水驱砂岩油藏特高含水期注水井细分界限初探

Study on Subdivision Adjustment Measure Limit of Injected Well during Ultra-high Water Cut Period of Water Flooding Sandstone Reservoir

非均质严重的水驱砂岩油藏进入特高含水期,注水井细分调整对于提高非主力油层动用程度、控制产量递减和含水上升,是一种有效的常规手段。根据油藏的布井现状,以面积井网为例,应用平面径向稳定渗流的微分方程,推导组合层段内各小砂岩层液体的移动时间和驱替面积,以驱替时间最长或驱替面积最大小层为标准,计算各层的液体移动时间比值和驱替面积比值,根据比值的变化趋势确定组合层段小层级差范围。根据驱替面积比值计算不同个数小层组合层段的驱替体积比例,确定合理组合小层个数。通过细分段顶底砂岩层生产压差和不同级差小层液体移动时间比值分析,得到合理纵向跨度。在特高含水期层段组合最大界限是渗透率级差小于7,组合小层数小于7。

When severely heterogeneous water drive sandstone reservoirs came into ultra-high water cut period,subdivision adjustment of injected well was a commonly effective way to improve the producing degree of non-essential oil layer and to control the production rate declination and water cut increasing.This paper took the repeating pattern for an example.Using the differential equation of radial fluid flow,the migration time and displacement coverage of the respective sandstone member in the composite layer were inferred and the fluid migration time ratio and displacement coverage ratio of each member were worked out under the criteria of the member with the longest displacement time or biggest displacement coverage.The range of permeability differential in the member was defined based on the change tendency of the ratio.The displacement cubage ratio of sets with different amount of members was worked out based on the displacement coverage ratio to define the reasonable number of members in a set.And a reasonably longitudinal span was obtained by means of the analysis of the ratio of the drawdown pressure between the top and the bottom of the subdivided section and the fluid migration time of members with different permeability differential.The big limit for a set during extra high period could be concluded that the permeability differential was less than 7 and the number of the members composing a set was less than 7.