Routine to Extreme: Rotary Steerables

Weatherford has drilled one million feet with its Revolution rotary-steerable system and along the way has set new milestones for some of the deepest, hottest, highest-pressure environments encountered in the E&P sector.

Rotary-steerable systems (RSS) outperform conventional directional systems by significantly improving the drilling process through better hole cleaning, higher rates of penetration (ROPs), precise directional control and extended reach of horizontal wells.

Weatherford's Revolution RSS uses "point-the-bit" technology to deliver a gun-barrel in-gauge wellbore. The high-quality wellbore provides significant benefits, including improved formation evaluation, reduced drilling-fluid costs, easier installation of tubulars and enhanced production.

Point-the-bit technology has been proven to drill a much straighter and smoother hole than competitive "push-the-bit" systems.

Enhancing the capabilities of the Revolution system is Weatherford's logging-while-drilling (LWD) system, which provides key downhole data to optimise wellbore placement.

A better system for LWD

Weatherford's PrecisionLWD system components are entirely new generation, designed from the outset to handle tough drilling conditions.

The hostile-environment logging (HEL) measurement-while-drilling (MWD) system transmits basic positional measurements in real time, while the total PrecisionLWD system includes all HEL MWD components plus multi-frequency resistivity, thermal neutron porosity and azimuthal density sensors.

Of course, it is not enough to measure what is going on down in the borehole. The data must also be conveyed to the surface. LWD tools rely on sending data as pulses in circulating drilling mud.

If the mud is not circulating or is aerated (as in most Controlled Pressure Drilling scenarios), it will not transmit a pulse.

To overcome this obstacle, the PrecisionLWD system is the only triple-combo system in the industry that can use electromagnetic (EM) technology, which transmits data by sending data pulses electrically through the earth rather than through the drilling mud.

Weatherford's system can acquire data at logging speeds of 400 feet (122 metres) per hour, achieving one of the industry's highest data-acquisition speeds in an LWD triple-combo system. This means that LWD operations can now contribute positively in high-ROP drilling environments.

Milestone 1: Deepest well, highest pressure

In the Green Canyon section of the Gulf of Mexico, a major operator was drilling a vertical exploration well from a drillship, the daily operating costs of which approached US$500 000.

At close to 29,000 feet (8,839 metres), the 8 1/2-inch hole started to drift away from the vertical position.

To solve the problem, Weatherford deployed the Revolution RSS with the HEL MWD and PrecisionLWD systems, and within 24 hours drilling was once again back on target. Successfully operating the Revolution RSS at this extreme pressure and depth remains a Gulf of Mexico drilling record.

The well ultimately reached total depth at more than 34 000 feet (10 363 metres)-nearly 6.5 miles, or 10.4 kilometers. This achievement broke the previous record depth of 32 727 feet (9,975 metres)-6.2 miles, or 10.0 kilometers-set earlier in 2005 by Shell, which also used the PrecisionLWD system.