Sonic LWD service delivers real-time data in deepwater, unconventional formations
By Katie Mazerov, contributing editor
Halliburton’s Sperry Drilling Services has added a new azimuthal and ultrasonic service to its sonic logging-while-drilling (LWD) tools. The XBAT Azimuthal Sonic and Ultrasonic LWD service measures sonic properties, such as rock mechanics and porosity, in a wide range of formations, including deepwater and unconventional plays. It uses sensors and electronics that are less sensitive to drilling noise and have a wider frequency response, making it suitable for noisy drilling environments and poor hole conditions, according to the company.
The service uses compressional and shear velocity measurements to deliver real-time pore pressure prediction, seismic correlation, gas detection, sourceless porosity, rock mechanics and wellbore stability, shale logging and cased-hole and cement bond logging.
“The XBAT tool delivers an enhanced signal-to-noise ratio, as well as increased firing flexibility, so we can get optimum measurements in a wide range of formations,” said Dr Paul Cooper, LWD sonic product manager for Halliburton. “The service is particularly advantageous in exploration wells where we often don’t know the properties of the formation, and in long runs, where rock properties may change significantly over the course of the run.” The tool is also appropriate for unconventional plays where the azimuthal feature provides measurements of anisotropy in the shear velocity, allowing optimization of the completion program.
The XBAT LWD service uses four discrete transmitters and four azimuthally spaced receiver arrays, each of which is sensitive across a broad range of frequencies and is isolated from the collar to eliminate bit and mud circulation noise. It also has the capability of firing in five modes downhole, compared with previous tools that had two firing modes. “This gives us greater flexibility to choose different frequencies in exploration wells, which can have a wide range of formation slowness,” Dr Cooper said. “It provides us with the ability to fire in a number of ways and frequencies, which is more likely to give us good quality data.”
The service has been deployed in more than 100 runs globally and has been tested extensively in Gulf of Mexico and North Sea environments. In one offshore well, where the customer faced formation uncertainty, the XBAT service provided the flexibility of firing four modes on the same run. “This gave the operator the opportunity to get good data on the well to better understand the properties of the formation and how it would respond to the sonic tool,” he said. “With conventional sonic LWD, we would not have had that flexibility because we would have been limited to two firing modes.”
Another feature of the service is the four ultrasonic calipers, placed 90° apart around the tool, which provide a more robust dispersion correction measurement, a function in part of how far the sensors are from the formation. The calipers provide a real-time azimuthal borehole image, including hole size, hole shape and breakout. “The four-caliper arrangement allows us to correct for the tool position and motion in the borehole, giving a better caliper measurement for wellbore stability analysis,” Dr Cooper explained.
“With this new service, we can provide more reliable information that is useful to drillers so they have a better idea of what is going on the wellbore,” he continued. “By getting information early, during the drilling process, they can anticipate drilling problems, keep control of the well and understand borehole stability to drill successfully.”
XBAT is a service mark of Halliburton.
