GEOCHEMICAL AND PETROPHYSICAL TRANSFORMATIONS DURING ROCK-FLUID INTERACTIONS IN CANEY FORMATION, SOUTH CENTRAL OKLAHOMA

Production of unconventional hydrocarbon resources is key to satisfying growing demand for energy globally. In the United States, production from hydraulically fractured reservoirs is the main thrust of recent increases in hydrocarbon production. Applications of hydraulic fracturing technologies in hydrocarbon recovery is however relatively new with vast knowledge gaps. To harness the full potential of this technology, it is essential to understand the geochemical interactions between fracturing fluids and subsurface formations post-hydraulic fracturing.

This work involves controlled batch reactor experiments using rock powders and rock core (discs) to study rock-fluid interactions during and after hydraulic fracturing. Rock samples from selected depths within the Caney Formation in the Ardmore Basin are used. Powder samples are prepared by crushing, grinding and micronizing rock to particle sizes passing 100µm. This exposes more surface area for reaction. Rock discs are cut to sizes of 1in diameter and 0.4in height. The reactions are conducted over a 30-day period at temperatures of 95^oC and atmospheric pressure with minimal oxygen interaction during experiment. Fluids used in experiments are field hydraulic fracturing fluid, field formation fluid and deionized water.

Tools employed for sample evaluation include Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). Preliminary results reveal transformation in samples mineralogical compositions due to dissolution of carbonates and pyrite and transformation of feldspars to clays. XRD peaks reveal increased composition of amorphous entities, supporting the theory of illite de-flocculation and fines migration. CT scans and SEM studies show precipitation of new minerals on rock surfaces. Increased elemental compositions of Ca, Al, Si, Mg, Na, and Fe in solution points to considerable geochemical reactions.

This work highlights mechanisms controlling rock-fluid interactions in the subsurface. Findings from this study are critical to developing optimal hydraulic fracturing fluids to mitigate undesirable impacts during and after hydraulic fracturing.