Wellbore Blockage in Shale Gas Wells: Mechanical Properties and a Physical Unblocking Model

Longqing Zou¹Jianfeng Xiao¹Liang Yang¹Cai Deng¹Yixuan Wang¹Shaoping Deng^2*

• ¹China National Petroleum Corp Chuanqing Drilling Engineering Co Ltd, Chengdu, China
• ²Sichuan University, Chengdu, China

Wellbore blockage is a significant challenge hindering the efficient production of shale gas in the Sichuan-Chongqing region. To enable precise unblocking, it is crucial to understand the physical and mechanical properties of these complex downhole deposits. This study conducted a comprehensive analysis of blockage samples retrieved from a shale gas well in the Weiyuan area. We employed X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and thermogravimetric analysis (TG-DTG) to characterize the samples' composition, microstructure, and thermal behavior. The results identified the blockage as a complex mixture primarily composed of quartz, Fe3O4, BaSO4, rock cuttings, and rubber particles. Furthermore, artificial blockage samples were fabricated under simulated downhole stress conditions (1-45 MPa) to evaluate their mechanical properties. Tests revealed that both compressive and shear strength increased with the forming stress. Based on the acquired mechanical parameters, a mechanical model was established to predict the pressure differential required to dislodge a blockage by wellhead pressurization. The model indicates that for blockages longer than half the pipe diameter (L > D/2), the required pressure becomes impractically high, rendering this method ineffective and necessitating combined unblocking strategies. This research provides a scientific basis for optimizing unblocking techniques and ensuring the safe, efficient development of shale gas resources.