Lithologic Reservoirs

Petroleum exploration of Huanghua Depression is very concerned due to the discovery of Nanpu Oilfield. Based on the deep crust structure features, there are double lowvelocity layers in the mid-crust, with depth of 15 km and 20 km respectively. It is known that the lowvelocity layer ofmid-crust is rich in gases （such as CO2, CO, H2 etc.） which can synthesized into hydrocarbons under the moderate temperature and pressure conditions. The mantle fluid activities （such as alkaline metasomasis and Mg 2+ metasomasis） and the mantle source CO2, CH4 and He gases （Gang 151 well） in the basin imply that they came from the deep hydrothermal fluids. Several buried hill structures developed in Huanghua Depression, such as Shenqingzhuang, Kongdian, Beidagang, Nandagang, Yangsanmu and so on. According to the inorganic genetic hypothesis, there are some large oil and gas reserves in the deep buried hills, rather than in the Tertiary sandstone lithologic reservoirs.

Typical gas reservoirs and main controlling factors of reservoir-forming of Upper Triassic Xujiahe Formation in central Sichuan Basin

XU Zhangyou，SONG Li，WU Xinsong，CHEN Ce

2009, Vol.21(2): 7–11 Abstract ( 504 ) PDF (415 KB) ( 692 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.002

Tongnan, Bajiaochang and Guang’an gas reservoirs are analyzed, which respectively represents the natural gas reservoir characteristics of the second, the fourth and the sixth member of Upper Triassic Xujiahe Formation in central Sichuan Basin. The research indicates that the gas reservoir-forming is characterized by short distance migration and accumulation of hydrocarbons in this area. The types of gas reservoirs in northern part are structural and structural-lithologic gas reservoirs, in central and southern part are lithologic and fractural-lithologic gas reservoirs caused by the distribution of ancient monadnock and palaeohigh, and in the western slope is mainly fractural-lithologic gas reservoir. Good source rocks provide enough hydrocarbons for gas reservoirs forming by means of distance migration and accumulation, large faults are the key factors for natural gas preservation, and ancient monadnock, palaeohigh and slope are effective areas to accumulate natural gas. This research provides theoretical basis for gas reservoirs exploration in Xujiahe Formation in central Sichuan Basin.

Division and evaluation of sand body assemblages：An example from Shan 2 and He 8 member of Upper Paleozoic in Ordos Basin

ZHANG Manlang，LI Xizhe，GU Jiangrui，XIE Wuren

2009, Vol.21(2): 12–17 Abstract ( 466 ) PDF (1025 KB) ( 379 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.003

Reservoir properties and gas-bearing properties vary significantly while sandstone is single-layer sand body or multilayer sand bodies assembled in different ways. Based on the fine evaluation of sandstone reservoir, sand body assemblages of Shan 2 and He 8 member in Ordos Basin are classified and evaluated. By analyzing well logging and core description, sand bodies can be divided into two categories and 16 different types of sand body assemblages. For different sand body assemblages, well logging and seismic response models are set up, and the reservoir characteristics and gas-bearing properties are evaluated. The results showthat thicker single sand body has better gas-bearing property than composite sand bodies, and that single sand body or composite sand bodies of distributary channel, underwater distributary channel and mouth bar have high porosity and gas-bearing property. Sedimentary system of braided river and braided delta is identified in He 8 member in Sulige area. The physical property of channel bar sand body is moderate-poor, and gets better downward to the delta plain and delta front. The single sand body of distributary channel in delta plain and superimposed sand bodies of distributary channel have the best properties. In Shan 2 member of Yulin area, single sand body and composite sand bodies of underwater distributary channel and mouth bar have the best physical properties. Single sand body of distributary channel and overlapping sand body have better properties. Through the sedimentary system, physical property becomes poor fromchannel center to channel flank.

