, Volume 27 Issue 3

    

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地质勘探
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  Some ideas on the direction of natural-gas exploration in China in early 21st century

  MA Xinhua; QIAN Kai; WEI Guoqi; LI Dongxu; LIU Ronghua and LI Yahong

  , 2000, 27(3): 1337-0.

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  Shiyou Kantan Yu Kaifa 2000, 27(3), 1-4. The tasks of natural-gas exploration will be very arduous for China in early 21st century, it needs to discover 8×1012 to 10×1012m3 of gas in place throughout the country, and to prepare well for opening up a new exploration field. The authors suggest that the main principles that should be considered for exploration direction determination from the high plane of strategy: ①the resource quality,the conventional resource is the main direction of the study during the first 10 years of the 21st century, and converting going up the low-grade resources (coal-bed gas, tight sandstone gas, shale gas) is the main task during the second 10 years; ②the exploration degree: the new area and the new field are the main direction for our country to increase natural-gas reserves; ③the resource distribution: it should take western, central and offshore areas as the main targets; ④the distribution law of large and middle-sized gas fields; and ⑤the exploration benefit. In recent years, three trends of natural-gas exploration (i.e., the gas reserves from sandstone reservoirs are rising steadily, the proportion of incremental reserves in Mesozoic group and Cenozoic group is growing and tight gas reservoirs have a bright future) Should not be ignored when the exploration direction is selected in the coming years. In this paper, the authors indicate that three main regions that can make the onshore natural-gas exploration of our country in the next 5-10 years developed sustainably: ①foreland basins in central and western parts, including 6 areas where the Mesozoic and Cenozoic foreland basins are developed (Kuqa of Tarim basin, the southwest of Tarim basin, the northwest fringe of Sichuan basin, the west fringe of Ordos basin, the south fringe of Junggar basin, the north fringe of Qaidam basin); ②three large cratonic basins (Tarim basin, Sichuan basin and Junggar basin); ③the deep zone of intracontinental rift basins in the east part of China. The three basins in the west part, two basins in the middle part and offshore areas of China are the main directions for the gas exploration in early 21st century; Songliao basin and Bohai Bay basin should be considered as the basins for both gas exploration and oil exploration.
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  A primary discussion on the network-like oil and gas pools in carbonate rocks—Taking the Lunnan Ordovician buried-hill pool in Tarim basin as an example

  ZHOU Xingxi

  , 2000, 27(3): 1338-0.

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  The network-like space of the reservoir made up of pores and vugs linked by fracture system, often exists in the carbonate rocks. The shape and the configuration of this type of pool is irregular, heterogeneous and well concealed, which should be classified as an independent basic type. It is proposed that this pool belongs to irregular one, paralleling to lens-like pool, and can be named “network-like pool”. The definition of this kind of pool is as follows: an independent network-like irregular petroleum accumulation which possesses reservoir space of pore fracture system and is closed by boundary tight rocks. According to the examples of Lunnan area in Tarim basin and the southern area of Sichuan basin, the major feature of this kind of pool lies in the multi-pore-fracture-systems, and the network-like fluid systems are not interconnected. Exploring such reservoirs needs paying much attention to the intensity of karst and fracture. The exploration of Ordovician buried hill in Lunnan area shows that the evaluation and forecasting of network-like reservoir needs a close integration of geological and geophysical technologies and ways. And after the discovery of commercial petroleum, test production should be taken first in order to identify the conditions for production stabilization. Combining the test data, the petroleum-bearing area can be elementarily estimated. The recoverable reserves can be forecasted by the method of pressure decline. The further drilling and test production can be proceeded in the area with similar geology conditions, then the reserves can be enlarged and the production capacity achieved. The understanding to the forming and distribution of network-like petroleum accumulation and the application of this exploration technique need further consummated.
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  A comparison study on the hydrocarbon productivity of pollen and algae

  JIN Xiaofeng

  , 2000, 27(3): 1339-0.

