Fracture characteristics and stress disturbance analysis for well optimization of Silurian in Shunbei area, central Tarim Basin

Abstract

The complex tectonic stress in the Shunbei area of the central Tarim Basin results in varied patterns of multilayered fractures. When drilling into the Silurian fracture zone and the formation pressure is lower than the drilling fluid column pressure, leakage easily occurs. To ensure efficient drilling, it is crucial to conduct an analysis of Silurian fracture characteristics and stress field disturbances to guide well design. Through enhanced interpretation and spatial analysis of Silurian faults, a comprehensive analysis of fractures was conducted in conjunction with the fault growth index. The overall characteristics of fractures in the study area included steeply dipping strike-slip faults and overlying en echelon normal faults with layered deformation. The Silurian fracture patterns primarily consist of echelon negative flower-like normal fault combinations, reflecting activity from late Caledonian to early Hercynian. The principal stress direction of the Silurian is 54° NE based on dipole array acoustic logging data from well SHZ1. By integrating three-dimensional seismic data interpretation with geological modeling and iterative boundary element numerical simulations, the current spatial distribution of stress fields, including maximum, minimum, and intermediate principal stresses, was established. The results of the stress field simulation were compared with interpretations derived from actual logging data. Due to the influence of fault occurrence and spacing, the width of stress disturbance zones varies on the plane, and stress disturbances above and below the fault plates show an asymmetric distribution. Through spatial sculpting of Silurian fractures and analysis of stress disturbances, optimal well locations and trajectories were selected to avoid areas with high fracture intensity, large dip angles, concentrated stress zones, strong energy anomaly fractures, and developed crack zones. The comprehensive analysis of Silurian fractures and stress field disturbance ensures efficient drilling and mitigates risks of significant Silurian leakage during well optimization.

Keywords

• principal stress
• strike-slip fault
• stress disturbance
• well optimization
• shunbei area
• tarim basin