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01 January 2019, Volume 36 Issue 5 Previous Issue    Next Issue

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Hydrocarbon MigrationAccumulation Characteristics and PoolForming Patterns in OverlapErosion Zones in Northwestern Margin of Junggar Basin SHEN Yang1, LIN Huixi2, ZHAO Leqiang2, ZENG Zhiping2, GONG Yajun2, GUO Ruichao2, MIN Feiqiong2 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150501 Abstract ( 114 )   PDF (300KB) ( 150 )   Save The overlap and erosion zones in northwestern margin of Junggar basin are characterized by frequent overlaps and erosions, far away from the hydrocarbon sources, and complex oil?gas migration and accumulation. Combining with geologic study, test analysis and basin modeling recognition, this paper analyzes the key factors of hydrocarbon accumulation and their matching relationships, and reveals that the overlap and erosion zones in this area have such pool?forming characteristics as charging by three sources and stages, transporting by faults?blanket sands?leached layers, and oil?gas accumulating by blanket sands margin?beneath weathering crust; the petroleum transporting styles include fault?blanket sand, fault?leached layer, and leached layer?blanket sand; and such hydrocarbon accumulation patterns as remote sources for hydrocarbon charging, fault?blanket sand?leached layer for oil?gas transportation, and the effect of transporting efficiency on controlling hydrocarbon accumulation and enrichment Related Articles | Metrics

Geochemical Evaluation of Shale Oil in Lower Es3and Upper Es4in Jiyang Depression LI Zheng1,2,3, WANG Xiuhong2, ZHU Rifang2, ZHAI Zheng2 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150502 Abstract ( 59 )   PDF (300KB) ( 230 )   Save Taking the shale members of Lower Es3 and Upper Es4 of the Paleogene in Jiyang depression as research subjects and starting from the hydrocarbon generation condition and oil?bearing property, the geochemical characteristics of the shale oils are evaluated. The results show that the shale members have favorable conditions for forming shale oil. This paper establishes the grading evaluation criteria of shale oil in terms of organic carbon content, chloroform bitumen“A”content and dissolved hydrocarbon content“S1”. Combined with the evolution of profiles, it proposes the shale members’oil enrichment thresholds, and suggests that the shale members of Lower Es3 and Upper Es4 in Dongying sag and Lower Es3in Zhanhua sag and Chezhen sag are favorable target zones for shale oil exploration in Jiyang depression Related Articles | Metrics

Detailed Geologic Study of Internal Sandbodyof Layer Units in Marine Sandstone: A Case Studyof Donghe Pebbly Sandstone SubMember of Bachu Formation in Tazhong16Oilfield ZHU Weihong1,2, WU Shenghe1, HAN Tao2, WEN Zhang2, TANG Chengwei1, CAO Xiaojiang2 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150503 Abstract ( 49 )   PDF (300KB) ( 183 )   Save The pebbly sandstone sub?member in Tazhong?16oilfield as marine coastal deposits is divided into five layers and has to make a fine description of internal single sandbody in the layers for the need of efficient reservoir development. By means of rock electric calibration and identification on the well logs, the single shoreface dam is classified as inner edge, main part and outer edge, and the single sandbody can be divided into such three types as offshore waterway split, lateral contact and vertical superimposition. The distributions of the internal single sandbody are described in detail on the section in directions of parallel, oblique and perpendicular to the coastline and on the plane in five layers. The case study shows that the single layer level is suitable for blocking high water?cut intervals according to interlayer heterogeneity in view of vertical well, which can effectively realize the water?cut control and stable production; while single sandbody level favorable for blocking high water?cut intervals according to seepage difference between single sand bodies in view of horizontal, which can effectively alleviate the quickly waterflooded problem Related Articles | Metrics

