Hydraulic effects of shales in fluvial-deltaic deposits: Ground-penetrating radar, outcrop observations, geostatistics, and three-dimensional flow modeling for the Ferron Sandstone, Utah

• Published in: Mathematical geology Vol. 34; no. 7; pp. 857 - 893
• Main Authors: NOVAKOVIC, Djuro, WHITE, Christopher D, CORBEANU, Rucsandra M, HAMMON, William S, BHATTACHARYA, Janok P, MCMECHAN, George A
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01.10.2002; Springer Nature B.V
• Subjects: Anisotropy; Boreholes; Cretaceous; Earth sciences; Earth, ocean, space; Exact sciences and technology; Flow; Hydrocarbons; Permeability; Radar; Sandstone; Sedimentary rocks; Shales; Simulation; Stone; Stratigraphy; Variance analysis; United States; Utah; USA, Utah; reservoir rocks; Mesozoic; conditional simulation; anisotropy; permeability; variograms; digital simulation; North America; sandstone; drill cores; boreholes; reservoir simulation; hydraulics; stochastic models; reservoir analog; experimental design; clastic rocks; high resolution; geostatistics; shale; outcrops; maps; Cretaceous; ground-penetrating radar; sedimentary rocks; fluvial environment; interpretation; semivariograms; three-dimensional models; distributary channel; Phanerozoic; petroleum exploration; deltaic environment
• ISSN: 0882-8121; 1874-8961; 1573-8868; 1874-8953
• DOI: 10.1023/A:1020980711937

Ground-penetrating radar (GPR) surveys, outcrop measurements, and cores provide a high-resolution 3D geologic model to investigate the hydraulic effects of shales in marine-influenced lower delta-plain distributary channel deposits within the Cretaceous-age Ferron Sandstone at Corbula Gulch in central Utah, USA. Shale statistics are computed from outcrop observations. Although slight anisotropy was observed in mean length and variogram ranges parallel and perpendicular to paleoflow, the anisotropy is not statistically significant and the estimated mean length is 5.4 m. Truncated Gaussian simulation was used to create maps of shales that are placed on variably dipping stratigraphic surfaces interpreted from high-resolution 3D GPR surveys, outcrop interpretations, and boreholes. Sandstone permeability is estimated from radar responses calibrated to permeability measurements from core samples. Experimentally designed flow simulations examine the effects of variogram range, shale coverage fraction, and trends in shale coverage on predicted upscaled permeability, breakthrough time, and sweep efficiency. Approximately 1500 flow simulations examine three different geologic models, flow in the 3 coordinate directions, 16 geostatistical parameter combinations, and 10 realizations for each model. ANOVA and response models computed from the flow simulations demonstrate that shales decrease sweep, recovery, and permeability, especially in the vertical direction. The effect on horizontal flow is smaller. Flow predictions for ideal tracer displacements at Corbula Gulch are sensitive to shale-coverage fraction, but are relatively insensitive to twofold variations in variogram range or to vertical trends in shale coverage. Although the hydraulic effects of shale are statistically significant, the changes in flow responses rarely exceed 20%. As a result, it may be reasonable to use simple models when incorporating analogous shales into models of reservoirs or aquifers.