Reduce Well Time with LWD Sonic Technology for Top of Cement Determination and Cement Evaluation in a Carbonate Reservoir, a Case Study from Onshore Abu Dhabi

Abstract This case study demonstrates an innovative approach to evaluating cementing operations in complex well environments in the UAE, where challenges such as tight clearances, depleted zones, weak formations, and mechanical failures are common. These challenges are often compounded by partial, or no cement returns during operations. Accurately determining the top of cement (TOC) is critical to confirming proper cement placement, which directly impacts well integrity. Traditional methods, like cased-hole wireline logging, can be costly, time-intensive, and pose operational risks. This study highlights the successful use of logging-while-drilling (LWD) sonic sensors as an alternative to wireline logging for TOC determination and cement evaluation. The evaluation was performed after drilling an 8½-in. section and installing a 7-in. liner. LWD sonic sensors, deployed during a clean-out run, were configured to collect compressional and refracted shear slowness along with raw waveforms. Pre-job planning was essential to optimize the tool's performance. This included configuring firing settings and frequency, determining the appropriate logging speed for enhanced data resolution across critical intervals, and selecting a suitable sample rate. The primary objective was to identify the TOC and evaluate the cement bond inside the liner. Key observations revealed that the compressional slowness was dominated by casing signals, making it less effective for TOC determination. However, the refracted shear waves provided a strong response, indicating a well-bonded cement sheath and good formation bonding. This confirmed the absence of a micro-annulus and demonstrated high cement quality throughout the logged interval. The LWD sonic tool successfully identified the TOC and evaluated cement quality without requiring a dedicated wireline logging run. By integrating the LWD sonic tool into the drilling process, the operation avoided additional rig time and costs associated with wireline logging. This approach reduced risks such as operational delays and potential well-integrity issues. The case study shows the ability of LWD acoustic technology to provide accurate cement evaluation, even in the challenging casing designs and cementing profiles prevalent in the UAE. In conclusion, this method proves the reliability of LWD sonic sensors for TOC determination and cement quality evaluation in complex well environments. It highlights the benefits of adopting advanced technology to enhance operational efficiency, reduce costs, and maintain well integrity. This success sets a benchmark for optimizing cementing operations in the UAE and similar challenging oilfield conditions worldwide.