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Archive » Abstracts » Search	*2004/ 2005 SEASON* **STAVANGER APRIL MEETING Venue: Rica Forum Hotel, Stavanger Forum Please note different location than usual. Contact hotel reception for room details. Date: Wednesday, 6th April, 2005 Time: 11:00 a.m. Lunch will be provided at 12:00 Geosteering a Gullfaks Well Using New Directional Electromagnetic Measurements by Jørn Gjerde, Statoil, and Erika Gustavsson, Schlumberger Abstract The Gullfaks Field was discovered in 1978 and came on stream in 1986. Gullfaks has so far yielded 1.9 bbl of crude, more than 50% above the volume thought possible when the field came on stream. The field has been developed with three platforms - Gullfaks A, B and C. These form an integral part of the infrastructure in the Tampen Area. Gullfaks is now in its tail-end production period. Consequently Statoil is greatly committed to improve oil recovery in an area with declining production. Measures to improve oil recovery include innovative drilling technology with the final aim of optimal well placement, which this well project is a direct example of. The main objective of this horizontal well was to produce oil from the Tarbert Fm in a specific fault segment. The well placement objective was initially to try to stay close (2-5 m) to the top of the reservoir for the entire well path and steer down if the Heather cap rock was encountered. The reasons to place the wellbore as high in the structure as possible were to stay away from the water and ensure that no attic oil was left behind. The seismic data is of variable quality in this area, and initially some minor faults were expected but fault locations and throws could be interpreted with difficulty only. To fulfill these objectives, a newly developed deeper Directional Propagation LWD tool was used. The LWD sensors were able to detect resistivity contrasts in any direction around the tool up to 5 m away from the wellbore. A workflow was agreed in advance to ensure efficient decision-making involving geosteering specialists, wellsite geologists and onshore company personnel. During drilling the directional measurements were pulsed up hole in real time and transferred onshore using a web based system. These data were processed in real time to directly create a structural interpretation, an unbiased model, including distance and direction of nearby boundaries. This information was continuously fed back to the company representatives. The data shows that the cap rock could be avoided at all times except when unexpected faults were encountered. With this exception, the sought distance to cap rock could have been achieved at all times, although in places the plan to stay close to roof was abandoned temporarily in order to achieve optimum drainage. By using the tool, Statoil achieved increased control over well positioning. Unexpected faulting did occur, but information given by the tool and an innovative 3D visualization workflow incorporating boundaries helped the understanding of the fault pattern and the well could be quickly positioned back into the reservoir. Utilization of this innovative tool and its workflow has resulted in a well path better placed within the reservoir section. The data derived from this job will provide vital information to the structural interpretation of this part of the Gullfaks Field. Jørn Gjerde, CV Jørn is the operations geologist responsible for planning and follow-up of this well project. He finished his Cand.Scient thesis in geology at the University of Bergen in 1998. He has been working as an operations geologist in Statoil since then. Erika Gustavsson, CV** Erika is Well Placement Team Leader Scandinavia for Schlumberger Data & Consulting Services. She graduated from the MSc Petroleum Geology programme at Aberdeen University in 2000. She subsequently joined Schlumberger Norway as a Geologist - initially involved in supporting wireline operations and processing various wireline data/images. She later on moved to support Real Time LWD well placement operations in West Africa and now currently Norway.

Abstract

The Gullfaks Field was discovered in 1978 and came on stream in 1986. Gullfaks has so far yielded 1.9 bbl of crude, more than 50% above the volume thought possible when the field came on stream. The field has been developed with three platforms - Gullfaks A, B and C. These form an integral part of the infrastructure in the Tampen Area. Gullfaks is now in its tail-end production period. Consequently Statoil is greatly committed to improve oil recovery in an area with declining production. Measures to improve oil recovery include innovative drilling technology with the final aim of optimal well placement, which this well project is a direct example of.

The main objective of this horizontal well was to produce oil from the Tarbert Fm in a specific fault segment. The well placement objective was initially to try to stay close (2-5 m) to the top of the reservoir for the entire well path and steer down if the Heather cap rock was encountered. The reasons to place the wellbore as high in the structure as possible were to stay away from the water and ensure that no attic oil was left behind. The seismic data is of variable quality in this area, and initially some minor faults were expected but fault locations and throws could be interpreted with difficulty only.

To fulfill these objectives, a newly developed deeper Directional Propagation LWD tool was used. The LWD sensors were able to detect resistivity contrasts in any direction around the tool up to 5 m away from the wellbore. A workflow was agreed in advance to ensure efficient decision-making involving geosteering specialists, wellsite geologists and onshore company personnel. During drilling the directional measurements were pulsed up hole in real time and transferred onshore using a web based system. These data were processed in real time to directly create a structural interpretation, an unbiased model, including distance and direction of nearby boundaries. This information was continuously fed back to the company representatives.

The data shows that the cap rock could be avoided at all times except when unexpected faults were encountered. With this exception, the sought distance to cap rock could have been achieved at all times, although in places the plan to stay close to roof was abandoned temporarily in order to achieve optimum drainage. By using the tool, Statoil achieved increased control over well positioning. Unexpected faulting did occur, but information given by the tool and an innovative 3D visualization workflow incorporating boundaries helped the understanding of the fault pattern and the well could be quickly positioned back into the reservoir. Utilization of this innovative tool and its workflow has resulted in a well path better placed within the reservoir section. The data derived from this job will provide vital information to the structural interpretation of this part of the Gullfaks Field.

Jørn Gjerde, CV

Jørn is the operations geologist responsible for planning and follow-up of this well project. He finished his Cand.Scient thesis in geology at the University of Bergen in 1998. He has been working as an operations geologist in Statoil since then.

Erika Gustavsson, CV

Erika is Well Placement Team Leader Scandinavia for Schlumberger Data & Consulting Services. She graduated from the MSc Petroleum Geology programme at Aberdeen University in 2000. She subsequently joined Schlumberger Norway as a Geologist - initially involved in supporting wireline operations and processing various wireline data/images. She later on moved to support Real Time LWD well placement operations in West Africa and now currently Norway.