Research on the Mechanism and Control Method of Azimuth Drift in Shale Gas Horizontal Wells

Abstract

Horizontal well has the technical superiority to improve recovery rate of unconventional reservoirs, which is widely used in shale oil and gas exploration. However, serious azimuth drift problems occurred commonly in shale gas horizontal wells in Weiyuan, Sichuan, China, which seriously affected the control of well trajectory, and the reason is not clear. At first, we measured the drillability anisotropy and acoustic travel time of rock sampled from field, and set up a model to evaluate rock drillability anisotropy by logging data. Then, combing the model with the previous study on formation force model, for a certain field instance, we analyzed and summarized the main factors influencing azimuth drift are:1) formation drillability indexes 2) the angle between the drilling azimuth and formation down dip azimuth. The main method to control the drift is to optimize angle between the drilling azimuth and formation down dip azimuth. Our research initially came up with the method to evaluate orthotropic rock drillability anisotropy by logging data and the main method to control the azimuth drift, so it`s significant for shale drilling.