Changes in Reservoir Fault Seal Behaviour through Time, Offshore Congo

The work presented examples of producing post-salt fields in the offshore Republic of Congo to illustrate how fault seal behaviour may change through time. Both examples of "non-sealing" faults on an exploration time-scale behaving as "sealing" faults on a production time-scale, and the converse of sealing faults breaking down during production, are presented. The hypotheses put formard in interpreting the field data are evaluated with simple flow calculations. Firstly, an illustration of the fault sealing behaviour during production shows the feasibility of flow retarding across-fault given likely fault permeabilities. Secondly, an in-house fault permeability algorithm is presented which is used as a test of the hypothesis of fault seal breakdown in a case of up-fault communication between reservoirs. These studies highlight the importance of integrating a wide range of data sources and approaches when assessing reservoir compartmentalisation and communication.