10 November 2016, Volume 27 Issue 11
    

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    Natural Gas Geoscience. 2016, 27(11): 1-2.
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  • The influence of reservoir physical properties on multi-stage oil accumulation: An example from Permian Pingdiquan Formation,Huoshaoshan area，eastern Junggar Basin
    Chen Shi-jia, Huang Hai, Zou Xian-li, Wang li, Ma Jie, Li Yong
    Natural Gas Geoscience. 2016, 27(11): 1953-1962. https://doi.org/10.11764/j.issn.1672-1926.2016.11.1953
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    Oil accumulation characteristics in low-permeability reservoir of Permian Pingdiquan Formation,Huoshaoshan area were studied through source rock evaluation,oil characteristics and reservoir physical properties analyses.Source rocks of Huobei and Huoshaoshan anticlines were at low-mature stage,and the diversity of reservoir physical properties influenced by sedimentary environment and diagenesis is the key factor to cause oil property differences.The reservoir porosity and permeability of Huobei are low because rock particles are fine and are affected by a strong compaction,and the oil maturity is low.While the reservoir physical properties of Huoshaoshan anticline are relatively high,and the oil maturity is higher than that of Huobei,which shows a property of mixed sources.Through the research above,reservoir-controlling mechanisms were established for tight oil of this area.Huoshaoshan anticline reservoir has the feature of “two stage accumulation” with good reservoir physical property,which accumulates not only local low-mature products,but higher maturity oil from Huodong syncline by the fracture adjustment.Because reservoir in Huobei is tight,the pore space is almost filled with its own low-mature crude oil,which has the characteristics of “self-generation and self-preservation as well as one-period accumulation”.
  • Stylolite occurrence and organic matter enrichment of the mixed sediments in the Lucaogou Formation of the Jimusaer Sag in Junggar Basin
    Gao Gang, Xiang Bao-li, Wang Xuan, Wang Yi, Zhou Ran-ran, Ma Wan-yun, Ren Jiang-ling, Zhao Ke
    Natural Gas Geoscience. 2016, 27(11): 1963-1969. https://doi.org/10.11764/j.issn.1672-1926.2016.11.1963
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    There are a large number of organic matter and stylolites in the mixed sediments of the Lucaogou Formation in the Jimusaer Sag of Junggar Basin.Based on the core observation of the Lucaogou Formation in the Well Jy74 etc.,there are not only fractures but also stylolits in the rock,but the stylolits are distributed at a lower degree.The saw-toothed stylolites have bigger variation amplitude,relation with pure pressure solution,larger distribution scope and can cut across rock bedding;and the undulating stylolites have smaller variation amplitude,longer or shorter strengthen scope,and are formed by pressure solution role on the basis of rock bedding plane.It is advantageous of the combination of stylolite and fracture to petroleum migration.Based on the contrast of organic matter abundance with mineral composition and the rock distribution with stylolites and without stylolites in Well Jy74,there are not obvious relation between stylolite formation and organic matter abundance,and carbonate content;there are more factors to control organic matter enrichment of the mixed sediments,more migrated hydrocarbons in the sandstones,dolomites,and limestones,and more residual hydrocarbons in the shales;a part of dolomites,sandstones and limestones contain original organic matter of different degrees and have hydrocarbon-generating potential,but the shales have the strongest hydrocarbon generation capacity.
  • Effect of microorganisms during diagenesis and its significance on petroleum formation
    Wang Wan-chun, Wang Cheng, Sun Min-zhuo, Ding Wan-ren
    Natural Gas Geoscience. 2016, 27(11): 1970-1978. https://doi.org/10.11764/j.issn.1672-1926.2016.11.1970
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    The development of microorganisms in the diagenetic stage and their alteration on organic matter are of great significance for the generation and accumulation of biogenic methane and the formation of high quality hydrocarbon source rocks.Based on the comprehensive study on the effects of microorganisms related to deposition and diagenesis processes in recent years,the role of microorganisms on biogenic methane generation,organic matter enrichment and preservation,and soluble organic matter production during diagenesis were discussed,taking the Quaternary of the Sanhu Depression,Qaidam Basin as an example.The relationships of biodegradation parameters of biomarker compounds with methanogen markers indicates the biodegradation of original sedimentary organic matter and the development of methanogens,which are the key factors for the accumulation of biogenic gas in the Quaternary sediments in the Sanhu Depression,Qaidam Basin.The relationship with the relative abundance of bacterial biomarkers reflects the transformation of the property of original organic matter by microbial development in the diagenetic stage.The relationship with the fractional conversion of the chloroform bitumen “A” and relative abundance of saturated hydrocarbons suggest that the development of microorganisms is an important source of soluble organic matter in the Quaternary sediments.
