In-situ combustion (ISC) is an effective thermal recovery process that provides an important alternative to steam injection. ISC is the process of injecting air into a reservoir to oxidize a small portion of the hydrocarbons present to generate heat and pressure. It suffers from fewer reservoir limitations than steam injection, but is not applied widely. One factor that has limited application of ISC is lack of predictability at both the laboratory and field scale. Proper experimental kinetic analysis (using, for instance, ramped temperature oxidation) provides critical parameters, such as activation energy, for modeling efforts. Conventional methods of kinetic analysis for crude oil assume, a priori, a two-step or three-step oxidation reaction. Any in- consistency between the assumed model and the real system is reflected as error in model parameters. Iso-conversional tech- niques, as applied here, provide model-free methods for estimating activation energy and naturally deconvolve multi-step reactions. The iso-conversional approach obtains the reaction kinetics for a given rock/oil sample at identical reaction extent from multiple experiments with different heating rates. The technique has never been applied to ISC kinetics, to our knowl- edge. Our work falls into two major sections. First, the applicability of the iso-conversional method to multiple step oxidation of oil in porous media is established via synthetic examples. Second, and on the practical side, the combustion kinetics are reported for two quite different crude oil samples thereby adding to the knowledge base of crude-oil and rock-matrix charac- teristics that make for successful ISC. The iso-conversional analysis of ramped temperature oxidation data appears to provide new insight into systems where ISC is/is not successful.
展开▼
