重复压裂裂缝系统产能对比与分析

Correlation and Analysis of Productivity for Refracture Systems

单井重复压裂的裂缝生成模式可以分为两种形式,包括在井筒处形成新的转向裂缝以及在原有裂缝的基础上形成扩充缝。如何评价重复压裂后不同形式裂缝系统下油气井的产能,对优化重复压裂施工方案至关重要。以重复压裂产生的两种不同复杂裂缝系统为研究对象,利用嵌入式离散裂缝方法建立数值模型,开展重复压裂后转向型和扩充型裂缝系统的生产规律研究,明确不同裂缝系统对井产能的影响。研究发现:储层及裂缝参数会在不同程度上影响重复压裂后井的产能,且对扩充型裂缝系统的影响程度始终大于转向型裂缝系统。考虑储层基质渗透率各向异性,正交于初始裂缝延伸方向的基质渗透率越大,重复压裂后增产效果越好,并且扩充型裂缝系统累计产量升高更显著。重复压裂裂缝与初始裂缝越趋向于正交,重复压裂后增产效果越明显,扩充型裂缝系统的增产率高于转向型裂缝系统。重复压裂裂缝渗透率和重复压裂裂缝长度均与重复压裂井产能提升呈现正相关,且扩充型裂缝系统的累计产量增大趋势更显著。结果表明,扩充型裂缝系统能更加有效地提高重复压裂井产能,为重复压裂增产机理与矿场应用结合提供理论指导。

Single-well refracturing treatment can be divided into two forms,including the formation of a new diverting refracture at the wellbore and the formation of an expanded refracture based on the initial fracture.It is very important to evaluate the productivity of wells under different fracture systems after refracturing for optimizing the refracturing construction scheme.Complex fracture systems produced by refracturing treatment were taken as the research object.The numerical model was established by using the embedded discrete fracture method.The production law of reoriented and expanded fracture systems after refracturing was studied,and the influence of different fracture systems on well productivity was clarified.By comparing the productivity of reoriented and expanded refracture systems,it is found that changing the reservoir or fracture parameters respectively will affect the productivity of refractured wells in different degrees,and the effect on expanded refracture system is always greater than that on reoriented refracture system.Considering the permeability anisotropy of the reservoir,the higher the matrix permeability orthogonal to the initial fracture extension direction,the better the effect of production increase after refracturing,and the more significant the cumulative production increase of the expanded refracture system.The more the refracture tends to be orthogonal to the initial fracture,the more obvious the increase in production after refracturing,and the increase in the production rate of expanded refracture system is higher than that of reoriented refracture system.Both refracture permeability and refracture length are positively correlated with refractured well production increase,and the cumulative production increase trend of expanded refracture system is more significant.As a result,the expanded refracture system can be more effective in increasing refractured well capacity.The results have guiding significance for understanding the mechanism of refracturing and field application.