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01 December 2010, Volume 31 Issue 6 Previous Issue    Next Issue

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Mechanism and Controlling Factors of Natural Gas Hydrate Accumulation WEI Wei, ZHANG Jin-hua, LIN Wen, WANG Li 2010, 31 (6):  563-566.  Abstract ( 120 )   PDF (362KB) ( 294 )   Save Gas hydrates are widely distributed in the world, mainly in the oceans and permafrost regions, and closely related with the geological and structural environment. Now, these gas hydrates deposits that have been found are mainly identified by BSR. The methane origin in gas hydrates includes biogenic, pyrolysis gas genetic and inorganic gases. The gas hydrates accumulation and mechanism explored by most researchers is mainly based on the genesis of methane gas. This paper analyzes the controlling factors of forming gas hydrates, including the gas source, deposition conditions, geological structural conditions, temperature and pressure conditions, etc. It is these that control the existing state, formation mechanism and scale of gas hydrates deposits. Also, this paper analyzes the favorable conditions of gas hydrate accumulation in the Gulf of Mexico for the purpose of being taken as a reference for China's gas hydrate exploration. References | Related Articles | Metrics

Deformation Model of Contraction Structure of West Kunlun Piedmont Thrust Belt in Southwestern Depression of Tarim Basin ZHANG Wei, QI Jia-fu, LEI Gang-lin, DU Zhi-li, ZHU Dou-xing 2010, 31 (6):  567-571.  Abstract ( 99 )   PDF (709KB) ( 312 )   Save Through comprehensive analysis of the surface geology, seismic profile and continuous electromagnetic profile (CEMP) data in west Kunlun piedmont thrust belt in southwestern depression of Tarim basin, a non subduction-like contraction structure interpretation model with the layering contraction and vertically stacking style is proposed, which means that different styles of structural contraction and deformation occur in shallow and mid-deep layers owing to the detachments caused by the salt-gypsum rocks of Upper Cretaceous- Paleocene and competent strata's distribution in vertical direction. It seems that the detachment fault could not be stacked with another regional detachment fault whose horizontal displacement is great. The Cenozoic competent strata above the shallow salt layer are dominated by decollement fold deformation, which appears near perpendicular and symmetrical long-axis anticline, being parallel to the orogenic belt. The Mesozoic of middle subsalt layer and the deep basement rock formation in this basin are dominated by tenacious contraction deformation, and a series of basement-involved thrust faults with high-angle dipping to West Kunlun are developed. Thrust uplift may be formed in the upper wall, and a series of branch synthetic faults which constitute the imbricate wedge fan are developed in the foot wall. Finally, these thrust faults terminate in the gypsum-salt rocks below the back-thrust fault. The high-angle basement-involved thrust faults have been formed by the reverse displacement of pre-existing normal faults, which dominate the local structural deformation in the foot wall. The occurrence of high-angle thrust and the reverse of the pre-existing normal fault may be related to the vertical shearing caused by the uplift of West Kunlun. References | Related Articles | Metrics

Identification Methods for Single-Channel Sand Body JIN Zhen-kui, SHI Xiao-zhang, HE Miao 2010, 31 (6):  572-575.  Abstract ( 151 )   PDF (522KB) ( 325 )   Save By outcrops studies, it is indicated that many laterally stable sand bodies are actually complex channel sand bodies formed by stacking of a number of single-channel sand bodies together. Single-channel sand bodies are much different in grain size, sorting, matrix content and barrier, etc., resulting in uneven oil zone in the complex channel sand bodies. Understanding of the distribution characteristics of these single-channel sand bodies is helpful for establishing more accurate geological reservoir model and finding out more remaining oil. In this paper, on the basis of outcrop, drilling and seismic studies, some identification methods for single-channel sand bodies are proposed, such as outcrop measure method, lithology contrasting method, electrical contrasting method, thickness center method, statistical restraining method, seismic facies and attributes analysis method. These methods are economic and practicable for lithologic reservoir exploration. References | Related Articles | Metrics

