Classification of Shale Geology-Engineering Types for Optimized Development in the Tiangongtang Structure

Abstract

This study examines the Tiangongtang Structure through an integrated geology-engineering approach, analyzing differential characteristics of the shale reservoirs and establishing a classification scheme based on key parameters such as continuous thickness of high-quality reservoirs(TOC >3%), gas saturation, pressure coefficient, fracture development, drilling and fracturing anomalies, and casing deformation risk. Results indicate that tectonic uplift and fault activities collectively control shale gas enrichment and escape, while discrepancies between paleo-depositional and current structural frameworks govern its heterogeneous distribution. Geologically favorable areas are defined by a continuous thickness of high-quality reservoirs exceeding 10 m, gas saturation >55%, and pressure coefficient >1.2. Zones with elevated engineering risks—including severe mud loss and casing deformation—are predominantly located near the Gong-1 Fault fracture-developed zone, the unidirectional fracture zone in the northern steep slope, and the central in-situ stress transition zone (Q-value >1.4). Based on geological properties and engineering risks, the study area is categorized into four types: the southern “dual sweet spot area” with superior geology and low risk, serving as the core production zone; the anticlinal “thick reservoir–medium risk area,” requiring optimized fracturing and fracture identification for risk control; the northern “unidirectional fracture area,” with good gas content and preservation conditions, necessitates tailored engineering strategies to enhance stimulation effectiveness and mitigate operational risks; and the central structural transition zone, where significant stress heterogeneity and abundant fracture development pose substantial challenges to efficient development.