基于体积源的分段压裂水平井产能评价方法

Deliverability evaluation method based on volume source for horizontal wells by staged fracturing

水平井裸眼和固井分段压裂技术已大量应用于低渗透气藏的开发,其产能评价方法是评价压裂效果和提高压裂设计水平的关键。为此,针对裂缝性低渗透气藏,采用体积源的思想建立相应的基础渗流模型,通过正交变换法求取常流率时体积源函数,并根据Duhamel原理推导了变流率时的计算方法;结合人工裂缝内流动压降并根据叠加原理分别推导出裸眼、固井分段压裂水平井的产能评价方法;最后通过现场实例及经典理论模型验证了产能评价方法的正确性,以及储层物性和人工裂缝参数对于两者产能的影响。结果表明:①裸眼、固井分段压裂水平井发挥了水平井段的生产作用,它具有较高的产能;②两者之间的差别受到储层物性和分段压裂参数的影响;③在储层物性差、压裂规模大时,裸眼、固井分段压裂水平井之间产能的差别变小。该成果对于低渗透气藏分段压裂水平井的分段压裂参数设计和压后效果评价具有重要的应用价值,也为分段压裂工艺的选择提供了理论依据。

Open hole and cementation staged fracturing technologies for horizontal wells have been largely applied to the development of low permeability gas reservoirs, and their deliverability evaluation method is critical for fracturing effect evaluation and fracturing design level improvement. Therefore, the basic seepage model which is specifically for low-permeability fracture-type gas reservoirs was built on the basic concept of volume source. The volume source function with constant flow rate was obtained by means of or- thogonal transformation. The calculation method was inferred for variable flow rates on the basis of Duhamel principle. And then combined with flow pressure drop inside artificial fractures, the horizontal well deliverability evaluation method by open hole and ce- mentation staged fracturing was derived on the basis of superposition principle. And finally, the deliverability evaluation method was verified by field cases and typical theoretical models to be correct, and the effects of reservoir physical properties and artificial frac- ture parameters on the deliverability after open hole and cementation fracturing were presented respectively. Based on the research findings, three conclusions were reached. First, the horizontal branches are brought into play in terms of production by means of open hole and cementation staged fracturing, thus having higher deliverability. Second, the deliverability difference between the two techniques is affected by reservoir physical properties and staged fracturing parameters. And third, their deliverability difference is small when the reservoir physical properties are poor and fracturing scales are large. These research findings are significantly applica- ble for staged fracturing parameter design and fracturing effect evaluation of horizontal wells by staged fracturing in low-permeability gas reservoirs, and also provide theoretical basis for the selection of staged fracturing techniques.