A Field Demonstration of Hydraulic Fracturing for Solids Waste Injection with Real-Time Passive Seismic Monitoring

Abstract

Abstract This paper documents the findings of the Deep Well Treatment and Injection (DWTI) field research project to demonstrate the use of hydraulic fracturing for non-exempt solids waste disposal. This test involved injection of a large quantity of simulated waste into a porous rock formation at a depth of 4500 feet. The inert material injected was designed to match appropriate properties of actual solid wastes. A total of 4 million pounds of sand and bentonite clay, plus 50,000 bbls of water, were pumped in four batch injection cycles spanning five days of operations. Fracture diagnostic tools used to measure the created fracture geometry included temperature and R/A tracer logs, hydraulic impedance, tiltmeters, and a new real-time passive seismic monitoring and analysis system. Seismic data was measured in two dedicated monitor wells offseting the predicted fracture azimuth. Each well contained 75 geophones that provided 700’ of vertical coverage. Over 2000 seismic events were obtained and analyzed for fracture height; 250 of these were analyzed further for three-dimensional fracture location. The fracture geometry was predicted in advance with a new computer model developed for this waste injection application. Results showed excellent agreement between the fracture height predicted and that measured by the seismic system, but that other diagnostic techniques were not sufficiently accurate. Good agreement between the maximum predicted fracture length and the length from the seismic system was also observed.