--> Abstract: Characterization of Fracture Networks Applied to Optimize Well Tracks in Deep Cretaceous Reservoirs of Lake Maracaibo, Venezuela, by R. C. M. W. Franssen, V. C. Vahrenkamp, E. W. J. E. Van De Graaff, and P. J. Munoz; #91004 (1991)

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Characterization of Fracture Networks Applied to Optimize Well Tracks in Deep Cretaceous Reservoirs of Lake Maracaibo, Venezuela

FRANSSEN, RAYMOND C. M. W., VOLKER C. VAHRENKAMP, KSEPL, Rijswijk, The Netherlands, EVERET W. J. E. VAN DE GRAAFF, Shell Expro, Aberdeen, U.K., and PEDRO J. MUNOZ, Maraven S.A., Caracas, Venezuela

Cretaceous Cogollo Group carbonates in the Lake Maracaibo basin, Venezuela produce mainly from fractures. Any improvement in production rate requires an effective assessment of the open fractures. This has been done using two paleomagnetically oriented cores from Lake Block IX (Central Lake Maracaibo). Wells SVS-225 and SVS-229 respectively represent the west and east flank of a structure defined by the left-lateral Icotea fault. Open fractures on both sides of the Icotea fault are subvertical. In the west flank the open fractures trend WSW-ENE and in the east flank the trend is WNW-ESE. For maximum rates of open fracture intersection the optimum well tracks are towards azimuth 330 degrees and deviation 60 degrees in the west flank and towards azimuth 030 degrees and deviation 60 degr es in the east flank. The open fracture networks consist of incompletely cemented or leached fractures which contain a "channel and island" structure of interconnected porosity. This "channel and island" structure of the open fractures, in combination with the high rock matrix strength and the subparallel E-W trend of the present-day maximum horizontal stress indicate that it is unlikely that the individual fracture conductivity is reduced drastically upon depletion. The structural model established for wells SVS-225 and SVS-229 is consistent with data obtained from wells VLA-711 and VLA-722 in the west flank of Block I, some 40 km to the north. This indicates that the reservoir model has regional validity and that the well track recommendation of azimuth 330 degrees should also apply to the west flank of Lake Block I.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)