Sedimentary Sequences and Control on Gas Reservoir of Permian in Dinan Swell SHI Xin-pu, YAN Ze-jiang, LI Chen, LIAO Wei, HU Qing-xiong, HU Zong-fang, LIU Ping, CHEN Fang-hong, FAN Tai-liang 2010, 31 (6):  576-578.  Abstract ( 99 )   PDF (402KB) ( 264 )   Save Using the data from cores, well logging, seismic profile and core lab, the sequence stratigraphy analysis and sedimentary facies identification of Wutonggou formation of Permian in Dinan swell in Junggar basin are conducted. The distribution and allocation relations of the sedimentary sequence system are studied, revealing the distribution regularity of the major gas reservoirs in this area. Wutonggou formation is divided into two third-order sequences—SQⅠ-1 and SQⅠ-2 ,SQⅠ-1 is sediment of braided river delta, mainly developing transgressive system tract (TST) and high system tract (HST), while SQⅠ-2 is flood plain sediment, mainly developing TST. SQⅠ-1 is the main producing gas reservoir section, in which the favorable oil-gas accumulation zones are mainly located in areas of channel sand and channel mouth bar in braded river delta front developed on the tectonic uplift. References | Related Articles | Metrics

Shale Daubing Effect and Its Control on Close of Faults—An example from Wellblock SX11-SX6 in Shixi field in Junggar basin LIU Jing, LU Shu-ping, MENG Xiang-chao, XU Jian-jiang 2010, 31 (6):  579-581.  Abstract ( 90 )   PDF (374KB) ( 196 )   Save Based on the regional structure evolvement and formation character, it is recognized that low dip and small break faults and high shale/stratum value exist in J2x-K1q in Wellblock SX11 in Shixi area, which are the mainly geological reasons resulting in close of the faults by developed shale daubing layers of J2x-K1q and restricting the hydrocarbon accumulation in SX11 well by migration of the lower oil-gas into higher positions (K1q) along the conductive faults. Also, such a close may control the migration of the lower oil-gas into K1q trap at the same wall in SX6 well. The research of fault closure formed by the shale daubing effect can help the researches of oil-gas exploration in studied area and similar areas. References | Related Articles | Metrics

Application of ICP-OES Analytical Technique to Igneous Rock Research in Santanghu Basin LIU Feng, QIN En-peng, ZHANG Cai-rong, ZHANG Sheng-bing, WANG Yun-cui 2010, 31 (6):  582-584.  Abstract ( 76 )   PDF (245KB) ( 155 )   Save Inductively coupled plasma atomic optical emission spectrometer (ICP-OES) analytical technique is widely used in a lot of research domains of subjects such as petrology, pharmacy, food nutrition, etc., but less applied to petroleum geology. At present, the oil and gas exploration of Carboniferous igneous rocks in Xinjiang Santanghu basin has achieved some success, but still confronted with numerous research difficulties and technical challenges. The lithology identification of igneous rocks is extremely difficult, "dumb" layer classification and correlation are in lots of problems, which baffle and restrict in-depth research of the igneous rocks in Santanghu basin. Introducing the ICP-OES analytical technique into the igneous rock exploration research will undoubtedly provide new thoughts, methods and means for solving these difficulties and challenges. Now, some substantive breakthrough and progress have been achieved in this basin. References | Related Articles | Metrics

Identification and Evaluation of Low-Resistivity Reservoirs in Hadexun Oil Field in Tabei Area, Tarim Basin ZHAO Jun, HOU Ke-jun, WANG Ling-guo, SONG Fan, LI Hua-wei 2010, 31 (6):  585-586.  Abstract ( 88 )   PDF (216KB) ( 191 )   Save The identification and evaluation of low-resistivity reservoir are of great significances to the growth of oil-gas production and reserves. Based on the genetic analysis of low-resistivity reservoir of the Carboniferous CIII in Hudson oil field, the paper proposes the mud filtrate invaded correction-based saturation calculation method and oil-water interface identification technology, allowing their calculation and determination to be more accordant with the actual conditions. References | Related Articles | Metrics

