A method for tracing the flow of a plurality of fluid slugs injected into a subsurface formation using a number of tracers smaller than the number of fluid slugs. Single tracers are used in a number of fluid slugs equal to the number of tracers. In the remaining injected fluid slugs, combinations of at least two of the tracers in predetermined concentration ratios are used. Recovered fluid is analyzed for the presence of each of the tracers and the ratios of the tracers indicates breakthrough of each injected slug.
A method is provided for troubleshooting gas-lift wells, to identify whether gas-lift valves on the production tubing are open or closed, without the use of wireline tools. The method may also be used to detect leaks in the production tubing or in the well casing. A quantity of a tracer gas is injected into the lift-gas at the wellhead, and its return in fluid produced from the well is monitored as a function of time. The tracer's return pattern may be correlated with the depth of entry points and volumes of lift-gas entering along the length of the production tubing.
Disclosed is a tracer fluid for use in connection with surfactant waterflooding or other chemicalized enhanced oil, recovery processes, and an oil recovery process using the fluid. Fluids containing easily identifiable components such as water-soluble, inorganic salts, specifically water-soluble nitrate salts, as well as low molecular weight alcohols may be used as tracer fluids for determining numerous flow and formation conditions between injection wells and production wells. Many of the most desirable tracers are degraded by bacteria present in field water or surface contamination. Incorporation of from 10 to 2000 and preferably from 50 to 1500 parts per million of an aromatic treating compound, preferably benzene, toluene, or xylene, stabilizes the chemical tracer against microbial attack.
In a method of radioactive tracer logging, two slugs of tracer material are ejected. The slugs are ejected either sequentially from a single location or simultaneously from two spaced-apart locations. The distance between the tracer slugs is measured by moving a detector through the tracer slugs as they move down the borehole. The distance between the two slugs of tracer material are repeatedly measured as a function of depth, and from the measurements the amount of fluid exiting the wellbore is calculated to provide an injection profile of the well.
The method for determining flow patterns within a subterranean formation penetrated by a spaced apart injection system and production system that comprises injecting into the formation at a predetermined depth from the injection system a solution containing a small amount of one or more water-soluble tracer compounds, recovering said tracer in the production system, determining the depth of recovery, and identifying said tracer compounds by gas chromatography and flame ionization detector; said tracer compounds being water-soluble organic compounds having phosphorus, nitrogen, or sulfur in the molecule.
The method for determining flow patterns within a subterranean formation penetrated by a spaced apart injection system and production system that comprises injecting into the formation at a predetermined depth from the injection system a solution containing a small amount of one or more water-soluble tracer compounds, recovering said tracer in the production system, determining the depth of recovery, and identifying said tracer compounds by gas chromatography and flame ionization detector; said tracer compounds being water-soluble organic compounds having phosphorus, nitrogen, or sulfur in the molecule.
