Investigation of Stress Arching Above Depleting Hydrocarbon Reservoirs and Its Effect on the Compaction Drive Mechanism

Abstract

In this paper, the compression drive mechanism, which can be considered as the most related oil drive mechanism with the reservoir geomechanical properties, has been investigated. The constant total vertical stress on the reservoir and uniaxial reservoir compaction with zero lateral strain are two main assumptions in the conventional reservoir compaction modeling. These assumptions are not considering the stress arching, which leads to a reduction in the total vertical stress and also affects the distribution of vertical and horizontal stresses. In this paper, it was tried to investigate the effects of three keys elastic parameters, including Young's modulus, Poisson's ratio, and Biot coefficient on the reservoirs stress paths and compaction drive mechanism using numerical modeling with ABAQUS software. Based on the modeling results the reservoirs stress paths is very different from simplifying assumption in uniaxial compaction models while the total compaction of reservoir obtained using numerical modeling and uniaxial model in some cases can be equal. Also, among the three geomechanical parameters, the ratio of Young's modulus of the reservoir and surrounding rocks has a significant effect on the reservoir stress paths and compaction. The results of modeling indicate when a reservoir rock is softer than its surrounding environment, due to the arching occurrence, the total vertical stress applied to the reservoir rock reduced even to half of the initial vertical stress, which leads to the oil recovery by the compression drive mechanism will be less than 50% of the predicted value.