  • The experimental research of filling gas saturation in sandstone gas reservoir
    Hu Yong, Xu Xuan, Li Jin-bu, Wang Ji-ping, Zhu Qiu-ying, Xie Kun, Shi Lin-hui
    Natural Gas Geoscience. 2016, 27(11): 1979-1984. https://doi.org/10.11764/j.issn.1672-1926.2016.11.1979
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    Aimed at the problem of the determination of charging gas saturation of low permeability in tight gas reservoir,a set of testing method of full sequence charging gas saturation of sandstone reservoir is established,taking into account the reservoir distribution,reservoir petrophysical property difference,driving force,geothermal condition and cap sealing capacity.The pressurized charging gas testing has been carried out on the sandstone with permeability of 0.034×10-3μm2 ,0.075×10-3μm2,0.244×10-3μm2,0.505×10-3μm2,0.683×10-3μm2,1.12×10-3μm2,1.47×10-3μm2,4.77×10-3μm2,10.7×10-3μm2,38.1×10-3μm2,49.1×10-3μm2,99.4×10-3μm2,and 126×10-3μm2,and the gas source pressure are 0.1MPa,0.2MPa,0.3MPa,0.5MPa,0.7MPa,0.9MPa,1.0MPa,1.2MPa,1.5MPa,1.8MPa,2.0MPa,2.5MPa,2.8MPa,3.0MPa,3.5MPa,4.0MPa,4.5MPa,5.0MPa,5.5MPa,6.0MPa,7.0MPa,8.0MPa,10.0MPa,15.0MPa,20.0MPa,25.0MPa,and 30.0MPa.In the charging gas testing,the varying law of pore pressure is recorded and the gas saturation is quantitatively evaluated by the nuclear magnetic resonance.The research shows that:①Higher intake gas pressure than the threshold pressure,slow balance progress of gas source pressure and reservoir pressure and gas gathering in high pressure are the three characteristics of the low permeability sandstone tight gas reservoir in the gas charging testing.The intake gas threshold pressure is related to the reservoir permeability closely and their relation chart is established.②The varying law of gas saturation with pore pressure and reservoir permeability is got and the gas saturation empirical formula is established by fitting the testing data.Taking the Sulige gas reservoir in the Ordos Basin as an example,the empirical formula of gas saturation is verified by lab testing and confined coring analysis and the relation chart of gas saturation and permeability is established,which can guide the gas content evaluation in the low permeability tight sandstone gas reservoir.③The reserve splitting method of different permeability reservoir is established,which takes into account gas saturation,reservoir permeability,porosity and thick,providing a basis for reserve classification evaluation.
  • Hydrocarbon source condition and accumulation mechanism of natural gas in deepwater area of Qiongdongnan Basin,northern South China Sea
    Xu Xin-de, Zhang Ying-zhao, Liang Gang, Xiong Xiao-feng, Li Xing, Guo Xiao-xiao, Liu Hai-yu
    Natural Gas Geoscience. 2016, 27(11): 1985-1992. https://doi.org/10.11764/j.issn.1672-1926.2016.11.1985
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    There has major breakthrough of natural gas exploration in western deepwater area of Qiongdongnan Basin resent years.This verified favorable source and accumulation conditions in the deepwater area of Qiongdongnan Basin.But because of the complicated geologic settings,the scale of source rocks and the hydrocarbon potential,accumulation mechanism and regularities of hydrocarbon distribution and exploration breakthrough fields in deepwater area of Qiongdongnan Basin are still indistinct.In this article,a serials of geochemical and geological methods are used.Research result shows that three types of source rocks such as Eocene lacustrine deposit,marine-continental transitional deposit and neritic deposit in Yacheng Formation of Oligocene developed in the central depression of Qiongdongnan Basin.Huge hydrocarbon potential provided a solid material basis for natural gas exploration in deepwater area of Qiongdongnan Basin.Deepwater area in Qiongdongnan Basin has favorable reservoir formation conditions with certain degree of differences.Axial channel deposited in the Upper Miocene around central canyon,submarine fan lithologic traps and Palaeogene traps in western deepwater area of Ledong and Lingshui Sags,step-fault zone in southern Baodao Sag and trap zone around western A sub-sag in western Changchang Sag of eastern deepwater area are significant exploration breakthrough field.
