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页岩气单井产量和累计产量影响因素分析_甘柏松

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页岩 气单井 产量 累计 影响 因素 分析 甘柏松
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 [收稿日期 ]2012-11-29[作者简介 ]甘柏松 (1973-),男 ,1997年西安石油学院毕业,工程师 ,现从事天然气田生产管理 。页岩气单井产量和累计产量影响因素分析甘柏松(中化石油勘探开发有限公司 ,北京100031)[摘要 ]通过递减分析方法和数值模拟方法重点分析页岩气单井产量和累计产量的影响因素 。以美国主要页岩气气田为实例 ,结合流动机理分析递减特征 ,认识到不同生产动态曲线的递减率在时间上基本一致 。同时 ,以数值模拟为手段 ,从理论上分析了水力压裂缝 、水平井段长度 、储层中自然裂缝发育程度 、基质孔隙度和渗透率物性 ,以及基质等温吸附曲线对单井累计产量的影响 。研究成果对于预测我国页岩气单井产量和累计产量 ,做好生产规划具有很好的实用价值 。[关键词 ]页岩气 ;递减曲线 ;递减率 ;数值模拟 ;水平井[中图分类号 ]TE32[文献标志码 ]A  [文章编号 ]1000-9752(2013)03-0127-032011年6月 ,国土资源部举行首轮页岩气探矿权招标 ,国内6家企业竞争4个页岩气区块 ;2012年10月举行了第二轮页岩气招标 ,国内83家企业竞争20个页岩气区块 。国家批准建立 “四川长宁-威远 ”和 “滇黔北昭通 ”国家级页岩气示范区 。页岩气发展规划[1]提出到2015年 ,国内页岩气产量达65×108 m3,2020年力争实现产量 (600~1000)×108 m3,将占据气体能源供应量的25%。页岩气开采在美国获得了巨大成功 ,但 “水平井+多段压裂 ”页岩气开采技术在2006年才开始在全美推广 ,该国页岩气产量飞速上升 ,2011年页岩气产量达到1800×108 m3,占其天然气产量的34%[2]。笔者采用递减曲线方法分析美国主要页岩气田典型单井产量的递减趋势 ;同时通过数值模拟计算 ,定量分析页岩气单井累计产量的各种影响因素 。研究成果为预测和评价新页岩气招标区块的产量和累计产量提供参考 。1 递减曲线方法研究笔者系统整理了美国Eagle Ford、Fayettevile、Haynesvile、Marcelus和Woodford页岩气气田的主要储层特征和开采数据[3~5],结果见表1。这些气田的典型递减曲线见图1。表 1美国部分页岩气气田的主要参数表气田名称储层埋深/m储层厚度/m总有机碳质量分数 /%测井孔隙度/%井网密度/(口 ·km-2)水平段长度/mEagle Ford  3200~3500  90~145  4.25  9.0  3.0  1150~1676Fayettevile  1200~2130  34~60  5.0  4.0~12.0  1.5~3.0  457~1524Haynesvile  3200~4120  60~90  4.0  10.0  3.0  1070~1158Marcelus  1220~2590  15~60  5.3~7.8  5.5~7.5  3.0  760Woodford  1530~3350  46~76  4.0~6.5  6.0~7.0  1.5  760~1525由图1可知 ,页岩气单井产量在投产的第1~2年下降较快 ,但页岩气井的大部分产量在这2年采出 ;此后产量平稳 ,下降速度趋缓 。这样的生产动态特征是由页岩气在储层中的流动机理决定的[6]。首先采出的是裂缝中的天然气 ,然后采出的是裂缝表面以及基质中的吸附气 。由于裂缝中的天然气是自由·721·石油天然气学报 (江汉石油学院学报 )2013年 3月 第 35卷 第 3期Journal of Oil and Gas Technology(J.JPI)Mar.2013Vol.35No.3  图 1美国主要页岩气气田单井产量典型曲线图气 ,可以快速地采出 ,并在裂缝中形成压降 ;后期吸附在裂缝与基质中的吸附气因压降而缓慢解吸后被采出 。储层的等温吸附曲线形态[7]决定了吸附气缓慢释放 ,产量低但相对稳定 。对上述美国实际页岩气气田的典型生产曲线进行递减分析 ,计算理论递减率b,发现各个气田单井产量的递减趋势相近 ,即递减率随着时间具有很好的一致性 (图2)。该规律对于预测页岩气单井产量变化具有很好的实用价值 。同时发现在投产后前半年左右 ,递减率b大于1,这与常规Aprs递减分析理论不符 。分析出现b图 2美国主要页岩气气田单井产量递减率分析图大于1的原因有 :开采初期 ,页岩气单井的流态还处于非稳定流态 ;页岩气储层为双重或多重介质模型 ;页岩气开采通常需要对水平井进行分段压裂 ,沿水平井段形成了类似多层的流动 。2 数值模拟方法研究目前页岩气数值模拟模型包括双重介质模型 、多重介质模型和等效介质模型[8~9],笔者选用双重介质模型 ,并假定基质表面的吸附气瞬时脱落 。用商业数值模拟软件的页岩气模块建立模型 ,模型大小在X方向和Y方向都是2000m,Z方向100m;X方向和Y方向各划分200个网格 ,Z方向划分4个网格 ,分段压裂缝为7条 ,模拟计算页岩气开发常见参数范围内单井累计产量的分布 ,以此研究这些参数对页岩气单井累计产量的敏感性和影响程度 ,见表2。表 2页岩气累计产量的主要影响参数的取值表取值基质孔隙度/%基质渗透率/mD自然裂缝孔隙度/%自然裂缝渗透率/mDLangmuir体积质量比/(m3·t-1)Langmuir压力/MPa水平段长度/m压裂缝半长/m储层厚度/m生产压差/MPa低值 0.021.0×10-5 5.0×10-5 1.0×10-5 0  3.5  600  15  50  20中值 0.061.0×10-4 4.0×10-4 2.0×10-4 1.5  8.0  1000  50  80  25高值 0.101.0×10-3 2.0×10-2 1.0×10-3 3.0  20.0  1500  150  120  30为了模拟如上主要参数变化对页岩气单井累计产量的影响 ,取表1的中值为基础模型的输入参数 ,模拟计算10a得到页岩气单井累计产量的基值 。然后 ,分别逐一对参数取高值和低值进行敏感性模拟计算 ,得到该因素对累计产量的影响 。通过敏感性模拟计算 ,取中值情况下 ,单井累计产量为6580×104 m3。