变压力扩展指数模型法在页岩气井递减分析中的应用
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摘要
近年来四川盆地页岩气的勘探开发取得了突破性的进展,水平井与体积压裂主体工艺技术被广泛应用于川南地区长宁区块的页岩气开发中。页岩气分段压裂水平井的产量递减规律与常规气井差异大:在初期的压裂液返排阶段,气井产量递减较快,与人造裂缝性低渗气藏气井的早期生产动态相近;后期由于页岩气的解吸附作用增强,气井长期处于低压低产阶段,产量递减慢。北美出现了多种针对页岩气井的产量递减分析方法,但这些方法局限于定压生产的假设,与页岩气井实际生产中受邻井压裂、地面管网建设等因素影响而出现的变压力变产量生产的情况不相符。通过引入压力重整产量,对扩展指数法进行改进,形成变压力扩展指数模型法(简称VP-YM-SEPD法,即Variable-Pressure drop YM-SEPD法)来解决页岩气井变压力生产数据分析的难题。应用VP-YM-SEPD法分析生产数据,需要气井生产史在半年以上,可以分析得到可靠的递减参数。该方法成功用于分析川南地区长宁区块一页岩气井的生产数据,解决了页岩气井变压力生产的递减分析难题。
In recent years,breakthrough has been realized in the shale gas exploration and development in the Sichuan Basin,and the principal technologies of horizontal well and volumetric fracturing have been extensively applied to the shale gas development in Changning Block,southern Sichuan Basin. The production decline law of shale-gas staged fracturing horizontal wells is different from that of conventional gas wells. In the early stage,i.e.,the stage of fracturing fluid flowback,the production rate of gas well declines fast. And this phenomenon is similar to the early production performance of the gas wells in artificially fractured low-permeability gas reservoirs. In the late stage,the gas well is low in pressure and production rate for a long term and its production decline rate slows down for the desorption capacity of shale gas is increased. In the North America,there are many production decline analysis methods available for shale gas wells,but these methods are confined to the assumption of constant-pressure production,which is not in accordance with the actual situation of shale gas well whose pressure and production rate are variable due to the fracturing of its neighboring wells and the construction of surface pipeline networks. In this paper,the stretched exponential production decline was modified by introducing the pressure to normalize the production rate,and thus the Variable-Pressure drop YM-SEPD(VP-YM-SEPD) method was developed to solve the difficulty in analyzing the variable-pressure production data of shale gas wells. When VP-YM-SEPD method is used to analyze the production data,the production history of the gas well shall be at least half a year,so that the reliable decline parameters can be obtained. This method has been successfully applied to analyze the production data of one shale gas well in Changning Block,southern Sichuan Basin,and it solves the decline analysis difficulty of variable-pressure production of shale gas wells.
In recent years,breakthrough has been realized in the shale gas exploration and development in the Sichuan Basin,and the principal technologies of horizontal well and volumetric fracturing have been extensively applied to the shale gas development in Changning Block,southern Sichuan Basin. The production decline law of shale-gas staged fracturing horizontal wells is different from that of conventional gas wells. In the early stage,i.e.,the stage of fracturing fluid flowback,the production rate of gas well declines fast. And this phenomenon is similar to the early production performance of the gas wells in artificially fractured low-permeability gas reservoirs. In the late stage,the gas well is low in pressure and production rate for a long term and its production decline rate slows down for the desorption capacity of shale gas is increased. In the North America,there are many production decline analysis methods available for shale gas wells,but these methods are confined to the assumption of constant-pressure production,which is not in accordance with the actual situation of shale gas well whose pressure and production rate are variable due to the fracturing of its neighboring wells and the construction of surface pipeline networks. In this paper,the stretched exponential production decline was modified by introducing the pressure to normalize the production rate,and thus the Variable-Pressure drop YM-SEPD(VP-YM-SEPD) method was developed to solve the difficulty in analyzing the variable-pressure production data of shale gas wells. When VP-YM-SEPD method is used to analyze the production data,the production history of the gas well shall be at least half a year,so that the reliable decline parameters can be obtained. This method has been successfully applied to analyze the production data of one shale gas well in Changning Block,southern Sichuan Basin,and it solves the decline analysis difficulty of variable-pressure production of shale gas wells.
引文
[1]杨洪志,张小涛,陈满,吴建发,张鉴,游传强.四川盆地长宁区块页岩气水平井地质目标关键参数优化[J].天然气工业,2016,36(8):60-65.Yang Hongzhi,Zhang Xiaotao,Chen Man,Wu Jianfa,Zhang Jian&You Chuanqiang.Optimization on the key parameters of geologic target of shale-gas horizontal wells in Changning Block,Sichuan Basin[J].Natural Gas Industry,2016,36(8):60-65.
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[12]IIk D,Rushing JA&Blasingame TA.Decline-curve analysis for HP/HT gas wells:theory and applications[C]//SPE Annual Technical Conference and Exhibition,4-7 October 2009,New Orleans,Louisiana.DOI:http://dx.doi.org/10.2118/125031-MS.
[13]Clark AJ,Lake LW&Patzek TW.Production forecasting with logistic growth models[C]//SPE Annual Technical Conference and Exhibition,30 October-2 November 2011,Denver,Colorado,USA.DOI:http://dx.doi.org/10.2118/144790-MS.
[14]Clark AJ.Decline curve analysis in unconventional resource plays using logistic growth models[D].Austin:The University of Texas at Austin,2011.
[15]Clark AJ.Determination of recovery factor in the Bakken formation,Mountrail County,ND[C]//SPE Annual Technical Conference and Exhibition,4-7 October 2009,New Orleans,Louisiana.DOI:http://dx.doi.org/10.2118/133719-STU.