Formation Mechanism of Toutunhe Abnormal Pressure of Middle Jurassic in Fudong Slope Area, Junggar Basin YU Jingwei1, REN Wei2, WANG Wuxue3, WANG Zesheng4, LIU Ni2, OUYANG Xueqi2 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150504 Abstract ( 45 )   PDF (300KB) ( 257 )   Save Toutunhe formation of the Middle Jurassic in slope area of eastern Fukang sag (Fudong slope area) in Junggar basin is a significant exploration target zone in this region. Based on the measured formation pressure data from key wells in this study area, this paper analyzed the vertical and horizontal distributions of abnormal high pressure in Toutunhe formation, presented three zones such as ultra?intense pressure zone, transition to overpressure zone and normal pressure zone in terms of the pressure coefficients, and discussed the formation mechanisms of these abnormal pressure zones by means of drilling, seismic, logging and thin?section data. The influencing factors for forming the abnormal pressure in this area are sedimentary facies and diagenesis as well as tectonic movement. The formation of the regional abnormal pressure is the result of multifactor combined actions, among which the tectonic movement is the key factor Related Articles | Metrics

Analysis on Causes of Reservoir Resistivity Differences of Chang81Reservoir in Zhenbei Oilfield, Ordos Basin FENG Yuan1, YANG Weiwei1, LIU Yicang2, WANG Ye1, JIAO Tingkui1, ZHANG Haibo1 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150505 Abstract ( 67 )   PDF (300KB) ( 206 )   Save The ultra?low permeability reservoir of Chang81 in Zhenbei oilfield of Ordos basin is characterized by distinct formation resistivity which in west part of the reservoir is obviously lower than that in east part, even part of it closes to that of aqueous layers, which allows the western reservoir’s pay zone to be difficultly identified and developed. This paper analyzed the genesis of the resistivity differences in this reservoir. The results show that the causes of lower resistivity in the western reservoir compared with the eastern reservoir include three aspects as below:1) The salinity of formation water in the western reservoir is higher than that in the eastern reservoir;2)the western reservoir contains higher content of illite and chlorite with stronger capacity of cation exchange and additional conductivity; and3) it contains higher clay minerals and more complex pore structures as well as weaker hydrocarbon accumulation dynamics, which result in higher irreducible water saturation in it. This could be of significance for exploration and development of ultra?low permeability reserfvoirs Related Articles | Metrics

Genetic Model for M55SubMember Dolomitization of Majiegou Formation in Ordos Basin NING Bo1, WANG Qicong1, LI Baiqiang1, ZHU Yunfei2, JIN Chengguang1, YAN Zuo1 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150506 Abstract ( 76 )   PDF (300KB) ( 405 )   Save This paper analyzes and discussed the diagenetic mechanism for M5?5sub?member of Majiagou formation in Ordos basin by geochemistry approaches. The M5?5sub?member in Guanjiaya section is composed of powder crystal dolomite, calcareous dolomite and dolomitic limestone, belonging to a complete sedimentary cycle where the content, particle size and degree of order are gradually reduced from top to bottom. The power crystal dolomite’s carbon?oxygen isotope ratio is obviously negative, theδ18 O of calcareous and limestone matrix is partially negative, but theirδ13C values are close to the Ordovician water, and the87Sr/86Sr ratio is significantly increased. The results show that the original sedimentary sequence of this sub?member is characterized by micrite, packstone, disturbed biomicrite, calcarenite, and dolomicrite. With the loss of thee sea level, evaporated and concentrated seawater started various dolomitizations in turn from supratidal zone to subtidal zone until shallow burial environment. The powder crystal dolomite and dolomitic limestone originate in the reflux percolation of concentrated seawater Related Articles | Metrics

Characterization of Inner Structures of Fluvial Complex Sandbody of Minghuazhen Formation in Q Oilfield, Bohai Bay Basin GAO Yufei, HU Guangyi, FAN Tingn, WANG Hui, FAN Hongjun, ZHANG Yukun 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150507 Abstract ( 59 )   PDF (300KB) ( 163 )   Save Taking the fluvial sandbody of the Minghuazhen formation in Q oilfield in Bohai Bay as an example, this paper analyzes the inner superimposed characteristics of fluvial complex sandbody by means of single well analysis and seismic data, presents three types of the cut stacking, edge lateral cutting and edge superimposition of multi?stage sands, elaborates the significance of such a complex sandbody characterization, and proposes rational suggestions for well deployment and working out development plan in this area. For uncertainty of the cut stacking existence, it optimizes the drilling sequence and sets the drilling decision tree, and then proposes the suggestion of making evaluations followed by development; for the complex sandbody formed by edge cutting and edge superimposition, and the existence of inner interbeds, it proposesasuggestion of using horizonalwell process for development ofthis oilfield and optimizinginjection?productionrelations Related Articles | Metrics