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  By high temperature and high pressure simulation experiment, the authors studied the hydrocarbon productivity of pollen and algae, it tells us that oil production potential and gas and liquid hydrocarbon production of Pinus are higher than that of Pediastrum and Oscillatoria. ①At their respective maximum temperature in simulation, Pinus has a higher gas-generation rate than Pediastrum and Oscillatoria. Meanwhile, in the gas from Pinus the content and quality of methane are more and better than that from Pediastrum and Oscillatoria. The gas-generation rate of Pinus is 458mL/g, and more than half (51.81%) of the gas is gaseous hydrocarbon, almost being methane. The gas-generation rate of Pediastrum is 373mL/g, of which gaseous hydrocarbons occupy 34.26%, methane 20%, and some others. The gas-generation rate of Oscillatoria is 348mL/g, of which gaseous hydrocarbons occupy 40.42%, methane occupies only 5%. ②In thermal simulation, the liquid-hydrocarbon-generation rate of Pinus is higher than that of Pediastrum and Oscillatoria. The rate is 59.55 mg/g at the first peak temperature and 169.29 mg/g at the second peak temperature, they are 2.8 times of that of Pediastrum and twice of that of Oscillatoria. In addition, lighter hydrocarbon of the pyrolytic oil from Pinus is 67.25%, it is also higher than that from Pediastrum and Oscillatoria. ③The oil-generation potential of Pinus is higher than that of Pediastrum and Oscillatoria. The maximum potential of Pinus is 721.60mg/g, that of Pediastrum is 446.53mg/g, Oscillatoria 541.86mg/g. ④The liquid-hydrocarbon generation-rate curve of Pinus is bimodal, of which the first peak temperature is 260℃, the second 345℃. The inner matters (organs) of Pinus are considered to participate matters in the generation of early immature-low mature oil. Sporopollen is the main source matter for the mature oil.⑤The liquid-hydrocarbon generation-rate curves of Pediastrum and Oscillatoria are unimodal, of which both peak temperatures are 300℃. Peak temperature of Oscillatoria is always lower, Tmax ranges from 383 to 430℃, belonging to early immature-low mature periods. At highest temperature(395℃) in simulation, Tmax increases rapidly to 581℃. So we believed that the product of Oscillatoria is mainly early immature-low mature oil. The liquid-hydrocarbon generation-rate curve of Pediastrum is flat and wide. When simulation temperature is below 280℃, Tmax is below 438℃, the product is early immature-low mature oil; the temperature is between 280-360℃, Tmax is 438-559℃, the product is mature or over-mature oil.
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  A discussion on the method of economic evaluation in oil and gas exploration

  HUANG Xunan; BAO Shijie; FU Zhenhua; YOU Yang; CHENG Kunfang; XU Yiqin; MO Honghong; ZHENG Zehe and ZHU Chaoguang

  , 2000, 27(3): 1340-0.

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  The operation target of oil/gas exploration should consider the short-term economic benefit on one hand and long-term development on the other to give highest economic value under current market economic conditions. Oil/gas exploration is a system engineering characterized by long-term, high risk, large capital investment, and high rate of return on investment. In the whole process of oil/gas exploration and development, it is necessary to have a series of sequential decisions tracing the progress of exploration with the objective economic evaluation as a basis. The economic evaluation of oil/gas exploration can be divided into 3 stages: ①Economic evaluation of the basic exploration unit: exploration risk analysis and economic analysis of this unit are carried out. Exploration risk analyses include petroleum geologic risk, exploration technical engineering risk, policy as well as market risk analyses. ②Taking attractiveness (emphasized on oil/gas resource potential and exploration value) and risk as screening, indexes selecting the optimum project from various projects, preparing well the feasible projects and kicking out other non-profit projects. ③ Proposing several exploration programs for the optimized project; and then analyzing exploration economic and technical ability and best capital investment proration to make an exploration decision (including exploration strategy decision, exploration operation decision, and exploration tactic). It is suggested that CNPC should establish a set of strict specifications, unitized standards and evaluation method for exploration evaluation specifications to assure the uniqueness and authority of project exploration economic evaluation.
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  A pool formation analysis for Qianmiqiao buried hill structure

  JIANG Ping

  , 2000, 27(3): 1341-0.

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  Qianmiqiao buried hill structure is located in Banqiao structural belt in Huanghua depression. Well Banshen 7 produces oil 143.36t/d, and gas 275309m3/d, showing an important discovery for buried hill reservoir exploration in Dagang oil field. Compressive thrust made Paleozoic and Ordovician formations denuded and aeolated and dissolved, which formed fractures and dissolved pores, which are very important porosity spaces. It is also the most important situation that Qianmiqiao Ordovician buried hill reservoir formed as well. Correlating source rocks with oil shows that Qianmiqiao oil is from the third member of Shahejie oil source rocks. Oil migrated into Qianmiqiao buried hill trap at the end of the first member of Shahejie, which is later than the trap formation of Qianmiqiao buried hill. The thickness of shale cap of Mesozoic and Shahejie is over 1300m.The tertiary structural faulting had little influence on buried hill, which is favourable for conservation of Qianmiqiao buried hill reservoir.
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  Fluid compartment and hydrocarbon accumulation in Mosuowan area in central part of Junggar basin

  ZHANG Nianfu

  , 2000, 27(3): 1342-0.

