The damage mechanisms of fracturing fluid on production in tight gas reservoirs

Abstract

Hydraulic fracturing is generally required for tight gas formation with low matrix permeability to achieve economic production rate. Hydroxypropyl guar gum (HPG) fracturing is one of most commonly used technology. During fracturing, million gallons of guar gum fluid are pumped downhole to initiate fractures, and lots of fluid would filtrate into formation matrix. The guar gum will be adsorbed in the porous medium of sandstone and decrease the permeability of the reservoir. For improving the production of tight gas well after being stimulated, the adsorption mechanism between the guar gum and sandstone is studied. The action force is analysed through the Flourier transformation infrared spectroscopy (FT-IR), Zeta potential instrument and X-ray photoelectron spectroscopy (XPS). The result indicate that the hydrogen bonding is the key force between the guar gum and sandstone. To observe the adsorption morphology, scanning electron microscope (SEM) and atomic force microscope (AFM) are employed. Nuclear magnetic resonance (NMR) and computer tomography (CT) showed that the adsorption and retention of guar gum in tight gas reservoir resulted in the decrease of pore and throat ratio, the decrease of porosity by 2.7%~3.1%, and most adsorption occurs at grain edges and rock beddings.