Characteristics of Clay Minerals in Chang-6 Member in Southwestern Ordos Basin ZHOU Xiao-feng, HE Shun-li 2010, 31 (6):  587-589.  Abstract ( 85 )   PDF (404KB) ( 164 )   Save Based on the petrophysical property, clay mineral X-ray diffraction and SEM observation, the characteristic of clay mineral in super-low permeability sandstone of Chang-6 member of Yanchang formation in southwestern Ordos basin is studied. The result shows that the clay minerals consist of chlorite, illite/smectite mixed layer and illite; and the occurrence of chlorite is pore space lining or pore space filling, and the occurrence of illite/smectite mixed layer and illite is bridging or pore space filling; the relative content of clay minerals is characterized by obvious zonality, namely, high chlorite content appears in the eastern part of the studied area, and high illite/smectite mixed layer content occurs in the western part. According to the correlation analysis of clay minerals and the reservoir petrophysical property, the contents of illite/smectite mixed layer and illite show an inverse correlation to the porosity and permeability of the reservoir, while the content of chlorite manifests a positive correlation to the porosity and permeability, indicating that the quality of the reservoir in the eastern part is better than that in the western part of the studied area. References | Related Articles | Metrics

New Cognition of Sedimentary Facies of Sangonghe and Badaowan Formations in Karamay Zhongguai Area WU Yu-han, WU Cai-xi, QU Jian-hua, MA Hui-shu, GUO Wen-jian 2010, 31 (6):  590-592.  Abstract ( 110 )   PDF (242KB) ( 248 )   Save The Jurassic in Zhongguai area in Karamay field is a steep slope sedimentary system with high hydraulic gradient, quick change of facies belt and varied thickness. Based on its lithology, log facies and seismic facies marks in this area in northwestern margin of Junggar basin, the calibrations of log facies from core microfacies and seismic facies from log facies are conducted. The comprehensive study shows that Sangonghe and Badaowan formations of the Lower Jurassic in Zhongguai area is characterized by deposits of mediumsmall fluvial fans, braided river deltas, and can be classified into 5 facies, 16 sub-facies and 43 micro-facies. The most favorable reservoir horizons and facies belts are also determined in this paper. References | Related Articles | Metrics

Volume Calculation Merhod for Fracture-Cavity Reservoir Body in Tahe Oilfield, Tarim Basin LIU Xue-li, LU Xin-bian 2010, 31 (6):  593-595.  Abstract ( 95 )   PDF (372KB) ( 193 )   Save Ordovician carbonate reservior in Tahe oilfield is a deep buried formation. Karst caverns play an important role in the oil and gas storage. Due to the extremely strong anisotropism and the limited seismic resolution, the scalar of fracture-cave reservoir body is almost undeterminable. Based on the waveform analysis using seismic attributions extraction and pattern recognition technique, the boundary of abnormal fracture-cave reservoir body is recognized, and the correlation factor of waveform between cave and fracture is established, and the volume of abnormal fracture-cave reservoir body is calculated at last. By the seismic forward modeling of fracturecave in vary scales, the correction charts have been established to calculate the volume of fracture-cave using the actural formationsurface ratio as a reference. References | Related Articles | Metrics

Carbonate Reservoir Porosity-Permeability Characteristics of Digital Images Based on Matlab Platform WAN Neng, BAO Zheng-yu 2010, 31 (6):  596-597.  Abstract ( 106 )   PDF (226KB) ( 212 )   Save Actual measurement of rock samples of reservoirs is the main traditional method for obtaining their physical-property parameters, but this method can not be fit for analysis of carbonate microstructure. By means of Matlab powerful digital image processing functions, the digital images of carbonate rock samples obtained from the environmental scanning electron microscope (ESEM) are processed to get statistical pore characteristic parameters: image porosity, calculated permeability and circle-like parameters. And then, correlation analysis of these parameters with the actual measurement data of porosity and permeability is conducted. The results show that using digital image analysis method for obtaining characteristic parameters of carbonate rocks can correctly evaluate the physical properties of rocks, and get more information of the characteristic parameters than traditional methods. References | Related Articles | Metrics

