Predicting and characterizing fractures in dolostone reservoirs: using the link between diagenesis and fracturing

Abstract

Fracture geometries and fracture-sealing characteristics in dolostones reflect interactions among mechanical and chemical processes integrated over geological timescales. The mechanics of subcritical fracture growth results in fracture sets having power-law size distributions where the attributes of large, open fractures that affect reservoir flow behaviour can be accurately inferred from observations of cement-sealed microfractures and other microscopic diagenetic features, which are widespread in dolostones. Fracture porosity is governed by the competing rates of fracture opening and cement precipitation during fracture growth and by cements that post-date fracture opening.Combined analysis of structural and diagenetic features provides the best approach for understanding how fracture systems influence fluid flow.

Effects of sedimentary interfaces on fracture pattern, linkage, and cluster formation in peritidal carbonate rocks

“…Whether or not fractured carbonate reservoir rocks are permeable depends largely on the fracture connectivity, namely how and to what degree fractures link up to form a continuous network (Aguilera, 1995;Nelson, 2001;Zhang and Sanderson, 2002;Lonergan et al, 2007). Fractured carbonate reservoirs are seldom homogeneous, and the development of a network of fluid-transmitting fractures is controlled by the local stresses, mechanical properties, and layering of the various lithotypes, as well as their spatial distribution (Helgesen and Aydin, 1991;Gillespie et al, 2001;Rijken and Cooke, 2001;Stowell, 2001;Gale et al, 2004;Larsen et al, 2010).…”

Reservoir quality, textural evolution, and origin of fault-associated dolomites

“…Fault-associated dolomites are of considerable interest because (1) they may be sites of hydrocarbon accumulation or mineralization ( Warren, 2000;Smith and Davies, 2006), and (2) their origins are commonly controversial or poorly understood (Machel, 2004). Despite this interest, extensive dolomitization associated with faulting has only been detailed from a few localities, including North America (Duggan et al, 2001;Gale et al, 2005;Green and Mountjoy, 2005;Davies and Smith, 2006) and Italy (Antonellini and Mollema, 2000). Field studies have characterized the link between brittle deformation and/or dolomite recrystallization during fracturing (Newman and Mitra, 1994;Grimmer et al, 2000;Tarasewicz et al, 2005), highlighting the intimate relationship between multiple phases of fracturing and dolomitization (Mountjoy and Halim-Dihardja, 1991;Newman and Mitra, 1994;Duggan et al, 2001).…”

Comparison of digital outcrop and conventional data collection approaches for the characterization of naturally fractured reservoir analogues

“…Koestler & Ehrmann 1991;Odling et al 1999;Gale et al 2004;Sharp et al 2006), conventional methods of fracture characterization at outcrop scale suffer manifest deficiencies, with direct sampling of the rock face (i.e. via cell mapping/scanline surveys) biased, inefficient and subject to edge effects , and with fracture mapping from 2D photo-images resulting in poorly resolved datasets (especially with regards to orientation: e.g.…”