, Volume 34 Issue 6
    

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    油气勘探
  • Potential areas for coal-formed gas exploration in China
    DAI Jinxing
    , 2007, 34(6): 1532-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Coal-formed gas plays an important role in the natural gas industry in China, accounting for 2/3 of the proved reserves and 4/5 of the total reserves of giant gas fields, and it is the main part of all the large gas areas. The eastern basins (in China) of Central-Asian coal-formed gas accumulation domains and the shelf basins (in China) in the central part of the east margin of Asian coal-formed gas accumulation domains are all dominated by coal-formed gases. Based on the structural characteristics of the deposition of coal measures and overlying rocks, the development areas of coal-formed gas fields can be divided into four types, including bistable type, stable-active type, fault depression-stable type and depression type. Though coal-formed gas exploration has made great achievements recently, there are some good perspective areas which have not been well researched and explored, such as the central Sichuan Basin, Yingjisu sag in Tarim Basin, Ludong-Wucaiwan area in Junggar Basin, Nanpi and Qikou sags in Huanghua Depression, central part of the east margin of Asian coal-formed gas accumulation domains, deep part of Songliao Basin, etc.
  • Breakthroughs of geological concepts in exploration and evaluation of BZ25-1 field
    DENG Yunhua and LI Jianping
    , 2007, 34(6): 1533-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    BZ25-1 field is located in southern Bohai Bay. Four wells were drilled on this structure during 1980-1984 in Sino-Japanese cooperation and found oil with high flow rate in the Shahejie Formation. However, the evaluation of the wells concluded that the structure was a litho-stratigraphic trap, the oil came from the turbidite sand of Shahejie Member Ⅲ with poor reservoir connectivity, and it was uneconomic with the calculated OOIP of only 12 million m3. Fifteen years later, an integrated study of paleontology, litho-facies, depositional facies, and structural integrity was carried out in 1998. It showed that the trap was structural and the pay-zones in the Shahejie Formation are the Member Ⅱ section with fan-delta depositional facies and good reservoir connectivity. Estimated OOIP was 56 million m3. Besides, it was discovered for the first time that the Minghuazhen Formation in the shallower section had much higher potential. The exploratory well BZ25-1-5 confirmed this new understanding. Further exploration and evaluation of the structure discovered OOIP of 200 million m3, which made this field the third largest one in Bohai Bay.
  • Contrast of transporting characteristics between faults and sandbodies of medium and large gas fields in China
    ZHOU Guangsheng; PENG Shimi; ZHANG Xiuli; WANG Yusheng and YANG Yu
    , 2007, 34(6): 1534-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The gas transporting channels of 63 medium and large gas fields in China are classified into 6 types: fault, unconformity, sandbody, fault-unconformity, fault-sandbody and unconformity-sandbody. Faults are the main transporting channel of gas, and the fault-dominant medium and large gas fields account for 55.56% of the total number. In order to contrast the transporting characteristics of medium and large gas fields which transport gas by faults and sandbodies, the gas transporting rate is used as a parameter to reflect the transporting ability. The gas accumulation efficiency of 53 medium and large gas fields transported by faults and sandbodies is studied, and it is concluded that the gas transporting ability through faults is stronger than that through sandbodies, and the difference between them is about 4 orders of magnitude. The contribution of fault transportation to the gas accumulation efficiency of medium and large gas fields is more than that of sandbody transportation.
  • Thermal anomaly and thermal evolution of source rocks in Mesozoic, Ordos Basin
    CHEN Ruiyin; LUO Xiaorong; ZHAO Wenzhi and WANG Hongjun
    , 2007, 34(6): 1535-0.
