鄂尔多斯盆地致密油层混合压裂簇间干扰研究

针对鄂尔多斯盆地致密油层施工排量和簇间应力干扰作用对形成复杂缝网的影响开展了相关研究。采用离散缝网模型及有限元软件进行模拟分析,选择产层相同、压裂增产方案相近的2口试验水平井,进行压裂设计参数对比、产量对比及微地震监测结果对比。研究表明,施工排量过小,压裂效果以常规双翼缝为主,大排量是保证复杂缝网形成的条件;储层存在实现复杂缝网的临界排量,大于该临界排量时,主裂缝变短,次生缝网增加,带宽变大;多簇压裂时,主裂缝不同步开裂易引起主裂缝不同步延伸,率先延伸的主裂缝会抑制周围主裂缝的延伸甚至开裂,后延伸的主裂缝周围易产生剪切诱导的次生裂缝,利于形成复杂缝网。因此,选取大于临界排量的施工排量有利于增加储层改造体积,而多簇压裂时开裂延伸的主裂缝数量有可能小于设计簇数。

Inter-cluster interference in hybrid fracturing of tight oil reservoirs in Ordos Basin

Relevant research has been conducted to the effect of fracturing displacement in tight oil reservoirs in Ordos Basin and the inter-cluster stress interference on creation of complex fracture network. The discrete fracture network model and finite element software were used, and two wells were selected for comparison on fracturing design parameters, production and the results of micro-seismic monitoring. The research findings show that, large displacement and large liquid volume are the basis to guarantee creation of complex fracture network. There exists a critical pumping rate to create complex fracture network under certain formation conditions and fracturing parameters. In case of multi-cluster fracturing, the non-synchronous cracking of major fractures will lead to non-synchronous extension of major fractures. The firstly extended major fractures may suppress the extension or even initiation of the surrounding major fractures, but around the lately extended major fractures may occur shear-induced secondary fractures, which is favorable for creation of complex fracture network. Therefore, in hybrid fracturing design, a fracturing displacement which is larger than the critical pumping rate helps increase the area of stimulated reservoir and increase the oil well production, while the number of major fractures initiated and extended during multi-cluster fracturing may be less than the designed cluster quantity.