Characterization of complex fluvial architecture through outcrop studies – dealing with intrinsic data bias at multiple scales in the pursuit of a representative geomodel

• DOI: 10.35767/gscpgbull.67.4.231
• Publication Date: 2019-12-01
• Authors: Samuel M. Hudson; Scott R. Meek; Blake J. Steeves; Austin Bertoch; Chelsea Jolley; April Anahi Trevino; Jason Klimek
• Keywords: Outcrop; Characterization

Abstract The practice of building analog models and training images from outcrop exposures is an important tool in better predicting subsurface facies distribution the petroleum industry. As with data, however, incomplete information data bias can lead to inaccurate characterization geology at multiple scales. Cretaceous fluvial strata Wyoming offers excellent exposure two systems — sand-rich highly amalgamated Trail Member Ericson Sandstone sand-poor, isolated channels Dry Hollow Frontier Formation. For each system, outcrops were characterized through traditional means stratigraphic column measurement, as well photogrammetric survey acquisition interpretation. We saw both studies that, despite effort measure sections that representative entire outcrop, measured consistently overestimated reservoir proportions. Ten within show a Net-to-Gross (NTG) ranging 50–80% sandstone, average 72%. A more complete spatial interpretation suggests much lower NTG 53%. Similarly, for strata, ranges 8–50% 37% while model shows only 16%. These differences are significant very different models. Further, assumption commonly made if characterized, formation larger scale. Models Cumberland Gap this tenuous not system. Outcrops sparse often discontinuous, extrapolation calculated proportions between well-exposed led placement sands outcrops, where lack leads control model. This resulted increased connectivity even on sub-kilometer scale, detailed, quantitative be inappropriate, done blindly Through detailed systems, it shown geomodels exposures, using modern techniques such analysis, subject mischaracterization scales reasons care taken.