摘要
针对页岩气藏中水平井结合体积压裂开采、吸附气和游离气共存的方式,建立考虑储层改造体积的页岩气藏复合模型,定义新的参数表征基质中吸附解吸气量与游离气弹性释放量的比值,且将储层分为人工主裂缝区域、储层改造区域和未改造区域,其中人工主裂缝基于离散裂缝模型降维处理,储层改造区域为双孔双渗模型,未改造区域为单孔隙介质模型;模型采用有限元方法进行求解,与双重介质解析解对比验证算法的正确性.结果表明:页岩气藏水平井体积压裂复合模型主要存在主裂缝周围线性流、过渡区域拟稳态、窜流阶段、未改造区域的拟径向流动和到达边界后的拟稳态等5个主要流动阶段,且考虑吸附解吸后,定产量生产所需压差小,压力波传播到边界时间长,压力导数曲线凹槽更加明显,定井底流压生产时压裂水平井产量更大,稳产时间更长;储层改造体积越大,到达区域拟稳态流越晚,可判定储层改造体积;Langmuir吸附体积越大,压力波传播越慢,所需压差越小,压力导数曲线凹槽越深,页岩气藏稳产时间越长,产量越大,但产量的增幅越来越小.
Due to the horizontal well with volume fracturing,the adsorbed gas and free gas coexistence phenomenon in shale gas reservoir,a composite model of volume fracturing horizontal well in shale gas reservoir is built with considering the stimulated reservoir volume,at the same time a new parameter was defined to demonstrate the gas production ratio of desorption gas and free gas in matrix system.The reservoir is divided into three main areas including artificial main fractures,stimulated reservoir volume and unstimulated reservoir,where the dimension of artificial main fracture is reduced based on the discrete fracture model,the stimulated reservoir volume follow the dual permeability model,and the uns-timulated reservoir obey to the single porosity model.The composite model is solved using the finite element method,and verified by the analytical solution in dual porosity reservoir.The result show that:There are five main flow regimes in the volume fracturing horizontal composite model including linear flow around the main hydraulic fractures,pesuo-steady flow of transition area,crossflow period,radial flow of unstimulated reservoir volume and the outboundary pesuo-steady flow.When the mechanism of desorption in shale matrix is considered,fractured horizontal well pressure become lower,propagation time of pressure wave to boundary is longer,and the pressure derivative curve grooves more serious,at the same time,the rate with constant wellbore pressure becomes higher and stable time is longer.The bigger the size of SRV is,the later the pesuo-steady flow of transition area arrived,so according to the arrival time of pressure wave to the SRV outboudary,namely the pesuo-steady flow of transition area appeared,the size of SRV can be determined;Then the bigger the Langmuir absorption volume become,the slower the wave propagated,more serious the pressure derivative grooved.
出处
《东北石油大学学报》
CAS
北大核心
2015年第2期77-84,9-10,共8页
Journal of Northeast Petroleum University
基金
国家自然科学基金重点项目(51234007)
山东省自然科学基金项目(ZR2014EL016
ZR2014EEP018)
中国博士后科学基金项目(2014M551989)
关键词
页岩气藏
体积压裂
储层改造区域
复合模型
有限元法
shale gas reservoir
volume fracturing
stimulated reservoir volume
composite model
the finite element model