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  Mosuowan area, located in the central part of Junggar basin, is a continuously developed uplift surrounded by Permian hydrocarbon generation depressions and with Jurassic generation center to the south. This area with its sufficient hydrocarbon source, favorable reservoir beds in the Carboniferous, Permian, Triassic and Jurassic strata, and large, early formed structural traps is one of the most favorable areas for hydrocarbon accumulation in the basin. Investigation on the formation pressure structure showed that there are two fluid compartments in the sedimentary column of this area. The lower compartment is in Permian and Triassic and formed in late Triassic or early Jurassic, the upper compartment is in the lower part of Jurassic and formed in late Cretaceous. The formation and evolution of fluid compartments in this area had significant influence on hydrocarbon accumulation. Hydrocarbon from Permian source rocks accumulated mainly in the lower compartment during late Triassic and early Jurassic time. The breakthrough of seal during middle and late Jurassic led to the forming of hydrocarbon accumulation in Jurassic outside the lower compartment. After the forming of upper compartment and the closure of seal break in late Cretaceous, the two compartments became no hydraulic communication and hydrocarbon accumulation only took place separately within two compartments.
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  An approach to the Qaidam central-fault-belt and its pre-Cambrian basement

  TAN Ying; LIU Deliang; YANG Xiaoyong and YE Hefei

  , 2000, 27(3): 1343-0.

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  Research results of GS (gravity survey), SE (seismic exploration), AMS(aerial magnetical survey) and Surface-Geology data bear evidence of the existence of the Qaidam central-fault-belt (QCFB). QCFB apparently divides the Qaidam basin basement into different parts. It shows that an old crystalline continental kernel of pre-Lüliang-movement exited. With the additional research results of local intermediate-acid intrusive geochemical data, a conclusion can be drawn that there was an old-Altyn-ocean, which expanded the scope of the old-Qingqikun-ocean. Altyn-movement closed the old-Altyn-ocean, made island-arces to become pre-Cambrian folded-accreted-belt.
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  The source of natural gas in Nanbaxian gas field of the Qaidam basin and its exploration significance

  ZHAO Lin; HONG Feng; DAI Jinxing and SUN Dongmin

  , 2000, 27(3): 1344-0.

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  Based on the analysis of geochemical features, thermal evolution degree of Jurassic coal measures and gas potential evolution, this paper discusses the source of Nanbaxian gas field. δ13C1 value and Δ(δ13C2-δ13C1) of natural gas show that thermal degree of natural gas in Nanbaxian gas field is higher than that of Jurassic coal measures in Nanbaxian and surrounding areas such as Saishiteng sag and Beilingqiu sag, but corresponds to that of Jurassic coal measures in Yikeyaruwu sag. According to the evolution of gas potential of Jurassic reservoirs, natural gas of Nanbaxian-Mahai is derived from Yikeyaruwu sag which is an important gas-generating center. Thus the southeastern Lenghu structure belt, Eboliang Ⅲ structure and Nanbaxian-Mahai which are nearby Yikeyaruwu sag are favorable areas for gas exploration.
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  Determination of three Middle Jurassic lake coastal zones by trace fossils in Taibei sag, Turpan basin, Northwest China

  ZHANG Jianping; WU Yinye; YANG Shibo and XUE Shuhao

  , 2000, 27(3): 1345-0.

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  This paper provides evidence to prove that the trace fossil assemblages are of great value in determining lake coastal zones. The abundant animal and plant trace fossils have been discovered in the Middle Jurassic strata of Taibei sag, Turpan basin. Through a detailed study on these trace fossils, three different lake coastal zones are determined in the study area. The descriptions of three zones are as follows: during middle-late Xishanyao deposition period, the southern lake coastal zone (near to Qoltag mountain) extended along the line from Shengjintai on west to the north of Lianmuqin on east; and the northern one (near to Bogda mountain) laid at the north of Wells K7 and K6. To the Sanjianfang deposition period, the south zone moved to the north, extending from Well SH101 of Shengjintai on west to the Lianmuqin section on east, which was roughly at same position to that in Xishanyao deposition period. In the Qiktim deposition period, the lake area reached its maximum, the southern lake coastal zone extended from the south of Well SH101 on west to the south of Lianmuqin on east, and the northern zone was shifted northward. In general, from early to late period, the lake area in the Turpan basin was expanding, and lake coastal zones was shifting backward, most of wells in Qiuling oil field were located in shallow lake with a relatively deep water.
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  Key techniques for improving accuracy and benefits of progressive exploration in the complicated fault block areas of Jizhong region

  LIANG Xingru; DU Xinjiang; LI Fu and HUANG Jie

  , 2000, 27(3): 1346-0.

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  This paper, based on the actual geological conditions for petroleum exploration and development in Jizhong, discusses the importance of progressive exploration and development in improving the accuracy and benefits of petroleum exploration in complicated fault blocks. Based on different geologic conditions, the author mainly proposes the key techniques, i.e. use of changeable velocities for time-depth conversion, process of high resolution and three dimension seismic data, interpretation of complicated fault blocks and identification of oil-bearing formations of low resistivity, etc.. The key techniques are of great significance for improving exploration accuracy and benefits in mature areas, that is, reserves increment and producibility improvement. Good economic effects have been achieved through actual application of these techniques in the mature areas.
油田开发
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  The diffusion and dispersion mechanisms in chemical flooding processes

  WANG Jian; YAO Hengshen and LUO Pingya

  , 2000, 27(3): 1347-0.

