Techniques for well-abandonment log evaluations have been studied in the Gulf of Mexico since 2012. Legacy practices typically used acoustic methods consisting of cement-bond-log (CBL) and ultrasonic-scanner devices. The new methods described in this paper consist of adding nuclear sensors to supplement the acoustic measurements and introduce novel processing methods. The overall solutions package consists of behind-pipe-evaluation techniques (BPETs). When properly modeled and analyzed, these data have the potential to reduce the cost of removing casing strings significantly.
Introduction
Much of the nonproductive time associated with well abandonments is attributed to difficulty circulating the stagnant material left behind in the casing-to-casing annuli during well construction. Many improvements have been made in the design of these fluids; however, drilling muds using barite as the weighting agent still suffer phase degradation over time, leaving a column of material with a density that increases with depth, except when solids bridging occurs.
