页岩气藏压裂水平井产能及其影响因素

Productivity and influencing factors of the fractured horizontal well in the shale gas reservoir

为研究页岩气藏产能及其影响因素,基于页岩气的特征、聚集规律、吸附解吸特性,利用Fick扩散法建立解吸气稳态扩散速率表达式,并在Genliang Guo矩形裂缝性水平井模型的基础上,建立页岩气藏压裂水平井稳态产能模型;此外,通过考虑裂缝与气体解吸的相互作用,将页岩储层气体渗流分为裂缝两边及裂缝两端的流动,并建立新的页岩气藏压裂水平井产能模型。对比2种模型计算结果,并结合现场数据分析结果表明:稳态产能模型误差更小,计算结果更为准确;裂缝、水平井长度和半径、孔隙度、C_m-C(p)差对产能有影响,裂缝越多,缝间干扰越严重,产能增量越少;水平井长度对极限产能的影响小于水平井半径; C_m-C(p)差及孔隙度增大时,产能随之增加。产能影响因素的分析可以更准确地优选水力压裂参数,对优化页岩气藏开发模式具有现实指导意义。

In order to research the productivity and its influencing factors of the shale gas reservoir, based on the characteristics of the shale gas, aggregating laws, and properties of the adsorption and desorption, the steady-state diffusion rate expression of the desorbed gas was established with the help of Fick diffusion method. And moreover, based on Genliang Guo rectangular fractured horizontal-well model, the steady-state productivity model of the fractured horizontal well in the shale gas reservoir was built;in addition, by means of considering the interaction between the fracture and gas desorption, the gas seepage was divided into two-side and both-end fracture flows, and furthermore a new fractured horizontal-well productivity model was established for the shale gas reservoir. Comparing the calculated results by the two models, and combined with the field data analysis, it shows that the steady-state capacity model has smaller error and its result is more accurate;the fracture, horizontal-well length and radius, porosity and C m- C(p) difference possess a certain influences on the productivity, the more the fractures are, the more serious inter-slit interference will be, the less the productivity increment will be;the horizontal well length has less influence on the ultimate productivity than that of the horizontal well radius;when the C m- C(p) difference and porosity increase, the capacity will increase as well. The analyses of the influencing factors on the productivity can be more accurately optimize the hydraulic fracturing parameters, and moreover possess the practical guiding significance for optimizing the development mode of the shale gas reservoir.