Drilling events and the eventual outcome of a drilling campaign can be unpredictable, with some incidents leading to costly or catastrophic outcomes. To solve problems such as wellbore instability or sloughing shales, the drilling industry has traditionally responded by introducing new technologies, techniques or processes. This can include reducing downtime, especially after extensive openhole logging, or after any operation that requires the wellbore to be left open for a prolonged period of time, as this can be critical for the E&P sector.

Cementing challenges

One such challenging area is cementing. The strength of the cementing operation on a well depends on how the cement is deposited. In a vertical well cementing is usually relatively straightforward since the cement comes up the sides evenly. The more inclined the well is, however, the more likely it is that fluid will follow the path of least resistance—in other words, flow to the top of the casing and not the bottom.

Furthermore, in high-angle and horizontal wells when displacing cement, conventional technologies are not designed to apply the slurry evenly around the casing string, with more cement usually going preferentially to the high side of the hole rather than radially around the string.

Uniform deposition

The GeoproHYDRA is a low-torque high-speed tool that addresses cementing issues affecting high-angle and horizontal wells. It disperses fluid uniformly by rotating as cement passes through at very high rotational speeds. The result is cement deposition at the top and bottom. This more uniform deposition of cement around the borehole significantly improves the quality of cement at the shoe in all well types and thus the integrity of the cement behind the casing or liner.

By rotating part or all of the tool at high speed, a cyclone effect is created, which also helps to clear the borehole of all debris and contaminants prior to cementing—a useful additional capability in sticky hole conditions or through unstable formations. Rotation of the entire tool is beneficial when working on a long high-angle section, where rotation is needed at the bottom to work the string down.

Thanks to the high rpm achieved, the envelope of application is widened. This tool also can be used as a jetting tool or a core tripping cleanup tool. In addition, well brushes can be installed to make it a cleanup tool for cement. Alternatively, a bit can be put at the bottom of it to clean the casing line before drilling out.

Field trials

Trials of this dual cementing/reaming technology are currently taking place on wells in Murmansk in northwest Russia, with positive results so far. On the first well where the technology was trialed, previous attempts to land 7-in. casing at the target depth had failed, costing the operator 35 days of nonproductive time (at a monetary cost of more than $1 million) and resulting in the entire casing string having to be pulled out of the hole, resulting in broken centralizers and other accessories.

The formation was unstable, a significant proportion of the hole was at high inclination and the casing shoe also went through an azimuthal turn of more than 100 degrees. Having used the tool described above, the cement at the shoe was of good quality when tested, and debris removal also was improved. The operator plans to use the tool on two more wells this year and a further 20 next year.

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