Investigation to Integrated Geomechanics of Casing Deformation and a New Technique: A Case in Deep Gas Shale of Sichuan Basin, China

ABSTRACT To investigate the mechanism of casing deformation and failure during volumetric fracturing of deep gas shale in Sichuan Basin, we put forward targeted comprehensive prevention and control measures. Based on the idea of geological-engineering integration, a three-dimensional geo-mechanical model is established, which coupled the formation - cementing sheath - casing during hydraulic fracturing of deep shale reservoir. Taking TB01 well as an example, the correlation between induced stress, cementing quality, fault or natural fracture dislocation and other factors in the process of hydraulic fracturing was analyzed. The main cause of fault or natural fracture dislocation under the influence of multiple factors is determined firstly. Then, the effectiveness of fracturing scale controlling, casing and cementing quality improvement and other process measures are investigated. Finally, based on the above study, a novel process and supporting tools for fault pre-slip are proposed in this paper. The feasibility of the process is demonstrated, and the structural parameters of the supporting tools are optimized. Taking Luzhou as an example, it provides theoretical and technical support of deep shale gas in safety and high efficiency. INTRODUCTION China has abundant reserves of shale gas with great development potential. Speeding up the development of shale gas is of great significance for relieving the pressure on natural gas supplies and adjusting energy structure. Shale gas is developed according to the causes of casing deformation, many of those who learn to conduct the research, puts forward the effect of thermal stress[1-3], asymmetric fracturing[4-9], the cementing quality [10-15] and fault slip[16-30], etc. At present, most scholars have recognized that fault activation in the process of hydraulic fracturing may be the main controlling factor leading to casing deformation[17-29], which has been verified by more and more field data. These research understandings provide theoretical guidance for the field, however, casing deformation still occurs from time to time, and there is still a lack of specific measures to solve the problem, which needs further research.