Semester

Fall

Date of Graduation

2021

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Geology and Geography

Committee Chair

Amy Weislogel

Committee Member

Kathleen Benison

Committee Member

Jaime Toro

Abstract

This study includes a sedimentologic and petrographic study of cores and thin-sections from the Jurassic Norphlet Formation in the Flomaton Field in southern Alabama to define a specific paragenetic history of each facies encountered and to identify key controls on reservoir quality. Eolian dune, nearshore, sand flat, and wadi facies were likely encountered in Norphlet core and thin-section samples that displayed a high degree of heterogeneity between them in terms of porosity, grain contacts, cement abundance/type, intergranular volume, and overall diagenetic processes. These distinct petrographic differences suggest that the paragenesis in the Flomaton Field is primarily facies controlled. The eolian dune facies, which serves as a significant oil and gas reservoir in the Norphlet Formation, exhibits a mean porosity of 16% despite being buried to depths exceeding 16,000 feet in southern Alabama. This preservation of porosity likely resulted from an introduction of a halite cement, prior to compaction, that tended to keep the grains apart during eogenesis, but was later removed due to dissolution resulting from migrating fluids associated with hydrocarbon charging of the Norphlet reservoir.

Authigenic clay coats are present in the eolian dune and sand flat facies but they are not suggested to be the primary factor in porosity preservation as they were in the Norphlet Formation of Mobile Bay. In the up-dip Flomaton Field, saline groundwater was closer to the surface than the down-dip Mobile Bay Field which inhibited vegetation growth. This resulted in more active dunes and increased sand grain remobilization that led to increased clay coat abrasion and hence, discontinuous to no clay coat formation.

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