In these times of budget conscious oil and gas companies, finding solutions to save money without compromising output is always on the minds of management. The idea of reusing fracturing fluid flowback has gained popularity over the years. However, care must be taken to properly recycle these fluids to allow for multiple reuses without major destabilization of the fracturing system.
Hydraulic fracturing is used for stimulating the production of wells, in particularly gas wells. Fracturing can be performed using either hydrocarbon based fluids or water based fluids. Due to issues such as water blockages and swelling of formation clays, the use of hydrocarbon based fluids for fracturing remains popular despite the cost difference. In general successful fracturing fluids must be gelled (increase in viscosity) and broken (decrease in viscosity). Completion companies use three main chemical components to gel and break a hydrocarbon fracturing fluid: gellant, activator and breaker. Recycling fracturing fluid flowback will involve the removal of these completion chemicals as well as other contaminants.
This paper will look at a case study which shows the economic benefits of employing a high quality hydrocarbon fracturing fluid recycling process; and the resulting successful performance on the overall production of using such fluids.
Fracturing of formation to increase the production is a practice that has been done since the 1950's. A fluid is injected into the formation at a rate and pressure great enough fracture the rock. Once the fracture is initiated fluid is continued to be pumped to propagate the fracture. A proppant such as sand, ceramic spheres or similar product is added to the fluid and will be left in the fracture to enable the production to increase due to a relative permeability difference with the formation.
Chemicals are added to the fluid to enhance the characteristics of friction, viscosity, leakoff and other variables. These chemicals that increase the viscosity are added to greatly increase the viscosity during the pumping and then decrease after the pumping to aid in the placement of the proppant and then to recover the fracture fluid.
The choice of fluids is dependent on economics and formation compatibilities. Fracturing with water, although less expensive, has associated problems of water phase trapping and fracture permeability reductions1,2. In Canada, hydrocarbon based fracture fluids have become the preferred product in deeper, lower permeability gas zones.
The basic chemicals added to these fluids are gallant, activator and breaker. These chemicals will work together to increase the viscosity of the base hydrocarbon from 10 cP to well over 400 cP, and then break the density back to 10 cP range. The time to break and the maximum viscosity are based on the loadings of the chemicals, and the temperature of the formation being stimulated (Fig. 1).
The cost of hydrocarbon fracture fluid is dependent on the quality, but all follow the cost of crude. During the last few years the process of recycling fracture hydrocarbons has become an economical decision.