Research program on fractured petroleum reservoirs. Final report, January 1, 1996--December 31, 1996

Multiphase flow in fractured porous media is a complex problem. While the study of single phase flow in a fractured or a layered medium can be pursued by some kind of averaging process, there is no meaning to averaging two-phase flow when capillarity is an active force. For a two-layer system comprised of high and low permeable layers, the performance of gas-oil gravity can be less efficient than the homogeneous low permeable medium. On the other hand, heterogeneity may enhance water imbibition due to capillarity. Due to the above and various other complexities, current tools for predicting the performance of fractured hydrocarbon reservoirs are not reliable. Based on the research work carried out at the Reservoir Engineering Research Institute, and some other Institutions, a good deal of progress has been made in recent years. But still we are a long way from good predictive reservoir models. In this final report, we summarize some of our achievements in the understanding of multiphase flow in fractured media. Since some of the features of two-phase flow in fractured and layered many are similar due to the capillary forces, the work includes progress in both types of media. There are some basic issues of flow in both fractured and unfractured media that are currently unresolved. These issues include: (1) new phase formation such as the formation of liquid phase in gas condensate reservoirs, and gas phase formation in solution gas drive process and (2) composition variation due to thermal convection and diffusion processes. In the following, a brief summary of our findings in the last three years during the course of the project is presented