Wellbore instability is a very common engineering problem in the process of drilling, completion and development of carbonate reservoirs. In the Ordovician carbonate reservoir of the Halahatang Oilfield in the Tarim Basin, the borehole wall instability and mud sand production are serious. The wellbore instability has brought a series of questions into production, such as low opening rate, high difficulty of operation, and large loss of productivity. In order to effectively analyze the instability phenomenon, clarify the source of instability and the form of instability, and give full play to the productivity of oil wells as soon as possible, this paper proposes a dynamic evaluation index system for the degree of wellbore instability based on engineering appearances and operating data. Above, a dynamic evaluation method for wellbore instability is formed. Using the method of dynamic evaluation of the degree of wellbore instability, the Halahatang wellbore instability law and correlation analysis were carried out on 109 unstable wells, and the wellbore instability pattern analysis was carried out by using washed sand samples and reservoir cores. The results show that the main factors affecting sand burial are the open hole completion, whether the open hole section of the Tumuxuke Formation is completely blocked, and the hole size. The instability of the Halahatang Oilfield is mainly caused by the collapse of the non-productive layer group and the production of the sand filled in the cracks and pores of the productive layer group. The instability patterns are mainly caused by collapsed blocks and fluid-carrying mud and sand. It is recommended that when new wells are drilled, suspended screens should be used for sand control completion in the pay zone first, and the Tumuxuke Formation and other vulnerable formations should be sealed. For open-hole wells in old wells, sand exploration and sand scouring operations are carried out, and screen completion with reasonable parameters is carried out to clean up and obtain productivity.
