Abstract
The effectiveness of hydraulic fracturing (HF) largely depends on how well fracture conductivity is preserved after the fracturing fluid interacts with the reservoir rock. This paper systematizes the permeability-damage mechanisms related to the water sensitivity of clay minerals interlayer smectite swelling, osmotic effects, deflocculation and fines migration and examines the non-target consumption pathways of clay stabilizers (KCl, quaternary ammonium compounds) and gel breakers (ammonium persulfate, hydrogen peroxide, enzymes) on rock minerals and co-additives. It is shown that the nominal reagent dosage, evaluated without a material balance, can simultaneously overestimate both the degree of clay stabilization and the extent of polymer network degradation. A minimum laboratory testing matrix is proposed, including oriented-sample XRD analysis, sorption isotherms, coreflood tests and retained fracture-conductivity tests. Using the Vostochny Moldabek field (Embamunaigaz JSC) as a case study, it is shown that the permeability decline observed when the reservoir is saturated with low-salinity water is caused by clay and mica swelling, whereas formation water does not cause such degradation. A formationwater-based fracturing technology is substantiated and implemented, using a polyacrylamide-based gel instead of guar gum, which is unsuitable at a water salinity above 130 g/L. Field results from eight wells show that production rates after fracturing on formation water with the synthetic polymer exceeded those of the standard technology by more than five times.