Unlocking Oil Potential: Utilizing Paraffin Inhibitors to Mitigate Challenges Faced During Hydrofracturing in Shallow Waxy Oil Reservoirs
Authors: Dadwani A. , Jain A. , Patel H. , Shah M. 
Published: May 2024

The paraffin components present in crude oil reach equilibrium under reservoir conditions. However, during the hydraulic fracturing process, when fracturing fluids are introduced at ambient temperature there is a localized temperature variation leading to a drop in reservoir temperature below the cloud point. This phenomenon leads to the coalescence of paraffinic components, resulting in the wax formation within the reservoir pore throats. The wax accumulation in turn diminishes the productivity of the formation. Wax deposition is an irreversible process, and it is difficult to redissolve them even after the establishment of the formation temperature. In this paper, wax precipitation was envisaged at the laboratory scale utilizing the MCR–52 rheometer. Paraffin inhibitors provide resistance to wax precipitation as they prevent the paraffin crystals from nucleating and forming wax in the reservoir pore throats. Paraffin inhibitors are organic and insoluble in the water phase, and they are not able to prevent wax formation, thus may screen out in the reservoir. To enhance proppant placement in induced fractures, optimization is attained by dispersing inhibitors in water-based fracturing fluids using an aromatic solvent.

The concentration of paraffin inhibitors in both aromatic solvent and water within the fracturing fluid is critical for optimal performance. Deviating from the optimum concentration can lead to wax deposition in the reservoir at lower concentrations and inhibitor screen-out at higher concentrations. The rheometer was used to determine the pour point and cloud point of the crude oil at reservoir conditions. Subsequent experiments with 50% V/V crude oil-5% KCl brine solution assessed the cloud point using viscosity and temperature plots. The different concentrations of paraffin inhibitors in aromatic solvent, brine, and crude oil solution were analysed for viscosity-temperature behaviour. Micro-dispersion of paraffin inhibitors in the water-based fracturing fluid resulted in reduced viscosity indices. The optimum concentration of paraffin inhibitor was determined considering reduced cloud point-slope. This concentration was selected for testing with fracturing fluid to optimize guar gum concentration for effective proppant placement, acknowledging the challenges introduced by paraffin inhibitors in proppant placement, requiring careful calibration.

At the laboratory scale, a reduction of 26 % in cloud point was observed while using a homogeneous concentration of 1000 ppm paraffin inhibitor along with an aromatic solvent. A colour change was observed when the inhibitor was treated with a 50% V/V crude and brine mixture to compensate aromatic solvent concentrations introduced. Field-scale implementation of the method from the laboratory experiment will help the operators in the prevention of formation damage caused due to pore throats plugging from the wax precipitation during the fracturing treatment at shallow Reservoirs.