Oxidative Kerogen Degradation: A Potential Approach to Hydraulic Fracturing in Unconventionals

Abstract

Oil and gas production from shale formations has proven to be economical because of advances in hydraulic fracturing but remains very challenging in part because of the presence of the ductile, polymer nature of the hydrocarbon source material, kerogen. This organic matter is intertwined among silicates, aluminosilicates, and other minerals as fine laminae that weave among the shale rock fabric, adding soft mechanical cohesion to the material. A potential solution has been developed, a new type of reactive fracturing fluid composed of strong oxidizers such as bromate (BrO3 –), which could mitigate the adverse effects of the polymeric nature of kerogen on the hydraulic conductivity of the fractured shale formation. High-resolution scanning electron microscopy of kerogen-rich shale samples before and after fluid treatment demonstrates notable porosity enhancement evident by cracks forming in the macerals and augmenting the volumetric porosity. The stability of the reactive components at elevated reservoir temperatures in addition to the demonstrated results suggest the potential for measureable improvements in hydraulic conductivity and hence in the ultimate recovery of oil and gas from future hydraulic fracturing operations.

Effects of Carbonate Minerals on Shale-Hydraulic Fracturing Fluid Interactions in the Marcellus Shale

“…It is likely that the oxidation reactions with organics led to the binding of the sulfur species with shale organic matter. Evidence of sulfur uptake by organic matter in shale-HFF reactions has been reported previously, particularly during kerogen oxidation (Yan et al, 2013;Hull et al, 2019). It is also possible that some of the sulfur reacted with BTEX compounds or the oxidized products of BTEX compounds.…”

Reactive force fields for modeling oxidative degradation of organic matter in geological formations

“…Oxidizing agents composed of oxyhalides such as bromate BrO 3 À and chlorate ClO 3 À are effective in breaking down shale's organic matter under reservoir temperatures. 9 To further identify and develop oxidizers for various organic matter treatment, at depth, the earlier studies had to be generalized and optimized. In this work, we concentrate on oxychlorine ClO n À oxidizers as a class of effective oxidizing reagents to elucidate the oxidative degradation pathways likely to lead to organic matter cleavage, porosity enhancement, and increase in organic surface area.…”

“…Chemical treatment of the polymeric properties of kerogen while taking into account its nanoscale porosities and ultra-low permeability, will introduce open flow channels, increase its permeability and eventually optimize recovery purposes. Recently, in an attempt to address the challenges associated with the kerogen's low permeability, Hull et al 9 designed fluid oxidizers as additives to the slick water in hydraulically fracking source rocks. The designed fluid additive has strong oxidizers with very high concentrations, and was successfully used recently.…”

“…Oxidizing agents composed of oxyhalides such as bromate BrO 3 − and chlorate ClO 3 − are effective in breaking down shale's organic matter under reservoir temperatures. 9 …”

Synthesis and structural characterization of CO2-soluble oxidizers [Bu4N]BrO3 and [Bu4N]ClO3 and their dissolution in cosolvent-modified CO2 for reservoir applications

“…10 A second uid system incorporating bromate was designed to fracture unconventional shale source rock by oxidizing the ductile polymeric organic matter dispersed on the fracture faces. 11 Both water-based stimulation uids capture the effects of delayed oxidizer activation using natural reservoir heating as well as the high oxidizing power of bromate. Laboratory studies indicate that Br À ion, the fully reduced species, is the ultimate fate of the bromate system in the presence of hydrocarbon-bearing formation rocks such as carbonate and shale.…”