Tectonic Setting and Characteristics of Natural Fractures in Mesaverde and Dakota Reservoirs of the San Juan Basin, New Mexico and Colorado

Abstract

A set of vertical extension fractures, striking N-S to NNE-SSW but with local variations, is present in both the outcrop and subsurface in both Mesaverde and Dakota sandstones. Additional sets of conjugate shear fractures have been recognized in outcrops of Dakota strata and may be present in the subsurface. However, the deformation bands prevalent locally in outcrops in parts of the basin as yet have no documented subsurface equivalent. The immature Mesaverde sandstones typically contain relatively long, irregular extension fractures, whereas the quartzitic Dakota sandstones contain short, sub-parallel, closely spaced, extension fractures, and locally conjugate shear planes as well. Outcrops typically display secondary cross fractures which are rare in the subsurface, although oblique fractures associated with local structures such as the Hogback monocline may be present in similar subsurface structures.Spacings of the bed-normal extension fractures are approximately equal to or less than the thicknesses of the beds in which they formed, in both outcrop and subsurface. Fracture intensities increase in association with faults, where there is a gradation from intense fracturing into fault breccia. Bioturbation and minimal cementation locally inhibited fracture development in both formations, and the vertical limits of fracture growth are typically at bedding/lithology contrasts. Fracture mineralizations have been largely dissolved or replaced in outcrops, but local examples of preserved mineralization show that the quartz and calcite common to subsurface fractures were originally present in outcrop fractures.North-south trending compressive stresses created by southward indentation of the San Juan dome area (where Precambrian rocks are exposed at an elevation of 14,000 ft) and northward indentation of the Zuni uplift, controlled Laramide-age fracturing. Contemporaneous right-lateral transpressive wrench motion due to northeastward translation of the basin was both concentrated at the basin margins (Nacimiento uplift and Hogback monocline on east and west edges respectively) and distributed across the strata depth.

Combining power plant water needs and carbon dioxide storage using saline formations: Implications for carbon dioxide and water management policies

“…In all three cases, the layered sequences are discretized into grids for use with the TOUGH2 reservoir simulator. For purposes of the feasibility study presented here, all three cases examine a two-dimensional north-south oriented simulation domain consistent with the regional structural trend of extension fractures in this portion of the San Juan Basin (Lorenz and Cooper, 2003) and thus the trend of highest hydraulic conductivity.…”

Modes of Shale‐Gas Enrichment Controlled by Tectonic Evolution

“…Regional black Lewis shales were deposited by large-scale transgression during the Cretaceous and Laramie tectonic movement in the Late Cretaceous, which formed the current tectonic structures. The San Juan Basin is 241 km long in the north-to-south direction, 161 km wide, and covers an area of 2849 km 2 (Peterson et al, 1968;Curtis, 2002;Lorenz et al, 2003).…”

“…These two fracture groups are present not only in the Lewis shale, but also in its surrounding sandstone reservoirs. Consequently, they provide excellent channels for the supply of hydrocarbon substances from the Lewis shales to the adjacent sandstone oil and gas reservoirs (Laubach, 992;Hill and Nelson, 2000;Lorenz et al, 2003).…”

Geochemical evidence of groundwater flow paths and the fate and transport of constituents of concern in the alluvial aquifer at Fort Wingate Depot Activity, New Mexico, 2009

“…1) (Cather, 2003(Cather, , 2004. The Zuni uplift is a northwest-striking, asymmetric uplift (Lorenz and Cooper, 2001). The uplift gently tilted the bedrock underlying the majority of the Depot to the northwest at an angle of approximately 5 degrees from horizontal (Lorenz and Cooper, 2001); subsequent erosion has exhumed the various Triassic sedimentary layers that are visible across the surface of the Depot (fig.…”