超低渗透油藏分段多簇压裂水平井产能影响因素与渗流规律——以鄂尔多斯盆地长8超低渗透油藏为例

A study on productivity and flow regimes of segmented multi-cluster fractured horizontal well in ultra-low permeability reservoir-a case of Chang8 ultra-low permeability reservoir in Ordos Basin

水平井分段多簇压裂是开发超低渗透油藏的有效手段之一。以鄂尔多斯盆地长8超低渗透油藏黄平34-22分段多簇压裂水平井井组为研究对象,对裂缝参数与分段射孔参数进行了优化。利用网格加密技术,建立了分段多簇压裂水平井井组数值机理模型,研究了储层应力敏感、裂缝半长、裂缝导流能力、改造区和非改造区渗透率以及采油速度对分段多簇压裂水平井产能的影响。研究结果表明:弹性开发时上述参数对产能的影响比注水开发时更加显著;储层应力敏感对产能不利,裂缝半长和导流能力的增大对产能有利,但综合考虑收益与施工成本及难度,与采油速度一样,它们均存在最优值;进一步提高改造区的渗透率对产能的提升有限,而提高非改造区的渗透率可以大幅提高产能;封闭油藏分段多簇压裂水平井的渗流可分为井筒储集影响阶段、初始拟径向流动阶段、裂缝线性流阶段、系统椭圆流阶段和边界影响流阶段。

The segmented multi-cluster fractured horizontal well is one of the effective measures to develop ultra-low permeability reservoir. Based on the typical ultra-low permeability reservoir in Ordos Basin, the HP-34-22 well is selected and its fracture and segmented perforating parameters were optimized. The numerical simulation model of HP-34-22 well was built and its fractures were realized by local grid refinement(LGR).With this model factors influencing productivity effect of segmented multi-cluster fractured horizontal well were analyzed, which contain stress sensitivity, fracture half-length, fracture conductivity, permeability of stimulated region and un-stimulated region and oil production rate. The results of this study show that when the reservoir is developed by natural depletion, the influence of these factors is more significant compared with that of water flooding. Stress sensitivity is detrimental to productivity. Fracture half-length and fracture conductivity is beneficial to productivity, but considering the benefits, costs and the difficulty of measures, they have reasonable value range as well as oil production rate. The productivity improvement by further enhancing the permeability of stimulated region is limited, while it's remarkable by enhancing the permeability of un-stimulated region. There are five flow stages for segmented multi-cluster fractured horizontal well in bounded reservoir.