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    Based on the logical boundary conditions defined, the results of thermal evolution modeling of the Ordos Basin show that the temperature gradient of the Mesozoic Erathem during middle-late Jurassic is mainly from 43℃/km to 46℃/km, and locally (at Xifeng, Qingyang and their southwestern areas ) beyond 57℃/km. Combining the relationship between heat flow and lithospheric thickness with the evidence of seismic, gravity and magnetics, this paper concludes that the pattern leading to the Mesozoic thermal anomaly of this basin may be the stacking of crustal thinning regionally and concealed magma heating locally. In the context of thermal anomaly, hydrocarbons would be generated from the Triassic Yanchang Formation source rock when its burial depth reached 1600 meters in the Jurassic period. The mass hydrocarbon generation occured in the early Cretaceous epoch. Multiple-phase hydrocarbon-fillings are due to long expulsion process and tectonic adjustment.
  • Preservation and deliverability characteristics of coalbed methane, North China
    YAO Yanbin; LIU Dameng; TANG Dazhen; TANG Shuheng and HUANG Wen-hui
    , 2007, 34(6): 1536-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    One hundred and forty-four coal samples from 9 coalfields (or coal basins) in North China were examined using the microfracture analysis by fluorescence microscope, liquid nitrogen adsorption analysis and mercury-injection analysis. Microfractures in coals are dominantly less than 5μm wide and less than 300μm long, and frequency is about 20~200 strips per 9cm2. Porosity of the coals ranges from 2.38% to 10.3%, and is mainly of adsorption-pore (pore size less than 100nm) which is favorable for adsorption and accumulation of gas, but unfavorable for desorption and recovery of gas. Accumulation ability is best in Jiaozuo, Xinggong, secondarily in Pingdingshan, Datong, south Qinshui, and followed by others, while deliverability is best in Huainan-Huaibei, Pingdingshan, Anhe, and worst in Yongxia and Datong. Poor-developed microfractures in Jiaozuo, poor connectivity in Xinggong, and low proportion of seepage-flow pores (pore size larger than 100nm) in Qinshui bring about "bottleneck problems" for the recovery of coalbed methane.
  • Sequence stratigraphy and depositional system of Paleogene Shahejie Formation in Liaodong Bay Depression
    LI Dejiang; ZHU Xiaomin; DONG Yanlei; ZHANG Xiaojing; CHEN Jianqing; SUN Qi and XIONG Zuowei
    , 2007, 34(6): 1537-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Liaodong Bay Depression in Bohai Basin is one of the main petroleum provinces in the east of China. It includes 3 sags and 2 uplifts, 5 secondary structural units in total. The Liaozhong sag is the biggest and deepest one and is filled with Paleogene and Neogene sedimentary deposit. Based on the data of seism, drilling, logging and paleontology, the sequence stratigraphy framework is built up. The strata of Shahejie Formation in the depression can be divided into three second-order sequences and six third-order sequences. The distribution characteristics of the sequences are analyzed and contrasted. The braided delta, the fan delta and deep water turbidite fan are the main sedimentary facies. The depositional model of Shahejie Formation is drawn out. The depositional area of Es4 is smaller, while those of Es1+2 and Es3 are larger. The depositional water of Es3 is deeper than Es1+2. The braided delta front of Es1+2 sequences is a favorable exploration area.
  • Facies controlled modeling of close spacing Es31, Block Long 10, Liaohe Oilfield
    LI Yu-jun; DENG Hongwen; ZHANG Xinpei; LONG Guoqing and TIAN Wen
    , 2007, 34(6): 1538-0.
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    The environment of Es31 in Block Long 10 of Liaohe Oilfield is a fan delta near the source, the sand-body distribution is very complicated and the reservoirs have strong heterogeneity. To better characterize the discontinuity of the reservoir physical properties, micro-facies modeling is built in a deterministic way with the "hard data" of closely spaced wells and geologist's experience. Under the micro-facies modeling, the reservoirs and their parameter distribution are predicted by Sequential Gaussian Simulation. The accuracy and practicability of the method in the prediction are verified by application.
  • Fluid inclusions of Palaeogene Eh2 reservoir of Hetaoyuan Formation, Nanyang Sag
    SHI Zhongsheng and HE Sheng
    , 2007, 34(6): 1539-0.
