A Combined Experimental and Simulation Workflow to Improve Predictability of In Situ Combustion

Abstract

Abstract In-situ Combustion (ISC) is widely accepted as an enhanced oil recovery method that is applicable to various oil-reservoir types. Prediction of the likelihood of a successful ISC project from first principles, however, is still unclear. Conventionally, combustion tube tests of a crude-oil and rock are used to infer whether one expects that ISC works at reservoir scale and the oxygen requirements. Combustion tube test results may lead to field-scale simulation on a coarse grid with Arrhenius reaction kinetics. If ISC is unsuccessful at field scale whereas tube tests are positive, the reservoir geological heterogeneity or operational problems are generally blamed. As an alternative, this paper suggests a comprehensive workflow to predict the likelihood of a successful combustion at the reservoir scale, based on both experimental laboratory data and simulation models at all scales. In our workflow, a sample of crushed reservoir rock or an equivalent synthetic sample is mixed with water/brine and the crude-oil sample. The mixture is placed in a kinetics cell reactor and oxidized at different heating rates. An isoconversional method is used to obtain an estimate of kinetic parameters versus temperature and combustion characteristics of the sample. Results from the isoconversional interpretation also provide a first screen of the likelihood that a combustion front can be propagated successfully. Then, a full-physics simulation model of the kinetics cell experiment is used to simulate the flue gas production. The model combines a detailed PVT of the multiphase system and a multistep reaction model. A genetic algorithm is used to estimate reaction parameters and thereby match oxygen consumption and gas production. A mixture identical to that tested in the kinetics cell is also burned in a combustion tube experiment. Temperature profiles along the tube and also the flue gas compositions are measured during the experiment. A high-resolution simulation model of the combustion tube test is developed and validated. This simulation uses the reaction model we have obtained from the genetic algorithm and/or isoconversional analysis. Finally, the high-resolution model is used as a basis for upscaling the reaction model to field dimensions employing nonArrhenius kinetics.