Horizontal Well Productivity Evaluation for Stress Sensitive Elliptical Reservoirs

Abstract

Well productivity model is one of the vital tools required to evaluate well performance. Most horizontal well productivity models are idealistic in nature, mainly developed for homogeneous reservoirs and conventional reservoirs, and ignore the influences of the pore pressure and stress changes. However, as the capillary in low permeability porous media is tiny, the medium permeability is quite sensitive to pressure change. Thus, there is an urgent need for new realistic productivity models that describe the actual reservoir inflow performance behavior more efficiently than the available models. This paper presents a new horizontal well productivity model which accounts for the stress sensitive permeability in an elliptical reservoir. Then, the proposed model was extended to investigate the effects of reservoir heterogeneity, eccentricity, and formation damage on horizontal well productivity. The results show that the thinner the formation is, the greater the impact of the horizontal well lengths on production. As the horizontal well length is longer, the impact of stress sensitivity on the production becomes more significant. Horizontal well would be a better well type option for elliptical reservoirs. The longer the horizontal well is, the more impact of heterogeneity, eccentricity distance, as well as skin factor on productivity. The new model provides a simpler and more reliable means to optimize horizontal well length and efficiently forecast well behavior in stress sensitive reservoirs, such as tight gas reservoir and shale oil reservoirs, with respect to horizontal well productivity to vertical well productivity.