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    Based on the Eh2 reservoir core samples from the Dongzhuang, Zhangdian and Beimazhuang Oilfields of Nanyang sag, a systematic analysis of fluid inclusions is employed to study the hydrocarbon charging histories in the reservoir. Fluorescence observation on petroleum inclusions and micro-thermometry of both petroleum and aqueous inclusions indicate that the Eh2 reservoir experienced three stages of thermal fluid activity, and the first and second stages were associated with petroleum charging. The homogenization temperature and time-temperature burial history shows that the first petroleum charging occurred in the late rifting period and uplifting stage of Nanyang sag, and the second petroleum charging happened in the depression stage. Analysis of fluorescence observation and homogenization temperature distribution of petroleum inclusions, and the source rocks thermal evolution during the petroleum charging shows that the first petroleum charging is composed of low-middle maturation oil and the amount is little, and the second petroleum charging is composed of middle-high maturation oil and is the main petroleum charging of Nanyang sag.
  • Two extreme modes of reservoir sedimentation: Active rift and passive rift
    OUYANG Wensheng; ZHANG Zhihuan; LU Huangsheng; ZHANG Minghua and CHENG Yandong
    , 2007, 34(6): 1540-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Active rift and passive rift are the two extreme modes of rift basin. These extreme modes are embodied in the sedimentation of reservoirs. Active rift basins originated from the apophysis of mantle heat flow or the plate subduction have the development sequence of volcanic activity followed by rift activity. The sedimentation of reservoir rocks is bimodal and monocyclic. Passive rift basins originated from the weakening of lithospheric intensity which is caused by extensional stress. The development sequence is rift activity followed by volcanic activity. The sedimentation of reservoir rocks is bimodal and multi-cyclic. The petrologic structure and physical properties of reservoirs also correspond very well with the two modes, that is, local reservoirs of poor properties are developed in the fault depression stage, regional reservoirs of good properties are developed in the depression stage, and the reservoir properties in passive rift basins are better than those in active rift basins.
  • Perspective of development in detailed reservoir description
    JIA Ailin; GUO Jianlin and HE Dong-bo
    , 2007, 34(6): 1541-0.
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    Detailed reservoir description is a multidisciplinary research of remaining oil, aiming at studying its distribution and control factors. The main contents of detailed reservoir description include the reservoir characterization and detailed geological models, the dynamic behavior of reservoirs and fluids during the oilfield development, and the distribution of remaining oil. Based on the current technology situation at home and abroad, this paper points out that its key scientific problems consist of reservoir sedimentology, reservoir prototype geological model, quantitative geology, sequence stratigraphy, dynamical property and the distribution of remaining oil. Finally, the paper shows the future development trends of detailed reservoir description which include fine reservoir sedimentology, digitalization reservoir, multi-discipline study, and popularization and application of new technologies and theories.
  • Additivity of hydrocarbon-generation kinetic parameters for organic macerals and its application
    WANG Feng; ZHANG Dajiang and XU Guanjun
    , 2007, 34(6): 1542-0.
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    The pyrolysis data of several macerals are studied in terms of chemical kinetics and the distribution and the mean of activation energy for these macerals can well explain their hydrocarbon-generation characteristics. According to the additivity property of these kinetic parameters, a new method of allocation is suggested. It consists of two parts: in forward process, obtaining the kinetic parameters of mixture samples from the pyrolysis data of macerals, and in inverse process calculating the kinetic parameters of macerals from mixtures. The calculating results show that the forward process is feasible, suggesting that the "representative parameters" of the geochemical characteristics of certain formation or area can be artificially synthesized and used to improve the precision of the quantitatively modeling of hydrocarbon-generation in geologic history. The reverse process, however, is unsuccessful, owing probably to the negligence of errors of the pyrolysis data and/or the effect of inorganic minerals on hydrocarbon-generation which result in the failure of the iterative calculations.
