Petroleum Exploration and Development

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Exploratory prospects of unconventional oil-gas resources in China

NIU Jiayu and HONG Feng

, 2002, 29(5): 231-0.

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China is rich in unconventional oil-gas resources (namely, heavy oil, tar-sands, deep basin gas, coal bed gas, and so forth). It is estimated that this resources size, in contrast with conventional oil resources, is over 8×1010t (oil equivalent). They are unique in their accumulation and distribution. A lot of Tertiary heavy oil reservoirs were formed in East China, Meso-Paleozoic asphalt veins and tar sands in South China, as well as Meso-Paleozoic heavy oil reservoirs and tar sands distributed at north and northwest margins of basin in West China. Approximately 2.5×1010t of heavy oil is predicted in China. Initial study shows that there are favorably geological conditions for deep-basin gas formation in some large-scale coal-bearing basins of our country. It is estimated that the resource extent of deep-basin gas in the middle part of China amounts to 4×1013-5×1013m3.The pilot exploration of coal-bed gas in Dacheng and Xinshui areas, Huabei region, indicates that there are great exploratory prospects in Carboniferous-Permian coal-bearing strata, Huabei region. At present, the proven extent of unconventional resources is quite less explored in China; so, China possesses a huge potential in unconventional oil-gas exploration.

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Rock mechanics characteristics in northern Tarim basin and its geologic significance

ZHOU Xingui; CHEN Yongqiao; SUN Baoshan; XU Hongjie; CAO Chengjie; DUAN Tiejun and SHE Xiaoyu

, 2002, 29(5): 232-0.

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The cores collected from outcrops of Kuqa depression, Keping uplift and Bachu uplift in Tarim basin involve three main types of rock (i.e. metamorphic rock, igneous rock and sedimentary rock), thirty-three horizons (Pt-N2k) and fifteen kinds of lithology. The rock mechanic factors (modulus of elasticity, Poisson's ratio and compressive strength) of 215 sets of samples were tested and analyzed. The rock mechanic features, deformation behavior and their major influential factors were studied; and a comprehensive profile of rock mechanics in Tarim basin was established. Combining with previous studies, five major detachment layer systems were proposed, improving the divisions of detachment layer systems and tectonized layers and providing solid experimental evidence for studying deformation behavior of a basin.

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Characteristics and occurrence of immature oil in southern Songliao basin

GU Zuqing; LIU Hongyou; JING Chengjie; SHI Zhongbin; GAO Yu; SHENG Li and SUN Hong

, 2002, 29(5): 233-0.

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In this paper, the author directs the source rock and distribution law of immature oil by analysis of geochemistry characteristics of crude oil. Immature oil only exists in Heidimiao reservoir among six oil-bearing strata. To immature oil, the relative density, and the content of saturated hydrocarbon are high, the content of pregnane and homopregnane are low and the ratio of saturated hydrocarbon to aromatics are high, asphaltene content is low, the maximum of OEP index is 2.22 with an average value of 1.34 and the ratio of protane to phytane is 1.53. There is the “V” pattern distribution of 20R-5α(H), 14α(H), 17α(H)-cholestane, 20R-24-Methy1-5α(H), 14α(H), 17α(H)-cholestane and 20R-4α-Methy1-5α(H), 14α(H), 17α(H)-cholestane, content of methyl sterane, diasterane and methyl sterane is low. The immature oil mainly comes from immature source rock of Nenjiang Fomation. The latest potential exploration areas are located in Xinbei-Xinli, Tahucheng, Dalaoyefu, southern Honggang and Heidimiao areas.

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Formation mechanism and main controlling factors for lithologic reservoirs in northern Songliao basin

FU Guang; ZHANG Yunfeng and DU Chunguo

, 2002, 29(5): 234-0.

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Based on studying the types and characteristics of lithologic oil reservoirs in northern Songliao basin, this paper puts forward three formation mechanisms for lithologic oil reservoirs: oil or gas from source rock migrating into lithologic traps in sourcerock and forming oil or gas reservoirs under the action of capillary pressure; oil or gas from source rock migrating into lithologic traps over source rock and forming oil and gas reservoirs under the action of abnormal pore fluid pressure and buoyancy, and oil or gas from source rock migrating into lithologic traps under source rock and forming oil or gas reservoirs under the action of abnormal pore fluid pressure. Delta and ancient river are the main places where the lithologic oil and gas reservoirs were formed in northern Songliao basin. Fault is the sole passage for oil or gas to migrate into the lithologic traps over or under source rock. The key that oil or gas accumulates in lithologic trap would be in the source rock.

