Abstract: Geological Interpretation and Reservoir Geometry of Submarine Fan and Channel Deposits

Lambertini, Roberto; Pedro Ivo De Assis; Steven M. Hansen and Roy Nurmi - Schlumberger

Structural interpretation and high-resolution sequence analysis of offshore deep water deposits encountered by drilling are optimally and cost-effectively done using borehole imagery on a geological workstation. Precise geometrical analysis of depositional facies, erosional channels and sedimentary structures as well as tectonic features is critical in assessing both wildcats and development wells. This assessment usually includes fault characteristics slumping and channel orientations that are extrapolated three dimensionally by integration with the seismic data on a workstation. Borehole imagery, including electrical, a variety of acoustic imagery techniques and new density/lithology imagery, is routinely providing new insights into reservoir geometry. In addition, recent breakthroughs in sonic imaging allows geometrical definition of features away from the borehole which is invaluable for assessing attic oil left behind because of faulting and/or erosional channels.

Detailed reservoir bedding characteristics has been found to be a function of the processes forming modem submarine fans, (i.e. such as bed thickness variations in the Amazon fan. In addition, other, high-resolution data can be used to improve the geological interpretation of borehole imagery, as does an integration of nuclear magnetic resonance data, which helps to define reservoir texture, the presence of authigenic clays and permeability profiles. Early testing of imagery logging and coring in Brazil revealed that some of the offshore submarine channel, turbidite and fan reservoirs are texturally complex and include coarse-grained facies. These data are compared to detailed studies which include outcrop, seismic, borehole imagery, core, pressure and production data from similar complex reservoirs in other parts of the world.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil