the future of offshore site ivestigation- robotic drilling ...

THE FUTURE OF OFFSHORE SITE IVESTIGATION- ROBOTIC DRILLING ON THE SEABED J.P. Carter, P.J. Davies University of Sydney P. Krasnostein Protech Development Corporation Pty Ud, Sydney

ABSTRACT A revolutionary new development in sub-seabed drilling and sampling is described. A Portable Remotely Operated Drill (PROD) has been designed and manufactured in Sydney, Australia, for use in offshore deployments by a university-industry consortium. The capabilities of PROD are described and the results of sheltered and open water trials are discussed. Plans for operational deployment of PROD are also mentioned. INTRODUCTION In the last years of the twentieth century, a consortium of university and industry partners has been quietly toiling away, planning, designing, constructing, testing and commissioning the PROD, a portable, remotely operated drill for use on the seabed. Much hard work has been done and the scene is now set for PROD to revolutionise the recovery of drill core from the ocean floor, well into the twenty-first century. PROD is capable of penetrating at least 100m into the seabed to recover high quality core samples in water depths out to 2000 m. Drilling and core recovery is possible in both soft and hard sediments. PROD is fitted with both triple tube core barrels and thin-walled piston samplers. In the future it will also be fitted with tools such as cone penetrometers and borehole loggers to provide in situ testing data. The major components of the PROD drill system are illustrated in the drawings presented as Figures 1 and 2. A major attraction of PROD is its potential to slash the cost of conventional core recovery and obtain high quality core samples beyond the reach of other current technologies, making it attractive to companies and research organisations poised to investigate the benthic unknown. It represents a major advance for core recovery in deeper waters to 2000 m.

THE NEED The need for new technologies capable of recovering samples from the seabed, particularly in deep water, has become more pressing in recent times. Benthic GeoTech Pty Ltd, a company formed by university and industry partners bas responded to this need with the development and manufacture of PROD, and was guided by the following trends in industrial development. •

• •

•

The last few years have seen rapid growth in the exploration and development of offshore oil and gas prospects, with a progressive move to deeper water. Discoveries have been made in water depths greater than 3,000 m and oil is currently being produced from water depths of 2,000 m. Increasing global telecommunication traffic can be satisfied only through the deployment of submarine fibre optic cables. Scientific research into earth structure, climate change, global warming, sources of pharmaceuticals, and the origin of life, has demanded the development of new sub-sea tools and technologies, for the recovery and analysis of samples and data. Recent discoveries of potentially rich mineral resources in parts of the world's oceans, have led to a resurgence of interest in the development of ocean mining techniques.

Collectively, the above factors represent a large and growing requirement for advanced tools and technologies which will allow scientists and engineers to explore and develop the vast resources in the world's oceans.

CORPORATE BACKGROUND The multi-million dollar PROD is now a reality, under the ownership of Benthic GeoTech Pty Ltd (BGT), formed in 1997 to manufacture and operate the PROD. Capital to develop PROD was raised both internally by BGT's partners and by an R&D START grant from the Australian government. BGT brings together interests and a broad spectrum of expertise from three countries: Australia, Japan and the USA. The shareholders in BGT are: The University of Sydney,

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ROBOTIC DRILLING ON THE SEABED

Australia; MD Research Company Pty Ltd, Australia; Protech Development Corporation Pty Ltd, Australia; Nichiyu Giken Kogyo Co. Ltd. (NGK) of Japan; and Williamson and Associates of Seattle, USA. Brief details of each of these organisations are listed in Table 1. Together these partners provide an unparalleled combination of expertise and experience in marine geotechnics and geology, offshore and seabed surveying, mechanical design, mechatronics, project management and marketing, and offshore operations. While all partners in the PROD venture perceive commercial benefits from its development and operation, numerous research opportunities should also flow from its creation. The University of Sydney plans to plough a large proportion of its share of operational profits back into research, and to use PROD to position itself at the forefront of research iTI marine geology and geotechnical investigations.

