A detailed approach to up-scaling of the Toe-to-Heel Air Injection (THAI) In-Situ Combustion enhanced heavy oil recovery process

Abstract

Toe-to-Heel Air Injection (THAI) is a variant of conventional In-Situ Combustion (ISC) that uses a horizontal production well to recover mobilised partially upgraded heavy oil/bitumen/tar sand. For the promise of THAI to be fully realised, realistic and validated field scale simulations are required to design process operations. Firstly, a brief review of the available laboratory to field up-scaling techniques was presented. Then sequential volume up-scaling was used to obtain larger length scales predictions. It was found that, as with conventional ISC, the kinetics parameters had to be altered to obtain a realistic representation of the physico-chemical processes occurring at larger length scales. Consequently, a new approach, which is grounded in theory, to up-scaling laboratory-scale simulations, already validated against experiment, has been proposed and tested. It is shown for the first time that for the fraction of fuel formed and consumed at laboratory scale to be the same as that at field scale, the Damkhöler number must be the same. From this relationship, it has been shown mathematically that the frequency factor of the reactions must be down-scaled from laboratory values to field values in order for the fuel deposition and consumption at the laboratory scale to be the same as at field scale. This is clearly another key finding in this study that has not been shown before. Therefore, an initial estimate must be made and iterative runs used to determine the value of the down-scaling factor. The new model led to improvements in the key prediction of the distribution of fuel (coke) deposition over previous field-scale works.