非均匀污染下水平气井酸化效果及影响因素分析

Acidification Effect Evaluation and Influencing Factors Analysis of Horizontal Gas Well with Heterogeneous Damage

在水平井井筒周围会形成呈非均匀分布的污染带,因受地层各向异性影响较大,最终影响水平井产能。从水平井表皮因子沿井筒分布的非均匀性入手,提出了一个井筒附近酸化带渗流物理模型,考虑酸化半径大于或等于污染带半径及小于污染带半径,求得一个酸化后表皮因子计算新公式,利用该公式对Joshi产能公式进行了改进,同时根据实例研究了水平井段长度、地层各向异性系数、污染带渗透率以及泥浆最大侵入距离对酸化效果的影响。分析认为:水平段长度、气层厚度、地层各向异性系数、污染带渗透率及泥浆最大侵入距离等是影响水平井酸化后增产倍比的主要因素。

Near the wellbore of a Horizontal well, there also exist damage zones, besides, it is in heterogeneous distribution and affected by the anisotropy of strata. Therefore, it may impact the productivity of the horizontal wells. This paper proposes a flowing physical model for the acidizing zone near the wellbore, based on the heterogeneous distribution of skin factor along the wellbore, by which a formula for the skin factor after acid treatment is given through considering the fact that the acidizing radius is greater or less than the radius of damage zone. According to the formula, the Joshi＇ s productivity formula is modified, meanwhile, the influences of horizontal section length, strata anisotropy coefficient, damage zone permeability and the maximum distance of mud immersion zone on the acidification effect are studied. It is concluded that horizontal section length, gas layer thickness, strata anisotropy coefficient, damage zone permeability and the maximum distance of mud immersion zone are the main factors that affect increase productivity after the acid treatment of horizontal gas wells.