Application of CSSI to Reservoir Prediction of Oolitic Shoal Facies in Puguang Gas Field LIU Hong-lei, ZHANG Ji-xi, WU Jun 2010, 31 (6):  598-600.  Abstract ( 74 )   PDF (327KB) ( 205 )   Save The oolitic shoal facies reservoir of Feixianguan formation in Puguang gas field is characterized by big thickness, deep burial, strong heterogeneity and small difference in lithology between II- and III-type reservoirs and neighboring rock. This paper analyzes carbonate sparse spike inverse (CSSI) method and the key parameters, and highlights the fair wavelet extraction, fine reservoir calibration and exact geologic modeling, etc. The spatial distribution of reservoir is predicted quantitatively using the limits between petrophysical parameters of the reservoir and non-reservoir. This method has been applied to the main development well locations design of Puguang gas field, with the prediction rate of 83.9%, which can be as a guide for quantitative prediction of surrounding blocks in Puguang gas field. References | Related Articles | Metrics

Basic Property Research of Heavy Oil in Northwestern Tahe Oilfield LI Ping, ZHAO Hai-yang, LIAO Zhi-yong, HUANG Yun 2010, 31 (6):  601-603.  Abstract ( 109 )   PDF (207KB) ( 295 )   Save The Block 10 and Block 12 in northwestern Tahe field are characterized by high density （0.95~1.09 g/cm3）, high viscosity （700~1 800 000 mPa·s）and strong heterogeneity, which restrict the efficient development due to the big difficulty of viscosity break. This paper studies the basic properties and group components of crude oil from several 10 wells and analyzes the affecting factors of such a high viscosity. This will be as a guide for effectively taking viscosity break measures in this area in future. References | Related Articles | Metrics

The Complex Fractured Reservoir: Staged Numerical Simulation and Remaining Oil Distribution Prediction—An example from $H^1_4$ layer in Huoshaoshan oilfield, Junggar basin WANG Zhi-zhang, HAN Hai-ying, LIU Yue-tian, XU Xue-cheng, WANG Guo-xian, WU Cheng-mei 2010, 31 (6):  604-606.  Abstract ( 81 )   PDF (347KB) ( 232 )   Save For long-term stable production of a complex fractured reservoir, several measures have to be adopted, such as multi-round large scale fracturing, acidifying, plugging and profile controlling, etc., which allow the reservoir attribute parameters to be changed repeatedly during its development process. The outstanding performances appear in its dual porosity media and the distinct development stages and so on. Taking Huoshaoshan complex fractured reservoir as an example, a complex fractured reservoir numerical simulation is conducted using the method for staged numerical simulation of dual porosity media, by which more accurate prediction of the remaining oil distribution of this reservoir is made during the middle-late period of development, and remarkable effects have been gained in practical application. References | Related Articles | Metrics

Pressure Calculation Element Selection Following Overall Hydraulic Fracturing in Anisotropy Low Permeability Reservoirs CHENG Yuan-fang 2010, 31 (6):  607-609.  Abstract ( 81 )   PDF (425KB) ( 185 )   Save The oil and water two-phase flow equation is established based on generalized Darcy's law, with which the effect of permeability anisotropy on the pressure calculation element selection after whole hydraulic fracturing is simulated and it is found that obvious errors may exist by conventional element selection method. Considering the formation permeability anisotropy and artificial fracture arbitrary angles, etc., a new method for such a selection suitable for five-spot, nine-spot and inverted nine-spot well patterns is proposed. The simulation indicates that calculation element selection is reasonable and the important analyzing wells within the element are of high calculating accuracy, which provides theoretic reference for complex anisotropy low permeability reservoir development by whole hydraulic fracturing process. References | Related Articles | Metrics

New Model for Transient Deliverability Prediction of Herringbone Gas Well HE Zhi-xiong, JIANG Kai, LI Min, LIU Zhong-qun 2010, 31 (6):  610-613.  Abstract ( 82 )   PDF (344KB) ( 198 )   Save Based on gas transient flow theory and the pressure drop analytical solution of the horizontal gas well obtained by Newman's product principle and Green function, combined with rotation of axes deriving the pressure drop equation of the sidetrack, the transient deliverability prediction model of herringbone gas wells is presented and solved by discretization. Computational analysis shows that: ① The production of herringbone gas well decreases with time, followed by tending to a certain rate, and characterized by pseudo-steady state flow; ②The unit length flow rate of main wellbore trends to great at both ends and small in the middle, with the smallest in the intersection, and the farther from the main wellbore, the greater the unit length flow rate of sidetrack wellbore is. References | Related Articles | Metrics