Porosity Prediction of Mesozoic Sandstone and Mudstone with Overlapped Wave Impedance:A Case Study of X Block in North Yellow Sea Basin WAN Xiaoming, WANG Liaoliang, LIU Jinping, JIAN Xiaoling, CHAI Yi 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150508 Abstract ( 59 )   PDF (300KB) ( 305 )   Save The target zones of the Mesozoic in X block in North Yellow Sea basin are characterized by deep, tight and vertically-horizontally varied reservoirs. According to the statistical analysis of logging data, the velocities of sandstone and mudstone in the target zones are similar, and the distribution range of P?wave impedance is overlapped. This paper proposed a set of approaches for dealing with the problem of prediction of reservoir porosity in sandstone and mudstone with overlapped wave impedance: 1)using sensitive lithology curve to reconstruct interval transit time curve and then take inversion;2)distinguishing the sandstone and mudstone by reconstruction and inversion of interval transit time curve, obtaining the original wave impedance value of the sandstone by using sandstone matrix constraining and inversion data;3)based on the relationship between the original wave impedance and porosity, convert the sandstone wave impedance into porosity. The case study shows good results in application of this method to this area Related Articles | Metrics

Application of Seismic Data Structure Characteristics to Prediction of Favorable Hydrocarbon-Bearing Areas in BlockLX1of Tabei Uplift, Tarim Basin WU Meilian1, XIE Zhou1, WANG Jingyi2, ZHANG Haizu1, ZHAO Haitao1, FENG Lei1 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150509 Abstract ( 84 )   PDF (300KB) ( 195 )   Save The Yangxia and Kezilenuer reservoirs of Jurassic in Block?LX1of Tabei uplift in Tarim basin are of deep buried and few wells characteristics. Using seismic data structure characteristics, combined with drilled data and modeling structural analysis, to predict the favorable oil?gas?bearing zones in the Block?LX1. Results show that such zones have characteristics as follows: the small time window seismic data structure characteristic abnormal value is in relative big error; the large time window seismic data structure characteristic abnormal value is in obvious anomaly; the seismic waveform appears in non?return?to?zero and not smooth multi?peak, and the abnormal value profile shows the strong structural anomalies. Base on these features, the Block?LX1is divided into four levels in oil?gas?bearing property, and Level?I belongs to very favorable zone with an area of about6.28km2, distributing in northern Block?LX1; Level?II belongs to favorable zone with and area of about14.26km2, mainly distributing in southern Block?LX1. This paper suggests that where the abnormal value is big and located in structural high could be taken as targets for further rolling petroleum exploration in this area Related Articles | Metrics

Molecular Optimization Design and Evaluation of Miscible Processing Aids Applied to CO2Flooding YANG Siyu1, LIAN Liming1, YANG Yongzhi1, LI Shi1, TANG Jun2, JI Zemin1, ZHANG Yongfei2 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150510 Abstract ( 85 )   PDF (300KB) ( 275 )   Save Aiming at the fact that universal high miscible pressures existed in domestic reservoirs by CO2 flooding technology available in China tend to resulting in poor miscible displacement, and low target oil recovery efficiency, this paper drew the experiences from available structural characteristics of surfactants applied in microemulsion of CO2?water systems, by taking fluoro?alkane chains and non?fluoro?OAc chains as the CO2?philic ends, taking alkane structure as the lipophilic ends, designed the synthetic organic assistants (aids). The aids’effects for reducing CO2?crude oil interfacial tension and minimized miscible pressure of CO2 flooding were analyzed and optimized by surface tension testing in CO2?kerosene system and CO2?crude oil system. The aids’effects for reducing CO2?crude oil interfacial tension and minimized miscible pressure (MMP) of CO2 flooding were analyzed and optimized by surface tension testing in CO2?kerosene system and CO2?crude oil system. The result shows that the new two aids with per?acetylated glucose dodecyl ester molecules and citric acid isopropyl ester molecules do have better miscible processing effects for minimizing the interfacial tension of the CO2?crude oil system and reducing the MMP. The case study suggests that per?acetylated glucose dodecyl ester could cause the surface tension down averagely by28.7% and the MMP of CO2flooding down by27.47%, possessing the value of further research in support of engineering application Related Articles | Metrics

