Deployment of New Sonic-While-Drilling Technology in a Large Development Project in the Middle East: A Case Study

Abstract

A new logging-while-drilling (LWD) sonic tool was successfully deployed in a large development project in the Middle East. The new LWD sonic tool offers robust compressional and shear measurements, irrespective of mud speed, and Stoneley information for a wide range of applications. The acquisition of LWD sonic measurements can be challenging. The introduction of the new tool with a novel hardware design, extensive tool modeling, and an alternative approach to data handling has significantly improved both overall data quality and the viability of advanced answer products while drilling.The fundamentals of both wireline and LWD sonic measurements are similar; however, differences in the measurements dictated by the deployment environment need to be considered. LWD tools are deployed on a drillstring and have a large diameter. Wireline tools are much smaller and are deployed on wireline after drilling is completed. Operational frequencies, acquired waveform modes, and transmitterreceiver source spacings are also different. The most fundamental difference is that the new LWD tool uses quadrupole technology to acquire shear slownesses in slow formations (shear formation slowness slower than mud speed), whereas, in the same environment, the wireline tool relies on dipole technology.Although there is considerable literature that discusses waveform quality, processing, and interpretation of wireline sonic measurements, very few such studies exist for LWD sonic measurements. In addition, no studies compare the measurements. To investigate the interpretation and use of the new LWD tool and to compare it with wireline sonic tool technology, both methods were deployed in the same wellbores in a large development project in the Middle East. Most observed disparities were across washed out boreholes where data quality from both wireline and LWD tools was negatively affected by the borehole environment.