Controlling factors of lithologic reservoirs of Sha 3 member in West Sag of Liaohe Depression

GUO Yongqiang，LIU Luofu

2009, Vol.21(2): 19–23 Abstract ( 455 ) PDF (506 KB) ( 519 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.004

West Sag of Liaohe Depression is a representative hydrocarbon-rich sag in eastern China, with a high degree of exploration. The deep stratigraphic-lithologic reservoirs are the main exploration targets in the further exploration of West Sag, and the lithologic reservoirs are considered tomainly distribute in the third member of Shahejie Formation. It is believed that lithologic reservoirs are mainly controlled by three factors, including effective source rocks, turbidite sand body distribution and hydrocarbon migration. Based on the analysis of petroleum accumulation factors, the favorable zones of the lithologic reservoirs of the third member of Shahejie Formation are predicted, and the most favorable zone is in Qingshui sub-sag ofWest Sag and the surrounding areas.

Study on horizontal heterogeneity in Serie Inferiere of Triassic in 438b block , Algeria

WEI Qinlian，ZHENG Rongcai，XIAO Ling，MA Guofu，DOU Shijie，TIAN Baozhong

2009, Vol.21(2): 24–28 Abstract ( 462 ) PDF (704 KB) ( 542 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.005

Based on the analysis of core, logging and drilling, the sedimentary characteristics of braided channel in Serie Inferiere of Triassic in 438b block are analyzed. Combined with porosity, sand density, onrush coefficient, variation coefficient, permeability graded difference and frequency-interlayers, the entropy weight method is used to calculate the heterogeneous synthetic index in Serie Inferiere ofTriassic. The distribution map of reservoir heterogeneity is drawn based on sedimentary facies. This method can take fully advantages of entropy weight method, and it can accurately characterize the horizontal heterogeneity.

Carbonate ramp facies and sedimentary evolution of Middle Jurassic Buqu Formation in northern Qiangtang Basin

XIA Guoqing， YI Haisheng， HUANG Huagu， LI Junpeng

2009, Vol.21(2): 29–34 Abstract ( 481 ) PDF (499 KB) ( 472 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.006

Different viewpoints have been proposed about the sedimentary environment of Jurassic Buqu Formation in northern Qiangtang Basin. Based on the geological settings, paleogeomorphological features and the sedimentary characteristics of Buqu Formation in Qiangtang Basin, it is confirmed that Buqu Formation belongs to carbonate ramp sedimentation. Based on outcrop observation and description, combined with lithofacies analysis, the ramp is divided into three kinds of subfacies, including inner ramp, mid-ramp and outer-ramp, and seven kinds of microfacies, such as tidal flat, lagoon and shallowshoal etc. The sedimentary facies sequences and evolution of this period are established.

Provenance analysis of Shuixigou Group in southern margin of Junggar Basin

WAN Yanzhou，ZHOU Lifa，BAI Bin，XIE Qifeng，PU Lei

2009, Vol.21(2): 35–41 Abstract ( 486 ) PDF (483 KB) ( 616 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.007

Based on systematic analysis of conglomerate constituent, paleocurrent direction, detrital composition, heavy mineral and major element, the provenance characteristics of Shuixigou Group in southern margin of Junggar Basin are studied. The analysis of conglomerate component of Shuixigou Group shows that Yilinhabierga Mountain, northern Tianshan Mountains and northern margin fault of central Tianshan Mountains were the source areas in the sedimentary period of Badaowan and Xishanyao Formation. The paleocurrent analytical data of Shuixigou Group show that paleocurrent directions ofBadaowan Formation and Xishanyao Formation are mainly northeast and west, soYilinhabierga Mountain is the primary source area. The paleocurrent directions of Sangonghe Formation are mainly SSW and SE, which indicates that Bogda Mountain and Yilinhabierga Mountain are not the primary source area in that period. Shuixigou Group in the western and eastern segment of the southern margin of Junggar Basin has heavy mineral assemblage of basic magmatic rocks, which shows that the material supply might be from the northern Tianshan Mountains. The middle segment of the southern margin of Junggar Basin has genetic features of medium-acidic magmatite and basic magmatic rocks, which shows that the source area is in Bogda Mountain.

