Fully Coupled Geomechanical Analysis Assists in Risk Management of Subsea Layout and Well Design in Deepwater Field

An oil company is currently preparing the Field Development Plan for a deepwater gas field, offshore Malaysia. A decline in field pressure of 2500psi over a period of 10 years is expected to give rise to large amounts of reservoir compaction, lateral deformations, and associated seabed subsidence, which will necessitate careful design considerations for planned production wells and seabed facilities. A series of fully coupled 3D analyses was carried out in order to predict an envelope of anticipated deformation, both in the reservoir and in the overburden to the sea floor.

Having established a representative field-wide stress condition throughout the production schedule, a 3D near-wellbore model was constructed to assess a preliminary casing string and completions design for a future appraisal well to be drilled to acquire further logs and cores. The operator would ideally like this well to become a “keeper” and side-track within the reservoir, thereby turning the appraisal well into a producer.

The results of both the field-wide and near-wellbore analyses with regard to reservoir compaction, seabed subsidence, and wellbore deformations throughout the anticipated life of the field highlighted the design considerations necessary for well integrity and subsea architecture.