Energy from True in Situ Processing of Antrim Shale: Preparation of in Situ Retort Bed by Explosive Underreaming and Fracturing

摘要

This report summarizes the work carried out on the explosive underream and fracturing of Antrim shale. This experiment involved the creation of a cavity in the shale by detonating successively larger explosive shots in a central wellbore. Two more wells were located, drilled and cored 15 feet either side of the central well. Core analysis of these wells indicated that one well had a high concentration of fractures which were likely induced explosively, while the other well had few fractures thought to have been explosively induced. Interwell communication established by fluid injection confirmed the differences. A gyroscopic survey of the borehole shed some light on this difference. The well containing the extensive fracturing remained 15 feet from the bottom of the central well, while the distance to the second well had increased 63%. The wells were loaded with a slurry explosive system and detonated. The wellbores were cleaned out and the results were evaluated with flow logging, air permeability, tracer gas, differential temperature, borehole television and vertical seismic profiling techniques. The results defined the degree of interwell communications, the location of major fractures, and indicated that five of the seven wells were in some degree of communication. The major zone of permeability was through vertical fractures forming a wedge between three of the wells. An effective system for monitoring and pumping of formation fluids was designed and installed. The results of a post-fracture vertical seismic profile survey corroborated other logging techniques and confirmed the existence of a complex fracture system at depths ranging from 1230 to 1375 feet. The fracture system was defined as being a larger planer zone, 70 to 100 feet wide and 70 to 100 feet high. (ERA citation 05:034573)