Research on Comprehensive Evaluation Method of Cementing Quality for Pre-Exploration Wells in the Yingshan Block of Sichuan-Chongqing Region

At present, the cementing quality mainly adopts acoustic amplitude logging (CBL) [1] and acoustic variable density logging (VDL), and quantitatively evaluates the first interface and the second interface of cementing by interpreting the quantitative results of cement bond index (BI) [2], thus forming the comprehensive interpretation results of cementing quality. At present, the evaluation of single well cementing quality mainly focuses on developing the target layer and evaluating the reservoir, and a unified evaluation method of single well cementing quality has not been established. The geological conditions in Sichuan and Chongqing are complex, and the pre-exploration wells and production wells are usually drilled and completed in sequence, and the cementing quality of individual intervals is tested every time. The cementing curves of overlapping intervals have great interference and cannot show the real cementing quality. Based on the existing cementing quality testing methods, this paper uses the statistical methods of horizontal interface superposition and vertical interface superposition to determine the thickness and proportion of high-quality, qualified and unqualified intervals, forms a cementing quality evaluation method for single well and whole well, and objectively evaluates the cementing quality. Using this method, the cementing quality of three pre-exploration wells in Yingshan structure of Sichuan basin was evaluated, and the poor cementing quality positions of different completion procedures (surface casing, technical casing and production casing) and different stratigraphic sequences (SXM group, LGS group, ZLJ group and XJH group) were identified and quantified. At the same time, the drilling process and cementing process are analyzed and studied to determine the main influencing factors of cementing quality. By studying the evaluation method of single well cementing quality and tracing the influencing factors of cementing quality, the methods of improving cementing quality are clarified, which can guide the next drilling, cementing and completion work and lay a solid foundation for the integration of exploration and development in Sichuan and Chongqing areas.