Study on Oil and Gas Reservoir Types of AT1Well Block in Tahe Oilfield, Tarim Basin LIU Lina, MA Yong, LIU Jie, MA Xuejian, ZHANG Chunfu, YIN Ting 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150511 Abstract ( 58 )   PDF (300KB) ( 159 )   Save The Akekule reservoir of Middle Triassic in AT1well block in Tahe oilfield is a bottom?water reservoir with complex fluid properties controlled by faults and low amplitude structure. At the initial stage of development, the AT1well block was identified as a condensate gas pool by means of PVT data. With the deepening of the development, most of the gas wells were in big drop in gas?oil ratio. And at the beginning of water breakthrough, oil cutting appeared like oil production rise and gas production decline, resulting in poor exploitation effect. By means of the data of PVT, fluid property, oil and gas component analysis, production performance and reserves coefficient, this paper draws a conclusion that the reservoir type in AT1well block belongs to an oil reservoir with condensate gas cap, analyzes the effect of AT1well block development and proposes the countermeasures for this area in high water?cut state, which can be available for reference for type discrimination and development of similar reservoirs Related Articles | Metrics

Influences of Water Lock Starting Pressure Gradient and Stress Sensitivity on Tight Gas Reservoir Deliverability: A Case Study of Well XX4of Sulige Gas Field in Changqing Oilfield SUN Panke1, XU Huaimin1, ZHENG Xiaomin2 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150512 Abstract ( 73 )   PDF (300KB) ( 192 )   Save Tight gas reservoir is characterized by complex pore structures and gas?water percolation flow pattern, which allows its deliverability evaluation to be influenced by many factors. Under the available conditions of the pore structure, fluid viscosity and volume factor, the gas?water flow could be more influenced by water lock starting pressure gradient and stress sensibility, thus resulting in more influence on its deliverability of gas wells. Taking XX4gas well in eastern Sulige gas field of Changqing oilfield as an example, this paper develops the model for the fluid flowing deliverability, analyzes the effects of water lock starting pressure gradient and stress sensibility on the tight gas reservoir’s deliverability based on two?phase flow theory, which plays a positive role in guiding accurate prediction and evaluation of the deliverability of tight gas reservoir Related Articles | Metrics

Optimal Water Injection Temperature of High PourPoint Oil Reservoir in Jingguan2Block in Liaohe Oilfield YU Peng1, MA Teng1, ZHOU Wei2, TANG Zhonghua1 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150513 Abstract ( 70 )   PDF (300KB) ( 299 )   Save Aiming at the poor development effect by cold waterflooding of Jingguan?2block, the properties of crude oil were qualitatively analyzed, the reservoir cold damage was studied by water injection well抯 temperature buildup testing and waterflooding experiment. The thermodynamic method was used to determine the optimal injection temperature based on solving the numerical model of reservoir. Furthermore, the development efforts under cold and hot water displacement were compared and the interwell temperature field distribution was predicted by reservoir numerical simulation. The result shows that temperature is a very sensitive parameter with oiling. Varying degrees of cold damage is a consequence of paraffin deposition and reservoir channel plug from decline of temperature below the cloud point temperature. Simultaneously, precipitated paraffin changes the rheological properties of crude oil thereby increasing the filtration resistance and reducing the oil displacement efficiency. The hot water displacement process can effectively improve the high pour?point oil reservoir development effect, increasing oil mobility and enhancing oil recovery. Nevertheless, water injection temperature is not as high as possible, the limit of development cost must be taken into account with the increase of displacement efficiency, the final optimal water injection temperature of Jingguan?2block is80℃ Related Articles | Metrics

