Heavy Oil Offshore UK: Recommended Mariner Reservoir Development Strategy

Abstract

Abstract The Mariner field - license 9/11 in the UK – was discovered in 1981 and is situated on the East Shetland platform. Mariner consists of two tertiary reservoir intervals of unconsolidated sand at depths between 1200 and 1500 mMSL. The deeper Maureen reservoir consists of stacked non-channelized sheet-like sand lobes deposited in a shelf to slope setting. The Maureen oil water contact (OWC) is stepping considerably and is shallower to the west. The Heimdal reservoir consists of deep-marine slope-channel sands within the mudstone-rich Lista interval, ranging in thickness from a few meters up to 40 m. The reservoir is heavily remobilised. The Heimdal OWC is uncertain with variable ODT (Oil Down To) observations and anticipated perched water. The total Mariner oil reserves are estimated to app. 400 MMBO (Million Barrels). The Maureen reservoir has 67 cp oil (14°API) in a 0–40 m oil column and a large bottom aquifer. The Heimdal reservoir contains two thirds of the reserves and has 508 cp oil (12 API). Steady State SCAL studies indicate that Krw may be viscosity dependent. The Heimdal reservoir is planned to be developed using an inverted 9-spot well pattern due to uncertainty in mapping of the reservoir. The Maureen reservoir will be developed with horizontal wells. As the recovery factors are only 22%, Enhanced Oil Recovery using polymer is investigated as an upside to be matured towards production start. IOR through use of down-hole inflow control devises is progressed in a technical qualification program. OBC (Ocean Bottom Cable) data will be acquired to improve the mapping of the Heimdal reservoir.