Multi-Section Analysis of Production Decline for Low Permeability Gas Reservoirs WANG Li-qiang, WANG Zhong-lin, YU Jia-yi, WU Mei-e, DU Chun-mei, JIAO Fu-hui 2010, 31 (6):  614-615.  Abstract ( 71 )   PDF (262KB) ( 194 )   Save Distribution of production data tends to be sparse in low permeability gas reservoirs. The traditional production decline analyses, no matter Arps or modified attenuation decline analysis, are all poor in forecast effect. This paper analyzes the standard deviation of the sample space set up by differences between the predicted and actual production data, finding out that in view of actual data of multi-section weak step distribution in low permeability gas reservoir, multi-section decline analysis results are far better than overall decline analysis, which is easy to attain in Excel, so being accurate and efficient. For low permeability and super-low permeability oil-gas reservoirs with sparse distribution of production data, this method is recommended for production decline dynamic analysis. References | Related Articles | Metrics

Material Balance Equation for CO2 Gas Reservoir Considering Phase State Changes LV Jian-jiang, TANG Hai, LI Chun-qin, HAI Tao, DU Chun-hui, LV Dong-liang 2010, 31 (6):  617-620.  Abstract ( 77 )   PDF (310KB) ( 218 )   Save CO2 can be dissolved in irreducible water, intrusion water and produced water in CO2 gas reservoirs. This paper presents the material balance equation for CO2 gas reservoir based on mole conservation theory. The physical property and phase change of CO2 are closely related to the pressure and temperature conditions, and the solubility of CO2 is affected by the formation water salinity. Using Newton interpolation polynomial, the parameters of physical properties under different reservoir conditions can be calculated, and based on the material balance equation, integrated with high pressure property of CO2 and its changes with pressure and temperature, the CO2 inplace or geological reserves and the average reservoir pressure in different recovery factors can also be estimated, and the phase state changes of CO2 in the development process can be determined. The relative error of the recalculated geological reserves is 0.131%, showing this method is effective. References | Related Articles | Metrics

Interwell Dynamic Connectivity of J2x4 Reservoir in Wellblock Lu-9 in Junggar Basin DU Qing-jun, HOU Jian, LIU Ye-jun, LU Jian-guo, JI Cheng-wei, FENG Guo-jie 2010, 31 (6):  621-623.  Abstract ( 97 )   PDF (244KB) ( 265 )   Save In the late stage of an oil field development, the oil-water interwell connectivity presents dynamic variations with the change of development conditions. This paper proposes the oil-water well production performance-based inversion method for reservoir connectivity using multivariate linear regression. Field application in J2x4 reservoir of Wellblock Lu-9 in Junggar basin indicates that the interwell connectivity can be divided into 4 types: uniform connectivity, unidirectional connectivity, linear connectivity and single well onrush connectivity, of which the unidirectional and onrush connectivity-type waterflooding well groups are dominant, showing it is characterized by heterogeneity. For the reservoir with active edge and bottom water, the producing energy can be recovered effectively while its interwell connectivity is good. References | Related Articles | Metrics

Unflowing Production and Pressure Research and Application for Condensate Gas Well ZHANG Jia-liang, YU Yuan-zhou, WANG Yan-hua, YANG Li-rong, XU Zhen-lin 2010, 31 (6):  624-625.  Abstract ( 115 )   PDF (134KB) ( 227 )   Save Using the abundant field data from Banqiao condensate gas reservoir, the unflowing pressure, unflowing production and their relationship for condensate gas well are studied, the applicable experiential formulae are given, by which the abandon production and abandon pressure for the condensate gas well or reservoir are predicted. And the more precise recoverable reserves of the condensate gas reservoir can also be predicted. These provide solid bases for efficient development, reserves management and exploitation planning of such a reservoir. References | Related Articles | Metrics

