An In-Depth Evaluation of Toe-To-Heel Air Injection Application in a Heavy Oil Reservoir Underlain by Bottom Water. Kerrobert Case

Abstract

Toe-To-Heel Air Injection (THAI) is an efficient in-situ combustion (ISC) process in which a horizontal producer is located close to the bottom of an oil layer with its toe close to a vertical air injection well. Once initiated, the ISC front propagates from the toe to the heel region of the horizontal section of the producer. THAI provides more control over the direction of the ISC front propagation (guided by the horizontal section of the producer), and it preserves the in-situ upgrading of the oil due to its short-distance oil displacement feature. Because of its controlled gas-liquid segregation, THAI is designed to mitigate the severe override experienced in conventional ISC processes. The Kerrobert THAI Project represented the second testing of THAI in the field, and it was designed and implemented by Petrobank Energy and Resources ("Petrobank"), based on the THAI patent (US Patent No. 5626191, 1997, Canada Patent No. 2176639, 2000). The patents basically describe two separate well applications: a direct line drive (DLD) configuration and a staggered line drive (SLD) configuration, for which birds-eye views are provided in Figure 1 and Figure 2, respectively. An illustrative cross-section of the process is shown in Figure 3; the start-up region is shown in all these pictures. The patents indicate that the vertical injector should be perforated high in the oil formation in both cases. The Kerrobert Project was designed to use DLD well configuration, but during the operation, SLD configuration was also tested in a few cases.