Gas Injection Modeling in Shale
Diego Sandoval, Erling H. Stenby,Wei Yan(presenter)
Center for Energy Resources Engineering (CERE), Department of Chemistry, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
Oil production from shale is perhaps the biggest game changer in the petroleum industry in the last decade. It has essentially doubled the oil production in the U.S.
Despite its massive contribution to oil production, the average recovery factor is rarely over 10%. There is an obvious need to improve the oil recovery both for better economics and for better utilization of the resources.
Gas injection, either continuous flooding or huff ’n’ puff, is proposed to be a possible approach to enhance oil production from shale. The approach is indeed attractive because the readily available gas resources and the higher injectivity of gas relative to other solvents.
Gas injection in shale can utilize the existing knowledge of gas injection in conventional reservoirs and use a similar strategy of analysis. Both require an adequate description of the underlying phase behavior as the basis of description.
However, we need to address some distinctive features of gas injection in shale in its modeling. First, due to the nano-scale pore sizes of shale, the capillary pressure effects are more pronounced in phase equilibrium. Second, due to the high organic content, the adsorption effect is non-negligible.
We tried to integrate these factors into the tools for analyzing gas injection at different levels, and this talk is to share some of the results. At the most fundamental level, we developed the phase equilibrium calculation tools that can robustly and efficiently calculate flash with strong capillary pressure and adsorption.
We investigated how to account for pore size distribution in the modeling of capillary pressure and how to reasonably model multicomponent adsorption on shale.
At the PVT modeling level, we developed a PVT simulation tool to perform constant mass expansion, differential liberation and constant volume depletion in the presence of capillary pressure and adsorption so that the influence of capillary pressure and adsorption can be analyzed.
We further integrated the flash module with capillary pressure into a slimtube simulator to investigate the influence of capillary pressure on the oil recovery and the minimum miscibility pressure. Finally at the simulation level, we integrated the capillary pressure into a compositional simulator and applied it to the simulation of depletion production.
Simulation of gas injection with capillary pressure is yet to be made . Gas injection with capillary pressure is yet to be simulated and injection cases without capillary pressure will be presented.