Application of Turbidite Facies of the Stevens Oil Zone for Reservoir Management, Elk Hills Field, California
S. A. Reid, Terry W. Thompson, and George S. McJannet
A detailed depositional model for the uppermost sand reservoirs of the Stevens Oil Zone, Elk Hills Field, California, contains three fades: turbidite channel-fill sand bodies, overbank sandstone and mudstone, and pelagic and hemipelagic siliceous shale. Sand bodies are the primary producing fades and consist of layered, graded sandstone with good permeability. The presence of incipient anticlines with subsea relief in the late Miocene resulted in deposition of lenticular and sinuous sand bodies within structurally created channels. Relief of these structural channels was low when the earliest sand bodies were deposited, leading to a wide channel complex bounded by broad overbank deposits of moderate to low permeability. As deposition proceeded, increased structural relief constrained the channels, resulting in narrower sand body width and relatively abrupt channel terminations against very low permeability siliceous shale. With post-Miocene uplift and differential compaction, stratigraphic mounding of sand bodies helped create structural domes such as the 24Z reservoir. Stratigraphic traps including the 26R reservoir were also created. Such traps vary in seal quality from very effective to leaky, depending on the lateral transition from sand bodies to siliceous shale.
Application of the Elk Hills turbidite model (1) provides a framework for monitoring production performance in the 24Z and Northwest Stevens waterflood projects and for tracking gas migration into and out of the 26R reservoir, (2) helps to identify undeveloped locations in the 26R reservoir ideally suited for horizontal wells, (3) has led to the identification of two new production trends in the 29R area, and (4) makes possible the development of exploration plays in western Elk Hills.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California