发现如下因素对页岩气单井累计产量影响巨大 :压裂缝半长 、自然裂缝渗透率 、水平段长度 、生产压差 、基质孔隙度 、储层厚度和自然裂缝孔隙度 ;其次是基质等温吸附曲线的两个参数Langmuir体积和Langmuir压力 ;而基质渗透率对页岩气单井累计产量影响很小 ,详见图3。也就是说 ,页岩气开采产量大小及累计产量关键取决于分段压裂效果 (包括压裂缝半长和分段压裂数量 )、水平段长度 、自然裂缝发育情况 (包括裂缝渗透率和孔隙度 ),而基质的孔隙度和渗透率影响相对较小 。·821·石油天然气工程2013年 3月  图 3页岩气单井累计产量影响因素模拟结果图3 结论1)通过对美国5个页岩气气田的典型产量曲线所做的实例分析发现 ,虽然单井产量差别较大 ,但其递减趋势一致 ,递减率曲线基本重合 ,这对于预测页岩气单井产量具有重要的指导作用 。2)页岩气单井产量在前1~2年快速下降 ,但单井产量主要集中在这段时间 ;此后产量低 ,但保持相对稳定 ,递减率低 。3)在页岩气单井投产前半年左右 ,产量递减率b大于1,其主要原因是单井处于非稳态流动阶段 ,以及储层为多重基质 、多层流动模型 。4)影响页岩气单井累计产量的主要因素包括压裂缝半长 、自然裂缝发育程度 、水平段长度 、生产压差 、基质孔隙度和储层厚度 ;而基质渗透率和等温吸附曲线形态对累计产量影响相对较小 。[参考文献 ][1]国家发展和改革委员会 ,国家财政部 ,国土资源部 ,等.页岩气发展规划(2011-2015年)[N].中国能源报,2012-03-19(B06).[2]中国能源网.美国页岩气发展概况[EB/OL].http://www.china5e.com[3]刘双莲 ,陆黄生.页岩气测井评价技术特点及评价方法探讨[J].测井技术,2011,35(2):113~114.[4]U.S.Energy Information Administration.Review of Emerging Resources:U.S.Shale Gas and Shale Oil Plays[EB/OL].ftp://ftp.eia.doe.gov/natgas/usshaleplays.pdf,2011-07-01.[5] (Ross)Crain E R.Unicorns in the garden of good and evil:Part 4-Shale Gas[EB/OL].www.spec2000.net/freepubs/2010-4UnconvGAS.pdf,2011-02-01.[6]Clarkson C R,Jensen J L.Reservoir engineering for unconventional gas reservoirs:what do we have to consider[J].SPE145080,2011.[7]Rick Lewis,David Ingraham,Marc Pearcy.New Evaluation techniques for gas shale reservoir[A]Schlumberger Reservoir Symposium[C].Los Angeles,2004-07-29~30.[8]Kalantarli A E.Numerical modeling of wel performance in shale gas[M].Netherlands:Delft University of Technology,2011.[9]孙海 ,姚军 ,孙致学 ,等.页岩气数值模拟技术进展及展望[J].油气地质与采收率,2012,19(1):46~49.[编辑 ]萧雨·921·第 35卷第 3期 甘柏松 :页岩气单井产量和累计产量影响因素分析tem.Unsteady JBN method was used to measure the gas-oil relative permeability curves in CO2flooding at different res-ervoir pressures.The change rules of gas-oil interfacial tension and relative permeability curves were studied.The resultsshow that the interfacial tension gradualy decreases with the increase of reservoir pressure.Simultaneously,the isopermpoints of gas-oil relative permeability curves are shifted towards the right side.And common percolation zones are grad-ualy enlarged.The residual oil saturation of CO2flooding is gradualy declined.The relative permeability curves aregradualy changed to the shape of diagonal line as the interfacial tension is equal to zero.Keywords:CO2flooding;low permeability reservoir;interfacial tension;relative permeability curve124 Characteristics of Bottom Pressure of Shale-gas Wel ConsideringSlippage EffectREN Fei,WANG Xin-hai,XIE Yu-yin,LI Qing-quan,REN Kai,XU Lei,WANG Zhao (First Authors Address:Faulty of Pe-troleum Engineering,China University of Petroleum,Beijing102249,China)Abstract:In order to understand the characteristics of bottom pressure of shale gas wel and exploit shale gas efficient-ly,its percolation mechanism was