Abstract
The non-corrosive, electrically resistive fiberglass casing materials may improve the economics of oil and gas field projects. At moderate temperatures (<120 °C), fiberglass casing is superior to carbon steel casing in applications that involve wet CO2 injection and/or production, such as carbon capture and storage, and CO2-based enhanced oil recovery (EOR) methods. Without a perfect protective cement shell, carbon steel casing in contact with a concentrated formation brine corrodes and the fiberglass casing is superior again. Fiberglass casing enables electromagnetic logging for exploration and reservoir monitoring, but it requires the development of new logging methods. Here we present a technique for the detection of integrity of magnetic cement behind resistive fiberglass casing. We demonstrate that an optimized induction logging tool can detect small changes in the magnetic permeability of cement through a non-conductive casing in a vertical (or horizontal) well. We determine both the integrity and solidification state of the cement-filled annulus behind the casing. Changes in magnetic permeability influence mostly the real part of the vertical component of the magnetic field. The signal amplitude is more sensitive to a change in the magnetic properties of the cement, rather than the signal phase. Our simulations showed that optimum separation between the transmitter and receiver coils ranged from 0.25 to 0.6 m, and the most suitable magnetic field frequencies varied from 0.1 to 10 kHz. A high-frequency induction probe operating at 200 MHz can measure the degree of solidification of cement. The proposed method can detect borehole cracks filled with cement, incomplete lift of cement, casing eccentricity, and other borehole inhomogeneities.
Highlights
According to the National Association of Corrosion Engineers ((NACE) https://www.nace.org/home), the total annual cost of corrosion in the oil and gas production industry is estimated to be $1.372 billion, broken down into $589 million in surface pipeline and facility costs, $463 million annually in downhole tubing expenses, and another $320 million in capital expenditures related to corrosion.As the oil and gas industry matures and it demands to sequester carbon dioxide at a massive scale, these corrosion costs may skyrocket
Carbon steel casing corrodes quickly in a wet CO2 environment [1,2] encountered in carbon capture and storage (CCS) and in CO2 -based improved and enhanced oil recovery processes
It is necessary to estimate the magnitude of the useful signal and quantify appropriate measurement methods. This leads to an accuracy assessment of the sensors or magnetometers that should be installed in the magnetic cement sensing tool
Summary
According to the National Association of Corrosion Engineers ((NACE) https://www.nace.org/. If a casing cement annulus is faulty or breaks down, the carbon steel corrodes when exposed to concentrated formation brine. It is necessary to estimate the magnitude of the useful signal and quantify appropriate measurement methods This leads to an accuracy assessment of the sensors or magnetometers that should be installed in the magnetic cement sensing tool. Kaufman [19] developed a theory of measuring formation resistivity in a cased borehole with a sufficient accuracy for practical applications. We propose a tool to measure and control the integrity of a weakly magnetic cement behind non-conductive fiberglass casing. We focus on detecting small changes in the magnetic permeability of a cement-filled annulus behind a non-conductive casing
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