Time-Lapse Evaluation from Ultrasonic Pulse-Echo and Pitch-Catch Configuration and Sonic Logging Data for Potential Formation Creep and General Annulus Solids Segregation

Abstract

Verification of annular well barrier elements is an essential process during the well construction and plug and abandonment phases. This topic has been the subject of many publications and is governed by regulations in different countries around the world. In this paper we focus on the evaluation of shale creep barriers. We describe how sonic and ultrasonic pulse-echo and pitch-catch configuration data are used to monitor the evolution of formations creep around the casing to eventually form annular barriers. Multiple annulus logging evaluations were performed across wells from the Valhall, Ula, Alvheim, and Jette fields on the Norwegian Continental Shelf (NCS). This was done using ultrasonic pulse-echo and pitch-catch configuration data as well as traditional sonic logs. The logging data were collected, reprocessed, and compared as part of a collaborative effort between the operator and a service company. In this study we examine the progression of annular solids through time from formation creep. Our intention was to study the ability of shales creep to form barriers, and to simplify the well design and achieve isolation around the production casing without the need for conventional cementing operations. The log data provide information of annulus material with a detailed map of the axial and azimuthal variations of the annulus contents. Crossplotting state-of-the-art measurements also helps to identify the material accumulating in the annulus as published in many other industry papers. This approach has garnered interest over the years as a novel solution during well abandonment operations. The results provide solid evidence of shale creep-forming barriers and has been used by the operator to further refine their zonal isolation strategy. Comparing ultrasonic data with a particular interest on the progression of formation creep, has become a popular subject within the NCS. Innovative use of historical logging data holds a great potential to help make decisions that result in reduced cost and environmental impact. Because of this novel usage and analysis of ultrasonic logging data, the operator was able to make informed decisions faster, saving rig time and cost while reducing the carbon footprint.