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  Diffusion and dispersion physical-chemistry phenomena existing widely in chemical flooding processes may cause concentration reduction of chemical slug, even make the chemical processes degenerating to water flooding in serious situation, leading to questionable validity and durability of chemical flooding processes. This paper builds the diffusion and dispersion mathematical model based on analysis of the diffusion and dispersion theories in chemical flooding processes, and derives out improved formula of calculating coefficients of diffusion and dispersion. Diffusion and dispersion coefficients of chemicals of Daqing oil field ASP combination system in flooding processes are tested, their molecular diffusion and mechanical dispersion degrees are studied in detail. Achievement of this paper can provide necessary parameters for ASP combination engineering and technology project design and dynamic monitoring.
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  A microbial transport compositional model simulator

  ZHU Weiyao; YANG Zhengming; CHI Li and SUN Yukai

  , 2000, 27(3): 1348-0.

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  The microbial flooding technique is a new effective method for enhancing oil recovery. In this paper a kinetic transport model with ability to account for two microbial transport-dispersions in the aqueous oil and solid are developed in porous media. According to porous flow mechanism of microbial with other components, a new microbial transport compositional model is presented and consequently a new numerical simulator is given. The microbial numerical simulation techniques are derived. The model considers 2 phases and 12 components. This model can be used to settle the problems of the growth and decay of microbial, chemotaxis and tumbling, microbial competition, induction and retardant, solubility, degradation, dispersion, diffusion, adsorption, etc.. The simulation results show that the microbial transport compositional simulator is the best one. It is a very practicable simulator of 3-D, 12-components. According to a series of investigation, the authors draw the following conclusion: ①At first a new microbial transport compositional simulator is presented, some porous flow mechanism of microbial transport are given. ②The numerical results show that oil recovery of microbial flooding obviously rise more than water flooding. ③The physico-chemical properties of microbials and reservoir characters affect oil recovery. On the basis of growth, decay and transport mechanisms of microbials, optimal scheme and chemical system is a good ideal system. ④The microbials change petroleum properties, reduce surface tension and oil viscosity and improve swell effectiveness. It is an effective method for improved oil recovery of water flooding.
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  A mathematical model of microbial enhanced oil recovery

  LEI Guanglun and CHEN Yueming

  , 2000, 27(3): 1349-0.

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  Based on the kinetics of microbial growth, the equations of microbial growth, nutrient consumption and metabolites production have been set up. According to the equation of material balance, the transport phenomena of microbes, nutrients, and metabolites in porous media are described. For black oil reservoirs a three-dimension, three-phase, multiple-species mathematical model has been developed. This model can be used to simulate bacterial growth, metabolism and transport, simulate porosity, permeability, pressure and saturation changes. This is a complicated mathematical model for microbial flooding.
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  Study and application of endurant high temperature bacteria

  FENG Qingxian and CHEN Zhiyu

  , 2000, 27(3): 1350-0.

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  The method of screening bacteria of endurant high temperature and the formulation of culture are introduced in the paper. 4 properties of bacteria are evaluated at high temperature: ①accretion: oscillating the mixture of bacteria and culture which inoculation at 5% in constant temperature water bath, the result shows: one order increase of the concentration of bacteria; ②metabolism: the type/quantity of metabolized material are analyzed, they are mixture gases (their main components are CH4 and CO2, 9-16mL gases per 100mL culture), surfactant and organic acid (0.16 % - 0.24 % ); ③improving oil properties: concentration of paraffin and gum decreases, the viscosity reducing ratio of oil is 28.9 % - 66.2 %; and ④ high oil displacement efficiency:microbial flooding on heterogeneous cores at laboratory shows that 5.4% (OOIP) recovery is higher in average than water flooding. Main factors influencing the effectiveness of microbial flooding are also analyzed in experiment, which include the concentrations of bacteria and yeast extract, acidity and alkalinity in culture and salinity of water. A method for calculating the quantity of bacteria used in oil wells is presented and applied in the pilot test. The test results show: success ratio is 69.2%, and 145.1 t of oil is increased by injecting 1 m3 of fermentative bacteria.
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  A study of petroleum reserve-production ratio and reserve-production balance rate

  ZHANG Zhengqing; QU Haichao and NI Hong

  , 2000, 27(3): 1351-0.

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  Petroleum reserve-production ratio and reserve-production balance rate are two very important development indexes in the process of oilfield development. The reserve-production ratio is closely related to the variation trend of the production rate empirically. Starting from the mathematical model for oilfield production rate prediction, an equation showing the lowest limit of reserve-production ratio required to maintain a stable oil field production is derived. Field residual reserve-production ratio should be larger than 1+0.746B-1(where B is a constant) to keep the production declining not too fast. In addition, reserve-production ratio is also related to the increase and declining rates of oil production quantitatively. Based on a consideration of reasonable reserve-production ratio principle, a rational reserve-production ratio can be anticipated. With a pre-determined reasonable reserve-production ratio and reasonable production rate, a reasonable reserve-production balance rate can be determined. A set of reasonable technical indexes for rational development of an oil field are thus determined.
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  Production decline law and water drive characteristic curves in low permeability reservoirs

  YANG Zhengming; LIU Xiangui; SUN Changyan and ZHANG Shengzong

  , 2000, 27(3): 1352-0.

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  Conventional Production decline law and water drive characteristic curves incorrectly reflect the production feature of low permeability reservoirs. In this paper, using the percolation law and the essential characteristic of low permeability reservoirs, the authors set up the production decline equations and water drive characteristic equations of low permeability reservoirs. Some helpful conclusion is drawn. When the production decline, water cut and water drive characteristic curves are analyzed, the effect of the threshold pressure must be considered. The higher the threshold pressure, the smaller the initial production, and the decline rate with the threshold pressure is less than the decline rate without the threshold pressure, and the cumulative production becomes smaller with threshold pressure increasing. In same condition except the threshold pressure gradient, when the threshold pressure gradient becomes bigger, water cut becomes bigger, and the threshold pressure gradient affects water drive characteristic curves of low permeability reservoirs.
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  A design of optimal well pattern for the development of low permeability reservoirs

  ZHANG Xuewen; FANG Hongchang and QI Mei

  , 2000, 27(3): 1353-0.

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  Reasonable well pattern and the factors affecting the well pattern's recovery are analyzed and correlated in the development of low permeability sandstone reservoirs in this paper. The presence of natural fractures increases the degree of permeability heterogeneity. Through numerical simulations of various fractured well patterns and after comparison of the features of different well patterns, it is proposed that lozenge inverted 9 spot well pattern is the relatively optimum well pattern for the development of low permeability reservoirs. Subsequently, a large number of heterogeneous geological models have been constructed for numerical simulation to determine the optimal ratio of distance between producer and injector to well spacing corresponding to different low permeability reservoirs. Furthermore, factors affecting the development of lozenge inverted 9 spot well pattern are analyzed, including fracturing status of producer and injector, fracturing scale of producer and injector, fining upward or coarsening upward sequences, Ky/Kx and timing for the conversion of corner producer to injector.
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  The optimization technology of block-wide injection profile control

  BAI Baojun; TANG Xiaofen and LI Yuxiang

  , 2000, 27(3): 1354-0.

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  To optimize block-wide injection profile control, this paper studies a set of simple, applicable optimum design methods. This set of methods is ready to select well, layer and agent, and to optimize volume and injection parameters. The fuzzy mathematic method is used to select well. Many parameters, such as injection ability of injector, pH and salinity, are considered to select chemical agent. Volume optimization model is based on well group numerical simulation. The main factors influencing plugging agent volume are considered, and these factors include the destination of profile control, variable factor of permeability, water cut of production well, recovery, formation thickness, water injection volume, oil and water relative permeability curve, oil viscosity,Kv/Kh and fr. This technology was applied in Long 11 block, Liaohe oil field. After operation, oil rate was increased, water rate was reduced and oil recovery was also improved.
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  Grey matter-element decision analysis and its applications

  XIAO Fangchun and JING Jiaqiang

  , 2000, 27(3): 1355-0.

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  At present, there is a large number of information in petroleum industry, which needs people to find a method to reasonably solve them. In this paper, based on the grey system theory combined with the concepts of fuzzy matter-element, a new method is proposed for evaluating and optimizing gas-field development projects, which is called the grey matter-element decision-making analysis. Owing to different characteristics that there are many technical and economic indexes which are dependent as well as contradictory in every development programs. The merits and demerits of various sorts of technical and economic indexes among the projects are considered comprehensively to appraise and optimize the development projects of gas-field in this paper. It shows through actual example calculated by Visual Basic that this method of data processing is simple and convenient to be applied at the work site. It can be also applied to appraise and optimize the development projects for oil field and corresponded to practice.
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  The high energy gas fracturing technique of liquid explosive and its application in deep-seated oil and gas reservoirs

  YE Xianjun; ZHANG Huisheng and TIAN Guoli

  , 2000, 27(3): 1356-0.

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  High energy gas fracturing (HEGF) technique is an oil enhanced technique that was developed recently. This paper gives its basic mechanism and actual production situations. For deeply seated and lowly permeable oil reservoirs in Zhongyuan oil field, a series of liquid explosives were developed based on the application of HEGF of solid explosive. This paper gives their action mechanism, formulation and series, as well as the well-choosing methods and operation techniques of liquid explosives. Its application in 16 oil wells in 1997 and 1999 totally increased oil of 6650t. This proves that high energy gas fracturing technique can improve the production effectiveness of deep-seated oil and gas reservoirs and have a broad application potential in deep low permeability oil and gas reservoirs.
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  The optimization of perforation plan for reservoirs, in Pinghu oil and gas field

  WEN Jian; CHANG Feng and WANG Qingyong

  , 2000, 27(3): 1357-0.

