HYDRODYNAMICS AND FAULT SEAL ASSESSMENT IN THE VULCAN SUB-BASIN, TIMOR SEA

Abstract

The study of hydrodynamics sheds light on the current day fluid flow regime of traps of different integrity and on the mechanisms leading to seal breach. It also provides insights into potential migration pathways and zones of secondary hydrocarbon accumulation. This is a preliminary hydrodynamic investigation carried out on a few selected wells in the Vulcan Sub-basin from high, moderate and low integrity traps, referred to here as HIT, MIT and LIT respectively (after O'Brien et al, 1996). The fields sampled include East Swan (LIT), Skua and Jabiru (MIT) and Montara and Oliver (HIT). The findings of this study suggest a trend between trap type and current day fluid flow. The best result was obtained for Skua-2, where pressure testing was conducted over the bounding fault for the field, indicating high integrity. Some wells showed upward head gradients, such as East Swan-2; others showed a low or no vertical gradient, such as Jabiru-1 A,−2, −3, −10 and Oliver-1. There was general agreement between the flow direction and the conductivity of the faults, as indicated by mud loss data. Preliminary potentiometric surface mapping of Jabiru indicated lateral flow, controlled by production, and hydraulic communication within the faulted reservoir. Wellbore hydrodynamics and potentiometric surface mapping of the reservoir heads on a regional scale promise to give indications of major structural controls on flow as well as secondary migration pathways.