Influence of Formation Pressure Fall on Irreducible Water Saturation in Sandstone Gas Reservoir LI Lian-ming, LI Zhi-ping, CHE Yan 2010, 31 (6):  626-628.  Abstract ( 93 )   PDF (209KB) ( 248 )   Save According to the Kozeny equation of the simplified model for capillary bundle in rock pore structure, on the assumption that the thickness of irreducible water homogeneously adhering on capillary wall keeps unchangeable, this article presents the theoretical formula for irreducible water saturation variation with formation pressure fall, and the calculated irreduclible water saturation variation is determined by core samples from five gas wells. The case analysis indicates that the irreducible water saturation is gradually increased with the formation pressure fall-off. This is significant to guide the rational and efficient development of the producing water gas wells in sandstone gas reservoir. References | Related Articles | Metrics

Quantitative Relationship Between Relative Permeability Curve, Water Drive Curve and Waterflood Reserve ZHANG Jin-qing, SUN Fu-jie 2010, 31 (6):  629-631.  Abstract ( 120 )   PDF (174KB) ( 271 )   Save According to the expressions of relative permeability curves and relative permeability ratio to oil and water, a quantitative relationship between relative permeability curve, water drive curve and waterflood reserve is derived. The result shows that water drive geological reserve is direct proportion to the sum of Corey exponent for water and Corey exponent for oil and inverse proportion to the product of slope of the first water drive curve and oil displacement efficiency. It also explains the reason why the formulae by Dr. Tong Xianzhang are not suitable for predicting waterflood reserves and geological reserves of low permeability fields. References | Related Articles | Metrics

Method for Productivity Analysis of Horizontal Gas Well While Producing Water LUO Qi-yuan, LI Xiao-ping, AO Yao-ting, JING Wei, XIAO Qiang 2010, 31 (6):  632-633.  Abstract ( 87 )   PDF (201KB) ( 281 )   Save In the middle or late period of a gas reservoir by horizontal well development process, the flow resistance may increase sharply due to producing water, and the gas flow theory of single phase isn't fit for two-phase flow of gas and water, anymore. This paper proposes composite model method to analyze the horizontal gas well productivity when producing water. It means that the near-well-bore permeability should decrease for the effect of produced water, while the permeability far from the well keeps the same. Also, this paper studies the effect of water on horizontal gas well productivity through building the productivity equation. References | Related Articles | Metrics

A Pilot Study on MEOR in Ansai Extra-Low Permeability Oil Field LIU Jian-ying, SHEN Kun, HUANG Zhan-wei, HUAI Hai-ning, CHEN Fu-lin 2010, 31 (6):  634-636.  Abstract ( 130 )   PDF (186KB) ( 293 )   Save The microbial enhanced oil recovery (MEOR) technique is applied to Ansai oil field of extra-low permeability for EOR. Following experimental study and evaluation of the rational injection project, a pilot test is conducted. The successful result shows that the previous raising water cut has been controlled and the composite production decline rate has been decreased, allowing it to be a successful case in this field by MEOR process. References | Related Articles | Metrics

Study on Proper Well Spacing of Hybrid Pattern of Vertical Injector and Horizontal Producer in Low Permeability Reservoir ZHENG Wei, JIANG Han-qiao, CHEN Min-feng, XIN Jun-wu, ZHAO Gang 2010, 31 (6):  637-640.  Abstract ( 93 )   PDF (308KB) ( 242 )   Save Based on percolation theory, the formulae of interwell on-way pressure and pressure gradient distribution for vertical injectorhorizontal producer hybrid pattern system are deduced for the first time, and their variations are analyzed. Integrated with mathematic expression of the start-up pressure gradients given by physical modeling experiment, the method for well spacing of this hybrid pattern in low permeability reservoir is proposed, by which the influences of injection-production pressure differential, permeability and horizontal section length on this well spacing are analyzed. The study shows that the producing pressure differential required by this hybrid pattern system is much smaller than that by vertical well pattern. It is easier to create an effective displacement compared with vertical wells pattern, and larger injection-production well spacing can be taken. References | Related Articles | Metrics

