, Volume 34 Issue 4
    

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    油气勘探
  • High-quality source rocks in Nanpu Sag
    ZHENG Hongju; DONG Yuexia; ZHU Guangyou; WANG Xudong and XIONG Ying
    , 2007, 34(4): 1489-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The Nanpu Sag is one of the hydrocarbon-rich depressions in the Bohai Bay Basin. The 4th section of the 3rd member of the Shahejie Formation (Es34) is the most important source rock with 250m effective thickness, about 100m high-quality source rock and above 0.8% vitrinite reflectivity. In the high-quality source rock with TOC exceeding 5% develop clay layers rich in organic material coming from amorphous and algal solids and fine-grained calcite lamination, which are the result of seasonal stratification of lake and algal blooming. The biomarker components indicate that the organic material of the source rock mainly comes from hydro-biont, which existed in a fresh water and deoxidation environment, and to a less extent from land organic matter. The resource evaluation indicates that the oil-generating amount of Es34 is about 6×109t which accounts for 40% of the total in the Nanpu Sag and the resource amount is about 7.5×108t.
  • Suggestions from the development of fractured shale gas in North America
    LI Xinjing; HU Suyun and CHENG Keming
    , 2007, 34(4): 1490-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The history of exploration and production in North America shows that shale gas is a realistic alternative energy. As an unconventional resource, its critical risk is whether the low permeability shale produces gas economically. Source rocks could be good reservoirs for gas if they had rich organic material and abundant silica which makes the shale more brittle. The complex production mechanism involves the relationships between absorbed and free gases and between natural and induced fractures. To enhance the permeability by artificial hydraulic fracturing is a key step for shale reservoirs on the basis of the evaluation of geology, geochemistry, wire line and seismic data. Many fractured reservoirs in China have been discovered in extensive fine-clastic source rocks from marine and lacustrine environments, with carbonaceous/calcareous mudstone or siliceous shale. The undiscovered resources within effective shale reservoirs would be significant, especially the resources due to the secondary thermogenic cracking of oil to gas at high maturity.
  • Geological characteristics and exploration prospect of Upper Paleozoic reservoirs in Yanchang area, Ordos Basin
    WU Fuli; ZHAO Jingzhou; YAN Shike; GUO Deyun; YANG Xianchao; YAN Yunkui; CAO Jinzhou; MENG Xiangzhen; WANG Yongdong and WANG Bian-yang
    , 2007, 34(4): 1491-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The degree of exploration is low in Yanchang area, SE Ordos Basin. The paper analyses its paleogeographic format, sedimentary facies and their distribution characteristics, rock characteristics, and reservoir conditions, and forecasts the exploration prospect for gas in the lower Shihezi and Shanxi Formations. The conditions of gas source and cap rock are favorable in the area, where develop the main gas productive reservoirs of the lower Shihezi and Shanxi Formations located on the delta front facies, delta plain facies and littoral-shallow lake facies. Quartzose sandstones and litharenites are the primary and secondary reservoirs respectively, and are of low porosity and permeability. Based on rock characteristics, physical property and pore configuration, the reservoirs are divided into four types. Industrial gas is formed in types Ⅰ to Ⅲ, and type Ⅳ doesn't contain industrial gas. The low production rate results from the dispersed distribution of reservoirs. The area of Zichang-Yanchuan-Yanchang, which has multiple-phase channel deposits and thick sandstones, is a promising gas exploration area.
    • 国际交流与合作
  • Structural geometry of Muglad Basin, Central Africa
    ZHANG Yamin
    , 2007, 34(4): 1492-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    This paper has studied the relationship between structural characteristics and hydrocarbon accumulation of the Muglad rift basin and also applied basin analysis to investigate the complex geometric tectonic characteristics of the basin. It suggests that the tectonic unit of the Muglad Basin is generally of asymmetric half graben, formed by two groups of half-grabens and half-horsts controlled by basement faults with NEE and NW trending. Half-grabens alternate asymmetrically by adjusting their distortion or displacement. The sags are relatively independent with separate tectonic systems and sedimentary systems, which become basic units for hydrocarbon generation, migration and accumulation. Big tectonic accommodation zones and successive low relief uplifts, developed between half grabens, are prolific with oil and gas.
