long-term N-S compression environment since Indosinian Movement. The fomation, distribution and structure of basins were controlled by mass accretion, oceanic crust subduction and inplate deformation induced by phrase terrane collision in Neo-Tethys Ocean, and also closely related with Qilian fold system and the inhomogeneous intracontinent block activities in/between adjacent land masses. The different inplate deformation mechanism in the different periods of Cenozoic and different stages of basin formation dominated the development of different types and styles of basins (prototype).
FRACTURES OF THE ORDOVICIAN LIMESTONE AND THEIR RELATIONSHIP WITH HYDROCARBON ACCUMULATION IN THE SANGTAMU FAULT BELT OF THE TARIM BASIN
YANG Wei, WEI Gui-qi, GU Qiao-yuan, YANG Wen-jing, ZHU Deng-chao, PENG Shi
2004, 26(5): 437-441. doi: 10.11781/sysydz200405437
Abstract(622) PDF-CN(381)
Abstract:
Sangtamu fault belt was located at Tabei uplift in Tarim basin. A lot of oil and gas resource was discovered in the Ordovician limestone of buried hill. Reservoirs are pore-fracture type. Many fractures were developed in the reservoirs. Average fractures density in cored inteval is 3.3 strap per meter. The fractures are characterized by small, oblique and half-filled ones. Two belt of fractures were vertically developed with the first one located under uncomformity surface. Its thickness is 20～50m. The second one is located below 100m of the first belt. Its thickness is 50～80m. In different position of fault belt, development level of fractures is different, and fracture is more developed inside the fault belt than the outside. Unconformity surface and lithology infleunced the vertical distribution of fractures. There is close relationship between hydrocarbon accumulation and fractures. The location with little fractures is poor for oil and gas production. Fractures are principal contributor of permeability and porosity of ressrvoirs. They supplied for 99.4% of total permeability and 12% of total porosity.
TRANSFORMATION DYNAMIC FORCES AND HYDROCARBON ACCUMULATION OF THE YINGEN-EJINAQI BASIN
WANG Xin-min, LI Xiang-bo, GUO Yan-ru, LI Tian-shun
2004, 26(5): 442-447. doi: 10.11781/sysydz200405442
Abstract(776) PDF-CN(518)
Abstract:
Three dynamic forces-ground stress, gravity and thermal dynamic force cause the transformation of basin and influence the hydrocarbon accumulation in the Yingen-Ejinaqi Basin. The transformation effect of ground stress is shown in 4 ways: uplift, extrusion, expansion and strike slip. Among which, the uplift postpones hydrocarbon accumulation in the denudation area, thus the thermal evolution of source rock remains the state before denudation, which is favorable for the preservation of palaeoaccumulation early generated and discharged. The extrusion effect results in fold, fracture and even tectonic reversal, offering not only various traps for hydrocarbon accumulation, but also force and passage for hydrocarbon migration. The expansion effect is shown by superposition of the Early Cretaceous rifts on the Jurassic ones. This transformation promotes the thermal evolution of Jurassic source rock, helping organic matters in source rock convert to hydrocarbon and migrate and accumulate. Meanwhile, extentional linked fractures partially change or destroy the original preservation condition of palaeoaccumulation, forming (secondary) hydrocarbon accumulation. The large-scale strike slip effect may form a series of transtensional and compresso-shear tectonic patterns, resulting in strike-slip pull-apart basin in the strike-slip expanding subsiding belt, and transforming preliminary basin. The influences on bydrocarbon accumulation include: a) providing environment and condition for accumulation; b) transformation and destruction. The gravity transformation effect is shown by deep burial and compaction, providing terrestrial heat field, geopressure field and preservation condition for hydrocarbon generation and accumulation. The quick occurrence of deep burial is also helpful for confining liquid pressure, resulting in abnormal overpressure, which is favorable for preserving primary pore, generating secondary pore and forming pressure seal, thus promoting hydrocarbon generation, migration and accumulation. The transformation effect of thermal dynamic force is shown by the transformation of sedimentary cover by multistage magma intrusion and effusion activity, providing favorable condition for hydrocarbon generation and accumulation.