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3-D sealing properties of Dazhangtuo fault in Dagang oil field

HU Wangshui; Lü Bingquan; GUO Qijun; LI Gongquan and LIU Baojun

, 2002, 29(5): 235-0.

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Fault seal can arise from reservoir/nonreservoir juxtaposition or by development of fault rock having high entry pressure. As for fault seal arising from reservoir/nonreservoir juxtaposition, a model is presented that is based on Allan method. 3-D fault surface has been produced showing reservoir juxtaposition areas. In addition, some parts of the fault have high entry pressure caused by clay swear. These two factors lead to fault sealing. As to fault seal due to fault rock having high entry pressure, some types of attributes can be defined, such as clay gouge ratio, pressure data from exploration and production wells. Then, these paramters are to calibrate them in areas where across fault pressure differences are explicitly known from wells on both sides of the fault. There are good sealing properties in the mid-low part of Dazhangtuo fault.

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Applying optimum combination of sciesmic attribute and gray correlotion analysis technology to the prediction of oil and gas reservoirs

SONG Weiqi; LIU Jianghua; WANG Xiaoma; LU Shihua and NIU Leqin

, 2002, 29(5): 236-0.

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In this paper, for the sediments of shallow lake shore faceis in Es2, the seismic attributes indicating variation of the bed with oil were studied, and the seismic attribute which can obviously show oil-bearing interval in seismic attributes of targets were revealed, then seismic attributes are selected and combined. In order to remove the local aberration data, we have studied processing and weighted filtering techniques of seismic attributes. On the groundwork, the authors of this paper discussed gray theory, and formed a new better method for oil-gas prediction with well joining the studied technique. The ideal results are obtained for field data.

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Siesmic reflection character of volcanic reservoir of Daqing and the comprehensive prediction technology

ZHAO Guolian and ZHANG Yueqiao

, 2002, 29(5): 237-0.

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Volcanic rock research is a main issue of oil-gas exploration of deep-seated reservoir in Daqing, foreign and native workers are paying more and more attention to it. This paper started with single well analysis, based on the geological background information and strata serial information, the character of seismic reflection of the volcanic rocks was studied, and the reservoir character of volcanic rocks was investigated by using seismic attitude technology and seismis-geology synthesis. The predicted space distribution of volcanic is more accuracy because of using visualization method. Geological-seismic technique can supply useful data for future exloration of oil and gas.

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An integrated study on biolithite reservoir in Wangxuzhuang oil field

WANG Wenrong; GAO Yinjun; LENG Jichuan and LIU Yonghe

, 2002, 29(5): 238-0.

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Wangxuzhuang oil field has entered into high water cut and high production period with composite water cut being above 90% and a rapid oil production decline. By carefully combining 3-D seismic data, drilling data, well logging data with oilfield development performance data, and making detail structural analysis of Wangxuzhuang oil field, and at the same time, taking intergrated study dominated by the micro sedimentary facies analysis on the main biolithite pay zone of E3s31, three potential areas of remaining oil have been found, which produced high commercial oil after putting into production, with an initial water-cut less than 20%.

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The influence of formation compressibility and edge and bottom water size of abnormally pressured gas reservoir on recovery performance

WEI Junzhi and ZHENG Rongchen

, 2002, 29(5): 239-0.

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Accuracy of the formation and water compressibilities used in productivity prediction of abnormally pressured gas reservoir significantly influences the prediction results. Considering the formation clay content variety and the bottom water size this paper predicted the recovery performance of abnormally pressured gas reservoir KL2 by using formation compressibility measured in laboratory. The methodology dealing with the formation and water compressibilities and bottom water size could be applied in abnormally pressured gas reservoir performance prediction.

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Research and practice on well-pattern type of ultra-low permeability oil field

SHI Chengen; LI Jian; LEI Qihong and ZHANG Aidong

, 2002, 29(5): 240-0.

