Influence of fluid pressure changes on the reactivation potential of pre-existing fractures: a case study in the Archaean metavolcanics of the Chitradurga region, India

Abstract

The metavolcanics of Chitradurga region host numerous shallow crustal veins and fractures and faults of multiple orientations. Several high and low Pf cycles have been recorded in the region, leading to the reactivation of most of the pre-existing fractures for high Pf and selective reactivation of some well-oriented fractures under low Pf conditions. The pre-existing anisotropy (magnetic fabric) in the metavolcanics acted as the most prominent planar fabric for fracture propagation and vein emplacement under both conditions, thereby attaining maximum vein thickness. In this study, we emphasize the reactivation propensity of these pre-existing fracture planes under conditions of fluid pressure variation, related to the high and low Pf cycles. Multiple cycles of fluid-induced fracture reactivation make it difficult to quantify the maximum/minimum fluid pressure magnitudes. However, in this study we use the most appropriate fluid pressure magnitudes mathematically feasible for a shallow crustal depth of ∼2.4 km. We determine the changes in the reactivation potential with states of stress for the respective fracture orientations under both high and low Pf conditions. Dependence of fluid pressure variation on the opening angle of the fractures is also monitored. Finally, we comment on the failure mode and deformation behaviour of the fractures within the prevailing stress field inducing volumetric changes at the time of deformation. We find that deformation behaviour is directly related to the dip of the fracture planes.

How do fault systems and seafloor bathymetry influence the structure and distribution characteristics of gas chimneys?

“…Fluid fill has significant impact on the reactivation and evolution of fracture networks (Bhowmick & Mondal, 2021). In the study area, hydrocarbon fluids originate predominantly from source rocks within the Oligocene Wenchang and Enping formations (i.e.…”

“…Additional fluid injection/filling would increase the fluid‐flux volumes and corresponding system pressure within the fracture networks (Brown, 2000; Paganoni et al, 2018). Cracks/fractures within a chimney may continue to open and scale up as a result (Bhowmick & Mondal, 2022; Gaffney et al, 2007; Ho et al, 2018). Isolated fractures also become interconnected to form fracture networks on a larger scale (Dichiarante et al, 2020; Gudmundsson, 2012).…”

Stress states during the emplacement of the eastern Rio Ceará-Mirim dike swarm, Borborema Province, northeastern Brazil

“…The warm zones consistent for high dilation tendency (Td = 0.8-1.0) values in part overlap the warm zones for high slip tendency values (Ts = 0.8-1.0). Dikes' pole data within the warm zone consistent with high dilation and moderately high slip tendency will certainly encounter high fracture susceptibility (Figure 11d) (Bhowmick and Mondal 2021). Notably, the dikes' poles clusters are majorly located in zones of high dilatation, suggesting a greater participation of normal dilatation rather than strike-slip as observed in the morphological analyses.…”

“…We considered morphological patterns presented and/or discussed by Nicholson and Pollard (1985), Pollard (1987), Rickwood (1990), Hoek (1991), Rubin (1995), Correa-Gomes et al (2001), Ernst and Buchan (2001), Clemente et al (2007), Ghodke et al (2018) and Magee et al (2019). Mechanical models were performed according to Jolly and Sanderson's (1997) method and integrated with dilation tendency, slip tendency, and fracture susceptibility (Morris et al 1996;Ferrill et al 1999;Mildren et al 2002;Stephens et al 2018;Bhowmick and Mondal 2021).…”

“…While a high dilation tendency presumes reactivation through normal dilation, a high slip tendency indicates opening through simple shear. Fracture susceptibility (Sf) represents the potential planes that can lead to fluid-induced reactivation in a particular stress condition (Mildren et al 2002;Stephens et al 2018;Bhowmick and Mondal 2021).…”