Stress field propagation characteristics of deep complex fault blocks based on digital speckle deformation simulation experiment

Abstract

In the process of oilfield exploration and development, the study of crustal stress plays an extremely important role in understanding the patterns of deep oil and gas migration and accumulation, enhancing reservoir fracturing efficiency and assessing drilling engineering risks. Previous studies on crustal stress have mainly focused on 2D/3D simulations, with very little research on regional structural changes and stress dynamic changes in the process of production and development. Taking block G of the Nanpu Sag of Bohai Bay Basin as an example, by creating similar geological models, setting boundary conditions, and conducting digital speckle deformation dynamic simulation experiment, the spatial propagation characteristics of stress/strain were obtained using the LOESS local regression analysis method. Combined with the classical stress wave theory, it was concluded that under the continuous action of tectonic force, the change of stress/strain at any point in the layer over time shows obvious cyclic volatility. This cyclic characteristic is more evident near the fault, with larger cyclic amplitude. Multiple reflections and transmissions occur when the stress wave passes through the fault. When numerous leftgoing waves meet rightgoing waves, the local stress and strain are concentrated, forming high-value areas. When a stress wave passes through a fault, the resulting strain causes a significant energy attenuation. Over time, the direction of stress/strain propagation is selective, always perpendicular to the direction of strong compaction and dense structure of the fault, leading to sharp energy decay after transmission. Over time, the propagation of stress/strain at any point in the formation appears as a wave cycle. However, unlike sound waves, the maximum and minimum amplitudes of the stress/strain cycle curve exhibit fluctuation characteristics along the direction of the applied force in space.

Keywords

• stress propagation
• digital speckle experiment
• complex fault block
• cyclical features
• stress wave
• nanpu sag
• bohai bay basin