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The reasonable well pattern disposition is a key factor that ultra-low permeability oil field is developed successfully because it is usually relative to fracture. This paper presents that the reverse rhombus 9-spot and rectangle well pattern match best the fracture and injection-production pressure systems. This is the result of reservoir engineering study including numerical simulation, driving pressure gradient analysis etc, and reviewing the evolution of well pattern for Changqing ultra-low permeability oil field. In development practice, reverse square 9-spot, reverse rhombus 9-spot and rectangle well pattern were adopted according to little, fair and well-developed fracture systems, which produced evident effect.

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The geological concept model of braided channel sand body in delta plain and its modification

LI Yuanjue; LI Yuegang and LU Tao

, 2002, 29(5): 241-0.

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Braided channel sand body in delta plain laterally migrates frequently. The lateral continuity of the channel sand body is good, but the shape of the individual sand body is different from each other and low permeability shoe-string and intercalated shale distribute here and there. According to the characteristics of the braided channel sand bodies in Changqing exploration area, three multi-layers geological concept models with interlaminated heterogeneity geological concept model have been put forward. These models were tested and modified by history match of reservoir simulation with well test and can be helpful in early reservoir study.

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“Single-point testing” empirical productivity formula and test conditions for gas wells in Lower Paleozoic of Changqing gas field

FAN Jiwu; HAO Yuhong and GOU Honggang

, 2002, 29(5): 242-0.

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The purpose of this study is to enhance the accuracy in determing open-flow capacity values of gas wells in Lower Paleozoic of Changqing gas field by “single-point testing” method. After studying the highly accurate modified isochronal testing data of Lower Paleozoic gas wells of Changqing gas field, it was discovered that there is a good relation between the empirical parameter “α value ” determined by “single point testing” method and the aeolotropies of gas reservoirs. Hence, the empirical productivity formulas for the gas wells of relatively homogenous and aeolotropic gas reservoirs were established with the “single-point testing” method respectively. After analyzing errors in the open-flow capacity calculated with “single-point testing” method in Changqing gas reservoir, the authors of this paper defined some needs that must be met in using single-point testing method for gas wells. If these needs are met, the errors of open-flow capacity calculated are generally less than 10%.

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A research for water shutoff in the bottom water reservoir

CAO Jiankun; YANG Shengzhu; ZHANG Hongqiang; HE Jiang and XIE Zhen

, 2002, 29(5): 243-0.

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In the light of Changqing oil field with the features of lower permeability and bottom water, three ingredients of blocking off agents have been developed, and three matching operation tests have been carried out in the work field, at the same time, some tough technical problems, such as the further perfection of the ingredients of blocking off agents, optimization of water blocking off technical operations, the choice of operating sites and oil wells, the judgments of water producing layer after water conning and the radius of the water conning body, the confirmations of intensity and parameter of water blocking off, have been studied comprehensively in the paper.Whether the tests are successful or not, oil reservoir potential analysis, judgment of bottom water conning, rationality of choosing the blocking agents, reliability of the operation techniques and on-site facilities will play an important role during the whole process, and the successfully tested wells have offered remarkable social economic benefits.

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Deep scaling control and removal techniques for oil wells

MA Guangyan

, 2002, 29(5): 244-0.

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The paper presents the technical features of complex scale removers REMOVAL Ba, CQ-3 and organic anti-scaling agent NTW-3, and their application results in oil wells by using squeeze treatments. The scale-dissolving rate of the scale remover REMOVAL Ba is 60% for Ba scale and 100% for Ca scale; and the scale-dissolving rate of the scale remover CQ-3 is 100% for Ca scale. Organic anti-scaling agent NTW-3 is characterized by both preventing the scale and stabilizing Fe ion, and has greater adsorption capacity and suitable de-adsorption rate in the formation. Based on the application result of the anti-scaling technique in 12 oil wells, it shows that the stimulation effect is obvious and the effective life is more than 20 months.

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High energy combined perforation technique and its application

LI Keming and ZHANG Xi

, 2002, 29(5): 245-0.

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High energy combined perforation technique, which combines perforation and fracturing, simultaneously ignites the perforating bullets and the solid propellant with the explosive fuse. The bullets explode and perforate in different phases, and the high-pressure gas coming from the detonation of propellant fractures the formation along the perforation tunnels. The fissure network of high conductivity near wellbore can increase the flow area greatly. A series of tests on large-scale surface cement target have certified that the radial fracture lengths are over 2.5m. Oil field application in more than 1200 wells shows that this technique evidently improves production and injection, with low cost and safety operation. The system of high energy combined perforation technique is composed of perforation equipment, production technology, surface detection technique, oil field operation technology, modern downhole testing and advanced software of optimization design and analysis, and it will made tremendous progress and innovation in oil perforation technique.

