Optimizing Well Integrity with Accurate Forecasting of Casing and Tubing Resistance Reduction Trends Through Innovative Numerical Modeling Techniques

Summary Well integrity is an essential aspect of well operations, and international standards are stringent on its application. Tubing and casing corrosion constitutes a major risk to well integrity and a challenge that must be analyzed preventively. Corrosion logs are programmed to verify the status of the barriers, but there is currently no methodology for planning future logs. In this paper, we propose a numerical modeling method to forecast tubular resistance reduction trends and estimate the barrier’s residual life. Corrosion logs are expensive and require the well to be shut in, which impacts the cost of the operation. Therefore, a numerical methodology for planning future logging is preferable to planning based on experience. Here we propose a methodology for predicting the point at which the downhole barriers will no longer satisfy the maximum allowable annular surface pressure (MAASP) criteria, using data from historical corrosion logs and a time-linear corrosion model. This innovative methodology recalculates MAASP for collapse and burst resistance of corroded pipes while considering well completion design and vertical depths resulting from the directional survey. The proposed methodology provides a comprehensive assessment of the corrosion progress, making it a more reliable tool for forecasting future corrosion trends. The methodology uses the last two corrosion logs for optimal prediction, but it also works when a single corrosion log is available. Numerical modeling is then used to calculate pipe resistance at each depth step of the LAS file, drawing a picture of the resistance vs. depth and time. The result of this new method is a chart that forecasts the progressive reduction of A-Annulus MAASP and the time at which it will cross the minimum criteria of the operator. Furthermore, the proposed methodology provides a probability window that takes into consideration the best- and worst-case scenarios. This is the first time that numerical modeling is used to recalculate MAASP and to forecast MAASP reduction trends in well barriers, based on corrosion/erosion measurements. The corrosion logging schedule can, hence, be programmed before MAASP reaches the operator’s limit, thus optimizing planning and costs for the operator. This, in turn, leads to a reduction in costs without affecting the overall operability and risking barrier failures.