Challenges and Learnings from Developing High Pressure Sour Reservoirs in Southern Oman by EOR MGI

Abstract

The commissioning of new Production Station (Station-H) in April 2012 marks the completion of the Phase 2AB project in the southern area of the Sultanate of Oman. The asset's liquid production has increased by 3 fold and contributes to more than 15% of Oman's production. This project is the world's largest Enhanced Oil Recovery (EOR) with Sour Miscible Gas Injection (MGI) integrating oil and gas field developments. Sour gas is processed through a state-of-the-art processing facility for sweetening and re-injecting gas under MGI to increase oil recovery up to 50%, (i.e. 6x increase over primary RF).The timeline from discovery of the field-Z in 2002 to commissioning of Station-H in 2012 is top quartile for mega-EOR projects of this type, considering the challenges: deep, high pressure, and sour fluid. Despite the delayed start-up, the first on-stream milestone is considered a commendable achievement. Building a facility to handle the extreme mixture of high pressure, sour corrosive fluids and gas is a technical step-out for PDO.One of the key challenges was maintaining the station's production despite 2 of the 3 production separators were deemed unsuitable due to compromised internal coating exposing the base material which was not NACE compliant. Therefore, there was no assurance against Sulphur Stress Corrosion Cracking (SSCC) in the event of any contact with sour fluids resulting in 40% capacity loss. A major shut-down of 4 months was recommended to complete several engineering activities (this could be shortened to 62 days by optimisation). Separator replacement was achieved safely resulting in reliable operation at design capacity after restart. The Turnaround was executed without any HSE incidents achieving GOAL ZERO, in total adherence to PDO HSSE standards.As part of a phased development prior to the 2AB project, several fields were produced beginning in 2004 through Early Development Facilities (EDF) to a nearby Gathering station, capturing of critical information while producing significant early oil. This resulted in sufficient revenues to fund for 2AB and more developments in the area. Within less than 3 years since commission of Station-H, the 2AB project has already achieved return on the investment. The EOR project life will continue to deliver value to Oman for the next 30ϩ years.The new station provides the infrastructure for long term development of the area and a number of follow-on projects, which will make use of these facilities: e.g. the already commissioned Phase 3 project in 2013 and Phase 4 development currently in execution and expected to be on-stream by 2019. This work will outline some of the key challenges on the phase 2AB project and how lessons learned were taken onboard to facilitate project delivery of the extended larger EOR/MGI development for follow-up phases and in similarly challenging projects in PDO.