CABRERA DE CASAS, LEYLA, and FERNANDO CHACARTEGUI, Maraven S.A., Caracas, Venezuela

ABSTRACT: Sedimentology and Diagenesis of Misoa C-2 Reservoir, VLE-305/326 Area, Block V, Lamar Field, Maracaibo Lake, Venezuela

The main purpose of this study was to characterize the Upper Eocene C-2 reservoir using sedimentological, petrophysical and biostratigraphic parameters. The reservoir quality was evaluated by defining its physical attributes, geometry, areal distribution and orientation, from facies analysis of sedimentary units identified in core samples. In evaluating the sedimentary features of the Misoa C-2 reservoir in VLE 305/326 area, Block V, Lamar Field, Maracaibo Lake, 2,000' of cores from five wells (named VLE-339, VLE-720, VLE-723, VLE-754 and LPG-1211) were analyzed. The sedimentary sequence studied represents upper-middle deltaic plain deposits, with no marine influence. These deposits were identified as interdistributary channels, crevasse splays and interdistributary bays deposited in northward prograding system. Seven sedimentary facies were defined from the physical, chemical and biological features observed in the cores. These facies were petrophysically and petrographically characterized then grouped in six sedimentary units which were then correlated over the entire area. One hundred well logs were correlated using sedimentological criteria. Finally, four flow units were identified in the reservoir, using the sedimentological parameters, petrophysical data and production behavior. A surface trend analysis program utilizing thickness values resulted in contours, trends, residuals and isometry maps of each unit with a generalized southwest-northeast trend orientation. It was determined that facies distribution in the units controls the reservoir quality. These res lts are the main input into reservoir simulation. An accurate reservoir modeling is needed to prepare for optimizing secondary oil recovery.

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