陆相源内非常规石油甜点优选与水平井立体开发技术实践——以鄂尔多斯盆地延长组7段为例

Optimal selection of unconventional petroleum sweet spots inside continental source kitchens and actual application of three-dimensional development technology in horizontal wells:a case study of the Member 7 of Yanchang Formation in Ordos Basin

鄂尔多斯盆地三叠系延长组7段(长7段)是一套典型的陆相湖盆沉积,整体以深色泥页岩的生油岩系为主,中—上段发育多套砂泥互层的细粒含油薄砂,该套页岩层系储层纵、横向沉积非均质性强,且盆地本身具有低压特征,以单套油层为对象进行开发时,表现出储层动用程度低、采收率低、单井递减快、开发成本高的问题,开发难度大。通过多年研究和开发实践,形成了针对长7段页岩层系平面小规模、垂向多套发育的细粒砂岩储层的优选方法,并提出了以平台为单元,"大井丛立体开发"的布署动用理念,构建了"大井丛立体布井、三维水平井钻井、集成压裂"等系列陆相源内非常规石油开发技术。针对长7段页岩层系储层甜点的地质特征,对砂体几何形态、空间分布、脆性指数和裂缝分布进行立体刻画,实现地质—工程一体化甜点评价,同时开展平面、纵向和水平段立体优选;基于优选结果,以实现甜点的空间最大体积控制和经济动用为目的,开展立体式大井丛布井;通过三维水平井钻井技术实现井丛防碰和大偏移距施工,优质快速完井;根据钻遇砂体的地质—工程特征,结合储层渗吸和低压特点,采用集成压裂模式,由传统单一压裂向"造缝、补能、驱油"三位一体升级;同时,平台一体化管理提高工作和作业效率,降低成本。应用大井丛立体式布署动用方式建立了鄂尔多斯盆地陇东示范区,取得了良好效果,为陆相源内非常规石油的规模开发提供了有益借鉴。

The Member 7 of Triassic Yanchang Formation(Chang 7)in the Ordos Basin is a set of typical continental lacustrine deposits,wholly dominated by source rock series composed of dark shale.There are multiple sets of fine oil-bearing thin sands with interbedded sand and mud in the middle and upper intervals.This set of shale strata reservoirs has strong vertical and horizontal depositional heterogeneity,and the basin itself has the characteristic of low pressure.For these reasons,to develop a single set of oil reservoir will encounter the problems such as low producing degree of reservoir,low recovery,and rapid decline of sing well production and high development cost,thus leading to great difficulty in development.Through years of research and development,the authors have established an optimization method for the planar small-scale,vertical multiple sets of fine-grained sandstone reservoirs of the Chang 7 shale strata series,proposed a deployment idea of"three-dimensional development of large well clusters"with a platform as a unit,and established a series of development technologies of unconventional petroleum inside continental source kitchens such as"three-dimensional well spacing of large well clusters,three-dimensional horizontal well drilling,and integrated fracturing".In view of the geological characteristics of the sweet spots of Chang 7 shale strata series,this paper three-dimensionally characterizes the geometry,spatial distribution,brittleness index and fracture distribution of sand bodies,realizes the integrated evaluation of sweet spot in terms of geology and engineering,and simultaneously carries out the three-dimensional optimization of planar,vertical and horizontal sections.Based on the optimization results,aiming to control the maximum spatial volume of and realize the economic utilization of the sweet spot,the authors have completed the well spacing of three-dimensional large well clusters.The three-dimensional horizontal well drilling technology is applied to realize the anti-collision of well clusters and construction in long offset distance,as well as high-quality and fast well completion.According to the geological engineering characteristics of the sand body encountered during drilling,in combination with the reservoir characteristics of imbibition and low pressure,the integrated fracturing mode has been established,i.e.,upgrading the traditional single fracturing to the trinity of fracture creation,energy supplement,and oil displacement.Moreover,the integrated management of the platform improves work and operation efficiency,and reduces costs.The Longdong Demonstration Area in the Ordos Basin was established using the three-dimensional deployment mode of large well clusters,which achieved good results and provided a useful reference for the large-scale development of unconventional petroleum inside continental source kitchens.