TAPPING THE POTENTIAL
More than 23 per cent of PDO’s production is expected from EOR projects by 2025
Despite the challenging economic environment, Petroleum Development Oman (PDO) is continuing its journey in growing the future EOR contribution to oil production. It is anticipated that by 2025 more than 23 per cent of PDO’s production will come from EOR projects.
PDO is currently operating a range of commercial-scale EOR projects including chemical EOR, miscible gas injection (MGI) and thermal applications. Concurrently, PDO is continuing to identify novel EOR technologies that have the potential to unlock difficult hydrocarbon resources. This is being done through a series of dedicated laboratory and field testing programmes, according to PDO’s Sustainability Report released recently.
The Marmul Polymer Phase 1 project has been running for the last seven years and has delivered 13.7 million barrels of oil. Phase 2 started in 2015 and involves injecting polymer into 19 additional injector wells, and has delivered 840,000 barrels of oil to date. The average combined production gain from both phases in 2017 was 5,755 bpd. A total of 14.6 million barrels of oil has been delivered as a result of polymer injection in the Marmul field to date. In 2017, the final investment decision was taken for Marmul Polymer Phase 3, which targets the infill drilling of the existing wells in the Marmul Al Khlata reservoir, waterflood and polymer rotation. The project will develop 80 million barrels of incremental oil, with first oil by Q1 2023. Near miscible sour gas injection in the Birba field for the past 23 years has yielded an additional 50 million barrels, (representing a recovery rate of 22%) for 5.5 billion cubic metres of gas injected so far, and is on target to achieve up
to 45% recovery from infill horizontal drilling and additional gas injection.
The Harweel 2AB project started miscible gas injection in April 2014 at a constrained rate of up to 1.7 million cubic metres per day. This has ramped up to a full-capacity injection rate of up to five million cubic metres per day since January 2015 after separator replacements. A clear response to the MGI process has been established in terms of incremental oil rates (incremental oil to date of around 10 million barrels and target pressures above the minimum miscibility pressure across the field.) The expected total recovery with MGI is about 45%.
Injection in Sakhiya field as part of the Sak miniflood project has continued since mid-2015 with high injectivity of up to 2.5 million m3 /d. A positive reservoir pressure response has been observed as the depletion rate slows down. One of the key highlights in 2017 for miscible gas was the start-up of the Al Noor 3A sour MGI pilot with positive initial indications, with both injector wells accepting the target rates.
The thermal gas-oil-gravity-drainage (T-GOGD) process in Qarn Alam has been underway since late 2011. In 2017, 3.3 million tonnes of steam were injected into the Shuaiba oil-bearing formation, producing 6.8 million barrels of oil and resulting in a steam-to-oil ratio of approximately three. Project record levels of steam injection were achieved with peak rates exceeding 15,000 tonnes per day. However, whilst oil production exceeded expectations, total steam injection for the year fell short of forecasts due to generator and steam injector well integrity issues coupled with prolonged produced gas compressor (PGC) outages. Recovery plans are in place to continue the performance improvement during 2018.
The Amal steam project continues to improve in all areas, and the yearaverage oil production for 2017 was 15,716 bpd. There was a continued strong steam injection performance with 2017 representing the highest annual average injection rate of around 7,700 tonnes per day.
There was improved availability of heat recovery steam generators in Amal West and more once-through steam generators in Amal East, and a thermal response has now been demonstrated in both fields. Reservoir performance continues to improve with good cold and thermal performance. Last year, 18 wells were drilled in the Amal West 3.3-acre infill project.