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Fracturing technique of super-low permeability reservoir development

ZHAO Jingzhe; LI Shuheng; QU Xuefeng and LIU Lili

, 2002, 29(5): 246-0.

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In the paper, the development character, the optimization design and test result of pilot test fracturing of Chang 6 reservoir in Jing′an oil field is introduced, and the adaptability and feasibility of the fracturing technique used in the reservoir with super low permeability is clarified. It indicates that development-fracturing technique can achieve the reasonable mate between well pattern and artificial fracture in the reservoir with low and super low permeability. On one hand, it can assure oil well of controlling enough economic recoverable reserves; on the other hand, it can fully satisfy the demand to improve the fracturing scale of low-permeability oil-bearing formation, and it is easy in the lateral to establish effective pressure-displacement system, and increase sweep efficiency and ultimate recovery factor. This technique has high popularizing value.

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Rules of petroleum source correlation and their application in the Changqing gas field—A reply to “Feature of mixed gas in central gas field of Ordos basin”

XIA Xinyu

, 2002, 29(5): 247-0.

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Works on petroleum-source correlation should comply with the following rules: the correlation results should first conform geologically to petroleum distribution, then conform to the evaluation of source rock. When to determine the main source from two sets of source rock of a gas reservoir, reserve amount represented by samples with each type of geochemical indices should be taken into account, instead of the numbers of samples. The concentration and geochemical indices of the remark minor components in each end member of mixing gas should be defined reasonably. Of the two different results of gas-source correlation of the Ordovician gas reservoir of the Changqing gas field, the opinion of “Carboniferous-source” conform to the distribution of gas pools and the evaluation of different types of source rock in Carboniferous, and can explain the difference between the geochemical indices of Ordovician pool gas and those of Permo-Carboniferous pool gas; while the opinion of "Ordovician-source" is contradicting to both the Ordovician gas reservoir distribution and Ordovician hydrocarbon potential evaluation. Natural gas in Ordovician reservoir is generated mainly from Carboniferous instead of from Ordovician.

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Some thought about critical time of petroleum system

CHEN Ruiyin and XU Sihuang

, 2002, 29(5): 248-0.

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Based on the Magoon and Dow's study on critical time, the paper analyzes the influence of critical time on terminal reservoirs. And the influence usually comes from sustaining petroleum system affairs. According to the analysis of affairs process, the authors hold that: there is some absurdity in the original petroleum system affairs analyzing chart. Through the rebuilding of petroleum system affairs analyzing model, people can probe quantitative appraisal method to critical time, simultaneously, and tap the other applications of the model in petroleum potential evaluation.

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Natural gas pool in Ordovician reservoir in Wumaying buried-hill and its formation history

FU Lixin; CHENG Shanyong; WANG Danli; LIU Shuzhi and WANG Xin

, 2002, 29(5): 378-0.

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Natural gas in Upper Ordovician system might be related to Upper Paleozoic sources by showing some similar geochemical criterion to coal-bearing units in former series. According to component and isotopic ratios of gaseous alkanes, the gas, which was drilled by Well Wushen 1 on the western Wumaying buried-hill, might be experienced multi-stage charging. The accumulation of gas pool in western Wumaying buried-hill was evidently influenced by succeeding tectonic evolution. And natural gas in Ordovician system in Well Wushen 1 was newly gathered through remigration of hydrocarbon which accumulated during latter Mesozoic era, after the former hydrocarbon trap being altered with dramatic faulted-block rotation during latter Oligocene. The forming time of which was inferred roughly during latter Tertiary according to fluid inclusion datum in cores of Wushen 1, delayed than critical moment of Paleozoic petroleum system in Wumaying district. Hydrocarbon generating history of Wumaying buried-hill was discussed in this paper based on analyzing process of ancient trap reconstruction by using paleostructure restoration technique. According to analyses, hydrocarbon in Ordovician carbonate reservoir in Wumaying buried-hill has undergone complicated remigration from northeastern to southwestern buried-hill, and hydrocarbon distribution changed from eastern condensate relic to western “wet gas”, owing to limitation of heterosphere of carbonate reservoir.