    • 油气勘探
  • Seismic acquisition techniques and their application in hill areas with thick loess, western foreland of Ordos Basin
    YAO Zonghui; DU Zhongdong; WANG Xuegang; REN Guanghui; YI Hongbin and DONG Tingxin
    , 2007, 34(4): 1493-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The surface geology and topography of the western foreland of the Ordos Basin are very complicated. There are thick loess, loess-deserts and mountain front hilly gravel-loess. The loess surface structure is systematically investigated using various methods, and the relationships between the loess geophysical characteristics, the shooting factors, and the surface loess structure are studied. Optimum shooting well location and depth are selected to guarantee the shooting results. High resolution and high signal-noise data are gained by using small trace intervals, small line intervals between three lines, and high density space sampling techniques. The following principles should be taken in thick loess areas: optimizing shooting location and lithology, reasonably selecting of shooting well depth; insisting on multiple and deep well combination shooting, with the whole quantity of charge being large while less charge in single wells; improving fold and resolution by high density sampling techniques.
  • Oil source of foothill fault-fold structural belt in western part of the southern margin, Junggar Basin
    KONG Xiangxing
    , 2007, 34(4): 1494-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The crude oils in the study area can be classified into three groups. Group one is characterized by δ13C values heavier than－27‰, Pr/Ph ratios higher than 2, the regular sterane with an inverted “L” pattern distribution of C29＞C27＞C28, and gammacerane/C30 hopanes less than 0.1; Group two by δ13C values ranging from －27‰ to －28‰, Pr/Ph ratios ranging from 1 to 2, the regular sterane with a “V” pattern distribution, and gammacerane/C30 hopanes values ranging from 0.2 to 0.3; Group three by δ13C values ranging from －29‰ to －30‰, Pr/Ph ratios less than 1, the regular sterane with a “V” distribution, and gammacerane/C30hopanes values around 0.5. The oil/source correlation shows that the first and third group oils are respectively attributed to the coal-measure source rocks and the lacustrine source rocks of the Badaowan Formation, and the second group oil is originated mainly from the lacustrine source rocks of the Sangonghe or Xishanyao Formation.
  • Thermal evolution of Dongpu Sag
    LIU Li and REN Zhanli
    , 2007, 34(4): 1495-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The vitrinite reflectivities of the eastern subsag, western subsag and central uplift are higher than those of the Baimiao region and western slope belt on the Carboniferous-Permian upper surface. The palaeo-temperature and present temperature of the eastern and western subsags are close, which means that the two subsags have a great sedimentation since Cainozoic era and the geo-temperature keeps rising. So the Upper Paleozoic source rocks are controlled by present temperature and the area belongs to the area of secondary hydrocarbon generation. According to the relationship between the vitrinite reflectivity and burial depth in the Baimiao region and in the western slope belt, the Neogene system and Eogene system are lack of compensation and the palaeotemperature is higher than the present temperature, which means this area has a great denudation since the Neogene period and the source rocks are controlled by the palaeotemperature, and the area hasn't the process of secondary hydrocarbon generation since the Neogene period.
  • Geochemical characteristics of kerogen in Yanchang Formation source rocks, Xifeng area， Ordos Basin
    JI Liming; WU Tao and LI Lintao
    , 2007, 34(4): 1496-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The kerogen's maceral, elements and carbon isotopes in the Chang 7 and Chang 8 source rocks of the Yanchang Formation, Xifeng area, southwestern Ordos Basin, suggest that the organic matter types in the Chang 7-2 and Chang 7-3 are good, containing sapropel and sapropel-humic kerogens,which are formed in a deep lake with a reducing environment and indicate algae input in productive period. The Chang 7-3 source rocks contain many terrestrial plant remnants due to turbidite sediments. The Chang 8 source rocks have worse organic matter type, mainly mixed type, formed in a shallow lake, with both terrestrial plant remnants and some algae input. Because of the difference of the sedimentary and preservation environments, the Chang 8 source rocks at some wells have mainly humic kerogen. The source rocks of the Chang 7-2 and Chang 7-3 have good potential for oil and gas, and are probably the main source for the oil reservoirs.
    • 资源评价与管理
  • Reasonable planning of oil production in China based on peak oil model
    FENG Lianyong; TANG Xu and ZHAO Lin
    , 2007, 34(4): 1497-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    In China, if oil production were not planned rationally, the peak of oil production would occur round 2017, the peak production would be about 185 million tons based on peak oil models; and the peak of oil consumption would occur around 2034, the peak oil consumption about 633 million tons, at that time, the national oil production would have entered a decline stage, and dependence on the outside would be as high as about 73%, the contradiction between oil supply and demand and oil security would become more prominent. China should do the oil production planning: reduce the present oil production in order to reduce the peak production to 170 million tons and put off the peak time to about 2030, so as to make the time of the peak oil production match the time of the peak demand; and drop the amount of oil import properly to ensure the safety of petroleum resources and decrease the dependence on oil import.
