Novel Techniques to Prevent Wax Deposition During Hydraulic Fracturing of Low-Temperature Waxy Oil Reservoirs

Abstract

AbstractHydraulic fracturing is the key well-stimulation technique to recover oil and gas from tight and unconventional reservoirs. The primary challenge encountered during hydraulic fracturing of the shallow waxy oil reservoir is cooling the reservoir while pumping low-temperature fracturing fluid, resulting in wax precipitation. Heating the fracturing fluid at the surface and blending water-dispersed paraffin inhibitor with fracturing fluid are the two techniques that prevent wax precipitation when the reservoir temperature decreases below the wax appearance temperature. This paper will suggest the best suitable technique for given reservoir conditions. When the formation temperature is cooled below the cloud point temperature, the paraffin precipitates and deposits in the reservoir pores causing formation damage. It is therefore suggested to maintain wellhead temperature above the wax appearance temperature of crude oil in the reservoir.An adequate concentration of viscosities would be selected to maintain desired viscosity at field conditions by identifying the suitable rheological model for propane placement in the reservoir. This would also suggest modification in infrastructure and formulation of cross-linked gel for the treatment. The paper would discuss the challenges faced when this method is upscaled at the field scale. This paper would also investigate a novel approach by incorporating insoluble paraffin inhibitors into a micro-dispersion system dispersible in water. Hydrofracturing fluid follows Herschel Buckley’s rheological model, which is a modification of the power law model. On increasing guar gum concentration by 1.5 gm/liter (50 lb/1000gal to 62 lb/1000gal), the average change in apparent viscosity is observed to be 14-20 cP depending on temperature. If we need to heat the fracturing fluid at 70°C, the concentration of guar gum needs to be increased. At 34°C, the apparent viscosity of standard hydro-fracturing is observed to be around 41 cP and at 68°C, viscosity decreases to 28 cP. After increasing the guar gum concentration by quantity 1.5 gm/liter, we observe that viscosity at 68°C becomes around 44 cP. The optimum concentration of guar gum needed to maintain viscosity is around 7 gm/liter (58.4 lbm/1000 gal). Hence it should be increased by about 16.67%.From the study of wax appearance temperature at the laboratory scale, the impact of water-dispersible paraffin inhibitors on paraffin control, oil quality, water quality, fracturing fluid compatibility, and production rates are evaluated. It is observed that production rates decline even after the hydraulic fracturing of the well, as paraffin damage reduces the formation's permeability. Thus, heated fracturing fluid and micro-dispersed colloidal paraffin inhibitors are the visionary methods to inhibit wax formation at the reservoir scale. It can be salubrious for the operators in stimulating +the reservoirs.