Controlling factors of hydrocarbon accumulation of Lenghu No. 3-5 structural belt in northern Qaidam Basin

ZHANG Zhenggang，YUAN Jianying，YAN Cunfeng，MA Xinmin

2009, Vol.21(2): 42–44 Abstract ( 405 ) PDF (423 KB) ( 418 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.008

Based on the research of Lenghu No.3- 5 structural belt, it is concluded that hydrocarbon accumulation of this structural belt is mainly affected by the following factors: ① the residual Lower Jurassic located in the western Lenghu area provides material foundation for the hydrocarbon accumulation of this structural belt; ② the Lower Jurassic which acts as the hydrocarbon source rocks was buried properly, and there exists an ideal matching of structure configuration and large scale hydrocarbon generation stage; ③ tectonic evolution of the residual hydrocarbon-generation depression makes Lenghu structural belt become the advantageous structural belt; ④ the tectonic setting of Lenghu structural belt has the characteristics of higher in north and lower in south, which results in that the Lenghu No. 3- 4 structural belt is better than Lenghu No. 5 structural belt in reservoir formation. It is indicated that Lenghu No. 3- 5 structural belt is still the advantageous direction of oil and gas exploration in this area.

Meteoric water karstification controlled by sequence unconformity of Cambrian-Lower Ordovician in Tazhong area

LI Yuxiang，LI Guorong，GU Yanwu，PAN Zhongliang，JIANG Zhongzheng,HU Wenyan，TANG Hongwei，LUO Peng

2009, Vol.21(2): 45–48 Abstract ( 451 ) PDF (315 KB) ( 475 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.009

The Cambrian-Lower Ordovician is mainly carbonate sediment in Tazhong area of Tarim Basin. Affected by sedimentary facies, the early meteoric water karstification under the control of the sequence unconformity boundary developed well. Based on the analysis of core, rock slice, carbon and oxygen stable isotope, strontium isotope and cathodoluminescence, the characteristics of petrology and mineralogy , geochemistry and karstification of the early meteoric water karstification are discussed. The early meteoric water karstification model under the control of the sequence unconformity boundary ofCambrian-Lower Ordovician in Tazhong area is established.

Fracture characteristics and geological significance of Upper Triassic Yanchang Formation in Jiyuan area，Ordos Basin

LIANG Xiaowei，HAN Yonglin，WANG Haihong，WANG Chengyu，NIU Xiaobing，XIN Honggang

2009, Vol.21(2): 49–53 Abstract ( 504 ) PDF (651 KB) ( 621 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.010

Natural fractures developed well in sandstone reservoirs of Upper Triassic Yanchang Formation in Jiyuan area, Ordos Basin. The fractures are high angle tectoclase generated in the slight tectonized areas. These fractures are generallyNW-SE striking, though some are NE-SWstriking. Lowpermeability sandstone reservoirs and the Yanshanian Movement are the key elements for the formation of these fractures. Because of the existence of the tectoclase, a uniquely petroleum migration and accumulation model is formed in this area: petroleum migrates to upper reservoirs through fracture multipoint; meanwhile, the distribution of oil reservoir is multi-area in horizon, and many oil reservoirs in vertical in the same areas.

Petroleum geologic characteristics and exploration orientation in Halahatang Depression of Tabei uplift

CUI Haifeng，ZHENG Duoming，TENG Tuanyu

2009, Vol.21(2): 54–58 Abstract ( 424 ) PDF (675 KB) ( 883 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.011

In order to investigate the conditions of hydrocarbon accumulation, the characteristics of petroleum geology have been analyzed in Halahatang area. There developed Cambrian and Ordovician source rocks. The Middle-Upper Ordovician source rocks are good and nowmainly in the mediummature evolutionary phase. There are several series of reservoir-seal assemblages. The one consisted of Carboniferous Donghe sandstone, breccia and overlyingmudstone and limestone, and the other one consisted of Ordovician limestone and Silurian mudstone are more favorable. Palaeozoic is a nose structure in the westward plunging end of Lunnan lower uplift. The nose structure has always been in the relatively higher position of structural belt since Hercynian as the oriented region of hydrocarbon migration. Several series of cap rocks developed well, which have good conditions for late Caledonian-early Hercynian hydrocarbon preservation. The results obtained showthat there is a good exploration prospect in Halahatang area.