    • 油气勘探
  • Distribution and controlling factors of glutinite bodies in the actic region of a rift basin: an example from Chezhen Sag, Bohai Bay Basin
    XIAN Benzhong; WANG Yongshi; ZHOU Tingquan and SUN Lidong
    , 2007, 34(4): 1498-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The geologic, drilling and geophysical data of the Chezhen Sag, Jiyang Depression, are used to investigate the distribution rules and controlling factors of glutinites in the actic region of a rift basin. Planar strips, vertical stages, continuous backpedal and strong succession are the characteristics of the glutinite body distribution in a rift extensional basin. The fault structures, tectonic transform zones, paleo-geomorphology and complex base levels in the actic region are the key factors controlling the filling and distribution of glutinite bodies. The geometry and structural movements of the basin-controlling boundary faults dominate the sequence configuration, the tectonic transform zone with weak stress is the master of the inflow ancestral current direction and source entrance, the paleo-geomorphology decided by basement subsidence and rising, fault movement intensity and occurrence plays a key role in the sandstone distribution, and the scale and strata of the glutinite bodies is under the control of complex base levels in different stages.
  • 4D seismic technology for water flooding reservoirs
    GAN Lideng; YAO Fengchang; DU Wenhui and HU Ying
    , 2007, 34(4): 1499-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    To estimate the residual oil distribution in long-term water flooding reservoirs, 4D seismic study is implemented based on the 3D legacy seismic and petrophysical data of reservoirs with high porosity and permeability in Bohai Bay, including feasibility analysis, pre-stack and post-stack cross-equalization, dynamic reservoir monitoring. Through the cross-equalization, the difference caused by the factor of acquisition is almost eliminated. For long-term artificial water flooding reservoirs, the seismic velocity decreases by 16%～18% because of the variation of reservoir properties and pressure, and post-stack seismic amplitude differences can be used to monitor the water flooding forefront directly. For natural water drive reservoirs, the only variable factor is fluid saturation which could cause subtle seismic velocity variation. In this case, the information from pre-stack seismic data should be used to highlight the reservoir variation instead of post-stack amplitude differences. For example, the differences of two pre-stack elastic impedance inversions can reflect the reservoir variation very well.
  • Relationship between present geotemperature and hydrocarbon generation in Haila’er Basin
    CUI Junping; REN Zhanli; SU Yong; ZHANG Sheng and LIU Li
    , 2007, 34(4): 1500-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Based on the comprehensive analyses of stratigraphic temperature measurements in the Haila′er Basin, this paper investigates the present geothermal gradient and heat flow of different units, the controlling factors of the present geothermal field and its function in forming oil and gas. The present geothermal gradient and heat flow are 3.0 ℃/100m and 55.00 mW/m2 respectively. They are high in the south and lower in the north， and lower than those of the Songliao Basin. They are controlled by crust thickness, basement topography and basin structure. The Wu′erxun Sag is a sag with increasing burial and temperature, and the present temperature controls the distribution and oil-gas generation of its effective source rocks. The present temperature is the highest one that the Tongbomiao, Nantun and Damoguaihe Formations have experienced, and the source rocks in them are in the stage of oil-gas generation. In the Bei′er and Huhehu sags, hydrocarbon generation is controlled by the paleotemperature which is higher than the present one.
  • Methodology and application of stochastic seismic inversion: A case from P Oilfield, M Basin, Sudan
    LI Fangming; JI Zhifeng; ZHAO Guoliang; WU Changji and LI Zhiming
    , 2007, 34(4): 1501-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Stochastic seismic inversion, which is an important part of geostatistical inversion, integrates seismic inversion and sequential simulation. The histogram distribution statistics, variogram calculation and the range determination in different directions of random variables are conducted. Seismic traces are synthesized based on the calculated reflectivity at the location of seismic traces for each realization, and the process will not be finished until they match the original seismic traces within required accuracy, then the inversion result is exported. With the P Oilfield in the north of the M Basin, Sudan as an example, the histogram, variogram and correlation of the impedance and well log data are conducted. The stochastic seismic inversion of impedance volumes in the whole study area and of density volumes in parts of the area by simulated annealing indicates that the inversion has a higher resolution, which can identify thin bedded sandstones of shallow layers and reflect thickness changes of sandstone and shale.
  • Quantitative evaluation of fault sealing capacity
    SUN Longtao; CHEN Changmin; ZHAN Wenhuan; HE Min; SHEN Jun and LIU Baojun
    , 2007, 34(4): 1502-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Fault sealing analysis is an important aspect of the fault trap evaluation. Probability statistics is used to quantitatively evaluate fault sealing. According to the fault sealing mechanism, sands are permeable strata and clay stones are impermeable strata. The paper determines the sedimentary facies and sand content of target stratum and plugged zone using seismic data and regional geological data, and then establishes the lithologic columns on both sides of the fault using random simulation, counts the sealing percentage of every sand layer, and confirms the sealing percentage of the whole reservoir rocks by probability statistics calculation. The results show: the lower content of sand and the more strata reservoir rocks contain, the higher the percentage of the fault sealing sandstones; the lower content of sand and the less strata sealing rocks contain, the higher the percentage of the fault sealing reservoir rocks. The method is applied in the deepwater area of the Pearl River Mouth Basin without wells and indicates that its sealing percentage is 40%-50%.
  • Effects of tectonic uplift on physical properties of high and low rank coal reservoirs
    CHEN Zhenhong; JIA Chengzao; SONG Yan and WANG Hongyan
    , 2007, 34(4): 1503-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The influences of tectonic uplift on the physical properties of high and low rank coal-bed methane (CBM) reservoirs are different. Low rank coal-beds have mainly matrix-type pores and high rank coal-beds are mainly cleat type. The stress analysis of coal reservoirs indicate that the matrix pressure decreases with the tectonic uplift. The uplift simulation and the sensitivity experiment of the matrix and cleat permeability show that tectonic uplift makes the coal seams pressure deliver faster, cleats open, and the permeability increase. The sensitivity of the cleat permeability is more obvious. The uplift affected the physical porosities of the high rank coal reservoirs. The strong uplifting of high rank coal sequences makes the permeability increase and the CBM diffuse, which is disadvantageous to the CBM enrichment. The uplift has less influence on the physical properties of low rank coal-beds and makes the pressure decrease and the migration speed of CBM increase, which is favorable for the CBM development.
    • 油气田开发
  • Measures to improve water drive recovery efficiency of offshore Chengdao Oilfield
    ZHOU Yingjie
    , 2007, 34(4): 1504-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Chengdao Oilfield has been exploited since 1993. Special development technical policies, such as one set of strata and wide spacing, were taken to make it develop quickly and efficiently under a lower oil price at that time. The low rate of oil production and recovery efficiency are contradictory to the present high oil price, badly needed resource and short lifespan offshore facilities. Integrated adjustment countermeasures are put forward based on comparing and analyzing the development countermeasures and their results of similar oil reservoirs at home and abroad. They include subdividing of strata, infilling well pattern, improving liquid amount, improving reservoir exploiting rate, and using horizontal well and fishbone horizontal well etc. It is predicted that the rate of oil production can improve by more than 2% and the recovery efficiency by over 10%.
  • Mathematical model for natural gas hydrate production by heat injection
    DU Qingjun; CHEN Yueming; LI Shuxia; SUN Junjun and JIANG Lanqi
    , 2007, 34(4): 1505-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    According to the first law of thermodynamics and the mechanism of natural gas hydrate decomposition, a mathematical model of thermal recovery comprising mass and energy conservation equations, kinetic equations of decomposition and the auxiliary equations is established on the basis of reasonable assumptions. Difference disposal is implemented for the mathematical model to obtain the difference equation set. Taking the pressure and temperature equilibrium conditions of natural gas hydrate decomposition into account, the model is resolved using the method of IMPES and a numerical simulator is built. The simulator can match well with the gas rate and temperature distribution of thermal recovery experiments and the validity is demonstrated. The thermal recovery process of natural gas hydrate can be divided into three periods: the release of free gas, the decomposition of natural gas hydrate, and the boundary effect. There exists decomposition front in the process of natural gas hydrate decomposition. The hydrate near the injection end is almost decomposed, whereas most of the hydrate near the exit end is not decomposed, exhibiting a high saturation.
  • Factors affecting production capacity of fractured horizontal wells
    ZENG Fanhui; GUO Jianchun; XU Yanbo and ZHAO Jinzhou
    , 2007, 34(4): 1506-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Multi-fractures are created when a horizontal well is fractured. Due to the stress difference along the well and the restriction in fracturing technology, the factures are different in length, conductivity, azimuth angle etc. Moreover, during production, the fractures' mutual interference makes the productivity prediction more difficult. The paper combines the shape of fractures and the fluid percolation mechanism to present a new model, and analyzes the factors affecting the productivity. As the number, length and conductivity of fractures increase, the production increase; the larger the angle between fractures and horizontal wells, the higher the production rate. With respect to different fractural layout, it is necessary to place the fractures stagger, leading to the distance among the outer fractures smaller than that among the inner fractures. Because of fracture's mutual interference, different fractures have different production rates with the production of the innermost fractures being the lowest.
  • Water injection profile variation of oil layers under polymer flooding
    HOU Weihong
    , 2007, 34(4): 1507-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Statistical analysis in Daqing Oilfield indicates that the water injection profiles of low-permeability reservoirs retrograde when the injected polymer volume amounts to 0.08-0.2PV in most wells, and the retrograde time is earlier than that of mid-permeability reservoirs, and high-permeability reservoirs remain highest injectivity during the whole polymer flooding, which is unfavorable for improving the development results. Simulation shows that the bigger the reservoir permeability contrast and the effective thickness ratio of reservoirs, and the smaller the molecular weight of injected polymers, the poorer the adjustment results of polymer solution to the water absorbing capacity of low-permeability reservoirs; the reservoir productivity factor contrast is the main factor affecting the retrograde time and retrograde period of the water injection profile. The following measures are proposed to improve the results of polymer flooding: avoiding big reservoir productivity factor contrast in the combination of strata; separate polymer injection; optimizing the molecular weight of injected polymers and the combination of injected polymer slugs; and depth profile control before injecting polymers etc.
    • 石油工程
  • Feasibility of two-phase closed thermosyphon heating method
    ZHANG Yufeng; WU Xiaodong and LI Weichao
    , 2007, 34(4): 1508-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Two-Phase Closed Thermosyphon (TPCT) is used in the course of wellbore heating by utilizing its characteristic of efficient heat-transfer, and several external factors are analyzed by comparing with hot fluid circulation method and electric heating method. As a kind of wellbore heating method, TPCT is feasible in oilfields and hollow sucker rods can provide working environment for work fluid. Through heat stowing and heat conduction, TPCT can increase the temperature of the upper cryogenic fluid in wellbores by absorbing the surplus energy of the lower, high temperature fluid in the wellbores. Compared with the two conventional methods, the TPCT technology improves the temperature distribution along the wellbore without extra energy consumed and meets the demand of production at the same time. With the increase of downhole temperature, setting depth and yield, the effect of TPCT improves. Physical properties of oil determine directly whether TPCT is feasible or not in wells.
  • Mechanical analysis and optimization design of oilfield workover derricks
    YANG Xiaohong; ZHANG Bangcheng and CHEN Zhaofeng
    , 2007, 34(4): 1509-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    A workover derrick is subject to primary loads, and the challenge facing design engineers is that a derrick has to be designed to be strong enough to bear those loads without wasting materials. A new derrick structure is designed on the basis of the finite element analysis of workover rigs. The distribution of the whole derrick stress is symmetrical in the new design. The maximal stress of the new structure is lower by 12 percent than the previous one. The stability analysis under pressure indicates that the whole stability is preferable, and can assure the normal work of the oil derrick. The modeling analysis shows that the inherent frequency of the oil derrick is different from that of the chassis engine and winch, so the resonance phenomena will not take place when the winch works at different rotary speeds.
    • 资源评价与管理
  • Real option valuation model for petroleum development projects
    LUO Dongkun and WANG Hua
    , 2007, 34(4): 1510-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    A distinct feature of a petroleum development project is the right to wait, which produces a flexibility value to the project. Valuating the option to defer scientifically will make the evaluation of a project more objective and reliable. Hedging the designed production in a development plan, assuming no technical uncertainty, and employing the oil price motion equation in which oil price follows Geometric Brownian Motion and oil convenience yield follows mean-reversion motion, the paper establishes a risk-free DCF model for petroleum development project valuation, in which LSM algorithm has been employed to calculate the value of the option to defer. The analysis results show that, a project with negative NPV(Net Present Value) possibly deserves to be developed, and sometimes developing a project with positive NPV immediately is not the best decision; the value of a development project is directly proportional to the duration of waiting within a certain time range, and long duration of waiting period would not increase the value of projects.
    • 学术讨论
  • Oil and gas are regenerative
    FANG Lehua and ZHANG Jinglian
    , 2007, 34(4): 1511-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The exploration and development of oil-gas fields in the world during the past several decades show that the actually proved reserves are higher than the calculated resources, the accumulative oil products are higher than the recoverable reserves, and there are some regenerative oil and gas in the fields. Oil and gas are regenerative. 14C dating and carbon isotopic tracing of hydrothermal petroleum in the Guaymas Basin show that the hydrothermal petroleum is generated in recent epochs. The possible generation models of hydrothermal petroleum are that hot fluids accelerate the petroleum generation by organic matter (such as plus H2), or petroleum is synthesized by Fisher-Tropsch reaction in the mid-crust. The current issues, such as gas rush eruption in the coal mines, forest fire, greenhouse gas (CO2) and so on, might be connected with the earth outgas.
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