INDUSTRY FOCUS OIL & GAS A DEEP DILEMMA
The continued demand for oil and gas is pushing exploration and extraction deeper and further into remote regions of the world. Here, Steve Kirk of Harmonic Drive UK, looks at the technological challenges and how precision gearing is being increasingly used to drill deeper
L
ying in the western Pacific Ocean, south of Japan and north of New
Guinea, is an archipelago known as the Mariana Islands. A collection of underwater volcanic peaks and harbouring the Mariana Trench, the deepest part of the world's oceans. Reaching a maximum known depth of
10,911m (6.83 miles) it culminates in a small slot shaped valley known as Challenger Deep - named after the exploration vessel that discovered it some 50 years ago. At this depth, the pressure of the water column above is equivalent to 15,750psi - a thousand times greater than at sea level. The temperature ranges from one to four degrees Celsius and only microbial life forms thrive.
GOING DEEPER Having exhausted reserves in many subsea oil fields, the pressure is now building on extraction companies to drill deeper and for longer, to obtain every last drop of the black gold. Existing equipment is not always rated for operation in the extreme temperatures, pressures and associated logistics of deep sea extraction. This is creating technological
challenges all the way from the top to the bottom of the supply chain. From topside platforms to subsea structures and all the way further downhole to the directional drill bit, original equipment manufacturers (OEMs) face the challenge of developing equipment that can withstand the harsh environment. Having encountered these challenges over the last 40 years in developing gearing systems and actuators, Harmonic Drive is currently experiencing a growing demand from the oil and gas sectors, as they move away from traditional hydraulic actuation systems towards electro- mechanical actuation systems. Gearing-based electrical actuation is
more economical, ecological, controllable and more reliable than traditional hydraulic actuation systems, which can develop oil leaks over time. The need to frequently service hydraulic systems at depths of 6,000m is neither economically feasible nor necessary with the advent of electromechanical systems.
16 FEBRUARY 2015 | AUTOMATION The high single stage ratio of Harmonic
Drive gears results in a compact unit with a high torque-to-volume and torque- to-weight relationship. When used downhole, the annular design of the gear allows optimal use of the available space with the addition of a hollow shaft.
PRECISION ACTUATION Starting topside, a single platform could be just one piece in a large extraction application spanning hundreds of miles. As these networks increasingly begin to operate further afield, adverse weather conditions, a lack of resources and signal issues can severely hamper communication between vessels. The positional antenna systems that enable radio communication between the platform, vessels and onshore teams often suffer from inaccuracy due to gearing with backlash characteristics. This problem can be solved using a Harmonic Drive servo actuator. Its construction offers a combination of fixed Circular Spline, Flexible Spline and elliptical Wave Generator Bearing - high reduction ratios can be achieved in a single stage. This simultaneously eliminates backlash and increases accuracy. As we leave the choppy surface of the sea and dive deeper, subsea applications vary from remotely operated vehicles (ROVs) all the way up to permanent subsea structures spread over many miles. ROVs are made to perform all types of
Above: having exhausted reserves in many subsea oil fields, the pressure is now building on
extraction companies to drill deeper and for longer, to obtain every last drop of the black gold
underwater operation and maintenance. A typical task would be to open and close valves on an underwater valve manifold using a torque tool. These ROVs rely on the pan and tilt action to operate the camera system. As cameras begin to be increasingly used in conjunction with robotic arms and manipulators there is a growing trend of replacing hydraulic actuators with electric actuators to take advantage of the increased accuracy and controllability. Whereas ROVs and antennas require accuracy, the challenge with valve actuation has always been reliability. Traditionally, hydraulic valve actuation has suffered from seal corrosion due to the prolonged exposure to high pressure and harsh saltwater. Subsequent leakage of the units has resulted in component failure, requiring them to be replaced at high cost. The low part count of a Harmonic Drive component set ultimately raises the mean time between failures (MTBF), resulting in a higher return on investment (ROI) over the product’s lifetime. As the oil levels in shallow fields begin to
Above: Steve Kirk, area manager at Harmonic Drive UK
diminish there is a drive to drill into deeper reserves. The problem is that the deeper oil is spread sporadically over vast distances, often in horizontal pockets. Using a continuous vertical wellbore is not feasible and so the concept of directional drilling was developed.
Rotary steerable systems (RSS) ‘point-
the-bit’ technology uses Harmonic Drive component sets to vary the angle of inclination of the drill bit. This flexibility allows operators to achieve complex 3D well designs, connecting multiple marginal targets for high volume, efficient recovery.
As fossil fuels continue to
Above: delving into oil and gas extraction using precision gears
diminish and our reliance on them increases, it will become essential that new exploration technologies are able to cope with the temperatures, the crushing pressures and the harsh environment of deep sea extraction.
Harmonic Drive
www.harmonicdrive.co.uk T: 01785 245 190
Enter 205 /AUTOMATION
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