Seeing further potential for oil and gas downhole sensors, GE Oil & Gas is not just seeking incremental improvements through its research and development, but new game-changing sensors altogether.

The company has been involved in the downhole sensor space since the 1950s, and offers three commercial sensors to the oil and gas industry: neutron, gamma, and directional sensors. But GE Oil & Gas believes the challenges associated with these sensors limit their full potential.

One type of sensor technology, gamma sensors, have been utilized in the oil and gas industry since the late 1970s and early 1980s. A common material used in gamma sensors, a salt crystal called sodium iodide, has served industry well. However, it has limitations. One is that it doesn’t perform well at higher temperatures, with its light output dropping by as much as 40%. With most oil and gas wells now being drilled to deeper depths, higher temperatures are being encountered. Therefore, that material is not very suitable for this application.

Another limitation is that it’s not very dense. The more dense the material, the more counts per second can be produced. More counts provide operators with better confidence in their measurement. Even if an operator is happy with their confidence level, a more sensitive sensor can create advantages in tool design, such as a more compact sensor. Sodium iodide’s long decay time also limits its use in more sophisticated measuring techniques, such as differentiating between elastic and inelastic interactions in pulsed neutron applications.

To address the shortcomings of sodium iodide, GE has developed a material called lanthanum halide to handle rugged oil and gas drilling environments and offer greater light and output. This material was developed in collaboration between GE Oil & Gas, GE Healthcare and the old GE Security business, as well as GE’s Global Research Center. Similar materials have been available for some time, but GE has been able to optimize the chemical composition to further enhance light output and resolution.

In addition, due to very high costs, oil and gas companies have been skittish about using lanthanum halide sensors, which can cost as much as $50,000, in environments where they could lose the sensor and halt operations. Besides cost, downtime is another major issue facing oil and gas companies. In fact, offshore operators can face losses of hundreds of thousands of dollars a day from downtime. GE is leveraging its ruggedization capability that has been proven over the last two decades to bring lanthanum halide scintillators to the harshest oil and gas environments, thereby offering customers the enhanced performance and high reliability that they need.

To meet its customer’s high temperature and reliability challenges, GE is seeking to replace the photo multiplier tubes in gamma sensors. Photomultiplier tubes rely on the traditional technology of bi-alkali photocathodes and amplifying dynodes to detect the light pulses and convert them to electrical pulses. The technology requires high voltage operation, and steadily drops in performance with increasing time and temperature, which severely limits operating envelope and expected life. GE is developing a silicon carbide-based photo detector that will be capable of operating continuously at 230 degrees Celsius with a 3x-4x increase in reliability due to lower voltage operation. This technology leverages extensive work that has been done by GE Power and the Global Research Center in the application of SiC to power generation and flame detection applications.

GE is also seeking to enhance the capability of directional sensor technology, which has not been enhanced in decades. By design, these sensors are sensitive to magnetic interference, limiting where they can be placed on the drillstring or wireline logging tool. Because they are sensitive to magnetic interference, the sensors also cannot be used in proximity of magnetic material such as existing casing from adjacent wells. Finally, due to their inherent design, the sensors provide a high quality response only every 90 feet as a new drillpipe stand is added and the mud pumps are turned off.

To compensate for shortcomings, these sensors must be complemented with dedicated gyro-while-drilling, requiring additional time and cost. GE’s new technology leverages gyro designs that were initially designed for GE Aviation. This technology is integrated with the existing directional sensor design, thereby saving the service company as much as 1-2 days and $20,000 per well. It also holds the promise of enhancing reliability by a factor of 2x, and enabling continuous surveying (instead of only every 90 feet), which in turn allows for closer well spacing, thereby enhancing ultimate recovery by as much as 40%.

Step changes in downhole sensor technology are needed as the oil and gas industry tackles the new challenges in offshore and onshore fields. GE’s interest in enhancing sensor technology also has grown along with shale development activity. Drilling wells faster is part of this strategy. In 2009, it took 15 to 20 days. Now, companies are pushing for as few as five days. With faster drilling and higher rates of penetration, the tools experience greater vibration. Every new downhole sensor technology development at GE is focused on enhancing performance and reliability under high temperature and vibration.

In short, GE is not just seeking to incrementally change technology, but take downhole sensor technology to a whole new level. This new level of technology – developed through the collaborative efforts of GE’s divisions – will be needed as the exploration and production game continues to grow in complexity.