TX 75083-3836, U.S.A., fax 01-972-952-9435.Abstract THAI -'Toe-to-Heel Air Injection' is a radically new process for the recovery and in-situ upgrading of heavy/medium crude oil and bitumen. It is an integrated-horizontal wells process, which creates its own natural sealing mechanism (in the horizontal producer well), enabling stable combustion front propagation along the horizontal producer well to be achieved. CAPRI is an extension to the basic THAI (thermal) process, which involves the emplacement ('gravel-packing') of a standard refinery HDS catalyst, around the horizontal producer well.A series 3-D combustion cell experiments were performed to physically simulate the THAI-CAPRI process, using Lloydminster heavy crude oil (11.9 o API). In separate THAI and CAPRI experiments, high temperature combustion was sustained (500-550 o C), achieving stable combustion front propagation. Very high oil recovery was achieved, exceeding 79 % OOIP for THAI and CAPRI. The first-stage of downhole conversion, or in-situ upgrading, is accomplished by thermal cracking (THAI), and thermally/catalytically, in the second stage (CAPRI). Thermal upgrading of the produced oil by THAI averaged 18.3 o API -an incremental conversion gain of 6.4 API points, with a maximum of 22 o API. Higher upgrading was achieved by CAPRI using a regenerated CoMo HDS catalyst. The produced oil averaged 23 o API, essentially a light oil product. The oil viscosity produced by THAI or CAPRI was as low as 20 to 30 mPas.