The Inter-Relationships of Scale of Heterogeneity in Subsurface, Deep Water E&P Projects: Lessons Learned from the Mt. Messenger Formation (Miocene), Taranaki Basin, New Zealand

Coleman, Jr., J.R., BP-Amoco Upstream Technology Group; G.H. Browne, New Zealand Institute of Geological and Nuclear Sciences, Ltd.; R.M. Slatt,, Colorado School of Mines; R.J. Spang,, Colorado School of Mines, (now at Texaco, Inc.); E.T. Williams, Colorado School of Mines (now at Williams Petroleum Consulting); P.R. King, New Zealand Institute of Geological and Nuclear Sciences, Ltd.; and G.R. Clemenceau, BP-Amoco Gulf of Mexico Deepwater Development and Production Group

Abstract

Sea cliff exposures, conventional and high resolution seismic profiles, conventional oil and gas field boreholes, and shallow behind-outcrop core holes along the west coast of the Taranaki Basin, North Island, New Zealand, afford an excellent opportunity to examine the inter-relationships of scales of heterogeneity within slope channel-levee-overbank and toe-of-slope deep water sediments. Here, the Taranaki sea cliffs, are nearly 200 m high and exhibit over 40 km of continuous exposure. Across the spectrum from seismic profile to microscopic and instrumental analysis, there are detectable features which affect reservoir heterogeneity that range across 11 orders of magnitude in size from 105 m to 10-6 m.

In using the exposures along the Taranaki Coast, it is possible to assess the extent and detectability of the various orders of heterogeneity and to estimate their effects on analogous intervals in the subsurface. Bed/bed-set heterogeneity ratios (vertical change divided by horizontal change, in meters), as detected by the tools mentioned above, cluster in two domains. Because of their limited radius of investigation, borehole logs have ratios between 1 and 10, whereas outcrop, seismic, and log profiles , which are based on a horizontal arrangement of data, have ratios between 10-2 to 10-3. Because of their limitations and strengths, each of the tools sees a different scale of heterogeneity.

Estimates of reservoir heterogeneity can be improved by the application of data sets, such as the Taranaki cliffs section, by imputing the degrees and variations in outcrop heterogeneity into the subsurface model.