studied.On the basis of dual porous model which was suitable for unconventional coal-bed methane,mathematical model of dual porous media for shale gas reservoirs considering slippage was estab-lished.Relevant numerical model of finite difference was given.Bottom hole pressure responses of different Langmuirvolumes,ratio of fracture and matrix permeability,slippage factor were simulated through programming.The result indi-cates that:①The desorption of shale gas cannot be neglected,the higher the Langmuir volume is,the slower the droprate of bottom hole pressure reduction is,the detection of stratigraphic boundary is later;②in order to achieve stableproduction of shale gas wel,during the process of shale gas exploitation,the ratio of fracture and matrix permeabilityshould be reduced as smal as possible;③the bigger the slippage factor is,the slower the bottom pressure drop is.Keywords:bottom-hole pressure;mathematical model;slippage effect;desorption;dual porous media;shale gas127 The Influential Parameters Analysis on Single-wel and Accumulated Productions of Shale Gas WelsGAN Bai-song (Authors Address:Sinochem Petroleum Exploration &Production Co,Ltd,Beijing100031,China)Abstract:After two rounds of bidding of domestic shale gas blocks in China,great attention was put on its explorationand development.Researches were carried out from different aspects.The parameters influencing its single-wel and ac-cumulative productions of shale gas were emphaticaly analyzed by using decline curve method and numerical simula-tion.By taking the main shale gas fields in USA for example,the characteristics were explained with porous flow mecha-nisms in shale gas reservoirs,it was considered that the decline rate of different production curves was basicaly thesame in time intervals.By numerical simulation al important parameters influenced the production of shale gas were an-alyzed theoreticaly,including hydraulic fracture,length of horizontal wel,natural fracture development,matrix porosityand permeability,and the effect of sorption isotherm of matrix on accumulated single wel production.The results arepractical for forecasting the production of shale gas wel and for making aplan for shale gas field development.Keywords:shale gas;decline curve;decline rate;numerical simulation;horizontal wel130 Conditions of Remaining-oil Re-enrichment bySteam Soakingand Its Control FactorsWANG Su-qing,JIN Qing-qing,HAN Jian,CHEN Huan-ying (First Authors Address:The 2nd Oil Production Plant,HenanOilfield Company,SINOPEC,Tanghe 473400,Henan,China)Abstract:According to the heavy-oil reservoir characteristics and the crude oil properties in Henan Oilfield,three kindsof geological models were established for the reservoirs in the central wel groups,the wel groups near faults and thewel groups