  • Origin and property differences of various types of low-porosity and low-permeability reservoirs and well logging evaluation strategies
    ZHANG Longhai; ZHOU Cancan; LIU Guoqiang; LIU Zhonghua and ZHANG Li
    , 2007, 34(6): 1543-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    The properties of low-porosity and low-permeability reservoirs are controlled by such factors as sedimentary source, sedimentary environment, diagenesis, structural stress, etc. By comparing the sedimentary sources，environments and facies, diagenesis of 3 typical target areas (Cretaceous of Songliao basin, Permian to Triassic of Ordos basin and Jurassic of Junggar basin), the origin of low porosity and low permeability reservoirs is summarized. Based on the analysis of the differences of the origins, reservoir properties and porous types, and the controlling factors, the reservoirs are divided into three types: distal-lithic sandstone reservoirs with low porosity and low permeability, dominated by secondary inter-granular dissolved pores; diagenetic arkose sandstone reservoirs with low porosity and low permeability, dominated by secondary pores and primary pores; proximal lithic sandstone reservoirs with low porosity and low permeability, dominated by inter-granular pores. Well logging strategies are put forward in view of the reservoirs. The application results indicate that the interpretation coincidence rate of well logging is increased by 10%-20%.
  • Application of tuning-energy-enhanced method to thin bed identification in Block Shinan 21
    SUN Xiping; LI Jinsong; ZHENG Xiaodong and ZHANG Yan
    , 2007, 34(6): 1544-0.
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    Tuning-energy-enhanced method (TEEM) is a new way to improve seismic imaging ability, which enlarges reflection energy of thin beds through pulse-constrained self-fitting enhancement according to seismic sequence model and thin bed tuning theory and on the basis of post-stack seismic data. Time-frequency analysis is an effective tool for TEEM. On the one hand, it can be used to analyze frequency distribution and sedimentary rhythm. On the other hand it can estimate the geological effect of seismic resolution improving. TEEM breakthroughs the limitation of traditional seismic resolution, and can be used to recognize very thin beds. In the Shinan 21 block, TEEM was used, and S/N ratio and resolution were improved simultaneously and thin bed recognition and characterization ability was improved correspondingly. According to the comparing results of modeling, calibrating, inversion, spectral-decomposition, it’s proved that TEEM is an effective tool for thin bed identification.
  • Pre-stack inversion oriented noise attenuation
    LIU Jianhong; MENG Xiaohong and CHENG Yukun
    , 2007, 34(6): 1545-0.
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    Pre-stack elastic inversion requires high-quality S/N ratios and well-preserved amplitudes of the input seismic data, but the S/N ratio-enhancing pre-stack noise attenuation processes often cause distortion to signal amplitudes. Therefore, one of the crucial steps to ensure the quality of inversion is to choose the most suitable noise attenuation technique and optimum parameters according to specific data conditions. Taking the L area of J Oilfield as an example, this paper introduces some ways to use the commonly-used noise attenuation techniques properly and ways to monitor amplitude fidelity, and shows the importance of pre-stack noise attenuation to elastic inversion. Through the comparison of the effects of the techniques, such as abnormally large amplitude noise attenuation, ground roll reduction, multiple elimination, and random noise attenuation, some ways are presented to monitor and control the effects of pre-stack noise attenuation on the seismic amplitudes in a "point-area-volume" manner using seismic amplitudes from neighboring traces, horizons/slices and data volume.
    • 油气田开发
  • Scale effects of anisotropy in fractured low permeability reservoirs
    HAO Mingqiang; HOU Jianfeng; HU Yongle; LIU Xiangui and YANG Zhengming
    , 2007, 34(6): 1546-0.
