LWD acoustic data has been available in real-time for nearly 20 years, but the data quality has not always been acceptable. Recent developments in data acquisition, including the transmission of semblance quality control (QC) logs, have greatly improved the quality and reliability of LWD acoustic data for applications such as real-time inter-granular porosity measurements, synthetic seismic creation, cement quality indications, and geo-mechanics applications.
This new development in LWD azimuthal acoustic logging enablesd expansion of these advanced applications into the while-drilling environment and presents the oil industry a robust geosteering and formation evaluation tool.
This paper presents a case study in a giant oil reservoir onshore Abu Dhabi, where back-to-back conventional logging was used to evaluate the new data acquisition advances. The data collected with an azimuthal unipolar sonic LWD tool provides 16-bin compressional and shear slowness images in memory and quadrant images in real time.
New algorithms have been implemented to enhance the quality of transmitted data. Several Middle East case studies comparing the real-time sonic images to the memory data, in terms of resolution and data quality, have clearly showed improved data acquisition quality, which is crucial tor real-time formation evaluation and decision making.
Examples presented in this paper prove that these advances in acoustic data acquisition are very helpful in the following applications:
Onshore horizontal wells in formations whose resistivity contrast is too low for conventional geosteering tools.
Sourceless porosity tool in horizontal extended-reach wells, where the risk of sticking and losing nuclear sources is higher
Real-time geomechanical modeling to determine the safe mud weight window, uniaxial rock strength, and mechanical rock properties