Quantitative characterization of volcanic expansion fractures based on thermodynamic coupling analysis

Abstract

In recent years, volcanic reservoirs in the Bohai Sea have become the focus of oil and gas exploration and development. Volcanic activity during the Cenozoic provided favorable conditions for the development of hydrocarbon traps. These volcanics also result in difficulties during the drilling and development of oil and gas fields. Furthermore, the high-temperature magma induced thermal expansion in the surrounding rocks, which changed the local stress field and affected the fracture distribution characteristics of the surrounding strata. The complexity of the fracture distribution makes predicting lost circulation difficult and causes substantial economic losses. Therefore, it is necessary to characterize the volcanic perimeter expansion-type fractures effectively. The distribution of volcanic rocks is identified through logging and seismic data, with perimeter fracture development characteristics being analyzed. The temperature conditions of the volcanic activity were determined through core mineral analysis and thin section observation. Based on the laws of energy conservation and geomechanics, the principle of thermal coupling was applied to quantitatively predict the thermal expansion fractures caused by volcanic activity using a finite element numerical simulation method. To determine the extent of volcanic influence on lost circulation, and the development characteristics of fractures under the influence of these rocks were analyzed. The results provide an important reference for drilling and volcanic reservoir prediction in the Bohai Basin and guide for elsewhere.