近废弃油藏延长生命周期开发调整技术

Development adjustment technology of extending life cycle for nearly-abandoned reservoirs

针对近废弃油藏特高含水、优势通道发育、剩余油高度分散、非均质性强等主要矛盾,以双河油田北块Ⅱ(2油组)4—5层系为例,采用油藏精细地质建模、数值模拟方法和微观驱替实验方法,表征了聚合物驱后油藏剩余油分布特征。聚合物驱后宏观剩余油平面上注采非主流线、主流线弱势区及注采井距较大的边部区域剩余油饱和度较高,纵向上正韵律顶部剩余油富集;微观剩余油以半束缚态为主,依据剩余油分布特征提出了非均相复合驱变流线井网加密调整技术思路。通过井网变流线加密调整,形成交错式行列井网模式,流线方向转变30°以上,流线转向率达80%,促使剩余油有效动用。数值模拟预测该技术可提高采收率10.96%,新增可采储量70.61×10^(4) t,延长生命周期15 a,为聚合物驱后油藏大幅度提高采收率提供新的技术方法。

Facing the challenges of extremely high water cut,developed preferential channels,highly dispersed remaining oil,and strong heterogeneity in nearly abandoned reservoirs,the study focuses on the 4-5 layer series of the North Block II(Oil Group No.2)in the Shuanghe Oilfield.By employing detailed reservoir geological modeling,numerical simulation methods,and microscopic displacement experiments,the distribution characteristics of remaining oil after polymer flooding were characterized.Post-polymer flooding,the remaining oil saturation is higher in areas away from the main streamlines on the macro scale,including nonmainstream areas,weak zones along main streamlines,and peripheral areas with larger injector-producer distances.Vertically,remaining oil tends to accumulate at the top of positive rhythm sequences.Microscopically,the remaining oil is primarily in the form of semi-bound state.Based on the characteristics of remaining oil distribution,a technical concept of heterogeneous composite driving and streamline well pattern densification adjustment was proposed.By adjusting the well pattern to alter streamlines,creating a staggered row and column well pattern with a change in streamline direction of over 30°and a streamline deflection rate of 80%,the effective mobilization of remaining oil is promoted.Numerical simulation predicts that this technique could increase the recovery factor by 10.96%,add 706.1 thousand tons of recoverable reserves,and extend the life cycle by 15 years.This offers a new technical approach for significantly enhancing the recovery factor of reservoirs after polymer flooding.