Forecasting Method for Wellbore Pressure in High-Pressure Gas Well by Considering Temperature Changes LAI Feng-peng, LI Zhi-ping, QU Jian-lin 2010, 31 (6):  641-643.  Abstract ( 94 )   PDF (238KB) ( 196 )   Save Well bore pressure is an important parameter for gas well production. The changes of wellbore temperature should be considered when predicting wellbore pressure distribution, because the temperature has an effect on the pressure calculation. This paper proposes different calculation thoughts for opening and shutting stages to analyze the nonlinear distribution of wellbore temperature, by which the corresponding distributions of wellbore pressure in two stages are predicted. The case study shows that the predicted wellbore pressure result considering nonlinear temperature distribution is more accurate. References | Related Articles | Metrics

Using Well Log Data to Automatically Identify Lithology of Reservoir with Low Porosity and Low Permeability—An example from Anpeng Paleogene in Biyang sag SHEN Hui-lin, FANG Peng, LIU Mei-jie 2010, 31 (6):  644-646.  Abstract ( 85 )   PDF (295KB) ( 194 )   Save The well logs response characteristic of low porosity and low permeability reservoir is analyzed in detail. The method for selection of key parameters of lithology identification by using grey correlation is proposed. Through the automatic stratification realized by intra-layer differentiation method to select sample layers and conduct cluster analysis using major components, divide the sample layers into several logging facies, and finally, the logging facies-lithology identification of uncertain layers is made by Bayes successive discriminate analysis. This method is effective in application. References | Related Articles | Metrics

Experiment on Capillary Pressure Determination with MNR and Semi-Permeable Plate ZHANG Shi-qing, dAI Shi-hua, ZHANG Xiao-liang, CHEN Ling, SAI Fei-ya 2010, 31 (6):  647-648.  Abstract ( 77 )   PDF (170KB) ( 176 )   Save This paper discusses the method for obtaining formation capillary pressure from MNR T2 spectrum by mercury penetration and semi-permeable plate experiment to determine the capillary pressure curve and further calibrate the MNR capillary pressure. Over 50 core samples from Jungar basin are tested with MNR and semi-permeable plate. Correlation between MNR T2 spectrum and aperture distribution is conducted. Comparison of capillary pressure curves from mercury penetration and semi-permeable plate is presented to establish the conversion between MNR T2 spectrum and capillary pressure curve. This provides a new method for log interpretation of complex pore structures and low resistivity hydrocarbon reservoir. References | Related Articles | Metrics

Application of Numerical Simulation to Geologic Study of Complex Fault Block Reservoirs LIU Bin, ZHANG Yuan-ping, ZHAO Zhi-long, SHI Xiao-yan, LIU Ying 2010, 31 (6):  649-650.  Abstract ( 85 )   PDF (110KB) ( 158 )   Save The rational gridding of complicated cross faults is the key of geologic modeling and simulation of complex fault block reservoirs and irregular-boundary reservoirs. In previous modeling software the faults are processed as staircase along the grid, while the boundary of an irregular reservoir is dealt with by deformed angular point grid, which decrease the accuracy of the model to a certain extent. By using SURE software developed by HOT company, this paper conducts the geologic modeling and numerical simulation for partial fault blocks in Tuha oil field, and more rationally deals with the complicated cross faults, realizing reasonable distribution of the grid block parameter around faults in the 3D geological model, and increasing the accuracy of fault block reservoir simulation. References | Related Articles | Metrics

A Single Point Deliverability Formula for Gas Well in Low-Permeability Gas Reservoir WANG Fu-ping, HUANG Quan-hua, SUN Lei, YU Zhi-bo 2010, 31 (6):  651-653.  Abstract ( 68 )   PDF (202KB) ( 227 )   Save In deliverability evaluation of a gas well, the single point deliverability test is widely applied to gas field with simple and easy operation as well as short test time. However, the calculation results tend to be in large deviation when it is applied to low-permeability gas reservoir. Starting from the theory which derives the single point deliverability formula and the low-permeability gas reservoir characteristics, and based on the trinomial deliverability equation considering the threshold pressure gradient, a single point deliverability formula for gas well in low-permeability gas reservoir has been deduced, and a method for calculating deliverability factors by a single point test data has been established. It is shown that compared with conventional single point formula, the number of the empirical parameter in the single point formula for low-permeability gas well has become two from one, and empirical parameters α, δ are also related with threshold pressure gradient. The case study indicates that this method presented in this paper is feasible. References | Related Articles | Metrics

