Use of Computers in the Operation of the Ekofisk Complex
- Bill L. Giles (Phillips Petroleum Co.) | Stanley W. Wells (Phillips Petroleum Co.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- July 1987
- Document Type
- Journal Paper
- 809 - 813
- 1987. Society of Petroleum Engineers
- 5.2.2 Fluid Modeling, Equations of State, 4.1.5 Processing Equipment, 4.1.9 Tanks and storage systems, 5.5 Reservoir Simulation, 4.2 Pipelines, Flowlines and Risers, 5.2 Reservoir Fluid Dynamics, 4.6 Natural Gas, 5.4.2 Gas Injection Methods, 5.8.7 Carbonate Reservoir, 4.1.2 Separation and Treating, 4.5 Offshore Facilities and Subsea Systems, 4.1.1 Process Simulation, 4.1.6 Compressors, Engines and Turbines, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 5.6.4 Drillstem/Well Testing, 5.5.8 History Matching, 5.6.9 Production Forecasting
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Summary. The Greater Ekofisk complex consists of seven fields that produce into a central processing facility at Ekofisk Center, where gas and oil are separated. Gas is pipelined to Emden, West Germany, and oil is pipelined to Teesside, England. The complexity of the operations requires broad use of computers. This paper gives an overview of one of the most extensive systems of computer programs ever developed for operational assistance and reporting in offshore production of hydrocarbon reservoirs. Systems for the capture, concentration, storage, and retrieval of data are included, along with systems for simulating the surface facilities, for production allocation by component weights through C5+ , for long-range production forecasting, and for operational and management reporting.
Fields composing the Greater Ekofisk complex were discovered in the Norwegian Sector of the North Sea between 1968 and 1972. In order of discovery, these are Cod, Ekorisk, West Ekofisk, Tor, Eldfisk, Edda, and Albuskjell. The initial discoveries represented the first commercial oil fields found in the North Sea. Fig. 1 shows the Greater Ekofisk complex,
Ekofisk and neighboring fields are located in the deepest part of the Tertiary basin in an area containing more than 1,350 ft [410 m] of Danian and Upper Paleocene sediments. About half of this interval consists of Danian and Upper Cretaceous chalk sections, and the other half is composed of Upper Paleocene clastics. The Danian and Upper Cretaceous chalks compose the primary hydrocarbon reservoirs in the Ekofisk, West Ekofisk, Tor, Edda, Eldfisk, and Albuskjell fields. In the Ekofisk area fields, an extensive fracture system extends both laterally and vertically in the chalk reservoirs. Oils are relatively volatile. with substantial variation in composition from field to field.
Facilities for producing these fields were constructed in several stages. During the first phase, four Ekofisk wells were produced through separation facilities located on a jackup rig. Oil was loaded to tankers through a single-point mooring buoy. About 42,000 BOPD [6680 M 3 /d oil] was produced for 18 months in this manner. Associated gas was flared.
The second phase consisted of installing three drilling platforms (two for production and one for gas reinjection and production), a field terminal platform, a four-story quarters platform, and a 1 X 106 -bbl [ 160 x 103-M3] concrete oil storage tank.
Subsequent phases included construction of processing facilities at Ekofisk Center and gathering systems from the other fields as they were developed. A 36-in. [91.4-cm] pipeline 274 miles [441 km] long was constructed to transport gas to Emden, and a 34-in. [86.4-cm] pipeline 220 miles [354 km] long was constructed to transport oil to Teesside. A natural gas liquids (NGL) processing plant was built at Teesside to stabilize the oil and to extract ethane, commercial propane, isobutane, and commercial normal butane.
The complexity of the operations made it obvious from a very early date that extensive use of computers would be required. A study was initiated in 1972 to determine computer hardware and software needed for Ekofisk operational reporting. The following major systems were found to be necessary.
1. A system was needed to capture, to integrate, to store, and to retrieve data for metered flows. laboratory analyses, process conditions, valve status, well status, and other information required for day-today operating and reporting.
2. A technical information system (TIS) was needed to produce operating and engineering reports from the data.
3. A computer model simulating the surface facilities was needed to allow evaluation of changing field operations, changing process conditions, and proposed changes in operations.
4. A means of allocating production from the various fields to the gas and oil product pipeline streams by components through C5+ was needed so that each field's light-component contribution to the gas and liquid streams would be properly credited.
5. Long-range production forecasts for the Greater Ekorisk complex were needed, including compositional forecasts for each field and quantities and compositions of the Emden gas stream and the Teesside oil stream.
These are not the only systems developed for use in operation of the Ekofisk complex. Many other programs, not discussed here, were later identified and developed.
Capture and Initial Processing of Data
Data are automatically obtained from a large number of points in the Ekofisk complex and at Teeside and Emden.
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