  • The influences of tectonic fractures on low-porosity and low-permeability sandstone reservoirs: A case study of the third member of Shahejie Formation in Dongpu Depression
    Liu Wei-bin, Zhou Xin-gui, Li Shi-zhen, Zhang Shi-qi
    Natural Gas Geoscience. 2016, 27(11): 1993-2004. https://doi.org/10.11764/j.issn.1672-1926.2016.11.1993
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    Fractures have a pivotal role in low-porosity and low-permeability sandstone reservoir.In order to study the relationship between fractures and the oil-bearing strata,production capacity,physical properties of reservoirs,the third member of Shahejie Formation in Dongpu Depression is selected as a subject,various techniques such as outcrop measurement,core overview,thin sections analysis,scanning electron microscopy and paleomagnetic core orientation were used.The types,characteristics,parameters of fractures were analyzed.The research results indicated that fractures can be divided into two categories according to their size which are the macro-fractures and micro-fractures.The size of macro-fractures is larger,while the development of micro-fracture is intensive.The porosity of fractures can be used as comprehensive quantitative evaluation parameters of fracture development.The macro fractures have porosity of 0.048% on average,and micro fractures have porosity of 0.54% on average.Fractures not only can be used as reservoir space,but also can be used as acid fluid flow channel.Flowing fluid in the fracture also can form dissolution pores,so fractures can improve the property,oil-bearing probability and capacity of the reservoir.Macro-fractures are mainly to improve the reservoir permeability,which play an important role in fluid seepage.Micro-fractures can increase the reservoir space and connect the pore of reservoir.Macro-fractures and micro-fractures formed a three-dimensional network which controls the oil and gas migration and accumulation.
  • Discussion on quartz dissolution and its mechanisms of the Upper Paleozoictight gas reservoirs in the eastern Ordos Basin
    Tian Xia-he, Qu Hong-jun, Liu Xin-she, Yang Huan, Dong Wen-wu, Chen Ya-hui
    Natural Gas Geoscience. 2016, 27(11): 2005-2012. https://doi.org/10.11764/j.issn.1672-1926.2016.11.2005
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    The Upper Paleozoic tight gas reservoirs in the eastern Ordos Basin are mainly composed of lithic quartz sandstones and quartz sandstones,with overall high quartz content.Quartz dissolution characteristics and its formation mechanism are studied via casting thin sections,scanning electron microscopy and X-ray diffraction analyzing test data in detail.Quartz dissolution manifest as quartz particles and siliceous cement dissolved into the harbor,serrated outlines,with corrosion pits in part of some particle surfaces.Quartz dissolution has mainly three patterns,including dissolution of the edge of the quartz grains,along quartz overgrowth boundary and in part of quartz particles or in the whole quartz particles.Associated cements characteristics of quartz dissolution has mainly two patterns,i.e.,one is more acidic kaolinite clay mineral associated and another is illite-rich associated.Quartz dissolution mechanisms mainly have two types,i.e.,one is acidic pore waters and Al3+ under an organic acidic background with dissolution of quartz,associated with kaolinite-based acidic clay minerals,which improved reservoirs pores of Benxi group and Shan 2 members,while the other is alkaline pore waters under alkaline diagenesis background with dissolution of quartz,mainly associated with illite-based alkaline or neutral clay minerals,which significantly improved reservoir pores of Taiyuan group.
  • Hydrocarbon distribution characteristics and main controlling factors ofaccumulation in South Konys Oilfield in South Turgay Basin,Kazakhstan
    Wu Ya-dong, Sun Chun-yan, Wang Dong-xu, Jiang Tao, Huang Ying, Gong Jian-hua
    Natural Gas Geoscience. 2016, 27(11): 2013-2022. https://doi.org/10.11764/j.issn.1672-1926.2016.11.2013
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    The South Konys Oilfield,one of the most important oilfields in the South Turgay Basin,Kazakhstan,is a combination of structural and lithostratigraphic reservoir.The study on hydrocarbon accumulation,influenced by strike-slip faults,is of great importance on oil and gas exploration and development,enrichment of hydrocarbon accumulation theory of strike-slip basin.On the basis of the analysis of petroleum geology of the South Konys Oilfield,the author summarized the oil and gas distribution characteristics.The results show that the oil and gas distribution in M-II layers in K1ln Formation was controlled by both structural and lithologic changes.The oil and gas distribution was characterized by:①The reservoir has a gas cap;②Oil column is controlled by the thickness and porosity of sandstones.③The South Konys Oilfield is a combination of structural and lithostratigraphic reservoir.Sandstones in the Jurassic J-0-1,J-0-2 layers show rapid lateral changes in thickness and oil and gas reservoirs are distributed in lenticular.Combining with the analysis of structural evolution and fault features,main controlling factors of hydrocarbon accumulation were discussed.The results show that:①hydrocarbon accumulation of plays in the K1ln and K1un formations is controlled by faulting activities.②Lateral distribution of the Jurassic lithostratigraphic reservoirs is controlled by lithologic pinch-out belts.③Vertical distribution of the Jurassic lithostratigraphic reservoirs is controlled by regional unconformities.
  • Evaluation and scale effect of aqeous phase damage in shale gas reservoir
    You Li-jun, Wang Fei, Kang Yi-li, Fang Chao-he, Chen Qiang
    Natural Gas Geoscience. 2016, 27(11): 2023-2029. https://doi.org/10.11764/j.issn.1672-1926.2016.11.2023
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    Shale gas reservoir is characterized by nanometer-scaled pore-throats,ultra-low water saturation,high content of clay and some micro fractures.The key technology of shale gas development is hydraulic fracturing.The fracturing fluid remained in factures invades into shale matrix and causes aqueous phase trapping and water sensitivity damage which decrease gas relative permeability sharply.Shale reservoirs have a nano-Darcy permeability;therefore,it is difficult to evaluate formation damage by traditional methods which measure permeability before and after the interaction of fluids and core plugs.The paper conducted experiments of pressure depletion,spontaneous filtration imbibition and nitrogen displacement using shale outcrop samples from Sichuan and four types of fracturing fluid to evaluate the damage of fracturing fluid.The evaluation indexes of shale gas reservoir damage are analyzed,and it is considered that the traditional permeability recovery rate or permeability recovery rate cannot be the only index for evaluating the damage of shale gas reservoirs.Based on the evaluation results,the abnormal phenomenon of low displacement rate corresponding relatively high gas output is analyzed.And some conclusions are gained: aqueous phase trapping caused by fracturing fluid is a dynamic process;the positive effects for gas flow must be considered in the evaluation of aqueous phase trapping;flowback of fracturing fluid in shale gas is the key point in the future 5 to 10 years.