Simultaneous Imaging of Ray Tomography and Wave Equation XIONG Gao-jun, XIAO You-jun, PENG Geng-xin, HE Zhen-hua, WANG Xu-ben 2010, 31 (6):  654-656.  Abstract ( 66 )   PDF (487KB) ( 220 )   Save In this paper, a simultaneous imaging of the velocity and structure is presented by composition of ray tomography and wave equation. Depth deviation calculation is based on migrated common imaging trace gather, by which the allowance of velocity is gained. This allowance is evenly distributed along ray path from top to bottom layers for modifying the velocity model layer by layer. And the modified velocity is used for wave equation migration to get common imaging trace gather, and calculating a new velocity allowance, and then, evenly distributing along the ray path. Such inversion and iteration of wave equation migration and ray tomography are conducted until the common imaging trace gather depth variance meets the preset accuracy. Finally, the simultaneous imaging of the velocity and depth structure is obtained. This method has been verified by simulation experiment. References | Related Articles | Metrics

Water Control Method for Stimulation by Inducing Salt Precipitation in Gas Reservoir WU Kai, PU Wan-feng, ZHANG Chao-ping, JIN Fa-yang 2010, 31 (6):  657-658.  Abstract ( 108 )   PDF (190KB) ( 190 )   Save In this paper, a method for plugging high permeability zones by salt precipitation is presented for the purpose of enhancing gas recovery. The effects of NaCl concentration, ethyl alcohol augmentation, induction agent and additive on the salt precipitation property are tested under normal temperature. The physical modeling experiment shows that when the water production rates are 47.0% and 84.0%, respectively, the injection of salt precipitation system into sand packing tube allows the water control rate to reach 6.0% and 4.0%, gas production rate to be 6.0% and 4.0% , correspondingly. It is proved that the salt precipitation system can effectively plug the water producing zones, hence keeping the gas production stable in a certain condition. References | Related Articles | Metrics

Exploration Prospects of Shale Gas of Upper Sinian-Silurian in Mid-Yangtze Region LI Yan-xia, LI Jing-hong 2010, 31 (6):  659-663.  Abstract ( 104 )   PDF (414KB) ( 323 )   Save Based on the outcrop, geochemistry and drilling data, this paper analyzes exploration prospects of Cambrian-Silurian shale gas resource in mid-Yangtze region. The analysis indicates that the Cambian-Silurian shale is dominated by Doushantuo formation of Upper Sinian, Shuijingtuo formation or Niutitang formation (Lower Cambrian) and Silurian in this region. These argillaceous rock and shale characterized by rich organic matter content, fine kerogen type and high thermal evolution (mature to overmature) are valid source rocks of the shale gas. The mid- Yangtze region undergoes multistage tectonic movements since Caledonian. The shale reservoir quality is improved by tectonic uplift and compression, increasing the accumulation amount of shale gas. It is concluded that the mudstone-shale of Upper Sinian and Lower Cambrian can be as favorable areas for shale gas exploration in western Hunan and Hubei. And the commercial shale gas flow of Silurian discovered by drilling reveals that this area is rich in shale gas resources of Silurian in western Hubei and eastern Chongqing. References | Related Articles | Metrics

Research Progress and Development Trend of Natural Gas Caprock WANG Xiao-bo, LI Jian, WANG Dong-liang, HU Guo-yi, FANG Jia-hu 2010, 31 (6):  664-668.  Abstract ( 107 )   PDF (349KB) ( 418 )   Save The research progress of natural gas caprock at home and abroad in recent years is reviewed, including caprock classification, sealing mechanism, controlling factors of the sealing ability, experimental technologies and geophysical research methods as well as comprehensive evaluation of its sealing ability, etc. The controlling effects of caprock on natural gas accumulation are analyzed, and the development trend of natural gas caprock research is predicted. Finally, it is suggested that strengthening research on natural gas caprock development trend of natural gas caprock research is predicted. Finally, it is suggested that strengthening research on natural gas caprock is of great theoretical and practical significances for perfecting gas accumulation geological theory and guiding natural gas exploration. References | Related Articles | Metrics