污染区对部分打开井井底压力响应的影响

钻井造成的污染区对部分打开井的影响不同于裸眼井. 为了分析污染区对部分打开井井底压力响应的影响，建立了一种部分打开井的二维轴对称渗流模型，模型考虑了真实的污染区以及储层渗透率各向异性特征.利用有限元数值方法对模型进行求解，获得了部分打开井的井底压力响应及储层压力分布. 根据压力响应及压力分布特征，将部分打开井的压力响应过程划分为5 个流动阶段，其中早期局部径向流动和椭球流动是该类井最典型的特征. 对污染区的影响分析表明：传统方法中的表皮系数S 并不等于污染区引起的机械表皮系数S_d；无量纲井筒储存系数不能与机械表皮系数组合. 修正了传统方法中部分打开井的井底压力公式，验证了部分打开井的总表皮计算公式，为该类井的井底压力响应解释及产能预测提供理论指导.

EFFECTS OF FORMATION DAMAGE ZONE ON BOTTOM-HOLE PRESSURE RESPONSE OF PARTIALLY PENETRATING WELLS

The effect of formation damage zone due to well drilling on partially penetrating wells is different from that on open-hole wells. In order to analyze the effect of damage zone on pressure response at the well bottom, this paper presents a 2D axial symmetry porous flow model for partially penetrating well. The model considers the actual formation damage zone around the wellbore and reservoir permeability anisotropy. The bottom-hole pressure response curves and pressure fields of partially penetrating wells are obtained by using the FEM method. The analysis of the pressure response curves and pressure fields shows that five flow regimes may appear in the pressure response process of partially penetrating wells. The early-time radial flow and the ellipsoidal flow are typical characteristics of partially penetrating wells. The effect of damage zone is studied. It shows that the skin factor S in traditional methods is not the mechanical skin factor S_d due to the formation damage. The dimensionless wellbore storage coefficient cannot combine with the mechanical skin factor. The wellbore pressure obtained from traditional methods is modified. The formula for total skin factor of partially penetrating wells is verified. Those conclusions provide theoretical guidance for the transient pressure data interpretation and productivity prediction of partially penetrating wells.