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    Based on fracture strike grouping and the fractal geometry which was utilized to describe a single group of fractures, a power law expression of fracture length was established. According to the definition of fracture permeability, an analytical expression of fracture permeability in the orthogonal orientation was obtained. Then, a scale transformation formula of anisotropy was derived with the matrix influences combined. The results show, in fractured low permeability reservoirs, anisotropy varies with scale transformation; accordingly only under very few special conditions does the conclusion of anisotropy being a constant come into existence. With two groups of fractures as examples, the factors which affect anisotropy intensity are discussed in detail: fractal dimensionality, strike angle and the ratio of initial length are primary factors; the permeability ratio of matrix to fracture and the matrix anisotropy intensity are the secondary factors.
  • Classification and evaluation of heterogeneous reservoirs of uncompartmentalized oilfields in Shengli Oilfield
    HUANG Yingsong
    , 2007, 34(6): 1547-0.
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    Uncompartmentalized oilfields in the Shengli Oilfield are rich in heterogeneous reservoirs. They have entered into the detail exploitation and late development stage, and the exploitation targets are focused on inner layers. According to the geological and fluid characteristics of the reservoirs, this paper carries out a study into reservoir classification using multi-parameter product method, grey correlation analysis, gross information content analysis etc., puts forth the concept of heterogeneous fluid coefficient, sets classification criteria for reservoirs, and gets different types of reservoirs. On this basis, recovery forecast models for reservoirs of different types are established, contributing to the further exploitation of the oilfield.
  • Numerical simulation research on percolation flow regularity of asphaltenic oil during CO2 injection
    JIA Ying; SUN Lei; SUN Liangtian; HUANG Lei; HUANG Chunxia and HONG Ling
    , 2007, 34(6): 1548-0.
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    Based on the research achievements of predecessors, a compositional model considering asphaltene deposition, adsorption and plugging and the non-Newton characteristic under low-pressure gradient during CO2 injection is constructed for the purpose of understanding the percolation flow regularity of asphaltenic oil through porous media in reservoirs during CO2 injection and its effect on production performance. To verify the accuracy of the model, a group of long core experiment data are simulated and compared. The calculation result by this model is closer to experiment values than that by the conventional compositional simulation model. Then a model of single injector and single producer is established to study the influence of CO2 injection on production performance. The results show that asphaltene adsorption and deposition decrease oil recovery and delay gas breakthrough time, and that the main influence of the non-Newton characteristic of asphaltic oil on oil output is at the initial period of gas injection.
  • Selective acidizing technique of novel emulsified acid
    XIONG Chunming; ZHOU Fujian; MA Jinxu; SHI Yang; YANG Xianyou; CONG Shengwei and HE Qi-ping
    , 2007, 34(6): 1549-0.
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    In the conventional acidization, acid fluid first flows into the pore paths of high water saturation, and it usually broadens the pore paths filled with water. However, the acidification isn't good for the pore paths filled with oil. To solve this problem, especially in heterogeneous reservoirs, this paper designs a new-style selective emulsified acid system whose viscosity will increase when it meets water and decrease when it meets oil in reservoirs. The core flow experiment shows that the system increases the permeability of oil-saturated cores by 96.1% on average, and increases the permeability of water-saturated cores only by 10.1%. The novel selective emulsified acid system has better retarding and protective capabilities to reservoirs. The acid fluid system has been used in 3 wells in the Gasikule oil field in Qinghai. After acidization, the average oil growth of each well is 8.5t per day, and the water cut decreases by 3.5%.
  • Analysis and application of specific productivity index
    WU Xianghong; HE Ling and FANG Hongchang
    , 2007, 34(6): 1550-0.
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    According to the early production and test data of the Sudan Block 6, North Buzachi in Kazakhstan, Gudao of Shengli in China, and other 4 oilfields, the relationship between specific productivity index and mobility is established. The ratio of specific productivity index to mobility is the coefficient of productivity index (COSPI), according to which, the 7 oilfields are classified into three grades. The COSPI values between 0.0543 and 0.0679 are in the normal range; those of less than 0.0543 are below the normal range indicating that the formation is harmed seriously; and those of more than 0.0679 are beyond the normal range indicating that reservoirs are loose sandstone. In establishing a permeability model, reservoir rock properties and well production data should be used to correct it. COSPI variation can be used to tell whether the formation forms worm-holes or not after sand-carrying oil production. For ordinary sandstone reservoirs, the coefficient can also be used to analyze the stimulation effects of wells and estimate the early productivity of oilfields.
