New Opportunities for an Old Field

Rojas, Temistocles¹, Rosmari Usta¹, Lehywis Villa¹, Villasmil Jose¹, Prieto Isabel¹, Chirinos Francisco¹, Miladis Blanco¹ (1) PDVSA, Maracaibo, Venezuela

Depositional fluvial systems develop a main area of sediment transport and deposition. Peripheral areas to this main depositional area can develop minor depositional systems, with lesser sandy deposits than the main system but with still prospective oil accumulations and rock properties.

Bachaquero Field located in west coast of the Lake Maracaibo produces heavy oil (11° API) from a Miocene reservoir since 1930, this field has almost 3000 wells, the reservoir original pressure was 1200 psi, nowadays the pressure is about 300 psi. Due to the present reservoir energy and oil conditions (heavy oil and high viscosity) it is necessary to use cyclic steam injection in order to enhance the oil recovery.

Previous works have interpreted this reservoir as deposited in a fluvial system, being the main production area the main area of the fluvial system. Throughout a multidisciplinary study it was possible to locate a secondary fluvial system at the west side of the main reservoir, where the sand thickness and extension are poorer than in the main area but with more energy (~1000 psi). Using seismic, geological, petrophysical a reservoir data it was possible delineate the sandbodies geometry within this relatively new area as well as to distribute the petrophysical properties within the sandbodies.

This static model allowed us to propose a drilling strategy based on horizontal wells in order to recover the oil from these thin sandy deposits. The production success obtained using this model has not been reported in Bachaquero field since 1960's.