Abstract: An Evaluation of Outcrop Analog Development Techniques for Deep Water Sandstone Reservoirs

Coleman, J. L., Jr. - Amoco; Browne, G. H. - New Zealand Institute of Geological and Nuclear Sciences, Ltd.; Clemenceau, G. R. - Amoco; Slatt; R. M.; Spang, R. J.; Williams, E. T. - Colorado School of Mines; King, P. R. - New Zealand Institute of Geological and Nuclear Sciences, Ltd.

Pre-development assessment of deep water sandstone reservoirs relies on 3-D seismic imaging of reflective reservoir intervals, sparse drilling and testing data, and application of pseudo-reservoir parameters from outcrop analogs. In order to understand better the potential for incorporating outcrop information into computerized fluid flow simulations of levee - overbank sand reservoirs in the Miocene of the Gulf of Mexico, data from Miocene turbidite channel - levee - overbank facies, in large coastal exposures along the New Zealand Taranaki Coast, were collected.

In comparison, the upper and middle Miocene of the Viosca Knoll/Mississippi Canyon area is an overall prograding passive margin submarine fan complex deposited within an active salt dome basin; whereas, the upper Miocene of the Taranaki Basin of New Zealand is an overall prograding, deep water sedimentary system within an active, submarine volcano-punctuated, basin margin.

Detailed sampling and photomosaicing of sea cliff exposures were combined with 190 meters of continuous core and wireline logs and a one kilometer high resolution reflection seismic profile to attempt to mimic a conventional GOM deep water reservoir interval data set. The results of this study indicate that a higher degree of complexity exists within the channel-levee complex than can be imaged with conventional seismic programs or imaging logs. Conventional CDP seismic with a typical frequency content in the 50 - 60 Hz range, and GOM interval velocities, will not reveal small-scale bed boundary changes. Simplified reservoir models derived from isochron thickness and well log correlations can lead to an inadequate reservoir model which might seriously misestimate reservoir flow performance. Depending on formation contrasts, imaging logs may or may not reflect clearly the true lithologies and surfaces (as compared to core analysis). The outcrop study reemphasizes the paradigm that all collected data must be integrated into a coherent data set, before that set is applied to the appropriate subsurface situation.

Outcrop-based, high resolution data reveal the variable degrees of heterogeneity of potential channel - levee - overbank reservoirs. Many GOM reservoirs scheduled for appraisal drilling and development occur in this depositional environment. While direct application of outcrop geometries and pseudo-reservoir parameters should not be attempted, the overall style and characteristics of outcrop analogs can be used to develop appropriate field management procedures.

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