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  The H3+4+56 reservoir of Pinghu oil and gas field is a structural one with bottom water, which has good oil property and reservoir quality, however whose oil pay is not very thick. The optimization of perforation plan is the key process for decreasing bottom water coning and increasing recovery efficiency. The paper began with working on the reservoir character, and then, from various aspects, optimized the perforating completion plan for H3+4+56. The reservoir characterization study showed that H3+4+56 is a structural reservoir with bottom water under normal pressure and temperature condition, which is of good fluid property and reservoir quality, and the reservoir rocks are well consolidated. The sensitivity study result showed that perforation should be made at the top of the reservoir, the perforating percentage should be controlled at about 30%, tubing conveyed underbalanced perforating technology and high quality perforation devices should be used. The proper azimuth of perforating gun should be 120°, and mediate shot density should be selected. On the base of detailed study the decision was made that shot be made at the top of H3+4+56 at Wells A1, A2 and A4 and perforation plan was made. After the implementation of the perforation plan two wells' (A1, A2) production performance went well. Though the wells were put into production in high speed, the rate and tubing pressure was kept stable, the water cut and GOR increased slowly, and no sanding was found.
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  A study on spatial distribution laws of reservoir sensitivity

  CAI Zhong and LIU Zhongyun

  , 2000, 27(3): 1358-0.

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  Taking the Linnan oil field in Linyi, Shandong province as an example, and by a series of analysis, such as reservoir sensitivity analysis, rock and mineral test and reservoir sedimentary study, the relationship between sedimentary microfacies and reservoir sensitivity is studied, and the spatial distribution laws of reservoir sensitivity is revealed. The main oil-bearing zones are Member 2 and Member 3 in Shahejie Formation in Oligocene Series in Linnan oil field of Huimin sag in Bohai Bay basin, whose sedimentary facies is delta. Rock thin section analysis and X-ray diffraction analysis show that different sedimentary microfacies have different petrographic properties. The experiment analysis also slows that same characteristics in reservoir sensitivity also exist. Generally, the sedimentary microfacies that have fine grains, such as bank and crevasse splay, have much more clay minerals than the sedimentary microfacies that have coarse grains, such as under-water branched channel and debauch bar. So the former has stronger reservoir sensitivity than the latter in water sensitivity, flowing velocity sensitivity and acid sensitivity. Compared with delta plain, delta front has weaker water sensitivity, flowing velocity sensitivity and acid sensitivity. On the basis of the above study, we can predict the spatial distribution of reservoir sensitivity according to the sedimentary microfacies and then, design program to protect oil-bearing reservoirs.
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  The study of influence factors and predicting method of water blocking in the low-permeable sandstone formations

  ZHANG Zhenhua and NIAN Jienian

  , 2000, 27(3): 1359-0.

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  Water blocking is one of the most important mechanism of formation damage in low-permeable reservoirs. The experimental study of water blocking in low-permeable sandstone formations was conducted. The influence of gas permeability, porosity, initial water saturation, drive pressure and interface tension between oil and water on water blocking has been evaluated. A gray predicting model of water blocking has been established. It concludes from this paper that, the extent of damage caused by water blocking increases with the decrease in gas permeability and increase in water saturation of the formation and increase in interface tension between oil and water. The gray predicting model can be used to predict the severity of water blocking in low-permeable sandstone formations quantitatively. The accuracy of the model is also related to the representative core samples and experimental data.
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  Application of double-target directional well to potential tapping of a mature oil field

  WANG Rui-yu; YU Chuanmo; WANG Wenzhong and WANG Yunmei

  , 2000, 27(3): 1360-0.

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  Zhongyuan oil field is a complex block-faulted oil field characterized by very well-developed fault systems. This oil field is now in its middle-late development stage and it is very hard to keep its stable oilfield production. The main object of development adjustment is to find and recover the remaining oil. Double target directional well techniques are applied and generalized in recent years and the relevant satisfactory results are obtained: ①The remaining oils in higher parts of fault-blocks are fully mobilized to increase the recovery factor. ②Injection-production well systems in a complex block-faulted oil field are perfected. ③Some microreservoirs are developed, improving single-well economic benefit. ④Some new pays underneath the developed pay zones are penetrated as results of further exploration. ⑤Some thick and weakly flooded single pays are penetrated. ⑥Well production is high at early period, and wells will have more intervals for further penetration in later period. ⑦Wells are penetrated with a moderate cost and capital investment can be recovered in a relatively short time. Based on a sophisticated reservoir description and accurate prediction of remaining oil distribution the application of double-target direction well technique can get a stable oil field production and increase the development oil reserves as well.
综合
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  Applying comprehensive interpretation technique to the study of igneous rock reservoir in Kongnan area.

  GAO Yinjun; GUO Chundong; YU Zhong; ZHAO Lingyi; CHEN Bin; CAO Guoming; SUN Dehai and CHEN Jun

  , 2000, 27(3): 1361-0.