A Feasibility Studyon EnhancingCondensate Oil Recovery of FracturedVuggy Condensate Gas Reservoir in Tazhong1Gas Field, Tarim Basin KANG Bo1, ZHANG Liehui1, WANG Jian1, DENG Xingliang2, GUO Ping1, LIU Zhiliang2 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150514 Abstract ( 71 )   PDF (300KB) ( 273 )   Save Tazhong?1gas field is a condensate gas reservoir with fractured?vuggy carbonate rocks. Production test indicated that the deplete development process just obtained the condensate oil recovery of about25%. As a result of poor interwell connectivity, conventional gas injection to maintain pressure process was difficult to use. This paper makes a comparison of retrograde condensation mechanism of fractured?vuggy carbonate condensate gas reservoir with that of sandstone condensate gas reservoir. On the basis of laboratory and field test researches, it demonstrates the feasibility of deplete followed by water injection process applied to the fractured?vuggy carbonate condensate gas reservoir. The result shows that the storage space and flow path in such a condensate gas reservoir are mainly fractures and cavities, and gravitational differentiation allows the retrograded liquid to concentrate at the bottom of fracture?vug unit, so single well water injection approach can be used to displace the condensate oil formed by retrograde condensation in these fractures and cavities, and to greatly enhance the condensate oil recovery with simplicity and effectivity Related Articles | Metrics

Tight Sandstone Gas Reservoir Damages in Dibei Area of Tarim Basin: Experimental Study CHE Xingxiang1a, LU Yuan1a, ZHOU Jun1a, WU Hongjun2, XING Haoting1b, ZHANG Hui2 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150515 Abstract ( 58 )   PDF (300KB) ( 225 )   Save Tight sandstone gas is the main type and the direction of development of unconventional gas in China. Study on the mechanics and factors for tight sandstone gas reservoir damage is more favorable to reservoir protection during the reservoir development and field operation. This paper presents the geological characteristics of the Ahe tight sandstone gas reservoir of Jurassic in Dibei area of Tarim basin, analyzes the potential factors of reservoir damage caused by pore structure and clay minerals, and makes the experiments of reservoir sensitivity and aqueous phase trapping. The results show that there exist such damages as moderate?strong water sensitivity, medium?strong fluid velocity sensitivity, medium acid sensitivity and larger aqueous phase trapping in the Ahe reservoir, and it is suggested that the well fluid type, flow rate and other related properties should be controlled, and acid liquid should be used very carefully for the purpose of efficient development of such a gas reservoir Related Articles | Metrics

Accumulation Process Analysis on Tight Sandstone Gas Based on Charging Simulation Experiment: An Example of Ordos Basin ZHAO ZilongZHAO JingzhouCAO LeiWANG Jiangtao 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150516 Abstract ( 67 )   PDF (300KB) ( 210 )   Save Based on the charging simulation experiment, this paper analysed the accumulation process of tight sandstone gas from Sulige and Yulin gas fields in Ordos basin, and also established a natural gas accumulation pattern. The starting pressure is existed in the tight sandstone gas, while such a charging is mainly non Darcy’s flow instead of following to Darcy Law. The porosity and permeability cutoff values of the accumulation physical property in tight sandstone gas are respectively1.5%and0.03mD, their upper cutoff values are respectively10.0%and1.0mD. Combined with production practices, further determination of the porosity and permeability cutoff values of industrial gas flow are4.0%and0.07mD, respectively. Three stages of the natural gas accumulation in tight sandstone are proposed, namely, relatively slowly charging stage of non?Darcy flow, relatively rapidly charging stage of non?Darcy flow, and stable stage of gas saturation while natural gas charging reaches limit gas saturation. The relatively slowly charging stage of non?Darcy flow is a major stage of charging accumulation among them Related Articles | Metrics

