| Popis: |
A group (the Cluster) of nine intra-salt Precambrian age reservoirs is located in the south of Oman 70 km from the nearest infrastructure and has been identified for potential development. Four reservoirs are currently producing via depletion. Although primary depletion provides a robust and economic development, Petroleum Development Oman (PDO) intends to implement a development based on EOR miscible gasflood at the earliest opportunity. If successful, a miscible gas injection project has the potential to triple the ultimate recovery compared to primary depletion. In order to demonstrate the technical feasibility and economic viability of a miscible gasflood, one of the identified Precambrian reservoirs (Field A) was extensively modelled both statically and dynamically. A complete subsurface reservoir characterization was underpinned with an extensive data acquisition program, including: new 3D seismic acquisition and processing, full-reservoir section coring and sedimentologic facies description, routine and special core analyses, standard wireline logging, bore-hole image logs and interpretation, well test data (stimulation and cleanup, stabilized flow test, pressure buildup, MPLT, and standard and miscible PVT analyses) and interference pressure testing (from permanent down-hole pressure gauges). Integrated static and dynamic compositional modelling of the field identified the primary subsurface uncertainties as: compartmentalization, permeability heterogeneity and injectant gas composition (to achieve miscibility). Pressure interference results indicate that faults locally act as baffles (not barriers) and that no field wide thief zone is present. Miscible PVT experiments show that an average Cluster gas should be multiple contact miscible at pressures below original reservoir pressure. A comprehensive suite of geological static model realizations and compositional dynamic simulations were generated to capture the spread in reservoir heterogeneity, STOIIP and ultimate recovery. Gasflood recovery factors from these full field simulations varied from 25% to 55% and demonstrated that a miscible gasflood in this reservoir is attractive even in the pessimistic case. Field A will be the first miscible gasflood in the Cluster. Based on the studies approval have been given to develop the field with miscible gasflood |
