Lu, Yunxing
(2023)
Novel Self-Sealing Materials and Poromechanical Analysis for Permanently Plugging Wells for Abandonment (P&A) in High Temperature Environments.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Permanent abandonment refers to the final stage of the life-cycle for a petroleum well. Because the goal is to render harmless a well that will never again be accessed, plugging must be done in such a way that the material is effective and resilient over geological time. The difficulties and cost of P&A are mainly coming from two parts: the harsh P&A conditions (high temperature, high pressure, acidic reservoir conditions, and mud contamination) and the lack of guidance from P&A codes and standards. Thus motivated, this research is firstly aimed at demonstrating the feasibility of generating new "Geologically Activated Cement" (GAC) plugging material that turns the above mentioned harsh conditions of deep-water wells into an advantage. More importantly, if damaged, the GAC can self-seal within a few hours when subjected to flow of acidic fluid under HPHT conditions. This self-sealing trait provides the potential for a resilient cementing system. Secondly, with aid of a new semi-analytical solution for thermo-poro-elastic (TPE) stresses in a cylindrical cement plug that includes consideration of full coupling between hydraulic and thermal transport models, this work rigorously challenges the status quo design assumption that a lower permeability barrier material always better. To the contrary, because extremely low permeability porous material is slow to drain excess pore pressure, low permeability cement can be prone to damage from thermally-induced pore pressure buildup. Furthermore, the analysis is the first to identify an important role of specific heat of the cement in preventing pore pressure buildup, thereby showing a new way forward for cement design that targets high specific heat additives. Thirdly, this research presents an experimental demonstration of a novel mode of periodic tensile cement failure that could be commonly encountered in the life span of wells that undergo rapid temperature and/or pressure cycling. This is the first demonstration of such predictably spaced periodic cracks under conditions relevant to P&A operations. Overall, these findings provide new materials and analysis methods that invoke change in P&A codes and practices and therefore aim make P&A more reliable and resilient over geological timeframes.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
19 January 2023 |
| Date Type: |
Publication |
| Defense Date: |
3 November 2022 |
| Approval Date: |
19 January 2023 |
| Submission Date: |
28 October 2022 |
| Access Restriction: |
1 year -- Restrict access to University of Pittsburgh for a period of 1 year. |
| Number of Pages: |
152 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Civil and Environmental Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
P&A, self-healing Material, Thermo-poroelasticity, dilation bands |
| Date Deposited: |
19 Jan 2023 19:17 |
| Last Modified: |
19 Jan 2024 06:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/43772 |
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