Study on Stability Evaluation Method of Concentrated Casing Damage Areas in the N_2 Bottom Layer in Lasa Xing Oilfield

Since 2013, there has been six concentrated casing damage areas of N_2 bottom layer in Lasa Xing Oilfield and more than 1600 casing damage wells found. And it has the characteristics of concentrated time, concentrated horizon, and easy to spread, easy to repeat after treatment. In order to control the expansion of the damage areas and prevent the occurrence of secondary casing damage. How to eliminate the hidden danger of the casing damage and determine the timing of reasonable management is particularly important. According to the mechanism of the casing damage of the N_2 bottom layer, the stability evaluation index system of the casing damage was established, and the adjustable factors such as the stratum stress in the equilibrium area and the influent water in the N_2 bottom layer were carried out. The data mining method was used to determine the pressure regulation and cementing. The quality difference is the upper limit of the index, and the comprehensive fuzzy evaluation method is used to comprehensively evaluate the stability of the casing damage area. The coincidence rate of the evaluation result reaches 74.5%, and the reasonable timing of the casing damage area is determined.