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Basic petroleum geological characteristics and resource potential of inter-salt non-sandstone reservoir

PU Xiugang; QI Zhixian; ZHENG Xiaoling and HAN Dexin

, 2002, 29(5): 379-0.

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Inter-salt non-sandstone reservoir is an exceptional particular reservoir all over the world. It is thin, but its horizontal spread is very stable, and its rhythm is very clear. This zone is not only source bed but also reservoir. Inter-salt source bed's TOC of Qianjiang Formation is mediocre, but its major organic matter is of sapropel type. The organic matter's HC conversion rate of this type is higher, vitrinite reflectance (Ro) is lower than normal Ro value. Main reservoir pore is solution cavity; the second is fracture. Reservoir's physical property is very bad; the reservoir has medium porosity but low permeability. Inter-salt non-sandstone reservoir is typical authigenic reservoir. Wangchang anticline is always located in the best migration direction of the inter-salt oil. The key forming times of inter-salt fractural reservoirs are the ends of Jinghezhen deposition and Guanghuasi deposition. The petroleum resource is very rich; the reservoir has already become another important area for oil and gas exploration and development in Qianjiang sag.

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Restoration of 3-D deformed surfaces

SHAN Yehua; SUN Hongbin; LI Zian and LIN Ge

, 2002, 29(5): 382-0.

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A novel algorithm of restoration of 3-D deformed surfaces was developed while adopting the theory of finite element. It is in the category of continuous restoration that is realized by constructing the reverse displacement gradient. Over most existing algorithms that belong to discontinuous restoration, it has the advantages of less data to be input and easiness to be programmed. An example from the bottom of Eocene-Oligocene Shahejie Formation in the eastern inshore of the Liaohe oil field was taken and applied to. The result showed that extension along the W-E direction varies from the northern part to the southern with the deformational styles, and that approximately E-W trending smaller faults in the vicinity of the NE trending boundary fault have a nearly dip slip without any apparent strike-slip component, as a school of geologists expect who agree that these secondary fault formed in a response to the strike slip of the boundary faults.

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The technique of permeability modeling in Jingbian carbonate gas reservoir

WANG Dongxu; WANG Caili; GOU Honggang and XU Wen

, 2002, 29(5): 383-0.

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As one of the most important parameters that affect gas field performance forecasting index, the reservoir permeability has direct influence upon evaluation of producing reserves, single well off-take potential, recovery efficiency and economy effect. The gas production has proved that flow capacity (kh) value obtained from well test is relatively reliable. Individual-layer flow capacity (kh) value can be calculated from producing proportion of each effective pay zone, divided individual-layer flow capacity (kh) value by net pay thickness can get individual-layer permeability. When protracting permeability contour map, the features of permeability distributing probability should be studied for present the rules of permeability distribution, so the contour interval and control area will consistent with permeability distribution probability, and the interwell permeability can be controlled effectively. The permeability model established based on the technique discussed above is maneuverable, it put emphasis on the relative high permeability of main reservoir, and presents the permeability distributing rule of certain area. Approved by gas producing history matching, the permeability model created and permeability value calculated can reflect the real permeability value of the gas reservoir impersonally.

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Using outcrop information of Kuqa depression to predict reservoir sand bodies in Tuziluoke gas field

WANG Shaohua; ZHANG Baiqiao; SHU Zhiguo; XIA Wenjun and WANG Changxun

, 2002, 29(5): 386-0.

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It is more practically significant to predict reservoir sand bodies of sand-shale member of Jidik Formation, Neogene using the abundant surface outcrop information because of the rare drilling data in Tuziluoke gas field, Kuqa depression. Based on the original different scale models of sand unit and reservoir member developed for the field and the fine description of the type, combination, scale and restraining barrier of sand bodies by the sedimentary microfacies analysis and the analytical hierarchy process of reservoir frame, the random prediction of inter-well reservoir sand bodies of sand-shale member, Jidike Formation has been developed using the conditional modeling and the parameters of geometry and structural feature of sand bodies provided by the original models combining with drilling and logging data. The study shows that the sand bodies are mainly longshore bar, with more tabular sand and less lenticular sand or wedge shaped body. The thickness of sand bodies is small in the concentrated sand member. There are three types of complex sand bodies (types of complex coarse upward, single coarse upward and rhythmic type). The vertical connectivity of sand bodies is poor and the lateral connectivity is good. Vertically, the most favorable exploration targets are No.1 and No.2 sub-members.

