Attic Oil Recovery in the Alvheim Field

Langaas, Kåre; Urazovskaya, Oxana; Gueze, Nicolas; Jeurissen, Emile

doi:10.2118/200719-ms

Cited by 10 publications

References 8 publications

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Overcoming Subsurface Challenges to Develop a Thin Oil Column - A Case Study from the Five Decade Old Gekko Discovery in the Alvheim Area

Tveiterå

Fismen

Bang

et al. 2022

Day 1 Wed, April 27, 2022

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The Alvheim field has been on production since 2008 through the Alvheim FPSO. While the FPSO has produced more than twice the initial Alvheim area production estimate of 250 mmboe, the ambition is to produce a billion barrels from the area via continuous infill drilling and near-field exploration and developments. An example of the latter is the joint Kobra East and Gekko (KEG) tie-in. This paper describes the various anticipated subsurface challenges, risks and proposed solutions in developing the Gekko field, discovered in 1974 (25/4-3) and subsequently appraised in 2003 (25/4-8) and 2018 (25/4-13S&A), revealing a thin oil column (6.5m) between a gas cap and a large aquifer. The Gekko reservoir is of Late Paleocene age and consists of turbiditic sand deposits of the Heimdal Formation. Two subtle four-way closures (Gekko North and Gekko South) define the trap. Reservoir properties are excellent with high porosities and multi-Darcy permeabilities. The technical challenges associated with producing a thin oil column sandwiched between the gas cap and a strong aquifer led to the field being viewed initially as a gas discovery and not included in the Alvheim development. New appraisal wells and additional seismic data sets, advances in seismic techniques and a new area petrophysical study helped to improve the subsurface understanding. Development of the thin oil column has been evaluated using detailed reservoir simulation models to determine optimal well placement and completion solutions, resulting in a well design comprising of horizontal tri-lateral wells of approximately 4000 m reservoir lengths. New completion technologies such as autonomous inflow control devices (AICD), independent inflow control valves (ICV) installed in each lateral and downhole water cut meters are expected to play a pivotal role in unlocking the development potential. The work done has resulted in a successful PDO submission (June 2021) for the KEG development. Four tri-lateral wells will be drilled during 2023, with first oil expected in 2024. This development represents the largest ongoing tie-in project to Alvheim, adding reserves of approximately 40 mmboe. Producing a thin oil column such as Gekko presents significant subsurface challenges. Such a development will require targeted technologies and multi-disciplinary coordination. Successful development will reinforce the near-field development strategy for the Alvheim FPSO and add to its production volumes and production life. To be able to finally develop the field fifty years after it was discovered can also serve as a benchmark for future stranded developments of similar scope and complexity.

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Overcoming Subsurface Challenges to Develop a Thin Oil Column - A Case Study from the Five Decade Old Gekko Discovery in the Alvheim Area

Tveiterå

Fismen

Bang

et al. 2022

Day 1 Wed, April 27, 2022

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Persistent Reservoir Management to Handle Unintended Crossflow Between Multiple Gas-Oil Zones in the Alvheim Field

Langaas

Stenvold

Skjærpe

et al. 2022

Day 1 Wed, April 27, 2022

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When drilling the East Kameleon structure in the Alvheim field in 2010, two pilot wells proved multiple and stacked hydrocarbon accumulations. The lower oil zone was developed in 2012 with a horizontal MLT well. When drilling the upper zone in 2014, the completion job failed, causing an undesirable zonal crossflow. A reservoir management strategy had to be established to secure long-term area development. To mitigate undesirable crossflow across the stuck sand screens, the well was filled with cement. A new horizontal producer was subsequently drilled and successfully completed to recover the oil from the upper zone. With potential lower-upper zonal crossflow, the reservoir model was updated to analyse the reservoir management options. Three scenarios were considered regarding zonal crossflow: a) No crossflow due to a successful cement plug, b) restricted crossflow representing mud/cement impairment, and c) fully open-hole crossflow without flow restrictions. A reservoir management strategy was established in 2015 to monitor zonal pressures and restrict upper zone production to minimize unwanted gas crossflow. Reservoir simulations showed that this was key to secure the oil recovery of the lower zone. The upper producer came on-stream with a high GOR, indicating gas crossflow according to scenario (b). From 2015 to 2020, the upper producer was choked back to low offtake rates. After five years with the lower zone oil recovery optimized, the reservoir management strategy allowed high offtake of the upper zone. Today, the upper horizontal well is one of the best oil producers in the Alvheim area, producing at a high oil rate with a declining GOR trend. The reality and the updated history matched reservoir model support scenario (b) as postulated in 2015. Analysis of recent pressure data has also strengthened the geological understanding of stratigraphical compartmentalization in this turbiditic sand deposit. This case study can act as an example of how to establish a reservoir management strategy in a complex multiple gas-oil zonal reservoir setting. It can also provide insight into the level of formation impairment when cementing a long horizontal well with stuck sand screens.

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Implementation of Autonomous Inflow Control and the Effect on Carbon Intensity

Elseth

Martiniussen

Halvorsen

et al. 2022

SPE Annual Technical Conference and Exhibition

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A lean approach for qualification of inflow control is presented, involving full-scale experimental tests. The experimental data are converted into optimized well design by a simple and robust workflow, incorporating internally developed software tools for pressure-drop modelling and for well modelling with inflow control. Production data from several Equinor operated fields are analyzed, and the increased oil recovery, as well as the impact on CO2 intensity, is discussed. Results from a full-scale qualification test campaign including five different autonomous inflow control devices (AICD) are presented. The intended application is a special case with high expected production and high pressure, in nearly vertical wells, which is unlike any of the more than 175 wells with AICDs in Equinor. The ability to choke gas and allow high oil production, as well as other selected qualification criteria, were examined for the five, already commercially available, technologies in a benchmarking study.

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Attic Oil Recovery in the Alvheim Field

Cited by 10 publications

References 8 publications

Overcoming Subsurface Challenges to Develop a Thin Oil Column - A Case Study from the Five Decade Old Gekko Discovery in the Alvheim Area

Overcoming Subsurface Challenges to Develop a Thin Oil Column - A Case Study from the Five Decade Old Gekko Discovery in the Alvheim Area

Persistent Reservoir Management to Handle Unintended Crossflow Between Multiple Gas-Oil Zones in the Alvheim Field

Implementation of Autonomous Inflow Control and the Effect on Carbon Intensity

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