超低渗透油藏老井宽带体积压裂缝网参数优化

Optimization of fracture network parameters of the wide zone SRV by old well in ultra low-permeability oil reservoirs

超低渗透油藏具有储层致密、天然裂缝发育等特征,难以建立有效的注采驱替系统,为提高单井产量,通常采用常规重复压裂,但常规重复压裂仅能增加裂缝长度,提高裂缝导流能力,而不能有效增加裂缝带宽,扩大裂缝侧向波及范围。提出了宽带体积压裂技术理念,即通过在原人工裂缝侧向开启次生裂缝或沟通天然裂缝,增加裂缝带宽,对宽带体积压裂裂缝的合理带宽进行了优化,建立了合理裂缝带宽计算方法,在此基础上采用正交试验方法对主、次裂缝的导流能力,裂缝半长等其他缝网参数进行了优化设计。结果表明:以超低渗透油藏某一井组为例,重复压裂合理裂缝带宽范围为13~46 m,其中G127-160井缝网参数最优方案为主裂缝导流能力0.15μm^2·cm,裂缝半长140 m,裂缝带宽50 m,次裂缝导流能力0.04μm^2·cm,在此方案下模拟的重复压裂可控制含水上升速度,显著提高措施累计产油量。该研究为挖潜超低渗透油藏老井裂缝侧向剩余油提供了技术思路。

Ultra low-permeability oil reservoirs are characterized by tight reservoirs and developed natural fractures,so the effective injection-production displacement system can be hardly established.And in order to increase the single-well production rate,the conventional refracturing technology is usually adopted,but the conventional refracturing can only increase the fracture length to improve the flow conductivity of fractures,but cannot increase the fracture zone width effectively to enlarge the lateral swept range of fractures.In this paper,the concept of wide zone SRV(stimulated reservoir volume)was put forward.That is to increase the fracture zone width by inducing secondary fractures or communicating natural fractures in the lateral direction of primary hydraulic fractures.Then,the rational fracture zone width of the wide zone SRV was optimized and the method for calculating the rational fracture zone width was developed.Finally,the fracture network parameters(e.g.flow conductivity of primary and secondary fractures and half fracture length)were optimally designed by means of orthogonal experiment method.It is shown by taking one certain well group in the ultra low-permeability oil reservoir as the example that the rational fracture zone width of refracturing is in the range of 13−46 m.And the scheme on the optimal fracture network parameter of Well G127-160 includes the flow conductivity of the primary fracture of 0.15μm^2·cm,half fracture length of 140 m,fracture zone width of 50 m and flow conductivity of secondary fracture of 0.04μm^2·cm.The refracturing simulated according to the scheme can control the water cut rising speed and increase the stimulated cumulative oil production greatly.The research results provide the technical idea for the potential tapping of the remaining oil in the lateral direction of the fractures of old wells in ultra low-permeability oil reservoirs.