PROD OPERATION PROD can be deployed from a relatively small (less than 50 m) anchored or dynamically positioned ship of convenience. It is lowered over the side or stem of the ship, using an A-frame and winch or it can be slid over the stem of some vessels on skids under winch control. Once in the water PROD is lowered to tile seabed on an umbilical cable. The cable provides mechanical lifting and hauling capability, as well as providing power to the drill on the seabed and allowing the return of data to the shipboard computer control centre via fibre optic cables. Thrusters aboard PROD allow for sub-sea positioning, with lights and TV cameras providing the ship-board operator with a view of the sea bottom. Once positioned on the seabed, PROD is fully robotically controlled via computers on the ship. All drilling operations, such as advancing casing, joining drill string, wash boring, rotary drilling, push sampling, and coring are achieved by robotic control. High voltage electric power is fed from the ship to the drill by the umbilical cable. On the drill, much of the electric power is converted to hydraulic power via a pair of underwater motors and pumps. Hydraulic power is then used to adjust leg positions and level the drill, position the drill head, provide rotary power to the drill, and operate a pair of rotary drilling tool magazines. The current version of PROD has no provision for wireline operation, so that continuous core recovery requires many phases of making and breaking the drill string. The tumaround time for drilling and recovery of lOOm of core will be in the order of 30 hours of seabed operation time. Drilling tools and core barrels are stored on a pair of rotary magazines (Figures 1 and 2). A swivel arm is used to retrieve the tools from the indexed magazines and to present them under the drill head. Making and breaking drill pipe is achieved by the robotic control system.

DEVELOPMENT To date, PROD has undergone a significant amount of shake-down testing, both on land and in the water. Several wet trials in sheltered waters have been conducted in Rozel~e Bay, within Sydney Harbour (see cover photograph). During this testing the ability to penetrate and to drill and then to recover high quality samples of both soft sediments and rocks (sandstones and shales) using robotic control was proven. Valuable feedback was also obtained from these tests, and this has resulted in a number of significant system improvements, both in hardware and control and monitoring software. In May and June 1999, two open water deployments of PROD were carried out off the coast of Western Australia, in Cockburn Sound near Rottnest Island. In one of these tests PROD was deployed from a ship in approximately 30 m of water (Figure 3). During this testing a 22m deep hole was drilled and almost 80% of the drilled length was recovered as high quality core. The sea surface conditions were bad during much of this drilling (swell 3 m, sea of 2.5 m and winds 30-40 knots) but this did not compromise the PROD operation, as it was resting on the bottom, relatively isolated from the sea state. This provided a very useful demonstration of one of the important advantages that PROD has over conventional ship-board drilling technologies. The latter require complex motion compensators in order to provide an opportunity for recovery of high quality cores. PROD was able to recover core samples of excellent quality without the use of motion compensators. Soft sediments and limestone caprock were recovered during the Cockburn Sound deployment and drilling trials. The soft sediment coring system utilised a unique piston sampler and hydraulic tether. This innovative sampler worked very well, especially considering the relatively shallow water and the low suction that this allowed before cavitation occurred. The recovery indicated a stratigraphy of unconsolidated muddy sands overlying limestone, overlying sands, muds and clays with inter-laminated limestone at various depths.

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MAJOR ADVANTAGES OF PROD Traditionally the offshore industry has relied on the deployment of very large, specialised drillships to provide a method of sampling the sub sea-bed. Drillships are expensive and have significant shortcom ings in their ability to provide the quality of results sought by their users. PROD, through its relatively low capital cost, ability to work on the sea-bed, and ability to be rapidly relocated and deployed from inexpensive "ships of opportunity'' offers a very high level of performance at a fraction of the cost of a drillship. These advantages have been recognised by potential customers, in a range of fields. The numerous advantages of the PROD system that have been identified, include the following. • • •

