Loading...
CO₂ geosequestration in the Lakota Formation, Powder River Basin, WY, USA
Erdinc, I. Burak
Erdinc, I. Burak
Citations
Altmetric:
Advisor
Editor
Date
Date Issued
2024
Date Submitted
Collections
Research Projects
Organizational Units
Journal Issue
Embargo Expires
Abstract
Deep saline aquifers have been identified as suitable repositories for geologic carbon sequestration due to their vast storage capacity, widespread distribution, and low potential for leakage. Among these potential sites, the Cretaceous deep saline aquifer Lakota Formation in the Powder River Basin has been suggested as a potential target.
This thesis presents a quantitative feasibility study for carbon geosequestration within the Lakota Sandstone Formation. The assessment consists of formation evaluation, seismic data analysis, geomechanical modeling, rock physics analysis, and thermo-hydro-mechanical simulation within the target reservoir. Various datasets were utilized during the evaluation, including geophysical logs, mud reports, drilling reports, drill stem tests, diagnostic formation integrity tests, core data, regional stress state maps, and a high-resolution three-dimensional seismic survey.
Formation evaluation is conducted using geophysical logs to estimate key parameters such as water saturation, formation water salinity, total and effective porosity. Permeability is estimated with empirical relationships and core data. The geomechanical model is constructed using a pore pressure model calibrated with drill stem test data from the study area. Static and dynamic elastic properties and strength parameters, including Young’s modulus, Poisson’s ratio, unconfined compressive strength, and friction angle, are estimated from both geophysical logs and empirical relationships. One-dimensional (1D) and three-dimensional (3D) mechanical earth models are developed based on regional stress state maps, poroelastic method, and offset diagnostic formation integrity tests.
Structural and attribute analysis is conducted on the post-stack seismic data. Additionally, 3D seismic inversions are completed for pre- and post-stack data sets. The seismic property changes within the Lakota Formation are investigated using Gassmann fluid substitution across a wide range of potential temperature, pressure, and CO2 saturation conditions. Storage constraints are also investigated, including storage capacity and injectivity.
A potential zone of approximately 45 feet in the Lakota Formation is identified for CO2 geosequestration evaluation. The formation has an estimated permeability of 0.5 - 5 mD and an average effective porosity of 11%, with formation water salinity exceeding 10,000 ppm. An existing drill stem test from one of the wells within the study area reveals a higher thermal gradient than previously reported in the literature. The 1D mechanical earth model results highlight overpressure compartmentalization in shale zones extending from the Frontier to Fuson Formations. Variance and ant tracking attributes indicate a minimal discontinuity in the southwest region of the study area. Post-stack and pre-stack seismic inversions show consistent lateral and vertical thickness variations of all formations above the Dakota Formation. Secondary seals, Mowry, Carlile, and Niobrara Formations, collectively contribute to a seal thickness of up to 300 meters /1000ft in this study area.
The extent of the Lakota Formation suggests a maximum potential storage capacity of ∼ 6.5 Mtons of CO2. The formation pore pressure is estimated ∼ 37 MPa, with a fracture pressure of ∼ 53 MPa, potentially allowing for a pressure differential of ∼ 15 MPa before compromising the geomechanical integrity of the Lakota Formation.
Based on the estimated reservoir and stress state conditions, a thermo-hydro-mechanical simulation is conducted at a constant CO2 injection rate for up to 10 years at a maximum injection rate of 0.1 Mtons/yr. Changes in pressure, temperature, saturation, and stress due to CO2 injection after one day, one month, one year, five years, and ten years are analyzed. The simulation shows significant differences between thermal and pressure fronts and the concentration of thermal stresses around the borehole, showing stress changes with the thermal shock fronts. Simulation results reveal limited injectivity compared to other potential projects.
This research highlights that the permeability and relatively narrow injectable zone within the Lakota Formation, coupled with a high-temperature anomaly, present challenges in achieving high annual injection rates without compromising the geomechanical integrity of the Lakota Formation. These conditions limit the feasibility of the Lakota Formation within the study area for large-scale CO2 injection projects.
Associated Publications
Rights
Copyright of the original work is retained by the author.