摘要
低渗透油藏流体渗流存在启动压力梯度,应用非达西渗流理论,对不同渗流形态下考虑启动压力梯度的弹性采收率计算方法进行了分析,给出了考虑启动压力梯度的直井、直井压裂、水平井和水平井压裂4种开发方式的弹性采收率计算公式,并通过实例分析不同参数对弹性采收率的影响。研究结果表明:随着启动压力梯度的增加,4种开发方式的弹性采收率均呈线性下降,其中直井降幅最大,水平井次之,水平井压裂降幅最小;4种开发方式的弹性采收率和单位压差弹性采收率均随压差的增加而增加,前者呈线性增加,后者增幅逐渐变缓;直井压裂开发的弹性采收率随压裂裂缝半缝长的增加而增加,但增幅逐渐变缓;对于水平井压裂开发,压裂裂缝半缝长较裂缝间距对弹性采收率的影响更大,且存在最优的压裂裂缝半缝长;对于启动压力梯度较大且弹性开发的低渗透油藏,宜采用压裂的方式来提高弹性采收率。
There is a threshold pressure gradient in the flow of fluid in low-permeability reservoirs. Based on the non-Dar-cy flow theory,a new computing method of natural depletion oil recovery considering the threshold pressure gradient in dif-ferent flow forms was analyzed. The calculating formulas for depletion oil recovery of the vertical well,fractured verticalwell,horizontal well,and fractured horizontal well in the low-permeability reservoir were developed. The effect of each pa-rameter on the depletion oil recovery was discussed while applying the formulas to real cases. The results show that the de-pletion oil recovery decreased linearly with the increase of threshold pressure gradient. The oil recovery of the vertical wellsis very sensitive to the threshold pressure gradient,the horizontal well is less sensitive,and the effect for the fractured hori-zontal wells is the weakest. The depletion oil recovery and the one per unit pressure drawdown increases with pressure draw-down linearly and in a gradually slower manner respectively. The depletion oil recovery of the fractured vertical well in-creases with the half fracture length,but the effect decreases gradually. Half fracture length is more sensitive than fracturespace to the depletion oil recovery in the fractured horizontal wells. There is optimized half fracture length. It is recommend-ed that the low-permeability reservoir with large threshold pressure gradient under depletion development should be devel-oped with hydraulic fracturing.
出处
《油气地质与采收率》
CAS
CSCD
北大核心
2015年第2期72-77,87,共7页
Petroleum Geology and Recovery Efficiency
基金
国家科技重大专项"海上油田丛式井网整体加密及综合调整技术"(2011ZX05024-002)
关键词
非线性渗流
启动压力
梯度
渗流场
弹性采收率
计算方法
影响因素
non-linear flow
threshold pressure gradient
flow field
natural depletion oil recovery
computing method
in？fluencing factors
