Analyzing Aqueous Solution Imbibition into Shale and the Effects of Optimizing Critical Chemical Additives

Abstract

Two methods of hydraulic fracturing most widely utilized on unconventional shale gas and oil reservoirs are “gelled fracturing” and “slick-water fracturing”. Both methods utilize up to several million gallons of water-based fluid per well in a series of stages pumped into direct contact with subsurface rock. Shale can absorb water through a process called capillary imbibition when the two come in contact. Additionally, since a common component of shale rock is clay, water may intercalate into clay structures in the shale causing them to swell and/or break off from a fracture face, potentially plugging the desired fluid conductivity of the created fractures. Currently the extent of water-based fluid imbibition and intercalation in major shale plays is not known; however it is not uncommon for only 15 – 30% of pumped fracture fluid to return to the surface during production from a well. How these issues affect fracture conductivity and thus production from unconventional oil and natural gas wells is poorly understood. Additionally, it is not known how various fracturing fluid additives affect the magnitude of water-based fluid imbibition and/or intercalation into shale. The work our group is conducting seeks to quantify the effects of pertinent chemical additives on fluid imbibition and intercalation into shale samples. We do this with the hope that we will eventually be able to determine how natural phenomena and additives affect long term resource production from unconventional oil and natural gas wells.