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YOUNG, GORDON A., Petroleos de Venezuela S.A., Caracas, Venezuela

ABSTRACT: Mara Field, a Unique Giant in Venezuela

The Mara field is located in Venezuela, 45 km northwest of Maracaibo, on the Mara-La Paz anticlinal trend. Discovered in 1945 by the Caribbean Petroleum Co. (Shell group), the field has produced 407 MMB as of 1991 and has remaining proven reserves of 60 MMB, and probable and possible reserves of 58 MMB, for an ultimate potential recovery of 525 MMB.

In addition to being a giant field, Mara is also unique in that it produces from fractured igneous basement rocks as well as from fractured Cretaceous limestones, which are the source rocks of the region, and Paleocene/Eocene sandstone and carbonate reservoirs. The sedimentary stratigraphic section comprises beds ranging from early Cretaceous to middle Eocene, which suffered considerable erosion, and overlying Plio-Pleistocene sediments, all of which were involved in the latest strong deformation.

The structure of the field is complex; a main thrust zone (consisting of numerous individual faults) borders the northwest flank of the elongated anticline and an opposing minor thrust zone cuts the southeast flank, forming a thrusted horst. Oblique transverse faults also cut the structure.

By studying the patterns of cumulative production and lost circulation, it was possible to derive relationships between the accumulations of oil and the faulting and conceptual patterns of related fracturing in the different types of reservoir rocks. The study indicates that one can prognosticate the more prospective drilling locations on this or similar structures involving basement and limestone. It is felt that this information may be applicable to other plays in other regions.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.