Reservoir characteristics of the second member of Triassic Jialingjiang Formation of Shuangmiaochang structure in Daxian-Xuanhan area of northeastern Sichuan

LIN Hui

2009, Vol.21(2): 59–63 Abstract ( 449 ) PDF (708 KB) ( 615 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.012

The characteristics of rock association, reservoir properties, pore structure, diagenesis, seismic response and thickness distribution of Jia 2 reservoir in Shuangmiaochang structure are expounded. It is concluded that Jia 2 reservoir is mainly composed of dolomite, and the reservoir is mainly fracture-pore type with good reservoir properties. The reservoir space is mainly intercrystalline solution pore and fracture. The seismic response characteristic is continuous and parallel medium frequency and middle-high amplitude with 2 or 3 phases. The reservoir thickness is thinner, general of 25 to 40 m.

Volcanic reservoir characteristics and genetic mechanism of Carboniferous in Niudong area of Santanghu Basin

LIU Juntian，LIU Yuanping，GUOMozhen，QIN Xinping，YAN Ligang

2009, Vol.21(2): 64–69 Abstract ( 552 ) PDF (960 KB) ( 620 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.013

Based on the petrological characteristics and sequence features, the volcanic facies and logging response characteristics ofCarboniferous inNiudongarea are analyzed. There are four volcanic facies in the the studyarea: effusive facies, eruption facies, empty accumulative facies and volcanic sedimentary facies, which can be well distinguished by logging curve GR and DEN. And volcanic sedimentary facies can get better response by Rt. The volcanic reservoir spaces include primary and secondary accumulation spaces. The primary accumulation spaces mainly include air pores, intercrystal pores, shrinkage pores and fractures. The secondary accumulation spaces mainly include dissolved pores, structural fractures and weathered fractures. The main factors for forming high quality volcanic reservoirs are magma composition, effusive facies belt and later reformation. Andesite, formed by intermediate rock with high viscosity, slow fluidity and slowgas dispersion, is the optimum reservoir. The end period of eruptive cycle is the favorable period for forming amygdaloid body, gas hole and auto-fracture. The weathering and eluviation in the period of eruptive cycle provide forming conditions for various corrosion pores. The genetic mechanism of volcanic reservoir space is of significance for seeking volcanic reservoirs.

Sedimentary facies analysis of Cambrian-Ordovician in eastern Tarim Basin

HU Jiuzhen，RAN Qigui，LIU Shugen，SUNWei，WANG Dong，ZHANG Changjun

2009, Vol.21(2): 70–75 Abstract ( 410 ) PDF (850 KB) ( 499 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.014

On the basis of sedimentary facies of single well, seimic data, as well as surface outcrop data，core observation，cutting logging and thin section analysis, the sedimentary facies in eastern Tarim Basin are defined, including abyssal facie, bathyal-contourite drift facies, near-shore deposits and carbonate platform. Several sub-facies and micro-facies are also recognized. Based on analysis of sedimentary microfacies, the sedimentary models, distribution and evolution in Early Cambrian-Middle Ordovician are analyzed. It is believed that plateau- basin model mainly developed in Early Cambrian in the east, and it is more obvious in Middle-Late Cambrian. Until Early-Middle Ordovician, the sedimentary facies in the study area is of typical trisection units, which are deep water aulacogen in middle part, carbonate platform and slope facies in the west and east. At the edge zone of platform and deep sea basin, reef flat reservoir developed, which is favorable for reservoir development. There also developed many types of diagenesis, and the destructive diagenesis is dominated one.

