摘要
建立了考虑解吸作用的煤层气无限导流垂直裂缝井试井模型,推导出其有限元方程,并求得模型的数值解。绘制出无限导流垂直裂缝井的双对数试井理论曲线和煤层中的压力场。从计算所得的试井理论曲线可以看出,无限导流能力裂缝井的试井理论曲线上存在一段压力和压力导数曲线平行且斜率为0.5的直线,表明了线性流动的存在。从计算结果的压力场图可知,裂缝周围是椭圆流动,而远离裂缝区是径向流动。分析了煤层气解吸作用对试井理论曲线的影响,主要表现为在试井理论曲线的中后期,压力和压力导数曲线下降,原因是煤层气解吸缓解了压力下降,分析了裂缝关于井筒的不对称性。计算结果表明,裂缝关于井筒的不对称性对试井理论曲线的影响很小,原因在于裂缝是无限导流垂直裂缝。
Considering the effects of CBM desorption and absorption in coalbed,a new infinite conductivity vertical fracture well test model is developed in this paper,the finite element equation was derived and numerical solution was obtained.The type curve in double logarithmic form and pressure distribution field in coalbed are all showed in detail.The well test type curves showed that there are parallel straight section lines in pressure and pressure derivative curve with slope equal to 0.5,which confirmed the existence of linear flow in coalbed.From the pressure distribution field map,we found that the elliptic flow around fractures,but the radial flow far away from fractures.The effect of CBM desorption to theoretical curves showed pressure and pressure derivative curves drew down in middle and later periods of curves.And the reason was CBM desorption delayed the pressure decrease.By analyzing the fracture asymmetry about the wellbore,the results show that there is less impact of fracture asymmetry on the well test type curve for the different calculation cases,since the fractures are infinite conductivity vertical fracture.wellbore asymmetry had well test theory curves.
出处
《油气井测试》
2010年第6期53-56,共4页
Well Testing
基金
国家重大专项"大型气田及煤层气开发"专项支持
课题编号2009ZX05038001
关键词
煤层气
数值试井
解吸
无限导流
裂缝井
理论曲线
CBM,numerical well testing,desorption,infinite conductivity,fractures well,type curve