    • 石油工程
  • A fluid-solid coupling model and its application in quantitative sand production prediction of oil and water wells
    XUE Shifeng; MA Guoshun; YU Laigang; SUN Feng and GE Hongkui
    , 2007, 34(6): 1551-0.
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    With fluid percolation, reservoir deformation or damage and other factors under consideration, a fluid-solid coupling model for predicting sand production volume is generated. Two types of sand production mechanisms are proposed: producing fine sands under hydro-dynamical erosion and producing coarse sands when reservoir structures are destructed. The matrix stress and the deformation of sandstone reservoirs in sand production are studied using the Drucker-Prager criterion. The results of finite element numerical simulation indicate that the change of formation permeability correlates closely with producing pressure drop and reservoir properties in the whole sand production. Under relative balanced pressure, because of the erosion of reservoirs and the destruction of reservoir skeleton structures, the formation permeability can increase by 30%; while under over high production pressure drop, because of the possible reservoir compaction near well-bores, the formation permeability can decline by 50%. A balanced pressure depletion strategy is the key to controlling permeability declining and retaining production.
  • Application of seismic while drilling technique in prediction of abnormally high pressure formation
    YANG Jin; XIE Yuhong and HUANG Kaiwen
    , 2007, 34(6): 1552-0.
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    The principle of SWD (Seismic While Drilling) is that the shock waves generated by cone bits breaking formation in the process of drilling are reflected to the surface of the earth by borehole formation, and then the stratigraphic information is collected by a ground receiving system. SWD can provide real-time information of several-hundred-meter formation below the drill bit, which can be used to calculate formation pore pressure accurately, predict abnormal pressure formation's depth, and provid a scientific foundation for the reasonable selection of drilling fluid density and casing setting depth. SWD is applied in a pilot well in South China Sea, and the result indicates that the abnormal pressure face's depth predicted by SWD nearly coincides with the actual drilled depth, and the formation pressure predicted by SWD is of high accuracy.
    • 资源评价与管理
  • A portfolio optimization model for petroleum exploration projects with consideration of geological risk
    GUO Qiulin
    , 2007, 34(6): 1553-0.
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    Based on the existing modern portfolio optimization models, a new optimization portfolio for exploration projects, which considers the geological risk, is proposed to meet the current needs of petroleum exploration decision making. After pointing out the shortcomings of the existing models in exploration, the paper discusses the concept of the geological risk NPV and its calculation method. By revising NPV and reserve in the existing models with risked NPV and risked reserve, the new model can take both portfolio uncertainty and geological risk into account. The application of the proposed model is demonstrated through a case study in the Songliao basin. The new model inherits basic properties from the original model and the economic indicators from the new model are smaller than those from the original model. The new combination of economic parameters provides more practical and valuable information for making exploration decision.
  • Optimal model of oilfield development programming under stochastic oil price
    KANG Xiaojun; LI Zhaomin and LIU Zhibin
    , 2007, 34(6): 1554-0.
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    To make the development programming of an oilfield scientifical and rational, an optimal model of oilfield development programming under stochastic oil prices is generated. The correlative relations between the oil output of oil companies of an oilfield and the factors which affect oil production are built up using functional simulation theories, such as the differential simulation method and NN method; based on the stochastic oil prices, the actual status of oilfield development, and the analysis of decision variables, object function and constraints, the actual situations of every oil company or development unit are studied and the optimal production assignment model with maximum economic benefit (stated oil output and stated cost) is generated, and the solution of the model is gained by improving interior point method. The optimal assignment of output, workload and cost of an oilfield under stochastic oil prices in oil development programming is solved in the process of the optimization. A huge economic benefit was gained in the actual application of the model.
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