Effective Pressure Maintenance and Fluid Leak-Off Management Using Nanoparticle-Based Foam

Abstract

Hydraulic fracturing is the most effective stimulation process to maximize resource extraction in unconventional reservoirs. However, water leakoff into the matrix of unconventional reservoirs, whether from a frac stage or from a pad placed in a parent well and pressured up to prevent frac hits, results in relative permeability reduction, decrease in hydrocarbon production rate and possible formation damage. This paper reports the application of a foam designed with an innovative combination of nanoparticles and surfactants to create a highly stable fluid with a low leak-off rate and non-damaging characteristics. A series of laboratory tests were conducted on tight core samples with variable permeability ranging from micro-to millidarcies, using different fluid systems including gas, water, and foam. A uniquely designed coreflood setup was used to imitate the wellbore/fracture-matrix condition. A fracture/matrix pressure difference of 1500 psi was used to evaluate the performance of each fluid with respect to maintaining pressure over time and minimizing leak off at a temperature of 80 °C. The test results show that the laboratory-designed nanofoam can effectively maintain elevated pressure in the fracture sufficient to reduce frac hits. The pressure depleted to 50% of original pressure in less than 3 hours when using gas or water and less than 15 hours in case of surfactant foam. However, the nanofoam maintained a pressure higher than 50% of the original pressure for more than 70 hours. The leak-off volume of the foam was low, and the foam could be easily cleaned up with no formation damage (i.e., no change in core permeability). This study reveals the potential of a highly stable foam as a fast and reliable method to prevent frac hit problems, saving operational cost and reducing water usage without compromising the well productivity. This foam can be potentially used as a base fracture fluid due to its high viscosity, high stability, and non-damaging characteristics.