Degree

Doctor of Philosophy (PhD)

Department

Petroleum Engineering

Document Type

Dissertation

Abstract

A significant portion of U.S. oil production originates from tight reservoirs; however, these reservoirs remain constrained by rapid production decline and low primary recovery. The Tuscaloosa Marine Shale (TMS), which shares geological and fluid-distribution characteristics with the Eagle Ford Shale, presents potential for gas-based enhanced oil recovery (EOR), particularly under gravity-assisted configurations enabled by its inverted fluid system.

This work experimentally evaluates the feasibility of gas injection EOR in TMS core samples and examines the effects of gas type, rock dimensions, injection mode – continuous gas injection (CGI), gas-assisted gravity drainage (GAGD), and cyclic gas injection (huff-n-puff (HnP)) – and mineralogical brittleness on recovery performance. Although gas injection has been investigated in other shale plays, its viability in the TMS has not been systematically assessed primarily due to the extreme brittleness of the formation, which poses significant challenges in obtaining and preserving intact core samples for experimental evaluation.

Core flooding experiments were conducted at 2000 psi and 700F using nitrogen (N2) and carbon dioxide (CO2) as injectants. X-ray diffraction (XRD) analysis was performed to determine mineralogical composition and evaluate brittleness. Detailed core dimensions and cleaning procedures are omitted here for brevity.

XRD results indicate quartz contents ranging from 54%–67% and clay contents from 12-30%, suggesting brittle rock behavior favorable for fracture development in unconventional reservoirs. CO2 injection achieved recovery factors of 22-26%, compared to 18-19.76% for N2. Continuous GAGD outperformed cyclic HnP under the tested conditions. Samples with higher quartz-to-clay rations exhibited increased brittleness and, in some cases, structural disintegration during testing, underscoring the importance of mineralogical characterization in experimental design and field-scale application.

These findings are consistent with the technical and operational potential of CO2-based GAGD in the TMS and highlight its dual benefited for EOR and CO2 sequestration. The study identifies mineralogical and operational parameters critical to optimizing EOR in unconventional reservoirs and provides the first comprehensive experimental assessment of gas injection EOR in the TMS. Flue gas compositions were also evaluated, with CO2 showing most favorable recovery performance among the injectants tested.

Date

5-27-2026

Committee Chair

Rao, Dandina N.

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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