Comparative wellbore integrity evaluation across a complex of oil and gas fields within the Michigan Basin and implications for CO 2 storage

Wellbore integrity is a fundamental aspect of site characterization and selection for storage in areas with existing or abandoned oil and gas wells. The condition of well cement, installed casing strings, and plugs determine if a well can sustain optimal hydrostatic pressures and prevent fluid migration. This is a necessary but underappreciated aspect of assessing potential storage sites when optimal and sustainable pressure conditions are critical for success. To apply the systematic wellbore integrity evaluation to realistic CO 2 storage conditions, seven fields in the Michigan Basin were selected which were actively being used for CO 2 injection for enhanced oil recovery. Data on wellbore construction were collected for wells on and surrounding the reefs and were evaluated to determine the overall condition of boreholes in the study area using EPA guidelines and industry standards. Available cement bond logs were also reviewed to assess the quantity and quality of cement in the wells. The majority of the wells in the study area were shallow and did not penetrate the confining layers, thus, posing little to no risk. Most of the deep wells demonstrated sufficient plugs and cement quality that meet the desired standards. Some wells have missing or incomplete records and inadequate cement and/or plugs making them candidates for further evaluation, should large‐scale CO 2 storage be considered in the area. The results of the study show that readily available well records and cement bond logs can be used to efficiently evaluate and characterize CO 2 storage study sites for overall wellbore integrity. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd.