--> Role of Sedimentological Modelling in the Success of Horizontal Drilling, C-7 Reservoir, Block I, Maracaibo Basin, Venezuela, by E. Sampson, B. C. Cortiula, and F. Escorcia; #90986 (1994).

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Abstract: Role of Sedimentological Modelling in the Success of Horizontal Drilling, C-7 Reservoir, Block I, Maracaibo Basin, Venezuela

Elizabeth Sampson, Bice C. Cortiula, Florangel Escorcia

A detailed sedimentological and petrophysical study was accomplished in the C-7 reservoir, area VLA-8, Block I, El Pilar, to evaluate the viability of horizontal drilling to recover bypassed oil. The objective of the study was to establish the orientation, distribution and physical quality of the sand bodies within the C-7 reservoir that could be exploited using horizontal technologies. Sedimentological facies description of 450 ft of cored interval resulted in the identification of seven different lithofacies. Based on facies associations and the nature of contacts, seven sedimentary units (I to VII) were recognized. Integration of sedimentological and petrophysical data were used to identify the prospective sedimentary unit (unit VII). These sedimentary units consist of sands, shale and coals deposited in upper to lower delta plain environments. The top C-7, which is composed of an heterolithic interval with a 4-ft

thick carbonaceous-rich bed at the top, represents an excellent marker in the study area.

The integration of fine-scale, sedimentologically-based correlations and combined with a petrophysical evaluation of the sedimentary unit VII, permitted the establishment of the location, orientation and direction of the horizontal drilling to ensure the optimal recovery of the remaining oil.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994