Oil recovery improvement through profile modification by thermal precipitation. Annual report, October 1, 1991--September 30, 1992

Abstract

The objective of this research project is to investigate the effect of temperature dependent precipitation of chemicals on the porosity and permeability of porous rocks. Different core samples are being saturating at different temperatures and are being allowed cool, precipitating the chemical. This technique has applications in enhanced oil recovery processes as a method of plugging high permeability ``thief zones.`` Over the last year the experimental apparatus has been fully commissioned and detailed operating procedures have been developed. A number of preliminary tests have been completed to prove the reliability and repeatability of the system. Three Berea sandstone cores have been successfully treated with potassium carbonate at 260 degrees Fahrenheit. All three cores showed similar reductions in permeability on the order of 50 percent and porosity declines of around 13 percent This level of permeability reduction is greater than early predictions, suggesting that thermal precipitation may be more effective in profile modification than previously thought. A microscopic study of the cores after precipitation using a Scanning Electron Microscope has revealed coating of individual grains and bridging of the pore space by the precipitate. The main series of precipitation experiments is now in progress to examine the full extent of themore » precipitation for a variety of core types, temperatures, and chemicals.« less