Fault and fracture distribution within a tight-gas sandstone reservoir: Mesaverde Group, Mamm Creek Field, Piceance Basin, Colorado, USA

Abstract

The distribution and orientation of faults, fracture intensity and seismic-reflection characteristics of the Mesaverde Group (Williams Fork and Iles formations) at Mamm Creek Field vary stratigraphically, and with lithology and depositional setting. For the Mesaverde Group, the occurrence of faults and natural fractures is important as they provide conduits for gas migration, and enhance the permeability and productivity of the tight-gas sandstones. The Upper Cretaceous Mesaverde Group represents fluvial, alluvial-plain, coastal-plain and shallow-marine depositional environments. Structural interpretations based on three-dimensional (3D) seismic-amplitude data, ant-track (algorithm that enhances seismic discontinuities) seismic attributes and curvature attributes are utilized jointly to understand the complex fault characteristics of the Williams Fork Formation. This study reveals that the lowermost lower Williams Fork Formation is characterized by NNW- and east–west-trending small-scale thrust and normal faults. Study suggests that the uppermost lower Williams Fork Formation, and the middle and upper Williams Fork formations, exhibit NNE- and east–west-trending arrays of fault splays that terminate upwards and do not appear to displace the upper Williams Fork Formation. In the uppermost Williams Fork Formation and Ohio Creek Member, NNE-trending discontinuities are displaced by east–west-trending events and the east–west-trending events dominate. Fracture analysis, based on borehole-image logs, together with ant-track and attenuation-related seismic attributes, illustrates the spatial variability of fracture intensity and lithological controls on fracture distribution. In general, higher fracture intensity occurs within the southern, southwestern and western portions of the field, and fracture intensity is greater within the fluvial sandstone deposits of the middle and upper Williams Fork formations. More than 90% of natural fractures occur in sandstones and siltstones. In situ stress analysis, based on induced-tensile fractures and borehole breakouts, indicates a NNW orientation of present-day maximum horizontal stress ( S H max ), an approximate 20° rotation (in a clockwise direction) in the orientation of S H max with depth and an abrupt stress shift below the Williams Fork Formation within the Rollins Sandstone Member.

Natural hydraulic fracturing of tight-gas sandstone reservoirs, Piceance Basin, Colorado

“…The sandstones of the Mesaverde Group contain subvertical natural opening-mode fractures (Pitman and Sprunt, 1987;Lorenz, 2003;Cumella and Scheevel, 2008;Hooker et al, 2009;Fall et al, 2012). The predominant strike of the fractures is WNW-ESE, locally changing to E-W in the western part of the basin (Pitman and Sprunt, 1987;Lorenz and Finley, 1991;Cumella and Scheevel, 2008;Lorenz, 2003;Baytok and Pranter, 2013). The fractures are confi ned to the sandstone layers, and do not cross the sand-shale contacts (Pitman and Sprunt, 1987;Cumella and Scheevel, 2003;Lorenz, 2003).…”

Conventionally trapped natural gas accumulations in the Jurassic tight sandstone reservoirs: A case study from the Center of the Western Sichuan Basin, SW China

“…Faults can act as conduits and efficient pathways for hydrocarbon migration (Aydin, 2000; Boles et al., 2004; Zhang et al., 2011). Many faults have been found in tight-gas reservoirs, and their distribution, forming mechanism, as well as their control on gas migration and accumulation have been characterized and discussed (Baytok and Pranter, 2013; Fall et al., 2012; Olson et al., 2009; Robert and Suzanne, 2004; Shanley et al., 2004). Faults, identified by seismic interpretation, are mainly developed in the eastern and northeastern Majing area, while few are present in the Shifang area.…”

Seepage Behavior of Fractures in Paleogene Sandstone Reservoirs in Nanpu Sag, Bohai Bay Basin, Eastern China

“…Fractures govern well patterns in low-permeability oilfields through controlling the seepage system (Tamagawa and Pollard, 2008;Laubach et al, 2018). Fracture permeability varies as a function of fracture density, filling degree, and current in-situ stress (Baytok and Pranter, 2013;Gong et al, 2019b;Wang Z. et al, 2020). The NE-SW strike fractures in the study area are characterized by their high density, large aperture, being weaklyfilled, and approximately parallel to the regional maximum horizontal principal stress (Connolly and Cosgrove, 1999).…”