启动压力梯度对致密油藏水平井裂缝参数的影响

The effect of start-up pressure gradient on fracture parameters of tight oil reservoirs with horizontal well

致密油藏流动能力差,水平井压裂后形成基质与裂缝两种差异明显的介质,流体在两种介质中的渗流规律不同,在基质中存在很高的启动压力梯度,不同渗流规律的耦合对致密油藏压裂水平井开发产能及开发动态规律的研究提出了新的难度。本文建立了考虑不同基质低速非线性渗流规律的致密油藏压裂水平井产能模型,并在此基础上研究了启动压力梯度对致密油藏压裂水平井开发动态的影响,将整个生产周期分成了第一线性流、裂缝干扰流、第二线性流和边界控制流四个阶段,并认为启动压力梯度具有缩短第一线性流与第二线性流的稳产阶段的作用,不利于致密油藏的有效开发;同时,启动压力梯度对裂缝参数的优化具有重要的影响,越高的启动压力梯度需要更长、更密、更多的裂缝才能进行有效的开发。

Fluid flow ability in tight oil reservoirs is poor,and two media with obvious difference in matrix and fracture are formed after horizontal well fracturing.The seepage mechanism of fluid in two media is different,and there is a high start-up pressure gradient in the matrix.Coupling of different seepage laws brings new difficulties to the study of productivity and production performance of fractured horizontal wells in tight oil reservoirs.This paper establishes a productivity model of fractured horizontal wells in tight oil reservoirs considering the low-speed non-linear seepage law of different matrices,and studies the influence of start-up pressure gradient on the development performance of fractured horizontal wells in tight oil reservoirs.The whole production cycle is divided into four stages:first linear flow,fracture interference flow,second linear flow and boundary control flow.It is recognized that start-up pressure gradient can shorten the stable production stage of first linear flow and second linear flow,which is not conducive to the effective development of tight oil reservoirs.At the same time,the start-up pressure gradient has an important impact on the optimization of fracture parameters.The higher the start-up pressure gradient,the longer,denser and more cracks are needed to develop effectively.