  • Numerical well test analysis of tight gas reservoirs basedon the three parameter nonlinear seepage
    Ouyang Wei-ping, Zhang Mian, Liu Yue-wu, Wan Yi-zhao, Yuan Dong-rui, Li Shan-shan
    Natural Gas Geoscience. 2016, 27(11): 2030-2036. https://doi.org/10.11764/j.issn.1672-1926.2016.11.2030
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    The well testing models in low permeability reservoir are normally realized by using pseudo-linear flow equation with the average start-up pressure gradient.However,the pseudo-linear flow equation can only reflect the characteristics of start-up pressure gradient in low permeability reservoir.It cannot describe the characteristic of nonlinear flow.The three-parameter nonlinear seepage flow equation not only reflects the characteristics of the starting pressure gradient,also describes the non-linear concave curve.In order to improve the interpretation accuracy of the well test data in tight gas reservoir and perfect the nonlinear well testing theory,this paper presents a nonlinear numerical well testing model based on the three-parameter nonlinear seepage flow equation.With the model,the wellbore pressure response curves and pressure fields were obtained by using finite difference method.The characteristics of pressure response curves and pressure fields were analyzed.Effects of minimum start-up pressure gradient and average start-up pressure gradient on pressure response curves and pressure fields were studied.The results proved that the pressure derivative curves in radial flow phase deviating from the 0.5 line.The upward amplitude of pressure drop curves depends on the average start-up pressure gradient;the upward amplitude of pressure buildup curves depends on the difference between the average start-up pressure gradient and the minimum start-up pressure gradient.Response time of the out boundary depends on the minimum starting pressure gradient.
  • Production performance patterns and forecasting methods of gas well in volcanic gas reservoirs
    Ren Dong, Dong Jia-xin, Wang Zhi-ping, Shi Wen
    Natural Gas Geoscience. 2016, 27(11): 2037-2042. https://doi.org/10.11764/j.issn.1672-1926.2016.11.2037
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    Different from conventional sedimentary reservoirs,the storage space in volcanic gas reservoirs,with different-sized pore-fracture array modes,is quite complicated.The existence of stress-sensitivity effect,slippage effect,and relay gas supply mechanism leads to complex nonlinear percolation mechanism,with the influence of which,the dynamic production performance pattern of volcanic gas wells is quite different from that of the conventional gas wells.Based on characters of multi-size and multi-medium,and combining the dynamic production data from several volcanic gas wells,the study divides the well production performance into 3 phases:The initial high-production period,production-declining period,and low but stable production period.Numerical simulation of Eclipse,the history matching result of which perfectly fits the actual production curve,verifies the rationality of the “3-phase” theory.A production performance prediction method is built with slippage effect and stress sensitivity effect taken into consideration.On the basis of the research results,productivity of 12 wells are predicted,and 10 of them are in accordance with the actual situation.This study has great significance in volcanic gas wells production prediction and proration.
  • Numerical simulation research on mechanism of induced stressperturbation between parallel fractures in horizontal wells
    Li Wang, Li Lian-chong, Tang Chun-an
    Natural Gas Geoscience. 2016, 27(11): 2043-2053. https://doi.org/10.11764/j.issn.1672-1926.2016.11.2043
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    The stress fields induced by parallel fractures of horizontal wells overlap on each other,making the initiation and extension of fractures more complicated.A numerical simulation is carried out to study the mechanism of induced stress perturbation between multiple parallel fractures.A comparison of the theoretical solution and numerical results of the induced stress both parallel and normal to the fracture is made firstly.The calculated results indicate that the additional stress is always higher in the direction perpendicular to the fracture than in the direction parallel to the fracture.Secondly,the stress distribution of two prefabricated fractures and two synchronously extended fractures is discussed.It is found that the small fracture spacing,long fracture length and small principal stress difference are conducive to the appearance of stress-reversal region and complex hydraulic fracture network.Lastly,the geometry of three synchronously extended fractures is analyzed,and the results show that in the case of small fracture spacing and big horizontal stress difference coefficient,the middle fracture propagates more difficultly or even stop propagating soon after initiation.The small principal stress ratio is advantageous to the appearance of branching cracks parallel to the direction of original minimum principal stress direction,thus the possibility of complex fractures in the reservoir formation by the subsequent hydraulic fracturing is greater.Under appropriate fracture spacing and in-situ stress condition,the middle fracture can overcome the “extension inhibition period” and step into the “secondary extension period”.