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Self-organizing mapping analysis of petroleum detection

CAO Siyuan; CAI Zhiguang and LIANG Chunsheng

, 2002, 29(5): 387-0.

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Self-organizing mapping analysis of reservoir study is a new technique developed through self-organizing mapping nerve network, whose major idea is the self-organizing mapping density map obtained from nerve network learning. Density map is a map of the data body used in nerve network learning. It maps two same or close samples in the data body to a position or two close ones, which shows that these two samples have strong comparability in original space. There are few well locations used to restrain reservoir prediction at the early stage of exploration. Therefore, the authors of this paper had to resort to the clustering relationship existing in original data body, apply self-organizing mapping technology to the performance of the clustering analysis on the implicit oil and gas information of the data body and locate the well finally so as to improve the success ratio of future drilling greatly.

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The effective driving pressure system study and adjustment techniques of waterflooding in Ansai oil field

LI Shujun; LIU Liangren and XIONG Weiliang

, 2002, 29(5): 390-0.

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The effects of many factors on waterflooding in Ansai extra-low permeability oil field, such as the stronger heterogeneity of reservoirs, the bigger starting pressure difference and driving pressure gradient, the natural fracture development and the declining productivity index after water breakthrough are getting increasingly strong. On the basis of Pressure Superposition Principle, the formation pressure distribution, the pressure difference and pressure gradient between producers and injectors were established, and the reasonable well array spacing and the effective driving pressure system were determined by using the start-up pressures gained from laboratory experiment and on-site measurement. These methods, combined with some other adjusting techniques of waterflooding, such as forced waterflooding, non-steady waterflooding, line waterflooding along the fracture, adjusting injection and production profile and infill drilling along the fracture, have provided good result in stabilization of oil production.

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Accurately calculating dynamic reserves of low-permeability gas reservoir

HAO Yuhong; XU Min and XU Xiaorong

, 2002, 29(5): 391-0.

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From analysis of the production performance and percolating characteristics of low permeability gas reservoir, the characteristics of elastic 2-phase method curves and pressure drawdown curves of low permeability gas reservoir were studied. If the production from wells drilled in low permeability gas reservoir is over high, it will cause insufficient gas supply, present “pseudo-steady state”, and create the dynamic reserve calculated by elastic 2-phase method being on the low side. Besides, low-permeability reservoir follows the natural percolation law of fluid flowing through “easily permeable zone first, difficultly permeable zone last” and “high permeable zone first, low permeable zone last”. In addition, the build-up time needed by artificial shut-in well is short and the present formation pressure measured is on the low side (unsteady), resulting in the pressure drawdown curve presenting “multi-section type”. Thus, if the dynamic reserves are calculated generally by pressure drawdown method—only by “a pressure drawdown curve”, the error will undoubtedly be big. Based on this, the authors put forward applicable conditions and new methods that can be used for accurately applying elastic 2-phase method and pressure drawdown method to the determination of dynamic reserves of low-permeability gas reservoir. This plays an important part in understanding the characteristics of dynamic reserves of low-permeability gas reservoir and getting reliable calculation result.

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Reservoir description of Lower Paleozoic in Changqing gas field during exploitation phase

ZHANG Minglu; WANG Yong; LU Tao and WANG Hua

, 2002, 29(5): 396-0.

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Lower Paleozoic reservoir in Changqing gas field is a deeply buried Karst carbonate reservoir. Following features were found: complicated distribution of erosion groove and trough in the gas field, strong heterogeneity, thin gas-bearing bed and big difference in production between single wells. In order to objectively describe reservoir character, search the high yield controlling factor and distributing rule of reservoir and enhance development well drilling success ratio, the paper fastening reservoir geology feature tightly，applying theory of geology and seismology, adopting dominance method, reconverting method and so on，carried through research of sedimentary and diagenesis micro-facies, quantitative description of reservoir and paleo-geography and description of small relief structure and cranny structure, pore structure research and description, description of gas and stratum water distributing rule, reservoir lateral prediction and so on. Based on above research results, the authors of this paper found out that microcosmically high yield well is controlled by dissolved hole, pore throat and fissure and microcosmically by paleo-geographic feature, small relief structure and sedimentary and diagenetic micro-facies. These above research results have been applied in placing development wells timely and offered wonderful exploitation economy benefit.

