Fracture porosity creation and persistence in a basement-involved Laramide fold, Upper Cretaceous Frontier Formation, Green River Basin, USA

Abstract

-Fracture-hosted porosity and quartz distribution along with crack-seal texture and fluid inclusion assemblage sequences in isolated, bridging quartz deposits show that open fractures can persist through protracted burial and uplift in foreland basins. Fractures oriented at a high angle to current maximum compressive stress remain open and were weak mechanical discontinuities for millions of years even at great depth. Upper Cretaceous Frontier Formation sandstones in the basementinvolved (Laramide) Table Rock anticline, eastern Greater Green River Basin, Wyoming sampled by two horizontal wells (cut parallel or nearly parallel to bedding and at a high angle to steeply dipping fractures) have 41.5 m of rock in four cores at depths of 4538-4547 m. Cores intersect older E-striking Set 1 fractures are abutted by or locally cross-cut by N-striking Set 2 fractures. Both sets contain quartz and porosity. Sequenced using quartz crack-seal cement texture maps, Set 1 fluid inclusion assemblage (FIA) trapping temperatures increase progressively from 140 to 165°C then decrease to c. 150°C, compatible with fracture opening over c. 15 Ma during rapid burial followed by uplift in Eocene-Oligocene time. Set 2 opened at c. 160°C, probably near maximum burial. After a period of quiescence, Set 2 reopened at c. 5 Ma at c. 140°C, on a cooling trajectory. Intermittent Set 2 movement could reflect local basement-involved fault movement, followed after a pause by further Set 2 reactivation in the modern stress field during uplift. Interpretations are sensitive to available burial/thermal histories, which have considerable uncertainty.

The Role of Chemistry in Fracture Pattern Development and Opportunities to Advance Interpretations of Geological Materials

“…Panchromatic cathodoluminescence (CL) and color CL partly transparent overlay image. Banding within bridge that parallels fracture walls are gap deposits similar to those shown at higher resolution in Laubach et al (). A, ankerite; P, porosity; G, grain; Gd, gap quartz deposits; Lq, lateral quartz deposits; R, rind deposit.…”

“…With the advent of horizontal coring and logging, valuable, albeit rare, information is emerging about fracture population statistics and spatial arrangement (e.g., Hooker et al, ; Li et al, ; Lorenz & Hill, ). These data show that fracture orientations, sizes, spatial arrangement patterns, and degree of cement fill vary considerably (Hooker et al, ; Laubach et al, ). These observations are compatible with fracture patterns that vary markedly, in some cases over short distances (approximately meters to tens of meters).…”

“…(a) East Texas, Becker et al (). (b) Northern Piceance Basin, after Fall et al (); (c) Southern Piceance Basin; Fall et al (); (d) Green River Basin, Laubach et al (); (e) Mexico, Hooker et al (). Curves show burial history of various units (primarily Mesozoic sandstones); gray and black bars on curves mark durations of fracture growth from reconstructed fluid inclusion assemblage trapping temperatures sequenced by crack seal texture reconstruction.…”

“…Modified from Anders et al (). (g) Cretaceous sandstone, core depth 6,200 m, Wyoming, after Laubach et al (). (h–k) Quartz bridge with crack seal texture, East Texas core.…”

Predictability of properties of a fractured geothermal reservoir: the opportunities and limitations of an outcrop analogue study

“…It has been shown, for example, by Barton et al (1995) and Rogers (2003) that such fractures can constitute preferable pathways for fluid flow. Noteworthy, also fracture sets normal to the maximum compressive stress were reported by Laubach et al (2016) to provide high permeabilities over long time spans.…”