Date of Award

2018

Document Type

Open Access Dissertation

Department

Earth and Ocean Sciences

Sub-Department

College of Arts and Sciences

First Advisor

Camelia Knapp

Abstract

This is the first assessment of Upper Cretaceous strata for offshore CO2 storage resources in the southeastern United States outer continental shelf. This research focuses on Upper Cretaceous geological units using legacy industry 2-D seismic reflection and well data. It provides an integrated description and reliable subsurface evaluation of Upper Cretaceous potential storage reservoirs. In addition, it provides a detailed evaluation on how rock porosities and permeabilities are distributed across the Upper Cretaceous strata restricted to the South Georgia Embayment (SGE). Structure and thickness (isochore) maps were generated for the main potential reservoirs and seals on a regional and local scale. This assessment is the first application of multiple seismic inversion techniques in SEG. It provides a reliable and reputable workflow of Model-Based inversion which gives an improved image to discriminate lithology and predict porosity. This workflow can be applied to future CO2 storage resource assessment studies elsewhere. The inversion results indicated that distinct porosity and permeability regimes are present and distributed in Upper Cretaceous within the SGE. The impedance and porosity relationships show well founded and reliable correlation. This relationship reveals low impedance coincident to the high porosity intervals which are proposed as potential reservoir intervals for CO2 storage. In addition, it shows that the Upper Cretaceous strata have two main potential reservoirs in the lower part. These are overlain by a thick impermeable interval, mostly shale which has high impedance, low porosity, and low permeability, which extends within the SGE. Since porosity distribution is estimated using different methods, it follows the trends of seismic signature and structures of Upper Cretaceous strata. The extracted values of porosity, ranging from 15 to 36 %, and permeability, ranging from 1 to 100 mD, are close to the measured values from the well core data at the Upper Cretaceous strata interval.

Five reservoirs and seals were recognized as potential storage units. Two reservoirs are particularly considered as the main CO2 storage units with quality and integrity capable to meet the CO2 storage requirements by the U.S. Department of Energy. They consist of limestone deposits with significant interbedded sandstones, shales and dolomites, and are sealed by thick shales interbedded with limestone. The porosity ranges from 20 to 30 % and the permeability ranges from 1 to 447 mD. Regional CO2 storage capacity is estimated to be approximately 32 GT in Upper Cretaceous units. The local storage capacity for the two significant reservoirs in the SGE contribute ~ 9 GT of that amount.

Included in

Geology Commons

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