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Technology for controlling injection water quality in Changqing oil field

WANG Xiaolin; WU Pingcang and XIANG Zhongyuan

, 2002, 29(5): 397-0.

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Changqing oil field is a low and extra-low permeability oil field developed mainly under waterflooding. The injection water quality plays an important role in oilfield development. Based on the geologic conditions and research and practice on injection water quality controlling technology of this oil field, this paper discussed the factors, which have effects on oilfield water injection, such as corrosion, scale, plugging, water-sensitivity, etc. The corrosion of injection water in Changqing oil field is mainly caused by dissolved oxygen and SRB cell. The low-permeability reservoirs of Changqing oil field will not be damaged when the content and mean diameter of particle in injected water are below 1mg/L and 1μm respectively. The injection water, which is generally not matched with formation water, will form scale if it gets into the strata. The styles of scale are mainly BaSO4 and CaCO3. The injeition intervals are mostly slightly water-sen sitive and velocity-sensitive strata, but Layer Chang-2 commonly presents slightlymiddle to middle water sensitivity. Through the laboratory and field experiments, some techniques which are suitable for Changqing oil field, such as, oxygen removing and fine filtration, sterilization and corrosion prevention for injection water, scale prevention for water injection formation, water-sensitivity controlling to water-sensitivity formation and injection water quality control, etc, are developed.

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A field test of gas injection in extra-low permeability reservoirs of Jingan oil field

YUAN Lin; ZHAO Jiyong; ZHANG Zhao and WANG Yongkang

, 2002, 29(5): 404-0.

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Technical policies of reservoir development such as the rational well pattern, well spacing, perforation interval, gas-injection mode, gas-injection speed for Chang-6 reservoir in Jingan oil field are determined in this paper, through indoor experiment, oil reservoir simulation, and reservoir engineering study. As a result of more than 3-year field test of gas injection, adaptability and feasibility of extra-low permeability reservoir development by gas injection are discussed. The authors analytically sum up the changing laws of indexes such as oil production, water cut, GOR, producing fluid level, formation pressure, and component of associated gas, and factors influencing the results of Jingan oil field development by gas injection. Rational limits or technical policy for water flooding the oil field at early stage, and advices of adjusting the implementation plan are put forward in the paper.

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A research on applying thermal insulating property of foam cement to the thermal recovery of deep viscous crude oil

GU Jun; XIANG Yang; HE Xiangqing and WANG Xueliang

, 2002, 29(5): 405-0.

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Deep viscous crude oil production is still a difficult problem in the petroleum-engineering circle at home and abroad. However, the borehole thermal insulating is indispensable, no matter what are used. The authors analyzed the ways that can avoid heat lost of borehole and offered a suggestion on applying foamed cement completion to borehole thermal insulating in view of the characteristics of Tuyuke oil field, a fracture-pores crude oil reservoir. Based on the study on the properties of foam cement for borehole thermal insulating, pilot testing was carried out. It indicated that ①for viscous crude oil, reducing the thermal conductivity of cement circle is an important way for borehole thermal insulating; ②the thermal conductivity of foam cement circle is only half that of clean cement; and ③wellhead oil temperature of testing wells is 3℃ higher than that of experimental wells.

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Oil and gas resources economic evaluation characteristics of international petroleum companies

CAI Jingong; WU Jinlian and CHAO Jing

, 2002, 29(5): 416-0.

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The situation and characteristics of economic evaluation of petroleum resources of international oil companies was presented in the paper. International oil companies consider the economic evaluation as the most important work before investment, and run economic evaluation through the whole course of exploration and development. They take single project as the center of cost keeping and evaluation object, combine risk evaluation with economic evaluation, evaluate the exploration and development integratively, strictly implement scientific exploration procedures and continuously developed new evaluation techniques. These measures of international oil companies are that our national companies can make use of.

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Methods for evaluating commodity value of oil reserves

RAN Yuxia; ZHANG Zhao; CHE Qijun and MU Guoquan

, 2002, 29(5): 417-0.