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  Kongnan area is located on the southwestern part of Fenghuadian structural belt, Huanghua sag, and is characterized by complicated structures. This igneous rock reservoir is large in size, with variable thickness and compact lithology. It is mainly distributed in Mesozoic and K1 Formation. A set of comprehensive interpretation techniques dominated by seismic data processing technique on work station and interactive technique are established, including formation correlation, formation identification, sophisticated structural interpretation and comprehensive interpretation. In the progressive exploration and development of this igneous rock reservoir in Kongnan area, this set of techniques are used to interpret the igneous rock reservoir in Jia-8-Well Block and Zao-22 natural fault block and the pattern recognition technique is used to identify the oil and gas potential. Both of them are predicted as favorable oil bearing area. These reliable predictions have been confirmed by production test results of newly drilled wells in these blocks. The successful application of this interpretation technique to the igneous rock reservoir in this area is based on an in-depth study of geologic regulations. The key to success is fully utilization of various information from every well and using various methods to make comprehensive analyses and interpretation.
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  A method of source rock evaluation by well-logging and its application result

  ZHANG Zhiwei and ZHANG Longhai

  , 2000, 27(3): 1362-0.

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  Source rock evaluation is the basis of geologically comprehensive evaluation. It is always bothered by lack of funds and rock samples. This paper suggests a evaluation method of source rocks in a continental basin by well-logging records. Suitably calibrated porosity curve (such as acoustic interval transit time log curve) is superimposed on a resistivity log curve. Two curves may be parallel and coincide each other in case of rock formation which are water saturated but lack of organic matters. In case of oil/gas reservoir rocks or non-reservoir rock but containing abundant organic matters, difference between two curves can be observed. Source rocks can be identified and evaluated by such differences of these two curves and their variations. Results of application show that this method is simple and feasible. It can evaluate the total thickness of source rocks and the vertical depth of their distribution rather correctly. It can be used to evaluate the total thickness of source rocks in each well and the depth of each source bed, grade the source rocks, determine approximately the threshold depth of hydrocarbon generation, and evaluate the areal distribution of source rocks as well.
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  A fracture density model for pelite reservoirs based on depth sequential analysis

  LAI Shenghua; XU Guosheng and ZHOU Wen

  , 2000, 27(3): 1363-0.

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  A fracture density model for the pelite reservoirs in several wells in the Gaojiaya oil field is presented by means of depth sequential analysis. The mean relative errors of the model only reach 13.5%. So its precision is higher than those of the regression analysis of constant coefficients and BP network model. The mean relative errors of the latter two are 38.7% and 17.9%, respectively. The data available have revealed that vertically the fracture densities decrease from 0.78 through 0.5 to 0.3 per meter as a function of depth and age (from late and early middle Pliocene to Miocene), and horizontally the fractures tend to be most developed along the structural axis. The mean fracture densities range from 0.58 to 0.6 and to 0.3 per meter, respectively in the Upper and Lower Pliocene and Miocene strata of the oil field.
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  Using the improved Boolean method to model sandbody framework

  LI Shaohua; ZHANG Changmin; LIN Kexiang; FANG ZHIXIONG and zhang Boqiao

  , 2000, 27(3): 1364-0.

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  Cretaceous stratum is the main gas producing zone in Kela area. It is important to know clearly the distribution of sand body of Cretaceous stratum in Kela area for exploitation in the future. However, it is difficult to build a sound sand body framework model by using general methods because there are very few wells and well distance is large in Kela area. In order to build up a rational sand body framework model based on information in existence, the authors adopt a method combining ground and underground data. On the basis of close investigation of two main field sections, the authors built sand body framework model by using Boolean method of stochastic simulation technology. Conventional Boolean method can be used to build framework model of only one kind of lithofacies. In order to characterize distribution of subtle sand body, the authors improved this method, then it can be used to build framework model of multi-lithofacies. In addition,its application example is given in the paper.
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  Well logging reservoir evaluation for Qianmiqiao buried hill condensate gas reservoir

  ZHANG Fengmin; SUN Guangbo; WU Zhanguo; XU Qizhong and LU Fengting

  , 2000, 27(3): 1365-0.

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  Qianmiqiao buried hill condensate gas pool is an important discovery made in 1999's exploration in Dagang oil field. Lithology of the condensate gas reservoir is carbonate rock and the reservoir space is of fracture-porosity type.This kind of reservoir is both the focus point and difficulty of exploration and a challenge to well logging interpretation at present. The paper presents the concrete application of special well logging program represented by imaging well logging to the carbonate rock reservoir evaluation for Qianmiqiao buried hill condensate gas reservoir. For instance, FMI (full hole microresistivity imaging) was used to macroscopically pick reservoir fracture and dissolved pores; FMI in combination with ARI (Azimuth Resistivity Imaging) were adopted to semi-quantitatively to quantitatively appraise fracture extension length and dissolved pore effectiveness; DSI (Dipole Shear Sonic Imaging) was used to diagnose permeable characteristics; CMR (Combine Magnetic Resonance Logging) was applied to discriminate reservoir fluid properties. Elanplus optimum model combined technology was adopted to acquire lithology profile; and effective thickness layering standards were established in association with conventional well logging data. Well test results showed that the application of special well logging program has played an important role in successful reservoir evaluation of Qianmiqiao buried hill condensate gas reservoir.
讨论
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  Self-potential detection principle of oil/gas reservoir and its application to field development

  WANG Junheng; DENG Mingsheng; PAN Zhuping; GUAN Zhining; WANG Shubin and SU Yongxin

  , 2000, 27(3): 1366-0.

