Design of a long term hydraulic fracture and flow system

A series of fracture and flow tests are being performed at the Sanford Underground Research Facility (SURF) as part of the EGS Collab project. The tests involve generating a communicating fracture(s) between two boreholes, and monitoring flow through the generated fracture(s). To perform these tests a robust, remotely operable pressure system is required, as much of the flow testing will be performed over long periods of time when the equipment is not monitored. The system utilizes several pumping systems to include air driven liquid pumps, syringe pumps, and a triplex pump. The syringe pumps and triplex pump are connected to a data acquisition and control system, and can be controlled remotely for pressure and flow. The triplex pump is controlled using a variable frequency drive and a pneumatically actuated back pressure control valve on an integrated flow bypass line. A secondary back pressure control valve can be used to generate back pressure in the production side of the system. The injection and production test intervals are connected at the surface via high-pressure tubing and a differential pressure gauge, and downstream of the production well a series of sensors are in place for detecting tracers injected into the system. The pressurization system is connected to the in situ fracture through a pair (one in each of the boreholes) of straddle packers with a proprietary measurement tool in the packer interval. The tool, dubbed the SIMFIP (Step-Rate Injection Measurement for Fracture In Situ Properties) packs off and allows flow into and out of the interval along with collecting data from numerous sensors. Data from the shakedown of the system, performed at Sandia National Laboratories prior to field deployment, will be presented.