MaxCOR Technology Improves Accuracy of Rock and Fluid Analysis
Authors: JPT staff _ 
Published: February 2015

Young Technology Showcase

The Baker Hughes MaxCOR rotary sidewall coring service provides fast, accurate 1.5-in. (3.8-cm) diameter core samples with 213% more volume than the standard Baker Hughes PowerCOR rotary sidewall coring samples.

The MaxCOR service was the first rotary sidewall coring tool on the market capable of acquiring larger, higher quality samples while operating at the highest temperature and pressure ratings in the industry. The service can reliably retrieve 60 samples during a single trip in formations that range from soft to hard lithology, in highly overbalanced formations, or in environments of up to 25,000 psi and 400°F (204°C). Its use improves the accuracy of reservoir rock and fluid analyses, such as porosity, relative permeability, capillary pressure, water saturation, geomechanical, and other special core analysis (SCAL) properties. 

“The step change in this technology gives you a bigger core sample, for more accurate lab measurements,” said Gigi Zhang, region geoscience manager at Baker Hughes.

Technology’s Development

The path to the tool’s development was twofold. First, with the goal of providing a faster and more reliable coring service, Baker Hughes engineers revamped the legacy sidewall coring tool to develop the PowerCOR rotary sidewall coring tool, which retrieves the industry standard of 1-in. diameter core samples. At this stage of the design, engineers focused on improving the device to deliver better performance. Many of the old generation tool’s complex components were simplified, such as a new core separator design with fewer moving parts to enhance the reliability of the operation.

To increase reliability, engineers designed the MaxCOR bit control mechanism on a piece of steel, which is then machined to reduce the parts count of the tool and to provide greater strength. The rigidity of the one-piece bit drive mechanism also contributed to an improved core break function by providing a more positive break when extracting the sample.

Since the legacy coring tool was hydraulically powered, it was saddled with unprotected tubing running over the outer surface. The new design eliminated the hydraulic motor and hydraulic lines and uses gun-drilled holes for the wires. This gives the tool a cleaner profile and makes it less prone to failure as a result of being exposed to the downhole environment.

The coring bit is the heart of the operation, and engineers determined that by replacing the hydraulic-driven powering mechanism with a direct current driven motor, the bit would rotate more than three times faster. The new motor design significantly reduces the time in coring each sample, from an average of 9 or 10 minutes to 4 or 5 minutes, thus saving valuable rig time.

The direct-drive electric motor is controlled by a sophisticated downhole power management system that ensures maximum power transfer efficiency under all load and borehole temperature conditions. The bit is a patented design that matches the greater rotational speed of the electric motor. The new bit design also allows cuttings to be cleared more easily, enhancing the tool’s performance in high overbalance conditions.