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  Self-potential is one of important criteria in geochemical exploration. The important content of self-potential study is the mechanism of natural polarization. This paper introduces theories of oxidation-reduction potential and non-polarized cracking of long chain hydrocarbons. Mechanisms for ion polarization of oil/gas-aqueous solution and that of rock-oil/gas are suggested. Conditions responsible for polarized potential production are diffusion-migration of oil and gas, downward descending of aqueous solution, as well as the change of reduction potential gradient in the former; and diffusion-migration of oil and gas in the later. A conceptual model polarization is established. The presence of polarized potential is a general property of the existence of an oil/gas reservoir. The whole oil/gas reservoir together with its diffusion-flowing belt can be taken as the source of the potential field, and the polarized potential can be described by a model of polarized dipole. An analytical expression of potential field is derived based on a viewpoint of polarized dipole and electrical current. Calculations by using in-house model, field model experiment, and various models prove the correctness of this theory. On the basis of laboratory experiment, self-potential technique is applied effectively to locate highly effective blocks and extension of oil/gas field. With the criteria of an oil/gas reservoir in Northeastern China such as size, wide, boarder gradient of its surface self-potential etc. and combined with other factors, the development results of 65 development wells are predicted with success ratio reaching 85%.
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  A discussion about the methods for predicting pore pressure

  SHAO Xinjun; XU Jun; LV Zhongfeng and MAO Tinghui

  , 2000, 27(3): 1367-0.

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  Predicting pore pressure has always been a hot spot in oil exploration. The relationship between log response and overpressure is discussed, using the data of sonic log and pore pressure of the overpressuring wells in Kuqa sag of Tarim basin. Subsequently the relationship between evolution of shale porosity and log response is also examined, showing the currently used relationship between effective stress and shale porosity is not always valid. Thus those methods for predicting pore pressure based on the relationship widely used in basin modeling need to be improved. When the relationship is determined for application, recognizing the causes of overpressure in the prospect area should be the most important. Then the validity of the method for predicting pore pressure is known and the results of modeling should be interpreted carefully.
应力场研究
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  Quantitative studies on palaeotectonic stress field by photoelastic experiments

  SHAN Jiazeng; MENG Qingren; YUE Leping and CHEN Yuee

  , 2000, 27(3): 1368-0.

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  Studies on palaeotectonic stress field are nowadays a hotspot at the researches of structural geology and petroleum geology. Stress that acts on rock/layer may result in its deformation, which are not same in the shape and the behavior, and then rising migration and accumulation of oil and gas. It is very difficult that all parameters of palaeotectonic stress field are immediately obtained from the geological body. In recent years, geologists tried to use a method of photoelastic experiments in the study of palaeotectonic stress field. Photoelastic experiment is an effective method which may directly observe and measure the stress state in the body under the action of outside force in the laboratory condition, so that it is a fact to gain quantitatively the orientation of maximum principal stress, the trajectories of principal stresses and the magnitude map of the stresses. Similar theory, apparatus, materials and method are also introduced simultaneously in the paper. Experimental results and considerations have been shown with the photoelastic experiments of palaeotectonic stress field in the Fuyu oil bearing strata of the Sanzhao depression, in the north of the Songliao basin as an example. Insights dependent on dynamic and physical analysis of experimental results may be summarized as follows: ①The relationship between the deformation of the rock and the migration of oil-gas under action of palaeotectonic stress are non-synchronous in time. The migration of oil and gas lagged behind the initial stage of structural deformation. ②The orientation and magnitude of maximum principal stress controlled the distributions of the stress concentration and high potential energy in the non-homogeneous media. ③Horizontal angle between the orientation of maximum principal stress and the trend of the fault is less than 90°. The orientation of minimum principal stress is approximately parallel to the trend of the faults. ④The map of the stress trajectories could describe geometric relationship between the orientation of the stress transfer and the orientation of the migration of oil-gas. It is important to determine the area of low potential energy and to predict favorable structural area for oil and gas accumulations in accordance with the isopleth map of the stress. Quantitative studies on palaeotectonic stress field by photoelastic experiments have provided a new way and effective experiment method for studying the dynamics of structure, and dynamics of oil and gas accumulation, which is very helpful to realize the conversion from qualitative investigation to semi-quantitative or quantitative analysis in the study.