PETROLEUM GEOLOGY OF BASALT-SOURCE ROCK PARAGENETIC ASSOCIATION IN BINNAN AREA, THE DONGYING DEPRESSION OF THE BOHAIWAN BASIN
ZHAI Qing-long, JIN Qiang, ZENG Yi, WAN Cong-li
2004, 26(5): 448-451. doi: 10.11781/sysydz200405448
Abstract(683) PDF-CN(526)
Abstract:
Different scales of basalt was developed in the major hydrocarbon-generating strata of Binnan area, the Dongying Depression of the Bohaiwan Basin, which composed basalt-source rock paragenetic association. In the association, the source rocks which were enriched with organic matter were composed of calcareous argillutite and oil shale lithologically, and the basalt which developed vesicles and solution pores was good re-servoirs. During the long time of burial, the interaction of volcanic material (including transition metals) with organic matter brought about catalysis and hydrogenation in the hydrocarbon-generating process of organic matter, and resulted in the generation of large amount of hydrocarbons at lower temperature. Meanwhile, the basalt underwent intense alteration under the action of organic acids, and formed a great amount of reservoir spaces. Therefore, the basalt-source rock paragenetic association is a very good habitat for oil and gas accumulation.
RESERVOIR FORMING MECHANISM OF LIANGJIALOU OILFIELD, THE DONGYING DEPRESSION
HAO Xue-feng, SONG Guo-qi, ZONG Guo-hong, ZHUO Qin-gong
2004, 26(5): 452-456. doi: 10.11781/sysydz200405452
Abstract(730) PDF-CN(380)
Abstract:
Effective source rock, passage system and infilling time are the chief study content of reservoir forming mechanism. Based on the conclusions of source rock contrast, passage system analysis, and reservoir infilling (history), it is pointed out that, effective source rock of the upper Es4 and middle-lower Es3 members is connected with reservoir of the upper Es3 member through growth faults, therefore faults play an important role in the passage system of Liangjialou oilfield. The main migration forces are seismic pumping caused by growth fault activities, and abnormal liquid overpressure caused by mudstone undercompaction and hydrocarbon generation. There is correspondent relation between the histories of fault activity and reservoir infilling. The mechanism of reservoir forming could be described as the episodic migration and infilling dominated by episodic fault activities.
EVALUATION OF NONSANDSTONE RESERVOIRS BETWEEN SALT BEDS OF THE PALEOGENE QIANJIANG FORMATION IN THE QIANJIANG DEPRESSION OF THE JIANGHAN BASIN
WANG Guo-li, ZHANG Yong-sheng, YANG Yu-qing, QI Zhi-xian
2004, 26(5): 462-468. doi: 10.11781/sysydz200405462
Abstract(587) PDF-CN(400)
Abstract:
Based on Ⅳ-order rhythms as the basic scale (scale: several to dozens of centimeters), the authors have, for the first time, made a detailed description and study of nonsandstone reservoirs between salt beds distributed widely in the Qianjiang subbasin, Jianghan basin, in respect to reservoir rock types, reservoir pore spaces, physical properties of reservoirs and vertical distribution of reservoirs and draw the following conclusions: Ⅳ-order rhythms and their association in relatively diluted intervals are the most promising reservoirs in which accumulations with industrial oil could occur. Among all types of reservoir rocks, dolostones have the highest porosity (average 19%) and lowest permeability (average 25.3×10-3μm2), mudstones have a medium porosity (average 13.4%) and the highest permeability (average 68.8×10-3μm2), and glauberite rock has the lowest porosity average 10.6%) and a medium permeability (average 36.2×10-3μm2). These data indicate that the permeability is not absolutely positive relative to the porosity but mainly relative to the pore texture and fractures. The porosity of reservoirs is influenced by the glauberite content. When the glauberite content is from 10% to 50%, the porosities of dolostones and mudstones decline with increasing glauberite content, and when the glauberite content is above 50%, glauberite forms glauberite rock and its porosity are maintained at about 10%. This suggests that the view that the porosity is positive relative to the glauberite content in dolostones is incorrect. Most nonsandstone reservoirs) between salt beds commonly have small pore throats and poor permeability. So if we want to develop) them effectively, it is necessary to improve their permeability according to the typical dissolution behaviors) of evaporite minerals.