Reservoir characteristics and distribution of T₁ j₂ of Zhaigouwan structure in eastern Sichuan

ZHANG Yongzhen, ZHANG Fan，WANG Xingzhi，MA Xiangjun，YU Yang，PU Rui

2009, Vol.21(2): 76–81 Abstract ( 454 ) PDF (925 KB) ( 575 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.015

Based on the outcrop features and conventional petrophysical properties, the reservoir characteristics of T1j2 of Zhaigouwan structure in eastern Sichuan are studied. The result shows that the reservoir rocks are mainly composed of crystal grain dolomite and particle dolomite. The reservoir spaces are mainly intercrystal pores and dissolved pores.The reservoir properties are poor. The reservoir types are fracture-pore and pore-fracture. Reservoirs mainly developedin T1j22 along longititudinal direction, less in T1j21 and partly in T1j23. Reservoirs of T1j22 developed well in Zhaigou 2 well and Zhaigou 4 well, while reservoirs of T1j21 developed well in Zhaigou 4 well. Sedimentation not only controls the development and distribution of reservoir, but also affects the basic pattern of reservoir and the type and intensity of diagenesis. It is the dominated factor controlling the reservoir development. Diagenesis determines the reservoir space and reservoir performance, and directly influences the forming and evolution of pore space. Tectonism provides conditions for the above activities.

Study on volcanic facies of Tertiary Guantao Formation in Nanpu Sag

DU Yang，LUOMinggao，WANYAN Qiqi，MA Qian，ZHAO Zhongxin

2009, Vol.21(2): 82–86 Abstract ( 470 ) PDF (611 KB) ( 568 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.016

Above the basement of North China platform, Nanpu Sag is a dustpan-like sag developed by fault-block movement during the Mesozoic and Cenozoic. The lithology of volcanic rocks is mainly composed of basalt and tuff. Based on the division of rock flow unit and rock flow group, explosive index and thickness are adopted to divide the lithofacies. The result shows that effusive facies is the main lithofacies in the study area, and outbreak is mainly concentrated in the vicinity of the eruption center. The distribution of volcanic rocks is studied, which provides basis for the further study on volcanic reservoir.

Seismic processing and logging recognition technology of volcanic reservoir in Niudong area of Santanghu Basin

LI Quansheng

2009, Vol.21(2): 87–90 Abstract ( 425 ) PDF (960 KB) ( 545 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.017

Due to the strong nonhomogeneity of volcanic rocks, related recognition and prediction technologies are still one of the problems existing in oil and gas exploration. Based on the analysis of velocity, seismic reflection characteristics and three-instantaneous information, combined with the techniques of constrained inversion of sonic logging, the reservoir rocks in Santanghu Basin are divided into four types, including breccia, andesite, basalt and tuff. The horizontal distribution is firstly determined. The prediction of fissure reservoir is effectively carried out, which provides theoretical foundation and technological methods for the exploration and development of volcanic reservoirs.

Application of mercury injection data to Chang 6 reservoir classification in Changqing area

LI Yanshan，ZHANG Zhansong，ZHANG Chaomo，CHEN Peng

2009, Vol.21(2): 91–93 Abstract ( 480 ) PDF (356 KB) ( 496 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.018

Capillary pressure curve can be applied to study the characteristics of reservoir pore structure. Reservoir can be divided by using reservoir properties and pore structure characteristics. Chang 6 reservoir of Upper Triassic Yanchang Formation is studied. The result shows that the reservoir is of lowporosity and lowpermeability. According to the reservoir properties and structure characteristics, Chang 6 is divided into three types of reservoir, which provides reliable geological basis for further development.

Feasibility analysis of reservoir prediction in Sulige Gasfield

LIU Weihua，GAO Jianhu，CHEN Qiyan，DONG Xuehua

2009, Vol.21(2): 94–98 Abstract ( 493 ) PDF (744 KB) ( 572 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.019

The study area is located in Sulige Gasfield. The reservoir gas-bearing sand is close to shale in density, Pwave velocity and impedance. So, it is difficult to divide gas-bearing sand from shale using conventional reservoir prediction methods. Based on well logging data, combined with rock physics analysis, elastic impedance analysis and AVO analysis, the studies on reservoir prediction and fluid identification in Sulige Gasfield are carried out. The results show that the elastic physical parameters can be used to distinguish sand from shale and determine the gas-bearing sensitive parameter. Elastic impedance of different angles can be used not only to divide sand from shale, but also to distinguish gas-bearing formation fromnon-gas-bearing formation. AVOattributes can be used to determine whether He 8 member is gas-bearing sandstone, but can not be used to predict whether it is commercial gas. These studies provide foundation for reservoir prediction and fluid identification.

