Development of a Giant Carbonate Oil Field, Part 3: How to Build Enhanced Oil Recovery Development Plan Aiming for 70 Recovery

摘要

The considered giant carbonate field is located offshore Abu Dhabi and has 50 years of production history through a series of pressure-maintenance methods. Chronologically, the implemented development approach includes gravity-driven dumpflood water injection, peripheral water injection, and immiscible crestal gas injection and a review of these methods is discussed in Pavangat et al., 2015. Since, the historical pressure maintenance methods are approaching its limitation in sustaining the production; a gradual migration towards sweep-oriented pattern development is required to further extend the plateau and is discussed in Nakashima et al., 2015. The pattern-based Improved Oil Recovery (IOR) not only extends the plateau and recovery but also set the stage for future enhanced oil recovery (EOR) development plan aiming for 70% recovery. This paper describes how a gas-based EOR development plan following the IOR plan was built, in an integrated manner, addressing the gaps and risks from core scale to field scale. The integrated development plan consists of (a) review of past gas injection pilots, (b) injectant screening based on experimental results, (c) injection scheme selection to maximize the recovery, (d) configuration of the EOR pattern, (e) EOR application timing and rate optimization considering interaction with current development plan, and (f) investigation of surface facility requirements for EOR development. A sector model study was done, using inputs from the SCAL and PVT experiments, for the screening ((b) and (c)) using the past pilot review (a). Learnings from the sector model simulation is deployed to the full field EOR application by dividing the field on the basis of maturity to water flood and historical development footprint, respecting the simplicity in EOR application without jeopardizing the ongoing production. Through simulation exercises, an integrated EOR plan was built ((d) and (e)). The proposed EOR plan efficiency is evaluated through full-field reservoir simulations, which takes practical drilling plan, well completion types and surface facilities constraints. The simulation results demonstrated that the proposed plan (a) can recover oil without bypassing remaining oil, (b) can achieves 70% recovery based on selected gas, (c) is vigorous in terms of well count and well-head tower, and (d) utilizes the available surface facilities resources at maximum. The methodology used to design and evaluate the EOR development plan is applicable to other similar fields.