Secondary Recovery Symposium, 5–6 May, Wichita Falls, Texas
Thermal methods of oil recovery are presently at the forefront of the research efforts directed at increasing the recovery of oil.
Existing techniques may be classed in various groups:
Forward Thermal Drives wherein it is desired to increase the bulk of the reservoir temperature for the purpose of lowering crude oil viscosity in place and/or of liberating solution gas.
Subclasses of this group are:
reservoir heating throughout the bulk of the pay.
reservoir heating through an induced fracture while simultaneously driving the oil by an external agent.
reservoir heating through an induced fracture followed by a delayed external drive after fracture plugging.
The reservoir heating means may be hot water (from warm to very hot in temperature), dry steam, exhaust gases, hot gases, or a combination thereof.
The reservoir prerequisites for the application of such a process are:
the absence of a gas cap and the presence of a dispersed gas phase within the oil zone, i.e., permeability to gas must exist through the bulk of the pay.
fracturing from well to well must be possible.
fracture realing from well to well must be possible.
A field project of this type was the Carter Research experiment in Vernon County, Missouri, where steam was injected into the Bluejacket sand at shallow depth. Another project of this type has been initiated in the Shallow Carrizos and overlying the Camp Hill field, Anderson County, Texas.
A similar project is the injection of hot water in the Cardium sand, Pembina field, Canada, but the avowed objective of the project is not increased recovery but rather an increase in water injection rate because of the reduced viscosity of the hot water.
The operation suggested by Squires and Merriam (1) to burn coal in place in a deposit closely related to the oilfield and to inject the combustion gases into the oil sand is closely related to this process.
2. Forward Continuous Combustion Drive with a Combustion Front substantially vertical and extending through the bulk of the pay thickness, gravity affects being negligible in achieving oil recovery. Combustion may be principally that of the gases of injection or of some of the oil in place.
Characteristics of this type of drive are that all the reservoir fluids are in motion most of the time and perhaps at all times, i.e., oil, water, and gases are simultaneously in motion in the porous reservoir rock. Such a three phase flow operation requires high differential pressure to achieve an economic producing rate.