Influencing Factors of Oil ProductionRate for Waterflooding Oilfields YANG Zhigang1,2, ZHANG Chenkai2, Abuduaini1, LIU Wangdong1, Halan Hayibai1, PAN Guohua1, YE Yong1 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150517 Abstract ( 62 )   PDF (300KB) ( 155 )   Save In view of influencing factors of oil production rate, the production performance data collected from130mid?high permeability clastic rock oilfields at home and abroad are analyzed, among which the most oilfields are developed by water injection process. In terms of crude oil viscosity and reservoir permeability, the oilfields were divided into six types such as low viscosity and high permeability, low viscosity and medium permeability, medium viscosity and medium permeability, medium viscosity and high permeability, medium viscosity and extra?high permeability, and mid?high viscosity and extra?high permeability oilfields. For these different oilfields, the influencing factors of crude oil viscosity, reservoir permeability, reserves abundance, well spacing density, injector?producer ratio on the oil production rate were analyzed. The results indicate that the oil production rate at early stage of water injection development is mainly influenced by the oil viscosity, reserves abundance and reservoir permeability rather than that at late stage of it; the oil production rate at mid?late stage is mainly influenced by well spacing density and injector?producer ratio, the factors have little influence on that at early stage Related Articles | Metrics

Using Relative Permeability Curves to Identify Sanjianfang Low Permeability Reservoirs Flooded Level in Qiuling Oilfield GAO WenjunHAN JifanGE XinchaoDUAN JumeiMA Jinlan 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150518 Abstract ( 72 )   PDF (300KB) ( 133 )   Save Low permeability oilfield’s dimensionless fluid productivity and productivity indexes variation characteristics have very big difference compared with high permeability oilfield，so high permeability oilfield water flooded layer’s defined standards cannot be applied to low permeability oil field. Otherwise，it will affect the productivity prediction of different levels of water flooded layers and the development of reasonable measures for tapping potential. In order to reduce the mutual crisscross between water flooded level and water?cut development stage with different boundaries，and make different types of reservoirs or the same reservoir be comparative between them，this paper proposes methods for determination of water flooded level limit in terms of the water?cut development stage，identification of the flooded levels，prediction of productivity and evaluation of remaining oil potentials by means of relative permeability curves. The case study indicates that by different water flooded layers testing，the water production rate is consistent with the prediction results，being worthy of reference for other oilfields Related Articles | Metrics

Application of Abnormal Formation Pressure Prediction Technologies in Junggar Basin XU Baorong, XU Haitao, YU Baoli, JING Hailu, GUO Jinyu 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150519 Abstract ( 48 )   PDF (300KB) ( 124 )   Save The results from drilling in Mahu sag of Junggar basin have confirmed that there exits abnormal formation pressure in the Permian and Triassic strata, with characteristic of high pressure and high productivity. The available prediction methods for formation pressure by well logs and seismic velocity data are all based on mudstone undercompaction theory. For glutenite reservoir, its formation pressure prediction may result in big differences between the predicted pressure and the measured one. According to such a characteristic, the well logsseismic velocity data combination for formation pressure prediction is adopted to form a set of technologies for it, including seismic interval velocity method, characteristic curve inversion method and improved Fillippone formula method. The application of these methods achieves better results in Mahu sag of Junggar basin and provides basis for scientific drilling and efficient well deployment Related Articles | Metrics

Spectral Decomposition TechnologyBased on Multiple Windows Reassigned Spectrum CUI Zhen, CAO Siyuan, LIU Wei, MA Yuanyuan 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150520 Abstract ( 81 )   PDF (300KB) ( 98 )   Save Spectral decomposition decomposes a time domain signal to the time?frequency domain, which can characterize the local timefrequency properties and instantaneous frequency. The time?frequency resolution of conventional spectral decomposition methods is not high due to Heisenberg uncertainty principle. The reassigned spectrum method avoids the Heisenberg uncertainty principle and the timefrequency resolution is increased. Besides, it also generates concentrated energy for random noise. The multiple windows reassigned spectrum is based on reassigned spectrum and gets reassigned spectrums using orthogonality and recurrence. At last,the reassigned spectrums are distributed by the weighted value based on least square estimation. Synthetic data and field data show that the proposed approach can get high time?frequency resolution and disperse the random noise; meanwhile the real position of time?frequency energy can be located and indicates the low?frequency shadow related with hydrocarbon effectively Related Articles | Metrics

