压裂投产低—特低渗透油藏井排距设计

Well spacing design for low and ultra-low permeability reservoirs developed by hydraulic fracturing

为了模拟压裂投产低—特低渗透油藏中的非达西渗流特征,在原有黑油模拟器的基础上,建立并求解了考虑两相启动压力梯度、渗透率敏感性以及裂缝导流能力失效性的三维两相数值模拟模型,基于模型分析了压裂井波及椭圆的计算方法及影响因素,并推导了矩形井网和菱形反九点井网的井排距公式。压裂井波及椭圆影响因素分析结果表明:渗透率对压裂水井初期的波及椭圆大小具有显著影响,随着时间的增加注入压差和启动压力影响增大;各因素对波及椭圆的形状没有显著影响。通过遗传算法改进的GA-BP神经网络模型可准确求取压裂井波及椭圆参数。为实现井网系统和裂缝系统的最优匹配,以压裂井对油藏波及系数最大为目标,推导了矩形井网和菱形反九点井网的井排距公式。现场应用表明,压裂后平均日产油量可提高1.25倍,且长期增产效果显著。

In order to simulate non-Darcy flows in low and ultra-low permeability reservoirs, based on the black oil simulator, a three-dimensional, two-phase model was established considering two-phase start-up pressure, permeability sensibility and fracture conductivity decline. Then numerous simulations were run to analyze the elliptic drainage area induced by a fractured well, the results show that： for water fractured well, permeability is the dominant factor affecting the elliptic drainage area at the beginning, and pressure difference and start-up pressure have increasing effects as time goes by. However, no factor has a marked impact on the shape of elliptic drainage area. Parameters of elliptic drainage area can be calculated with GA-BP neural network improved by genetic algorithm. Aiming at acquiring maximum sweep efficiency, well spacing equations were deduced for rectangular pattern and diamond inverted nine-spot pattern. Field application demonstrated daily oil production enhanced 1.25 times after hydraulic fracturing, and the long time stimulation effect is substantial.