Date of Award

Spring 5-4-2024

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Earth Science

Committee Chair

Dr. B. Todd Hoffman

First Advisor

Dr. Alysia Cox

Second Advisor

Dr. Curtis Link

Third Advisor

Dr. Robin Bullock

Abstract

Improved recovery from tight oil reservoirs will be accomplished through a more thorough understanding of primary and enhanced production mechanisms. This is true for both primary production and production following cyclic gas injection processes. The production mechanisms are controlled by reservoir fluid properties and pore network characteristics. The pore networks found in these reservoirs include large fractions of nanometer scale pores, which effect fluid flow and storage. A numerical model was developed to describe the impacts that nanometer scale pore networks have on the fluid properties and oil production. In order to describe the effects, the nanometer scale pore networks have on the fluid properties and oil production, a numerical model was developed. The model is used to quantify pore scale production mechanisms and determine how to best produce the oil from the nanometer scale pores.

Nanometer scale pore fluids have suppressed bubble point pressures due to high capillary pressure and increased fluid/pore-surface interactions. To model the pore scale effects, dual pore network models with scale dependent fluids are used. Tracers are placed on pore network fluid components and injection gasses to provide insight into pore network fluid transfer. Fluid sources and pore network production rates are quantified for primary production and production following cyclic gas injection. Fluid characteristics within the pore networks are examined throughout the model space during the production and injection times.

The results of this modeling effort show that much of additional oil produced following high pressure rich gas injection comes from nanoscale pores. This oil is not produced during primary production because the capillary forces tend to trap the oil. High injection pressure allows the injected gas to overcome the capillary forces and enter the pores. The injected gas reduces the oil viscosity and gas-oil interfacial tension, allowing the oil to be produced when the pressure drops during the production cycle. These results are consistent with observed field data that show higher production occurs when gas is injected at higher rates and pressures.

Download

Included in

Engineering Commons

Share

COinS