Abstract
NNPC E&P Ltd (NEPL) recently successfully drilled, completed and tested the Abura 6ST well which integrated multiple Improved Oil Recovery techniques to develop some heavy oil reservoirs in the Abura field. The 1AB6 and 2AB6 reservoir fluids have viscosities of 10 and 17 Centipoise and API gravity ranging from 16 – 20API° which is a marked variation from NEPL's conventional resources. NEPL is estimated to have over 1.2B barrels of heavy crude oil in her portfolio therefore an attempt to unlock the potential from these reservoirs had a lot of implication for the company. Conventional methods of producing this reservoir were not economically viable mainly due to the high oil viscosity and consequent preferential flow of water rather than oil.
The NEPL team resorted to integration of multiple improved oil recovery IOR techniques to ensure an economically viable well.The first of such improved oil recovery techniques was the use the ESP as the Abura field did not have any gas source for gas lift. Artificial lift was to eliminate flow assurance issues that such a hydrocarbon system would have. Another IOR technique was the combination of horizontal and deviated well bores to drain the reservoirs through a single wellbore in a commingled fashion. The well cuts across the shallowest reservoir as a high angle section and lands in the deeper reservoir as a horizontal well. To ensure preferential flow of oil from the reservoir into the wellbore, Autonomous Inflow Control Device AICD was deployed for both the horizontal and vertical sections of the completion which uses viscosity differences to prevent early water breakthrough and reduce water production.
To meet NUPRC's back allocation requirements, hydrocarbon fluid samples were collected during the drilling operation and unique fingerprint markers were identified which will aid in the determination of each reservoir's production contribution for proper hydrocarbon accounting. In the completions aspect of the design, Swell packers for zonal segmentation, Micro-emulsion breaker system for near well-bore remediation and improved permeability, downhole gauges & sensors and a Y-Tool assembly for alternate access in rigless intervention mode. The Abura 6ST well produced circa 2900 BOPD on choke 28/64 and ESP frequency of 40Hz.This paper seeks to elucidate on some of the IOR technologies and how they were integrated to facilitate the delivery of the first heavy oil ESP well in NEPL's direct operations.
