Discipline: Ecology Environmental and Earth Sciences
Subcategory: Environmental Engineering
Andrew D. Overbey - University of New Mexico
Co-Author(s): John C. Stormont, University of New Mexico, Albuquerque, NM
Hydraulic fracturing, the process of pumping highly pressurized fluids into a tight gas formation to increase its permeability and stimulate natural gas release, has led to an increase in active gas wells in United States, from 262,483 in 1989 to 553,495 in 2016. With this increase in active wells, there is an increased possibility of leaky wellbores that can allow gas to reach overlying water-bearing zones and even the surface. A principal cause of leaky wellbores is fractures in the wellbore cement that is used to seal the annular space between the wellbore casing and the adjacent formation. Natural gas flow through the leaky wellbore system will expose the wellbore cement to natural gas constituents, of which methane is the principal component. The objective of this study is to determine the effect of methane gas exposure on the physical and chemical properties of cement. We hypothesize that sorption of methane will soften the cement because the sorption product will be softer than virgin cement.
Samples of Type I/II cement were prepared in the lab. One set of samples was exposed to a methane gas mixture (5% CH4, 95% N2) at 3450 kPa for one week. To control for the effect of N2 in the gas mixture, a second set of samples was exposed to pure N2 at 3450 kPa for one week. Results are compared to unreacted cement. After exposure, XPS was used to determine if methane sorption has occurred. Samples were tested using a Vickers hardness tester to determine if sorption of methane has impacted the hardness of the cement. All results are compared to unreacted cement to assess the amount of and effect of methane sorption on wellbore cement. Additional studies include flow through experiments on fractured cement samples to determine the impact of methane on the permeability of fractured cement.
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Funder Acknowledgement(s): This material is based upon work supported by the National Science Foundation under Grant Number 1345169. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Faculty Advisor: John C. Stormont, firstname.lastname@example.org
Role: I was responsible for experimental design, data collection, data analysis, and data interpretation.