Energy Policy Act of 2005 (Ultra-deepwater and Unconventional Resources Program)
Gas Condensate Productivity in Tight Gas Sands
Stanford University, Palo Alto, CA 94305-2220
The objective of the project is to develop methodology to increase the productivity of gas-condensate fluids from tight gas reservoirs in the US.
Presently, gas-condensate reservoirs experience reductions in productivity by as much as a factor of 10 due to the dropout of liquid close to the wellbore. The reduction is worse in low permeability formations that make up tight gas reservoirs. The liquid dropout blocks the flow of gas to the well and lowers the overall energy output by a very substantial degree (90% if the productivity is reduced by 10). The combination of condensate phase behavior and rock relative permeability results in a change of composition of the reservoir fluid, as heavier components separate into the dropped-out liquid while the flowing gas phase becomes lighter in composition. This effect has been sparsely recognized in the literature, although there is clear evidence of it in field observations. The project will quantify the effect, develop a scientific understanding of the phenomena, and use the results to investigate ways to enhance the productivity by controlling the liquid composition that drops out close to the well. By optimizing the producing pressure strategy, it should be possible to cause a lighter liquid to be condensed in the reservoir, after which the productivity loss would be more easily remedied. The research will make use of experimental measurements of gas-condensate flow, as well as compositional numerical simulations.
The potential impact of the project will be to develop a production strategy (based on the control of well producing pressure) to limit the loss of productivity in gas condensate wells in tight gas sands.
Principal Investigator: Roland Horne