Can abnormal high pressure fracture the reservoir itself?

LI Chuanliang, CAO Jianjun

2009, Vol.21(2): 99–102 Abstract ( 529 ) PDF (293 KB) ( 461 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.020

Abnormal high pressure reservoir is one with a pressure coefficient over 1.2. The possibility of formation fracturing by the pore pressure of itself is discussed. The result shows that due to the pressure pressing between pores, pore pressure can never fracture the formation itself. The fractures in formations, if possible, are all resulted from the change of external pressure acting on the formations. The rock of highly abnormal pressure reservoir is quite tight, so the rock compressibility is not very high as researchers think usually, but takes quite lowvalue.

Application of linear regression method to analysis of oil and gas production rate decline

HE Jun，CHEN Xiaofan，YUE Ping，WANG Longfei

2009, Vol.21(2): 103–105 Abstract ( 528 ) PDF (250 KB) ( 846 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.021

The diagnosis methods for different types of production rate decline are studied. The methods are evaluated under the guidance of J. J. Arps production rate decline theory. Applying the linear relationship between output and time, we can edit programto linear regression, then compare the correlation coefficient and determine the decline type. The application result proves that this approach is simple and feasible.

Evaluation research of economic recoverable reserves

FENG Yina

2009, Vol.21(2): 106–109 Abstract ( 377 ) PDF (338 KB) ( 469 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.022

The general procedures of petroleum economic recoverable reserves calculation by cash flow method are summarized through the rationality of economic recoverable reserves evaluation unit division, the rationality of economic parameter value and the rationality of evaluation result. The questions and solutions in the process of taking value to investment and cost are also summarized.

Numerical simulation of mudstone creep under high pressure water flooding: A case study from SⅠ mudstone in anticline structure in northern Lamadian Oilfield

WU Shiyong，LI Zian，FANG Liang

2009, Vol.21(2): 110–112 Abstract ( 386 ) PDF (392 KB) ( 517 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.023

In consideration of the impact of reservoir pressure change on overlyingmudstone, finite difference method is applied to carry out the simulation study of mudstone creep on the top of SⅠ mudstone in anticline structure in northern Lamadian Oilfield. The result shows that the maximumhorizontal principal stress is of - 25.87～- 24.88MPa in a direction of near EW, while the minimum principal stress is of - 19.95～- 18.44 MPa in a direction of near SN. The change of strain and displacement mainly displays in vertical direction. The more near the oil layer, the greater the strain and displacement are impacted by reservoir pressure change. The maximum displacement （or variable） of mudstone creep all occurred on the contact interface with the oil layer. The study of maximum strain of mudstone creep is favorable for preventing and controlling casing damage in oilfield.

Geophysical response characteristics of coal bed methane

LIU Wenlin

2009, Vol.21(2): 113–115 Abstract ( 514 ) PDF (220 KB) ( 664 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.024

Coal bed methane has different petrophysics from conventional gas, and it absorbs in molecularity on the surface of coal. It is regarded as a component part of minerals contained in coal. The seismic velocity change resulted frommethane adsorbance is calculated. The result shows that P-wave velocity declined to 10%～16% due to the change of gas content, so it is also feasible using seismic technology to detect coal bed methane. The reflection amplitude has amplification effect on velocity change of coal, which conduces to detecting coal bed methane by using amplitude attributes. Using prestack inversion P-wave and S-wave impedance to calculate the elastic parameters of pore fluid can improve the detection accuracy of coal bed methane.

