(706e) Chemical Reactivity of Caney Shale to KCl-Brines at Elevated Temperature and Pressure

Development of unconventional resources beginning in the past decade has created a paradigm shift in the definition of reservoir and seal rocks. Formations that were previously considered seals are now being reappraised with the possibility of being considered reservoirs. The Caney Shale located in South-Central Oklahoma Oil Province (SCOOP) is one such plays that has been appraised and is currently being developed. Due to its previous classification as seal rock, little work has been conducted on the formation’s response to drilling and fracturing fluids.

Published literature on low permeability shale rock’s interaction with drilling and fracturing fluids have confirmed nano-scale, micro-scale and macro-scale physical-chemical interactions with implications on engineering technologies, from drilling to production. For instance, during rock-fluid interactions in the subsurface, dissolution of carbonates create secondary permeability whilst clay swelling, dislodgement and transport of clay fines lead to significant permeability reductions. Permeability-enhancing reactions as well as permeability-reducing reactions are significant considering the magnitudes of scale of permeabilities in shale reservoirs. These reactions and outcomes, though similar for different shale reservoirs, are unique for every formation in terms of the extent of damage or enhancement. These differences are due to mineralogical and microstructural differences in various shale rocks, which are result of depositional environmental and geological history.

In this study, rock-fluid interactions between the Caney Shale and simplified fracturing fluid at in-situ T, P conditions were examined to ascertain the responses of the formation to these fluids. Mineralogical and microstructural analyses of Caney Shale samples were done using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) methods. Results of mineralogical microstructural analyses show samples are mainly quartz, clay and carbonates with different degree of micro-fractures interspersed between the interlocking mineral grains. Core flooding experiments were conducted on propant filled fracture, simulated by two parallel plates (following API-19D), at constant temperature of 100^oC to mimic formation temperatures of the Caney Shale. Confining pressures were varied from 1000psi to about 12000psi. During the experiments, effluents are collected at predetermined time intervals and analyses conducted to ascertain the elemental concentrations. Preliminary results from effluent analyses shows the presence of Ca, Si, Al, Na, B, K as well as SO₄^-2. These changes will be discussed in relation to fracture permeability and ultimate production of hydrocarbons from Caney Shale, Oklahoma.