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Using the foreign methods of evaluating oil reserves value as reference, the methods for evaluating commodity value of developed oil fields were put forward. Forcasting production by Arps decline curve and calculating commodity value of recoverable reserves by cash flow can be combined to evaluatethe reserves, economic production life and momentary value of remaining reserves and supply the decision-making basis for oil field development. Resreves were evaluated and results were analyzed by taking an oil field in Changqing oil province as an example.

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Some new achievements in sequence stratigraphy research

JIA Chengzao; LIU Delai; ZHAO Wenzhi; WEI Guoqi and ZHANG Junfeng

, 2002, 29(5): 433-0.

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Sequence stratigraphy research is an important subject in 2002 annual meeting of AAPG. Its new achievements summarized the recent progress on sequence stratigraphy research in one year. The principle parts contain:①Some new theories were put forward, such as kinematics tract, periodic change of earth radius resulting in change of sea level over one thousand meter in deep-sea basin, recognizing sequence of deep-sea shale, landslip datum plane in continental shelf edge and sequence of landslip and the change of climate being the principal motivity that form high resolution sequence, which validate the system that change of sea level is led by 400,000 years eccentricity period of Milancovth cycle; ②There are big achievements in the application of sequence stratigraphy, for example carbonate sequence stratigraphy, the relation between diagenesis and sequence stratigraphy, sequence stratigraphy applied in oil and gas system, forecasting trap, fine description of reservoir, forecasting hydrocarbon source rock and simulation expoitation developments of reservoir; and ③In addition to traditional methods such as out-crop examination, core description, explained seismic and log data processing and interpretation and so on, some new methods such as the high resolution sequence stratigraphy of palaeotology, the sample analyzing and testing and organic geochemistry, 3-D vidualization, intelligentized analyzing of seismic attributes, geostatistics, numerical simulation, pattern recognition and so on are introduced.

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Study on the characteristics of carbon isotopic composition and hydrocarbon generation potential of organic matter of Middle-Upper Proterozoic in northern part of North China

WANG Jie; CHEN Jianfa; WANG Darui and ZHANG Shuichang

, 2002, 29(5): 456-0.

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Eighty-three samples were collected from Middle-Upper Proterozoic in Huabei area. Their carbon isotopic compositions of the analyzed kerogens range from -35‰ to -26‰(PDB); at the same time, their total organic carbon differ from 0.03% to 16.47%. The search indicates that: (1)The sapropelic type of kerogens have lighter carbon iotopic composition (δ13C<-28‰), so, their kerogen combines sapropelic and humic-sapropelic types. (2)Hydrogen index of organic matter has a better negative correlation with its carbon isotope composition, but oxygen index of organic matter has a positive correlation with its carbon isotope composition. (3)The abundance of organic cabon is higher, their carbon isotope composition of kerogens is ligher. (4)According to the abundance of organic carbon and the potential of forming hydrocarbon of analysed samples, it is concluded that Middle-Upper Proterozoic existed four bed positions of better potential of forming hydrocarbon, namely, Xiamaling Formation, Tieling Formation and Hongshuizhuang Formation.

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The difference in geochemical characteristics of natural gases between eastern and western parts in Hetianhe gas field of Tarim basin and its origin

QIN Shengfei; JIA Chengzao and LI Mei

, 2002, 29(5): 457-0.

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Based on the study of geochemical characteristics of natural gases of Hetianhe gas field in Tarim basin and in combination with the analysis of source rocks and geological conditions, it is concluded that the alkane gases in Hetianhe gas field is high maturing dry gases with high content of CO2 and N2. The gases are of oil-type, which are generated from high-over mature Cambrian source rock. Hetianhe gas field distributes mainly from east to west like a belt. The buried gas layer of the field's western part is shallower than that of eastern part. The geochemical characteristics of natural gases are different between the eastern and the western parts. Compared to the eastern part, the natural gases in the western part have more CO2 content; and the dry coefficient is higher; Carbon isotope of methane is heavier. The reasons that cause the differences of geochemical characteristics of natural gases between the western and eastern parts in Hetianhe gas field are as follows: the gases migrated from east to west in the gas field and caused the different component of natural gas; the pressure became lower in western part of the field caused the dissolved CO2 releasing from water, thus the CO2 content became higher; methane could easily disperse through cap rocks in western part made the methane isotope became heavier.

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, Volume 29 Issue 5