A Preliminary Numerical Simulation Study of In-situ Combustion In a Cold Lake Oil Sands Reservoir

Abstract

Introduction The thermal models of the Computer Modelling Group were used in a preliminary study of the behaviour of in-situ combustion fallowing steam stimulation in a Cold Lake oil sand reservoir. The study was performed in order to enhance operations of the BP/Partners Marguerite Lake Phase A Project. Chemical reaction parameters for the simulations were obtained by matching laboratory combustion tube experiments. History matching of field steam stimulation data was not performed in this study but rather temperature and fluid saturation distributions following steam stimulation were estimated using analytical techniques. One- and two-dimensional, cross-sectional simulations were carried out to study the effects of the amount of initial reservoir preheating and the vertical reservoir permeability distribution on ignition and maintenance of combustion. Both dry and wet forward combustion runs were performed. It was found that the size of the cold zone between wells following steam stimulation has a significant effect on the performance of combustion drive, as does the existence of a high-permeability zone in the reservoir. Expected oil production" rates, air-oil ratios. etc., are presented for this process. Introduction BP Exploration Canada Limited is currently operating a pilot project in the Cold Lake oil sands to investigate the recovery of bitumen using a sequential steam-stimulation and in-situ combustion drive process. The Marguerite Lake Project, Phase A, is located as shown in Figure 1. The project is funded by BP Exploration Canada Limited and its partners: the Alberta Oil Sands Technology and Research Authority (AOSTRA), Hudson"s Bay Oil and Gas Company Limited and Pan Canadian Petroleum Limited. In-situ combustion experiments began at the Phase A site in November 1979 following sixteen months of steam stimulation operations. (In this project, it was necessary to fracture the formation in order to obtain adequate injectivity.) A number of one- and two-dimensional numerical simulations were performed to investigate ignition and maintenance of combustion in the reservoir following steam stimulation. It was also desired to obtain estimates of air injectivities, combustion temperatures, production rates, oil recoveries and heat breakthrough times at the producing wells. Steam stimulation data from the Phase A project have not been history matched and many of the required input parameters for the model have been estimated rather than measured. For these reasons, the results of the study should be considered as qualitative only. Model Input Data Appendix A contains a listing of some of the physical property data input to the model. Much of the data were obtained from an earlier study conducted by Finbow and Koop (Ref. 1), Laboratory combustion tube data were history matched using CMG"s one-dimensional in-situ combustion tube simulator COMB, described in Reference 2. One dry and one wet forward combustion tube experiment were matched. Figure 2 shows an example of temperature profile matching at a time close to the end of the wet combustion tube run. The history-matching parameters employed for the combustion tube experiment simulations were the kinetic parameters of cracking and high-temperature burning reactions and the phase equilibrium constants.