基于启动压力梯度的火山岩气藏多重介质试井模型  

A dual porosity model for transient well tests in volcanic gas reservoirs considering threshold pressure gradient

作　　者：任东[1,2] 刘启国[1] 汤勇[1] 廖旭平[3] 

机构地区：[1]西南石油大学石油工程学院 [2]中国石油天然气股份有限公司 [3]中国石油天然气管道局国际事业部

出　　处：《天然气工业》2011年第10期50-53,118-119,共4页Natural Gas Industry

基　　金：国家科技重大专项"含CO2天然气藏开发技术"(编号:2008ZX05016-001)

摘　　要：火山岩储层发育气孔、粒间孔、溶蚀孔和炸裂缝、构造缝等,基质物性差,渗透率低,束缚水饱和度较高。物理模型实验结果表明气体流动过程中存在启动压力梯度,常规试井模型解释存在较大误差。为此,在物理模型实验的基础上,建立了基于启动压力梯度的火山岩气藏多重介质不稳定试井模型,采用拉普拉斯变换、格林函数等方法对该模型进行求解,推导了无限大边界和圆形边界两种条件下的Laplace空间解析解,获得了试井分析典型图版,并分析了启动压力梯度对典型版图的影响。研究结果表明:启动压力梯度越大,流体流动阻力越大,导致基质孔隙向裂缝的供给能力越弱,使得基质与裂缝发生窜流的时间向后推迟,无因次拟压力及其导数曲线上翘更加明显;如果忽略启动压力梯度的影响,试井解释渗透率、探测范围、弹性储能比等参数值偏小,窜流系数则偏大。Stomas,intergranular pores,vugs,cracks,and tectonic fractures are abundant in volcanic gas reservoirs,characterized by inferior property,low permeability,and high constrained water saturation.The experimental results of physical modeling show that there is the threshold pressure gradient(TPG) in the gas flow,showing a large difference from the regular transient well test model.Therefore,on this basis,a dual porosity model for transient well tests in volcanic gas reservoirs is built considering the TPG.First,the Laplace Transformation and Green's Function methods are adopted to obtain the solutions to this model.Then,the Laplace three-dimensional analytic solutions are deduced under two conditions of infinite and circular boundary.Finally,the classic type curves are thus achieved,on which the effect of TPG is discussed.The results show that the larger the TPG,the greater the flow resistance is,which leads to such results as that the efficiency of matrix drainage to fractures becomes worse,the occurrence of the corssflow between matrix and fractures is delayed,and the upwarping of dimensionless pseudopressure as well as the corresponding derivative curves becomes more obvious.If the TPG is ignored in the well test interpretation,the permeability,an investigation range and an elastic storage ratio will become smaller while the crossflow coefficient will become larger.

关 键 词：火山岩气藏 启动压力梯度 多重介质 数学模型 试井 特征 

分 类 号：TE353[石油与天然气工程—油气田开发工程]