Prediction of Heavy Oil Production Based on Geomechanical Analysis in Coupled Thermo-Hydro-Mechanical Process

ABSTRACT The geomechanical response concerning porosity, permeability, and water saturation, will directly affect the prediction of oil production as well as the economic benefits of oil fields. In this paper, different models are established for the three stages of the SAGD (Steam Assisted Gravity Drainage) production period by using the coupled thermo-hydro-mechanical method, aiming to understand the influence of rock volumetric dilation or compression on oil yield. The relationship between the evolved flow parameters and the deformation parameter characterized by volumetric strain is proposed, then a mathematical model with the dilation volume and yield is derived. The ratio of the new model considering reservoir geomechanics and the conventional model is exhibited as a function with the bulk strain, and it is found that different volumetric strains will affect the yield ratio of the new model and the conventional model. The stages of the steam chamber ascending and expanding laterally are selected for typical case studies, and the predicted yield of the new model is about 1.24 and 1.17 times, respectively, that of the conventional model when the volume strain is 2%. This method can help oilfield engineers obtain more accurate heavy oil production, and quantitatively evaluate the significance of reservoir geomechanics in the process of SAGD. INTRODUCTION In recent years, with the massive exploitation of conventional oil and gas and the discovery of unconventional reservoirs, how to exploit unconventional reservoirs efficiently has become increasingly important. For example, hybrid thermal recovery processes have become a primary technique used to improve the recovery performance of post steamed heavy oil reservoirs and been used to exploit marginal heavy oil reservoirs effectively. SAGD (steam assisted gravity drainage) is an efficient technique for recovering heavy oil, as proposed by Butler et al. (1981). SAGD technology develops heavy oil through the use of steam drive and gravity flooding. By transforming the reservoir through the injection well, water and heated heavy oil flow downward under the action of gravity, so as to improve the efficiency and production of heavy oil exploitation (Butler et al., 1981).