Geosciences and Reservoir Engineering Aspects in Optimizing Katla Field Development Plan
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Katla field was selected to be one of the first fast track projects in 2010. The field is operated by Statoil and the co-owners are Total, Petoro, Exxon Mobile and Conoco Phillips. The Katla template is connected to Oseberg Sør (OSS) platform, and will be developed through a direct tie-in to OSS. The primary reasons of selecting Katla as a fast track project were the available capacity at the Oseberg Sør platform, possible standard subsea equipment deliveries, oil volumes added to operator’s production ambitions, robust economy at an early stage and low reservoir complexity. One base case development plan (2P) has been selected, out of four different scenarios which have been carried out and evaluated. The selected scenario comprises a base case where the optimal drive mechanism is pressure support by water injection. The most robust and flexible development scenario includes two water injection wells and two horizontal oil production wells where there are one pair of wells in Katla North and one pair of wells in Katla South. The base case involves only Tarbert formation. Minimum (1P) and maximum (3P) profiles have been carried out. The major parameters which have been varied for the 1P and 3P profiles are fault transmissibility, porosity and permeability. As Katla North and Katla East are not proven by the exploration well located in Katla South, these panels are not taken into account in 1P. The recoverable oil and gas reserves in Tarbert formation only are respectively 8.9 Mbbls and 0.3 Gm3 in 1P, 19.5 Mbbls and 1 Gm3 in 2P, and 23 Mbbls and 1.2 Gm3 in 3P. There are two main upside uncertainties which have been carefully evaluated. These are the possibility of producing the gas in Lower Heather formation, and the improved oil recovery (IOR) impact due to gas injection from Katla to the nearby Omega Nord structure. Heather is regarded as resources mainly because there has never been production from Heather formation in any of the Oseberg areas. In addition, exploration well has only been drilled in Katla South, which makes the existence of Heather formation in Katla North questionable. If the resources in Heather formation and the IOR from Omega Nord are taken into account, the recoverable oil and gas reserves + risked resources of the 2P base case becomes 22.3 Mbbls and 1.4 Gm3 respectively. Katla fast track project is still under development. Production start is planned in January 2013.