DEPOSITIONAL SYSTEM OF THE THIRD MEMBER OF THE SHAHEJIE FORMATION IN LENGJIA OILFIELD OF THE LIAOHE BASIN
LAI Sheng-hua, YU Qian, MA Jian-ming
2004, 26(5): 469-473. doi: 10.11781/sysydz200405469
Abstract(743) PDF-CN(390)
Abstract:
With seismic facies analysis and core data, distribution of depositional system of the 3rd Member of the Shahejie Formation in Lengjia oilfield of the Liaohe Basin, is studied. According to seismic reflection structure, it can be divided into 3 types: slope, plat form and depressed area, including 16 seismic facies. Based on fan-delta front and pro-fan delta, slump deposition, island in the center of lake, sand bank, longitudinal fan, slope progradation complex, slope fan, sublacustrine fan and barrier system are found. Longitudinal delta is developed in the north, fan-delta in the east, and slope progradation complex in the west.
DISCUSSION ON THE HYDROCARBON SOURCE ROCK CHARACTERS OF THE LIULAOBEI FORMATION ON THE FRINGES OF THE HEFEI BASIN
ZHANG Jiao-dong, LIU De-liang, HUANG Kai-quan, CAO Gao-she, QIU Lian-gui, LEI Min
2004, 26(5): 474-478. doi: 10.11781/sysydz200405474
Abstract(668) PDF-CN(463)
Abstract:
Based on the data of outcrops and wells on the fringes of the Hefei Basin and the synthetical analyses of stratigraphic characters, organic geochemical indexes and lithofacies paleogeography, the authors believed that the organic abundance of the Liulaobei Formation reached the standard of hydrocarbon source rocks. Its matrix type was Ⅰ-type kerogen, it mudstone was thick, its hydrocarbon percent conversion was high, and its hydrocarbon productive amount was great. Though the organic material of the Liulaobei Formation was overmature, it can still split into condensate oil and humid gas. So, it was suggested that the Liulaobei Formation can be considered as the gas source rock of the Hefei Basin. Besides, based on the stratigraphic and geophysical data, it was inferred that the Liulaobei Formation was existing in the inner of the Hefei Basin. These conclusions provided theoretical bases for exploring gas pools in the Hefei Basin.
2004, 26(5): 478-478. doi: 10.11781/sysydz200405478
Abstract(600) PDF-CN(337)
Abstract:
SAND PRODUCTION PREDICTION DURING THE DEVELOPMENT OF SANDSTONE OILFIELDS
DUAN He-hai, SHI Huan-dian, LI Xiao-liang, WANG Qing-kui
2004, 26(5): 479-483. doi: 10.11781/sysydz200405479
Abstract(958) PDF-CN(395)
Abstract:
The reservoir of Wangguantun oilfield is a rapidly deposited fan-delta sandbody near source area. Because of fine lithology, thin layer, poor diageneses and loose reservoir structure, sand production is quite common in production wells. The problem of sand production is discussed from the aspects of sedimentary microfacies, reservoir heterogeneity, rock microstructure and development measure, and the mechanism, reason and law of sand production are found. Through quantitative analysis, the sand production layer and area are predicted, and the technique methods for controlling sand production are proposed, that is, sealing off sand layers in serious sand production wells, avoiding the thin oil layers and the top of thick oil layers during gun perforation in new wells, and controlling flood pressure and injection allocation.
VARIATION OF CARBON ISOTOPIC COMPOSITION OF KEROGEN DURING THERMAL EVOLUTION
XIONG Yong-qiang, ZHANG Hai-zu, GENG An-song
2004, 26(5): 484-487. doi: 10.11781/sysydz200405484
Abstract(1030) PDF-CN(533)
Abstract:
Purpose of this study is to reveal the variation characteristics of kerogen during thermal evolution by determining the residual rate of kerogen and the carbon isotopic composition of residual kerogen at (different thermal) (evolution) stages, thus providing evidence of carbon isotope for quantitative identification and assessment of effective gas source rock. The result indicates that, at the early stage of methane (generation) (Ro1.5%), kerogen (obviously) enriches in 13C with the increasing of thermal evolution, up to 3.8‰. However, when Ro reaches 1.5%-2%, δ13C values of residual kerogen display a trend of slight depletion in 13C, varying within about 2‰. When the thermal maturity is higher (Ro2%), the variation of carbon isotopic composition is less than 0.8‰ for residual kerogen.