  • Low-resistivity gas reservoir genesis and log evaluation method in Hangjinqi area
    Peng Zhen, Qin Zhen, Pan He-ping, Ji Yang, Guo Bo, Xu Wei, Sun Li-zhou
    Natural Gas Geoscience. 2016, 27(11): 2054-2063. https://doi.org/10.11764/j.issn.1672-1926.2016.11.2054
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    The exploration and production data in Hangjinqi area confirmed that there are many low-resistivity gas reservoirs.However,the genesis of low-resistivity is not clear,this situation affects the fluid identification and log evaluation,especially the calculation of water saturation.Thus,by using the laboratory measurements and well logs,genesis of the low-resistivity is analyzed and summarized as three reasons.They are additional conductivity of clay mineral,micro-pore development and the influence of formation water salinity.By using the “core scale logging” method,the conventional log calculation models of reserve parameters are established.Based on the genesis of low-resistivity gas reservoir,three conductive fluids,which can affect the electrical conductivity of formation water,are summarized such as shale (the bound water),micro-pore conductive fluid (the capillary water) and macro-pore conductive fluid (the free water).Therefore,the improved “dual-water saturation model” and the estimation solutions of the corresponding parameters are proposed to calculate the saturation in low-resistivity gas reservoir.Field examples confirmed that,by using the method,the reliable evaluation results,which matched well with the test results,can be obtained in the low-resistivity gas reservoir in Hangjinqi area.It can provide a technology solutions for log evaluation in low-resistivity gas reservoir.
  • Application of seismic motion inversion technology in thin reservoir prediction:#br# A case study of the thin sandstone gas reservoir in the B area of Junggar Basin
    Gu Wen, Xu Min, Wang Duo-han, Zheng Hong, Zhang Xiong, Zhang Dong-jun, Luo Jing
    Natural Gas Geoscience. 2016, 27(11): 2064-2069. https://doi.org/10.11764/j.issn.1672-1926.2016.11.2064
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    The accuracy of thin reservoir prediction is a hot debate in the oil and gas exploration and development.The key lies in how to combine well,broaden the band and get reasonable high frequency components in order to achieve a thin layer and accurate prediction.The traditional inversion technique is mainly through the deterministic or stochastic simulation and it sets up a broadband model.The high frequency component mainly comes from the well,which did not reflect the lateral constraint of the seismic.Seismic modeling inversion instead of traditional variation function,simulates the high frequency components,makes full use of the change of lateral seismic waveform information.It’s stronger than the traditional methods in certainty,and has lower requirements of well distribution.It has good application in thin sandstone gas reservoir prediction in the Junggar Basin B area,providing a reliable data basis for the evaluation and development phase.
  • Application of layer-constrained grid tomographic velocity modeling in onshore salt domes area
    Wang Zhao-qi, Ye Yue-ming, Zhuang Xi-jin, Chen Jian-wei, Zhang Jin-ling
    Natural Gas Geoscience. 2016, 27(11): 2070-2076. https://doi.org/10.11764/j.issn.1672-1926.2016.11.2070
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    Because of large velocity variance between salt domes and surrounding rocks and large thickness changes in spatial direction,seismic wave field is very complex.According to the complex geological characters and difficulties of velocity modeling in onshore salt domes,we proposed an idea called “layer-constrained grid tomographic velocity modeling techniques”,which uses layer-constrained technique to improve the precision of velocity modeling,and uses dip-steered structure oriented filter to improve the accuracy of tomography inversion.That adopts reverse time migration in depth domain and optimize the key parameters,can precisely image the reflected waves from steep dip.Through the methods above,we can solve the problem of velocity modeling accuracy of salt dome,and the flank of salt dome.Therefore,the pull-up impact from salt domes on the underlying strata can be eliminated and accurate images of complex sub-salt targets can be achieved.
