Abstract: Impact of Paradigms on Performance Predictions and Development Strategies for the Fractured Monterey Reservoirs of the Santa Ynez Unit, Santa Barbara Channel, California

LOHMAR, JOHN M., and JON R. SCHWALBACH, Exxon Company USA, Thousand Oaks, California

Development of the fractured Monterey Chert reservoirs in Exxon's Santa Ynez Unit project in the Santa Barbara Channel was guided for more than a decade by paradigms about what fractured reservoirs should look like and how they should perform. These paradigms had a significant impact on performance predictions and early development strategies. They have been overcome only by collecting extensive data, applying new technology and, most importantly, by using new ways of thinking.

Predevelopment performance predictions were based on a paradigm that a typical fractured reservoir should have a fracture porosity of no more than a few tenths of a per cent and should produce by solution gas drive and gas cap expansion and pressure deplete rapidly. Actual fracture porosity at SYU is much higher than expected, and there is ample pressure support from a strong water drive.

Early development strategies were greatly influenced by a paradigm that poorly connected fracture networks required close well spacing and that performance would be enhanced in wells drilled at high hole angles perpendicular to the fracture orientation. The Monterey fracture network is actually extremely well connected, due to the close spacing of fractures in the brittle cherts, and close well spacing is not needed to adequately drain the reservoir. The fracture network provides pathways for essentially radial flow over long distances through the reservoir, minimizing the benefit of drilling at high hole angles perpendicular to the fractures.

AAPG Search and Discovery Article #90935©1998 AAPG Pacific Section Meeting, Ventura, California