Hydraulic fracturing fluid systems are used to create the required fracture geometry and transport proppant into the fracture with a distribution that allows for the optimum performance of the well. Most systems currently use water-soluble polymers composed of guar or guar derivatives. Additional materials are used to optimize the fluid characteristics for the application and also to degrade the water-soluble polymer to make it easier to recover from the well prior to production. The recovered, degraded fluids cannot be used again and must be disposed of in a proper manner.
A new hydraulic fracturing fluid system has been developed that provides excellent performance during the fracturing process with post-fracture treatment fluid recovery approaching 100%. This fluid has the added benefit of being reusable after it is recovered following the treatment and prior to production. The benefits of reuse include the cost savings associated with capturing and reusing chemicals, the cost savings because of reduced water volume requirements for subsequent treatments, and the elimination of disposal costs. In addition, the total volume of chemicals required for fracturing operations is significantly less, thus reducing the demand on our environment.
Field analyses of the returned fluid determine parameters of maintenance and reconstitution for use in subsequent fracturing. This paper will outline the application of this fluid system, the concept for recycling and reuse, and the procedures necessary to properly use the recovered fluid in subsequent treatments.
Hydraulic fracturing of oil and gas producing reservoirs is an industry accepted technique used to enhance productivity. It plays a major role in the development of many oil and gas fields around the world.1 The development of fracturing fluid systems has progressed from gelled hydrocarbons to water/oil emulsions to guar gelled water-based fluids to transition metal crosslinked guar-based fluids. Fluid development has continued with the use of surfactant-based fluids and low concentration polymer fluids.
Fluid volumes for a fracturing treatment are dictated by the formations of interest in the well. They can range from a few thousand gallons to several hundred thousand gallons. The recovery and reuse of the fluid system can reduce the impact on the environment in several ways. First, the amount of water for subsequent treatments will be reduced by the volume recovered. Second, the required chemicals will be reduced based on the properties of the recovered fluid. Third, the cost of disposal will be saved.
The objective of a fracturing treatment is to place a proppant into the created fracture to maintain the open crack and provide a high-permeability pathway for reservoir fluids to the wellbore. The fluid system provides the means to create the fracture and place the proppant in it. The stimulating benefit of a fracturing treatment comes from the proppant holding the fracture open. The fluid system only facilitates the proppant placement and it must be recovered from the well before production can commence. Therefore, it is desirable to capture the fluid so it can be used for another fracturing treatment. Up to this point in time, the polymer-based fracturing fluid had to be degraded in place with strong chemical breakers before it could be efficiently recovered from the well, and it has simply been disposed of in pits or disposal wells. If the fluid systems were simply water, then disposal may not be a great concern. However, most fluid systems are composed of expensive, complex chemical formulations designed to provide specific rheological properties during the pumping of the treatment. Fluids have not been recovered and reused before now because they are purposely degraded to achieve fluid recovery and they therefore no longer have the desired properties for use.