[16]Zhang Xiaotao,Jiang Xin,Yang Jiyuan&Chen Man.A newly developed rate analysis method for a single shale gas well[J].Energy Exploration&Exploitation,2015,33(3):309-316.
[17]沈金才,刘尧文,葛兰,李鹏.四川盆地焦石坝区块页岩气井产量递减典型曲线建立[J].天然气勘探与开发,2016,39(2):36-40.Shen Jincai,Liu Yaowen,Ge Lan&Li Peng.Establishment of typical production-decline curves for shale gas wells,Jiaoshiba Block,Fuling Area[J].Natural Gas Exploration and Development,2016,39(2):36-40.
[18]张小涛,吴建发,冯曦,邓惠,杨济源.页岩气藏水平井分段压裂渗流特征数值模拟[J].天然气工业,2013,33(3):47-52.Zhang Xiaotao,Wu Jianfa,Feng Xi,Deng Hui&Yang Jiyuan.Numerical simulation of seepage flow characteristics of multi-stage fracturing in horizontal shale gas wells[J].Natural Gas Industry,2013,33(3):47-52.
[2]Arps J J.Analysis of decline curves[J].Transactions of the AIME,1945,160(1):228-247.
[3]Harrell DR,Hodgin JE&Wagenhofer T.Oil and gas reserves estimates:recurring mistakes and errors[C]//SPE Annual Technical Conference and Exhibition,26-29 September 2004,Houston,Texas.DOI:http://dx.doi.org/10.2118/91069-MS.
[4]Duong AN.An unconventional rate decline approach for tight and fracture-dominated gas wells[C]//Canadian Unconventional Resources and International Petroleum Conference,19-21October 2010,Calgary,Alberta,Canada.DOI:http://dx.doi.org/10.2118/137748-MS.
[5]Joshi K&Lee WJ.Comparison of various deterministic forecasting techniques in shale gas reservoirs[C]//SPE Hydraulic Fracturing Technology Conference,4-6 February2013,The Woodlands,Texas,USA.DOI:http://dx.doi.org/10.2118/163870-MS.
[6]Valko PP&Lee WJ.A better way to forecast production from unconventional gas wells[C]//SPE Annual Technical Conference and Exhibition,19-22 September 2010,Florence,Italy.DOI:http://dx.doi.org/10.2118/134231-MS.
[7]Yu SY&Miocevic DJ.An improved method to obtain reliable production and eur prediction for wells with short production history in tight/shale reservoirs[C]//Unconventional Resources Technology Conference,12-14 August 2013,Denver,Colorado,USA.Denver,Colorado,USA:Unconventional Resources Technology Conference,2013.
[8]Statton JC.Application of the stretched exponential production decline model to forecast production in shale gas reservoirs[D].Texas:Texas A&M University,2012.
[9]Can B&Kabir CS.Probabilistic performance forecasting for unconventional reservoirs with stretched-exponential model[C]//North American Unconventional Gas Conference and Exhibition,14-16 June 2011,The Woodlands,Texas,USA.DOI:http://dx.doi.org/10.2118/143666-MS.
[10]Ilk D,Rushing JA,Perego AD&Blasingame TA.Exponential vs.hyperbolic decline in tight gas sands:understanding the origin and implications for reserve estimates using Arps'decline curves[C]//SPE Technical Conference and Exhibition,21-24September 2008,Denver,Colorado,USA.DOI:http://dx.doi.org/10.2118/116731-MS.
[11]Ilk D&Blasingame TA.Decline curve analysis for unconventional reservoir systems--variable pressure drop case[C]//SPE Unconventional Resources Conference Canada,5-7 November 2013,Calgary,Alberta,Canada.DOI:http://dx.doi.org/10.2118/167253-MS.
[12]IIk D,Rushing JA&Blasingame TA.Decline-curve analysis for HP/HT gas wells:theory and applications[C]//SPE Annual Technical Conference and Exhibition,4-7 October 2009,New Orleans,Louisiana.DOI:http://dx.doi.org/10.2118/125031-MS.
[13]Clark AJ,Lake LW&Patzek TW.Production forecasting with logistic growth models[C]//SPE Annual Technical Conference and Exhibition,30 October-2 November 2011,Denver,Colorado,USA.DOI:http://dx.doi.org/10.2118/144790-MS.
[14]Clark AJ.Decline curve analysis in unconventional resource plays using logistic growth models[D].Austin:The University of Texas at Austin,2011.
[15]Clark AJ.Determination of recovery factor in the Bakken formation,Mountrail County,ND[C]//SPE Annual Technical Conference and Exhibition,4-7 October 2009,New Orleans,Louisiana.DOI:http://dx.doi.org/10.2118/133719-STU.
[16]Zhang Xiaotao,Jiang Xin,Yang Jiyuan&Chen Man.A newly developed rate analysis method for a single shale gas well[J].Energy Exploration&Exploitation,2015,33(3):309-316.
[17]沈金才,刘尧文,葛兰,李鹏.四川盆地焦石坝区块页岩气井产量递减典型曲线建立[J].天然气勘探与开发,2016,39(2):36-40.Shen Jincai,Liu Yaowen,Ge Lan&Li Peng.Establishment of typical production-decline curves for shale gas wells,Jiaoshiba Block,Fuling Area[J].Natural Gas Exploration and Development,2016,39(2):36-40.
[18]张小涛,吴建发,冯曦,邓惠,杨济源.页岩气藏水平井分段压裂渗流特征数值模拟[J].天然气工业,2013,33(3):47-52.Zhang Xiaotao,Wu Jianfa,Feng Xi,Deng Hui&Yang Jiyuan.Numerical simulation of seepage flow characteristics of multi-stage fracturing in horizontal shale gas wells[J].Natural Gas Industry,2013,33(3):47-52.