From 1981 when oil and gas production from the Gorm Field commenced until 1 January 2005, the field produced a total of 50.42 million m3of oil and 14.63 billion Nm3of gas.
Total oil production from the Gorm Field represented a 20 per cent share of total Danish oil production during the period from 1972 through 2004, equal to 255 million m3. Fig. 4.6 shows the annual production of oil, annual water injection and the content of water relative to total liquid production for the Gorm Field.
On the basis of production experience, investments in new production and injec-tion wells and new processing equipment have been continually made; see above. These investments impacted on the trend in both oil and water produc-tion; see Fig. 4.6.
Interestingly, the field recorded its highest annual oil production figure in 1999 – as much as 18 years after the first oil was produced from the field. Moreover, it appears from the figure that annual water injection increased substantially through the 1990s, subsequently boosting oil production. However, this has also stepped up water production. Thus, the water content of liquid production rose from about 26 per cent in 1990 to about 68 per cent at the end of 2004.
Gas production
The Gorm Field has a moderate content of gas, produced together with oil and water. During the first years of the life of the field, the bulk of the gas produced was reinjected into the reservoir. This was done to avoid gas flaring and to main-tain pressure in the field.
Since 1993, gas is no longer injected on a continuous basis. Instead, the gas pro-duced is transported to the Tyra Field, from where it is exported ashore.
However, small volumes of gas are reinjected in situations where the gas cannot be exported, e.g. due to temporary shutdowns of the gas-receiving facilities at the Tyra Field.
Reserves
Development and production generate more and improved knowledge about the field. Therefore, the amounts of oil recoverable from a field are continuously assessed. Such a reserves assessment is based on the principles mentioned in the section Reserves.
Fig. 4.7 shows the assessments of oil reserves in the Gorm Field and cumulative oil production since 1981. The sum total of these figures constitutes the expected ultimate recovery of oil from the Gorm Field.
Until the end of 1988, ultimate oil recovery was assessed at 19 million Nm3. Assessments regarding water injection indicated that ultimate recovery from the field might become somewhat higher. Particularly in connection with the devel-opment plan from 1991, the assessment of ultimate oil recovery was written up considerably, to 40 million Nm3. Since then, it has proved possible to continue adjusting the assessment upwards. Thus, as of 1 January 2005, ultimate oil recov-ery from the Gorm Field is estimated at 67 million Nm3.
During the period from 1983 to 2005, the estimate of ultimate oil recovery from the Gorm Field increased from 18 million Nm3to 67 million m3, thus more than tripling. The higher figure results from greater knowledge about the structure of the field as well as the development and application of new technologies, such as horizontal wells and water injection.
Based on present-day knowledge about the oil-in-place in the Gorm Field, the estimated recovery factor for oil increased from about 10 per cent at the begin-ning of the 1980s to about 39 per cent at the end of 2004. The recovery factor indicates the ratio of ultimate recovery to total oil-in-place.
Investments and operating costs
The above-mentioned increase in the ultimate recovery of oil has been contingent upon continuous investments in new platforms and wells and new processing facilities in the field. Fig. 4.8 shows the trend for investments in fixed installations and wells in the Gorm Field in nominal prices. A comparison of this figure with Fig. 4.3 shows that investments in drilling new wells have continuously been made.
D E V E L O P M E N T O F T H E G O R M F I E L D
83 85 87 89 91 93 95 97 99 01 03 05
30 20 10 0
Fig. 4.7 Oil production and reserves for the period 1983-2005 m. m3
Cum. production Reserves 20
40 60
A total of DKK 11.6 billion, in 2004 prices, has been invested in developing the field. This is equal to about DKK 170 per m3o.e. that is expected to be recovered from the Gorm Field until production from the field discontinues, based on the assessment made at 1 January 2005. To this must be added the cost of financing the investments. Moreover, it should be noted that investments will subsequently be required for the decommissioning of the installations.
The cost of operating the Gorm Field has fluctuated over the years, ranging between DKK 100 and DKK 250 per produced m3o.e. in 2004 prices over the last 20 years. Operating costs must be expected to vary over time and to increase per produced unit towards the end of the life of an oil field.
New development plan
Ongoing efforts are made to improve oil and gas recovery from the fields in the North Sea. In the autumn of 2004, Mærsk Olie og Gas AS submitted a plan for further developing the Gorm Field. The plan is based on an integrated study of geological and reservoir models, which have been updated with experience gained through the production history of the field. The study has identified areas in the field that are not drained optimally, and therefore the plan provides for the drilling of four new wells. At the same time, it is planned to expand and improve the capacity of the processing facilities.
The new wells are estimated to enhance recovery from the Gorm Field by about 3 million m3of oil until the year 2020. Total investments associated with the development are estimated at DKK 500 million, with well costs accounting for DKK 360 million.
Depending on experience from the first four wells, the plan outlines the option for drilling up to five additional wells.
Thus, oil recovery from the Gorm Field can still be improved, and in spring 2005, the Danish Energy Authority approved the development plan submitted. The first of the new wells is expected to be spudded in the course of 2005.
m. DKK
80 82 84 86 88 90 92 94 96 98 00 02 04
1000
800
600
400
200
0
Fig. 4.8 Investments in the Gorm Field, 2004 prices
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T H E E N V I R O N M E N T
5. THE ENVIRONMENT
The production of oil and gas from offshore installations results in emissions to the atmosphere, such as NOx and CO2, and in discharges into the sea consisting of chemicals and oil residue.