Producibility of Oil Re-Saturated in Initial Gas Gap - Proof of Theory

Abstract Oil re-saturation in original gas zones due to upward movement of gas-oil contact (GOC), occasioned by production of the gas cap gas is not a new concept and has been experienced in several reservoirs. However, the possibility of producing such re-saturated oil is not guaranteed - as several factors such as wettability, viscosity, residual oil and gas saturations, relative permeability hysteresis, etc., come into play. Post-production saturation logging data indicated an upward movement of both the original GOC and oil-water contact (OWC) in the B1000X reservoir. This suggested that a significant portion of the original gas cap has been re-saturated with liquid hydrocarbon. Considering that the reservoir still holds substantial expected recoverable reserves in place and is a major candidate for further oil development, it is planned to drill more wells to target the re-saturated zone. Prior to drilling the new wells, an existing offset well (OM-006) was selected for a non-rig workover operation to perforate the target interval and test producibility. The reservoir saturation logging and analysis that were carried out in well OM-006 prior to the perforation job, confirmed oil re-saturation of the initial gas cap, and validated the planned perforation interval. Water shut-off of the existing perforation, which had been flushed by water, was then executed. After the intervention activities, extended flow tests confirmed producibility of the re-saturated oil in the B1000X reservoir. Average oil production of ca. 1,350bopd, BSW of ca. 15% and gas-oil-ratio (GOR) of ca. 1,450scf/bbl were measured, and the well has since been lined up to production. Plans are mature to drill the first of several wells into the re-saturated zone by Q2, 2024. This paper, therefore, demonstrates the producibility of an oil re-saturated zone in an initially saturated reservoir.