A True In Situ Oil Shale Retorting Experiment At Rock Springs Site 12 PDF Download

A true in situ oil shale fracturing and retorting experiment was conducted near Rock Springs, Wyoming in 1977, 1978, and 1979. A 20-foot (6.1 m) thick zone of oil shale located 200 feet (61 m) below surface was hydraulically and explosively fractured. The fractured oil shale was extensively evaluated using flow tests, TV logging, caliper logging, downhole flow logging, core samples, and tracer tests. Attempts to conduct true in situ retorting tests in portions of the pattern with less than 5 percent void space as measured by caliper logs and less than 1 percent active void space measured by tracer test were curtailed when air could not be injected at desired rates. It is thought the fractures plugged as a result of thermal swelling of the oil shale. Air was injected at programmed rates in an area with 10 percent void measured by caliper log and 1.4 pecent active void measured by tracer test. A burn front was propagated in a narrow path moving away from the location of the production well. The vertical sweep of the burn front was measured at less than 4 feet (1.3 m). The burn front could not be sustained beyond 10 days without use of supplemental fuel. The authors recommend a minimum of 5 percent well-distributed void for attempts to retort 20 gpt (81 L/m ton) oil shale in confined beds. A void space of 5 percent may be roughly equivalent to 5 to 10 percent measured by caliper log and 1.4 percent or more by tracer test.