EVALUATION OF STEAMFLOODING IN MULTI-LAYERED HETEROGENEOUS RESERVOIR

Abstract

Steamflooding is a process performed by injecting heated steam into heavy oil reservoir in order to reduce oil viscosity, making oil readily to flow to production well. Effects of reservoir heterogeneity are important as it may indicate operational conditions such as steam injection rate and steam quality. Judging of the best operating parameters in this study is based on oil recovery factor, enthalpy consumed per barrel of oil and water production. From judging these three outcomes, steam injection rate of 80 STB/D (in barrel of liquid equivalent) and steam quality 0.6 yields the best result and these are selected for the entire study. Results show that reservoir heterogeneity plays an important role in heavy oil recovery. Reservoir heterogeneity is represented by Lorenz coefficient which is mainly aimed for variation of permeability. Increase of reservoir heterogeneity results in lower oil recovery by means of steamflooding. From the study of interest parameters, oil recovery is sensitive to change of end point saturation in relative permeability curve. Water production is relatively high in case of high irreducible water saturation. Oil API gravity is a key for choosing proper injection rate and steam quality. Oil with low API gravity requires higher energy that is adequate for initial low injectivity. In reservoir with very low vertical permeability, vertical flow is absent and steam overriding is diminished. This helps increasing volumetric sweep efficiency. However, benefit of low vertical permeability is decreased in reservoir with high Lorenz coefficient. Reservoir with fining upward sequence is more favorable than coarsening upward since steam overriding is mitigated. Quarter 5-spot flood pattern yields better oil recovery compared to 9-spot pattern when total injection rate of steam is kept constant because heat is consumed efficiently due to higher steam retention. Nevertheless, production constrains are also very important as they control period of steam injection, water production and eventually energy consumed of each case.