  • A research on low reservoir pressure of coal 3# of Shanxi Formation in Luan mining area,Qinshui Basin
    Cao Yun-xing, Chai Xue-zhou, Liu Tong-ji, Feng Pei-wen, Tian Lin, Shi Bin, Cao Yong-heng, Zhou Dan
    Natural Gas Geoscience. 2016, 27(11): 2077-2085. https://doi.org/10.11764/j.issn.1672-1926.2016.11.2077
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    Pressure is one of the most important parameters for characterizing coal reservoirs and for evaluating coalbed methane (CBM)production potential,and for designing the well drilling,well completion,stimulation and production.Reliable pressure data and the distribution of a CBM play are critical for CBM exploitation.Based on the pressure data obtained through injection falloff test (IFOT)in open-hole wells completed in 1990's,it was found that the pressure was over evaluated for coal 3# of Lower Permian Shanxi Formation.In this study,an advanced pressure test methodology was newly developed with cased holes and extending shut-in time.Though application of this new method from 2010 to 2013,34 data wells have been tested in Luan mining area,Qinshui Basin,China.It was found that: (1)The newly developed method is an advanced technology for obtaining reliable reservoir pressure in low permeability and low pressure CBM play.(2)The reservoir pressure gradient of coal 3# in average is 4.2kPa/m in the study area,characterizing a low to ultra low pressure reservoir.Ultra low pressure gradient was found in Changcun (2.6kPa/m),Gaohe (3.3kPa/m)and Yuwu coalmines (3.7kPa/m),and low pressure gradient was obtained in Wuyang (4.7kPa/m),Licun (5.2kPa/m)and Gucheng (5.4kPa/m).These values are significantly lower than those of previously collected data from open holes in the study area Yuwu coal mine.(3)The low reservoir pressure is related to the Xin'an Spring Group,located on the eastern edge of the Qinshui Basin,which discharges reservoir groundwater to the surface hydrological system.(4)For increasing CBM production in such low to ultra low pressure reservoir in Luan mining area,reservoir protect fluid system and optimizing stimulation technologies should be developed in the near future.
  • Logging response and parameters reconstruction of coal reservoir fractures in the southern Qinshui Basin
    Wang Jian, Cui Yong-qian, Shi Jin-xiong, Liu Guo-ping, Xiao Yang, Zeng Lian-bo
    Natural Gas Geoscience. 2016, 27(11): 2086-2092. https://doi.org/10.11764/j.issn.1672-1926.2016.11.2086
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    Effect of coalbed methane development is obviously influenced by the fracture characteristics in coal reservoir,and it is true for southern Qinshui Basin.According to the data on investigation in field with similar outcrops,core description,Formation Microscanner Image analysis and conventional logging,researches about fractures in coal reservoir formation were carried out on its development characteristics and response characteristics on conventional logging,based on which we get the method of identifying fractures in coal reservoir and analyse the application effect of this method.Fractures in research area are mainly tectonic shear fractures in NE,NW,near EW and near NS directions,and most of them are valid with high angle or some dip,small scale and great changeable density.The response characteristics of fractures in conventional reservoir are mainly represent as low resistivity,positive amplitude difference in laterolog resistivity of shallow and deep formation,some,but not obvious,deflection to larger porosity in three porosity log,high gamma value,obvious diameter extension,certain fluctuations in logging curve.On this base,anomaly index were reconstructed,fracture predictive index were composed by weighting processed logging curve to predict the fractures features in coal bed.The predictive result agrees well with core and FMI,which show that this method can provide certain reference function in identifying fractures in coal reservoir.
  • Study on the geological controlling effects on the enrichmentand high-yield of coalbed methane in Yanchuannan area
    Chen Gang, Hu Zong-quan, Zhang Yong-gui, Su Kun
    Natural Gas Geoscience. 2016, 27(11): 2093-2102. https://doi.org/10.11764/j.issn.1672-1926.2016.11.2093
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    Yanchuannan block is China’s first commercial development of deep coalbed methane field in southeast Ordos Basin,and now in the stage of the production.Due to the different main burial depth of coal seams,there is significant difference between gas and water production in the gas fields.Using comprehensive analysis of the large number of well logging interpretation,taking the test of ground water geochemical and production wells working condition as a basis,we discuss the geological controlling effect on the enrichment and high-yield of coalbed methane in Yanchuannan block.It can be divided into east and west two hydrogeological units,and the hydrodynamic intensity in eastern Tanping is higher than that in the west Wanbaoshan block.High ground water salinity in the weak runoff-retention area of Yanchuannan,and suitable hydro-geochemical parameters were in favor of coalbed methane enrichment.Based on the analysis of well logging interpretation of coal structure,it is found that the high-yield area was distributed in the cataclastic structure coal development zone,therefore,selection criteria of coalbed methane enrichment and high-yielding have been established,in Yanchuannan area  and the four favorable area will provide backup relay area for the gas field of subsequent development.
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