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New Ideas in Improved Recovery and Enhanced Oil Recovery

increase in recovery factor worldwide, would be equivalent to 85 billion barrels per day. That is the same as 8 years of exploration effort.

The Finding Petroleum Seminar held in London on the 18th April contrasted exploration success with the enhancement of oil recovery. A significant conclusion drawn was that it was more beneficial to develop improved oil recovery rather than exploring for new sources of oil.

Production from all oil wells will decline over time to the point of being marginal or uneconomic. However, significant quantities of oil are left underground. The global average for oil recovery has recently been quoted as 22 percent, with recovery in the North Sea oil wells achieving a hefty 47 percent. Despite, the Middle East being among those only achieving 25 percent, it is estimated that it is technically feasible to recover 60 percent.

One of the measures used is the production/exploration ratio where a ratio of 1 would indicate new discoveries achieving the same reserves as the oil being extracted. The current global oil production exploration ratio is 2:1 and

reserves have been in decline for 11 years. The ratio for the North Sea is 5:2 but more surprising is the ratio for the Middle East at 8:1. The regions in decline also include Asia, North Americas and Brazil (without pre-salt).

In 2010, the output of the North Sea was 3.34 mbpd (million barrels per day), and is estimated to be just 0.2 mbpd in 2030 (EIA). Oil production over the last 50 years can be represented with a classic S curve, and for the last 5 years, the North Sea has been sitting at the top of the plateau at 74 mbpd. So despite the best exploration efforts, it is evident that the oil supply is running out. Consequently, the demand for oil will ensure that the price will remain in excess of $100 per barrel.

However, as mentioned previously, there is plenty oil in the ground, which could be accessed with improved recovery techniques. Currently, 40 percent of global production comes from new discoveries, 10-15 percent from improved oil recovery (IOR), and only 3 percent from enhanced oil recovery (EOR). IOR involves the implementation of water or gas injection, and EOR by thermal, chemical or miscible gas injection. It is suggested that a 1 percent

In considering EOR, the thermal technology is applied to heavy oils to aid the flow properties, but is limited. The use of chemicals is questionable as the cost of the chemicals is in the same order of the value of the oil extracted. The preferred technology is therefore miscible gas injection such as hydrocarbon or carbon dioxide (CO2). If available, carbon dioxide is favoured as it is cheaper than hydrocarbon, versatile, and contributes towards the green agenda of carbon capture and storage (CCS).

Further advantages include the reduced cost of storage of CO2 from CCS, and the use of current offshore facilities. Against that, the challenges include the high cost of capture and public perception of storage risks. However, it is expected that the costs will reduce significantly during the demonstration phase up to 2020. When coupled with the carbon price, CCS will become economically justifiable. One model proposed is that the subsidies should be for the sole benefit of the emitter, and the oil recovered via EOR for the benefit of the storage provider. It is therefore foreseen that CCS for EOR will provide an acceptable linkage between climate protection, energy affordability and security of energy supply.

Case study - The Forties Oilfield

The Forties Oilfield which is over 40 years old, was owned by BP, and is estimated to contain between 4.2 and 5 bboe (billion barrels of oil equivalent).

When production declined from a peak of 400-500 kbpd (thousand barrels a day) to 40 kbpd, BP deemed the field uneconomic and sold it to Apache Oil with 144 mmbo (million barrels of oil equivalent) recoverable reserves. Together with Schlumberger, Apache developed a Forward Development Plan through a review of previous years using sophisticated analytical techniques and applying the lessons learnt.

The addition of new wells resulted in a net increase of producing wells from about 50 to around 70. Coupled with the utilisation of improved recovery techniques, production has

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increased to 60 kbpd since 2005.

The additional output resulted from the addition of 80 production completions and 4 injection completions. Through improved 4D seismic and detailed reservoir characterisation, a new well at Charlie 4-3 has been developed which produces in excess of 10 kbpd.

Another new platform is due to be installed this year and so far Apache has not applied EOR techniques.

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