in the vicinity of edge water area.Through the orthogonal experiments and data analysis method,the influ-ence of 7different geological factors on the steam huff and puff of heavy-oil reservoirs was studied by using numericalsimulation.And the controling factors of remaining oil enrichment of heavy-oil reservoirs are obtained at the late stagesteam huff and puff of heavy-oil reservoirs.Keywords:enrichment of heavy oil;orthogonal experiment;viscosity of crude oil;effective thickness;dip angle of thereservoir;permeability134 The AffectingFactors of Gas Wel Productivityin Kelameili Gas FieldLU Lin-lin,SUN He-dong,YANG Zuo-ming,YAN Li-heng (First Authors Address:School of Energy Resources,China Univer-sity of Geosciences,Beijing100083,China;Langfang Branch,Research Institute of Petroleum Exploration and Development,PetroChina,Langfang065007,Hebei,China)Abstract:Kelameili Volcanic Gas Field was mainly composed of 4important gas reservoirs,namely Dixi 17,Dixi 14,Dixi18and Dixi10Reservoirs.There existed huge difference of development effect in different welblocks,while in the samewelblock,there existed big difference of production in different wels.The uncertainty of productivity seriously influ-enced high effective production of the gas field.By analysis of volcanic lithofacies,lithology,fault development extent,driling and completion technology,it was considered that the volcanic lithofacies and lithology are the primary affectingfactors of gas wel productivity.In view of lithofacies,explosive facies volcanic breccia,orthophyre and dacite are highproductivity.Besides fracture growth,under-balanced driling and horizontal wel driling are also important affectingfactors yielding high productivity.Keywords:Kelameili Gas Field;Carboniferous;volcanic rock;productivity;affecting factor138 AnalyzingOilfield Dynamic Characteristics byUsingIsochronal MethodSUN Jing,LIU De-hua,LI Zhao-shun,TANG Jiang (First Authors Address:College of Petroleum Engineering,Yangtze Uni-versity,Wuhan 430100,Hubei,China)Abstract:Influenced by new wel production,the production decline law was not accurately judged and the productionoutput of the oilfield was not precisely forecasted by using the conventional analysis method of production declinelaw.The isochronal method was put forward.It was a production processing method that put the dynamic data of eachwel of each year into the same producing time.Some blocks from an oilfield in Northwest China are taken as back-ground for a study,the method is used to analyze the decline characters of the blocks,by which the precision of predic-tion is enhanced and interwel communication is judged.Keywords:characteristics of production decline;production forecast;isochronal method;oilfield dynamicsⅦ
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