Civil Engineering ETDs

Publication Date

Summer 7-8-2022

Abstract

The objective of this study is to determine the effect of the products from steel corrosion and cement dissolution after reaction with produced water (PW) on the permeability of a wellbore microannulus. The wellbore microannulus is the interface between wellbore cement and steel casing and is often identified as a leakage pathway in wellbore systems. The need to better understand the impact of PW on well integrity aids in the assessment of environmental impacts of energy production. Static batch reactors were used to expose a cement – steel microannulus to two PW solutions, a simulated PW, and a field sampled PW. Results from electron probe microanalysis (EPMA) show that reaction of PW in the microannulus between cement and steel causes precipitation of solids containing calcium (Ca) and magnesium (Mg). X-ray diffraction (XRD) results show the predominate solids of bulk cement are, portlandite [Ca(OH)2], CaH4Si2O7 and brownmillerite [Ca2(Fe1.45Al0.55)O7]. The weight % content of these predominant solids remained unchanged, and the weight % content of periclase [MgO] increased with increasing reaction time. Flow measurements interpreted as hydraulic aperture of the microannulus sample show an overall decrease in hydraulic aperture with increasing reaction time between 2.0 and 720 hours for all sample types. The cement-steel microannulus samples reached the hydraulic aperture value of 5 microns after 720 hours of with both PW solutions, which are comparable the measurements taken from an unreacted cement plug. The findings of this study suggest that PW can reduce the flow paths created by debonding of cement and steel by Ca- or Mg-bearing mineral precipitation. These results have implications related to understanding reactions that may be occurring in wellbore systems which are in contact with produced waters.

Keywords

wellbore, microannulus, produced water, cement, steel casing, hydraulic aperture

Sponsors

UNM Center for Water and the Environment

Document Type

Thesis

Language

English

Degree Name

Civil Engineering

Level of Degree

Masters

Department Name

Civil Engineering

First Committee Member (Chair)

John C. Stormont

Second Committee Member

Jose M Cerrato

Third Committee Member

Brian R Ellis

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