POST-DRILLING ANALYSIS OF THE NORTH FALKLAND BASIN - PART 2: PETROLEUM SYSTEM AND FUTURE PROSPECTS

Six wells were drilled in the North Falkland Basin in 1998. Five of these wells recorded oil shows, and up to 32% gas was also recorded in mud returns to the rig floor. However, none of the wells encountered commercially viable petroleum accumulations. The syn-rift and early post-rift intervals contain thick, lacustrine claystones with oil source potential as indicated by TOC values up to 7.5% and Rock-Eval S2 values of up to 102 kg HC per tonne of rock. These source rocks were immature or only marginally mature in five of the wells but had attained maturity in one of them. Modelling suggests that the main source interval may well be within the peak oil generation window in deeper, undrilled parts of the basin. Calculations of the amount of oil expelled range up to 60 billion barrels. Most of the wells tested a closely-related set of plays in large structures associated with a sandstone interval near the top of the late syn-rift to early post-rift source-rock succession. Post-drilling geological modelling of the basin suggests that oil is unlikely to have migrated into this sandstone play at the localities tested, and that the wells consequently failed largely due to a lack of charge. However, the play maintains exploration potential elsewhere. Other plays, particularly those stratigraphically associated with the base rather than the top of the source rock, may have a higher chance of exploration success.