NMR Logging Permeability Prediction Method Based on Dynamic Pore Structure Efficiency ZHU Linqi1,2, ZHANG Chong1,2, HE Xiaoju1,2, CHEN Yulong1,2, WEI Yang1,2, YUAN Shaoyang1,2 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150521 Abstract ( 63 )   PDF (300KB) ( 267 )   Save Traditional NMR logging permeability models are always poor in application effect to tight sandstone reservoir. Considering the affects of formation pore?throat structure, pore space distribution, pore specific surface area on tight sandstone reservoir permeability, this paper proposes NMR logging permeability prediction method based on dynamic pore structure efficiency by means of theory of equivalent rock composition, and presents the model using29rock samples. In order to improve the prediction accuracy of the irreducible water saturation and the pore structure efficiency in this model, it gives such idea for evaluation of these two parameters as using T2 geometric mean value and4~32ms NMR porosity to build BP neural network for point?by?point prediction T2 cutoff value, and then taking the T2 cutoff value as intermediate parameter to get the irreducible water saturation and the porosity structure efficiency. The handling of the data proves that this model is of higher calculation accuracy than SDR and Coates models, and can be applied to permeability calculation of tight sandstone reservoir, and helpful to the productivity evaluation of the reservoirs Related Articles | Metrics

Advances of Simulation Studies of Volumetric Fracturing Horizontal Well Productivity for Shale Gas Reservoir ZHOU Xiang, ZHANG Shicheng, MA Xinfang, ZHANG Ye 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150522 Abstract ( 72 )   PDF (300KB) ( 288 )   Save Shale gas reservoir is characterized by nanoscale porosity and ultra?low permeability, which usually has no natural productivity, and has to be economically developed by means of horizontal well and volumetric fracturing technology. The study on shale gas at home and abroad mostly focused on geological characteristic evaluation and development process technologies, with few theoretical approaches to its productivity by volumetric fracturing horizontal drilling process. The key to shale gas production research should be in exact description of multiple scale flow mechanism and fine characterization of complex hydraulic fracture networks. Through wide investigation and analyses, this paper discusses such a flow mechanism, reviews the model for multiple transverse fracture horizontal well test in shale gas reservoir, elaborates how to distinguish flow regimes and evaluate reservoir and fracture parameters according to different models, and systematically introduces the methods of numerical simulation for shale gas, including conventional numerical modeling, discrete fracture network modeling and finite element approaches. It is believed that the discrete fracture network modeling and finite element approaches will be the future research trend for numerical simulation of shale gas productivity Related Articles | Metrics

Discussion on Liquid Phase Adsorption of Coalbed Methane ZHU SuyangLI ChuanliangDU ZhiminPENG Xiaolong 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150523 Abstract ( 59 )   PDF (300KB) ( 154 )   Save The coalbed methane is in an undersaturated state under the initial reservoir condition. There exists the critical desorption in coalbed methane production. According to the production performance, it is demonstrated that the coalbed methane adsorption does not conform to gas?solid adsorption regulation. The gas?solid adsorption must be saturated, and cannot have the critical desorption process. The liquid phase adsorption theory of coalbed methane can not only solve the critical desorption problem, but also satisfy the situation of coalbed methane generation. Due to the difference of molecule polar, the liquid phase adsorption volume is larger than the gas phase adsorption. Meanwhile, the undersaturated solution state of coalbed methane in water leads to critical desorption phenomenon. The coalbed methane critical desorption pressure has no relation with liquid phase adsorption coefficient, and it is calculated by the solubility of coalbed methane in water and the volume fraction of coalbed methane in water in reservoir conditions Related Articles | Metrics

Discussion and Analysis about Horizontal Well Productivity Formulas SHAN Baochao, FU Yu 2015, 36 (5):  1-1.  doi: 10.7657/XJPG20150524 Abstract ( 117 )   PDF (300KB) ( 249 )   Save This paper introduces the deducing ideas and processes of steady?state productivity formulas for horizontal wells, and compares the commonly used formulas. Through the analysis, it is indicated that there are loopholes in the process of deducing the productivity formulas for horizontal wells, which should be corrected. There are little differences among the modified formula, Borisov’s formula, and RenardDupuy’s formula in the calculation results, thus providng the validity and practicability of the modified formula, and realizing the unification of productivity formulas for horizontal wells in form Related Articles | Metrics