长水平段非均质页岩储层非均匀分簇射孔优化研究

Horizontal well with staged fracturing is the main technology of shale gas development at present. The reasonable clustering perforation is the basic premise for the success of staged fracturing and the realization of crack propagation. Because the horizontal interval is fairly long and the formation heterogeneity is obvious, the current uniform clustering will cause the serious interference between fractures of partial layers. The cracks will close quickly and their extension distance will be short. At the same time, however, the interference between other layers may become weak. The fractures extend far away, but the effective fracture network could not be formed. Both of the above two cases make the stimulating reservoir volume (SRV) become poor, which reducing the effect of shale gas development dramatically. First of all, based on the reservoir characteristics of main shale gas reservoirs in China, this project aims to establish a method for evaluating the heterogeneity of shale reservoirs in long horizontal section. It will consider the key parameters such as shale strength, elasticity, brittleness and fracability. It could present the heterogeneity index profile of the long horizontal interval combined with the well logging data. Secondly, with the finite element method, the influence law of clustering parameters (cluster spacing, cluster length, cluster numbers) and perforation parameters (depth, diameter, density, phase) on the crack initiation and propagation will be studied. Thirdly, a quantitative model between the shale heterogeneity index of the long horizontal interval and the rational clustering perforation parameters will be established. Finally, we can get a new method for the optimization of clustering perforation which is suitable for the characteristics of shale gas reservoirs in China.

水平井+分段压裂是当前页岩气开发的主体技术，而合理的分簇射孔是分段压裂成功、实现控近扩远的基本前提。由于页岩气水平井水平段很长，地层非均质性突出，采用目前常用的均匀布簇方式，会导致部分层段缝间干扰加剧，裂缝过早闭合，延伸距离缩短；同时导致另一部分层段缝间干扰不足，裂缝延伸较远，但缝间无法形成有效缝网。上述两种情况均使压裂后的改造体积（SRV）大幅度降低，极大的降低了页岩气开发效果。本项目拟基于国内主要页岩气区块的储层特性，综合考虑页岩强度、弹性、脆性、可压性等关键参数，建立长水平段页岩储层的非均质性评价方法。结合测井资料，给出长水平段储层非均质性指数剖面。进而研究分簇参数（簇距、簇长、簇数）和射孔参数（孔深、孔径、孔密、相位）对非均质性层段裂缝起裂与扩展的影响规律，建立起页岩非均质性指数与合理分簇射孔参数间的量化模型。最终形成适合我国页岩气储层特征的长水平段非均匀分簇射孔优化设计方法。

水平井+分段压裂是当前页岩气开发的主体技术，而合理的分簇射孔是分段压裂成功、实现控近扩远的基本前提。由于页岩气水平井水平段很长，地层非均质性突出，采用目前常用的均匀布簇方式，会导致部分层段缝间干扰加剧，裂缝过早闭合，延伸距离缩短；同时导致另一部分层段缝间干扰不足，裂缝延伸较远，但缝间无法形成有效缝网。上述两种情况均使压裂后的改造体积（SRV）大幅度降低，极大的降低了页岩气开发效果。.本项目基于国内主要页岩气区块的储层特性，综合考虑页岩强度、弹性、脆性、可压性等关键参数，首先建立了长水平段页岩储层的非均质性评价方法，进而结合测井资料，给出长水平段储层非均质性指数剖面。其次研究分簇参数（簇距、簇长、簇数）和射孔参数（孔深、孔径、孔密、相位）对非均质性层段裂缝起裂与扩展的影响规律，建立起页岩非均质性指数与合理分簇射孔参数间的量化模型。最后集成所有研究成果确定了页岩储层非均匀分簇参数设计原则，形成了适合我国页岩气储层特征的长水平段非均匀分簇射孔优化设计方法。