Downhole Corrosion Sensors for Predictive Maintenance of Gas Well Under Harsh Conditions

M.H. Haque, R.K. Saini, M.N. Noui-Mehidi, J.L Jauregui
Aramco Americas,
United States

Keywords: corrosion, scale, erosion, sensor, coupon, gas well

Summary:

The service life of a well tubing is directly dependent on the conditions of the producing wells, especially on the degree of corrosiveness of the producing hydrocarbon gas in sour gas well. Such wells contain water, CO2, and H2S in general at high pressure and temperature. This combination of the chemical and physical harsh conditions trigger (1) corrosion damage, i.e., metal loss and pitting, leading to mechanical failures and cracks and (2) scale damage, i.e., scale deposition. Therefore reducing the production rate and shortening service of the well tubing. Monitoring the health of the well tubing as function of time is important in maintaining and ensuring uninterrupted production during the service life of the well. Coupon holders are popular corrosion indicator at downhole conditions and are traditionally used in passively monitoring the corrosion or scale damage where relative damage to a set of target metallurgies can be studied for tubing materials selection custom to the well of interest. Unfortunately, a standalone coupon holder cannot provide the history and the transient nature of the corrosion rate or weight loss due to corrosion as a function of time and temperature. In this work, we report an advanced downhole corrosion, scale and erosion monitoring tool coupled with a battery powered data-logger that can measure and store well data. The custom-made coupon holder can accommodate multiple coupons to study corrosion, scale, and erosion on different piping metallurgies. The proprietary design allows the coupons in such a way to ensure consistent chemical exposure. Coupon geometries have been optimized to ensure maximum exposure to downhole sour gas environment and minimum interruption to the hydrocarbon production. When retrieved from downhole conditions the tool provides simultaneous well data as well as opportunity to characterize and evaluate different coupon metallurgies to be correlated with the well data. Thus supporting an effective monitoring, evaluation and prevention strategy to enhance the service life of well tubing under harsh downhole conditions.