A modified vertical-horizontal well pattern for enhancing in-situ combustion performance in extra-heavy oil reservoirs

Abstract

A proper well pattern is critical for the efficient and economical exploitation of heavy oil and bitumen during the in-situ combustion (ISC). This paper brings a modified vertical-horizontal well pattern named the modified THAI process using additional injectors in staggered line drive with auxiliary gas producer wells and investigates its ISC performance using a 3D experimental simulation. The burning stability, spatial distribution of coke zone, pressure difference, and extension features of combustion chamber are studied and analyzed. Results show that a better burning state and stable propagation for the combustion front can be achieved in this modified well pattern. Spatial distribution of coke zone structure manifests a larger sweep volume of combustion chamber and a lower extent of combustion override. Combustion chamber extension characteristics are intuitively displayed by the variation of 350 °C isothermal surfaces, and its sweep volume finally enlarges to 53032.55 cm3 with a volumetric sweep coefficient of 47.95%. The production well intermittent shutdown (PWIS) method can improve unfavorable expansion behaviors of combustion chamber with little impact on the burning state and pressure difference. The oil displacement efficiency eventually reaches 85.6%. This well pattern exhibits significant potential for enhancing in-situ combustion performance, contributing to the economic and efficient exploitation of oil in commercial ISC application.