DISTRIBUTION OF NITROGEN COMPOUNDS AND CHARACTERISTICS OF HYDROCARBON MIGRATION IN THE YANQI BASIN
NAN Hong-li, LI Yong-lin, ZHAO De-li, TIAN Hong-ling
2004, 26(5): 488-491. doi: 10.11781/sysydz200405488
Abstract(730) PDF-CN(380)
Abstract:
Nitrogen compounds can be used as indexes indicating oil and gas migration. This paper discussed the application of nitrogen compound content to the migration of oil and gas in the Yanqi Basin. The results of analyses on some parameters of pyrrolic nitrogen compounds in the Yanqi Basin showed that there existed the migration fractionation of pyrrolic nitrogen compounds in the Jurassic crude oil. From hydrocarbon generating centers outward, the concentration of nitrogen compounds changed from high to low. The migration fractionation effects of pyrrolic nitrogen also existed in the same structural zone. It was showed that the hydrocarbon of Baolang oilfield migrated from south to north on plane and from deep to shallow longitudinally.
ANALYSIS METHOD OF LIGHT HYDROCARBOS WITH LOW BOILING-POINT FROM SOURCE ROCKS
JIANG Qi-gui, CHEN Wei-jun, JIN Ju-chang, RAO Dan, ZHANG Zhi-rong
2004, 26(5): 492-495. doi: 10.11781/sysydz200405492
Abstract(909) PDF-CN(434)
Abstract:
The most difficult thing in oil-gas-source rock correlation with fingerprints of light hydrocarbons is obtainment of light hydrocarbon extracted from source rocks. With a low boiling-point solvent, rock samples was extracted in a closed pot and analysed by high resolution gas chromatography using capillary columns. The results showed that this method could give out information of C5 to C31+, and could discrimanete over 100 hydrocarbons between C5 and C10 to satisfy the study of petroleum geology. It is ideal for correlation among oil, gas and source rocks.
EXPLOITATION METHOD OF A MULTI-LAYER WIDE TRANSITIONAL ZONE OILFIELD
YANG Zhi-xing ZHUANG Xin-guo
2004, 26(5): 496-499. doi: 10.11781/sysydz200405496
Abstract(651) PDF-CN(337)
Abstract:
The Xiwang 1-B oilfield is a multi-layer wide transitional zone oilfield which is located in South China Sea waters. The simultaneous exploitation in pure oil areas and transitional zones enhanced the control area of wells and the sweep efficiency of the whole oilfield. The best perforation percentage of the wells which are located in the oil layers with bottom water or in transitional zones is about 30%-40%, but the blocking action of sandwich layers and caliches to bottom water must be fully considered. The oil wells that are located in the pure oil areas with distance less than 200 m from edge water must properly avoid being perforated. Reasonable proration is important during well production. It can obtain good production effects to utilize the center casing string with packers inter layers, which controls each measures production, not only combined production but also single zone production. It becomes simple to exploit oil measures and easy to get well information by the individual layer sand control method.
CORE SCANNING IMAGE ANALYSIS AND ITS APPLICATION
LIU Ning, CHEN Pan-feng, ZHENG Sheng-li, XU Chun-hua
2004, 26(5): 500-504. doi: 10.11781/sysydz200405500
Abstract(592) PDF-CN(450)
Abstract:
The core scanning image analysis is a new technology of core observation generally rose with the rapid development of information sciences recently. From core scanning, image treatment and geologic analysis three respects, the technology was introduced systematically, and the methods of core image treatment and related sedimentary structural parameter calculation were expounded. Combined with examples, pore and fracture targets were picked up and related parameters were calculated automatically by core images. In the case of well Chegu-201, by core observation and core scanning image analysis and combined with laboratory rock and mineral identification and conventional petrophysical property testing, the pore development and oil-bearing characteristics of the Ordovician carbonate rock reservoirs in the Lower Paleozoic of the well were studied comprehensively.

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