Exploration prospect of shale gas and coal-bed methane in Sichuan Basin

HUANG Jizhong

2009, Vol.21(2): 116–120 Abstract ( 747 ) PDF (401 KB) ( 911 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.025

The exploration of shale gas and coal-bed methane is an important field of the non-conventional gas exploration. The shale gas reservoir formed in dark-colored high-carboniferous argillaceous hydrocarbon source rocks with the mechanism of adsorption-dissolution-free existence. Based on the study result of hydrocarbon source rocks of Sichuan Basin, it is demonstrated that Longtan Formation ofUpper Permian is favorable to form coal-bed methane reservoir. The favorable areas are located in HuayingMountains, and its southeastern side and southern side. The strata of this region mainly contain bituminous coal with the superiority of high gas content and shallow burying. For low gas content, the coal measures of Upper Triassic Xujiahe Formation are favorable for the accumulation of shale gas. There are two advantageous areas: the one includes the periphery ofWeiyuan Anticline （which is located in southwestern Sichuan Basin） and the north part of southern Sichuan Basin, while another area is frontier area of Micang Mountain with shallow buried target. The argillaceous hydrocarbon source sequence of petroliferous strata, being favorable for the accumulation of shale gas, is Lower Jurassic. The favorable areas are located in the precipitous structural flanks and shallowburied fringe of northeastern and northern parts of Sichuan Basin. The dark-colored argillaceous hydrocarbon source rocks of Lower Silurian Longmaxi Formation and Lower Cambrian Qiongzhusi Formation are favorable for the accumulation of shale gas in early-middle maturation period. At present, these sequences are unfavorable to preserve shale gas, due to the sharply increased organic maturity and deeply buried target zones. In frontier side of Daba Mountain and northwestern fringe of Jiangnan Ancient Land, organic maturity has a trend of decrease, so these areas are favorable for accumulation of shale gas too.

Current status and progress of exploration technology for lithologic-stratigraphic reservoirs in China

WANGWei，LI Zhen，TIANMin，ZHOU Jincheng，LI Ning

2009, Vol.21(2): 121–125 Abstract ( 733 ) PDF (304 KB) ( 951 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.026

Lithologic-stratigraphic traps （reservoirs） in China are characterized by complex boundary condition, irregular shapes, subtle occurrence, complicated reservoir forming condition and various migration and accumulation mechanisms. At present, China has formed basic research methods including sequence stratigraphic analysis method and “three-phase” interpretation technology for lithologic reservoirs exploration, and multi-parameter comprehensive evaluation methods for seismic data, such as pre-stack seismic inversion technology, seismic attribute analytic technique, fluid potential analytic technique and oil and gas detection technology. It is proposed that we should strengthen fundamental geologic research and continuously improve the standard and criterion, attach importance to the organic integration of geological and geophysical exploration studies, timely organize key technology research and carry out technical storage for lithologic reservoirs exploration.

Discussion on dynamics of Fuyang reservoir in Songliao Basin

PAN Shuxin，WANG Tianqi，TIAN Guangrong，WANG Jiangong，GUO Weihua，MA Fengliang，ZHAO Wei

2009, Vol.21(2): 126–132 Abstract ( 551 ) PDF (682 KB) ( 643 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2009.02.026

Dynamics of Fuyang reservoir accumulation in SongliaoBasin are studied. Fuyang reservoir has character of episodic accumulation. Overpressure is not the main force of primary migration but seismic pumping. The oil column height is not associated with the size of overpressure. The episodic reservoir is mainly controlled by regional tectonic movement and faulting. Capillary pressure and buoyancy play an important role in oil secondary migration. Fuyang reservoir has the coexistence of conventional oil reservoirs and deep-basin reservoirs. The organic matching of buoyancy and regional tectonic evolution makes the oil column height obviously increased and makes the reserve abundance improved along the slopes around central depression, nose-shaped structure and anticline. Low overpressure zones in Changchunling can also form reservoir, which is resulted from buoyancy and petroleum lateral migration. Sanzhao, Qijia-Gulong and Changling sags are the focus of deep-basin reservoir exploration. The uplift and slope, northeast and southeast uplift zones with good properties and low overpressure are the further exploration direction s of Fuyang reservoir. It is particularly important that the exploration of Yangdachengzi reservoir should be primarily laid on the slopes surrounding the sag, nose-shaped structure and anticline, instead of large overpressure zone in the central sag.