• • •

• • • • •

PROD is designed to work in deep water (out to 2000 m). The PROD system can be deployed from relatively small ;mchored or dynamically positioned vessels. In the case of DP vessels, the relocation time between boreholes is considerably reduced. All operational functions including drilling functions are computer controlled and recorded. This information will be a useful addition to site data, which should help with the correct interpretation of the actual sub-seaped profile. Suction can be applied on the internal surface of the piston sampler in conj unction with external insertion pressures. This allows more control for sampling weakly cemented material. The PROD equipment could be modified to incorporate larger core barrels and in situ testing equipment. Three hydraulically operated legs are deployed to support the PROD on the seabed. The length of these legs is sufficient to ensure that the surficial seabed layers being tested or sampled are not affected by the weight of the PROD. This is significantly better than the available conventional systems, where the unloaded area around the . drill string is typically approximately 20 em. The PROD equipment has been designed to tit into a standard 20 ft container, thereby facilitating its mobilisation and demobilisation . When unstable conditions are intersected, the PROD is capable if installing and recovering casing to stabilise the borehole. The PROD has been developed largely in Australia, thereby fostering local expertise. This has many potential long-term benefits to local industry. Excessively high mobilisation costs associated with bringing suitable vessels into Australian waters will be eliminated if local vessels could be made available for this purpose. Cost estimates to operate the PROD system are currently well below those of conventional site investigation equipment for all but shallow depth investigations.

THE FUTURE PROD is now poised for operations in the very large offshore technology market. Oportunities are perceived in the oil and gas industry, telecommunications, scientific research, and offshore mining. BGT is negotiating several potential

early deployments for PROD, including both research tasks and .oil industry-related projects. Further infonnation can be obtained from the BGT web site, www.bgt.com.au or via email at [email protected] .au.


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ORGANISATION University of Sydney

PROFILE •

• • MD Research Company Pty Ltd

• • • •

Protech Development Corporation Pty Ltd

• •

•

Nichiyu Giken Kogyo Co Ltd

• • •

•

Williamson & Associates Inc.

• •

• • • •

Australia's oldest University, established in 1850, and one of the largest in Australia with more than 30,000 students. Represented in BGT and the PROD venture by its Division of Geology and Geophysics in the School of Geosciences and the Centre for Geotechnical Research within the Depar:tment of Civil Engineering. Brings to BGT technical and scientific strengths and a wealth of experience in marine_geotechnics. Wholly owned subsidiary of the CH Warman Group. Operates through the Group's technical development division, CH Warman TechLink. In recent years the company has conceived, designed and developed significant mineral process technologies and related items of equipment. Provides project management, design and engineering skills used in the manufacture of PROD. Established in Sydney in 1996, to invest in prospective and innovative early stage technologies Provides skills and experience in: technology development, international technology marketing, business startup and development, business and strategic planning, project feasibility studies and analysis, and business management Specific industry knowledge and experience covers: mining and exploration, chemical process industries, pulp and paper, glass containers, plastics, recycling and environment Established in 1980 at Kawagoe City, Saitama prefecture, Japan. Developed many different products for use in a variety of fields, from the deep sea to outer space Products include: pyrotechnics installed in satellites, space craft and rockets, safety equipment for electric power transmission, automobile air bag initiators and gas generators for seat belt pre-tensioners, buoyant materials, reinforcement products for civil engineering applications, reliable and unique sub-sea acoustic releasers, various computer-based ocean observation surveying and logging equipmem, water samplers, deep sea sediment samplers, sediment traps, precise thennometers, heat flow meters, .etc. Cooperated with Williamson & Associates to win the bid to develop and construct an underwater rock core drill, the BMS (Benthic Multicoring System) for the Metal Mining Agency of Japan. The BMS is the prototype of PROD. Established in 1982 and based in Seattle, USA. A diversified geophysical consulting firm providing expert personnel and state-of-the-art equipment for a wide variety of scientific and engineering applications, specialising in the offshore sector. Clients include a wide cross section of international, industrial, military and academic organisations. Initiated and involved in numerous deep sea search and survey projects. Recent accomplishments include the development of a Deep Towed Isophase Interferometric Swath Bathometry system. Developed the initial remote control deep ocean rock drilling (the BMS drill) which is the prototype of PROD.

Table 1 Composition of Benthic GeoTech (BGT) Pty Ltd

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PERFORMANCE SPECIFICATION 2,000m lOOm B 48mm 2.8m 40mm 2.2 m (taken individually) 10 tonnes (using suction feet) 50kW 20% of depth 20 degrees

Operating Depth Maximum Penetration Drill Size Push Core Sample Diameter Push Core Sample Length Rock Core Sample Diameter Rock Core Sample Length Maximum Push Coring Thrust Maximum Rotary Coring Power Thruster Manoeuvring Side Slope Capability

DIMENSIONS Drill stowed for shipping Drill weight in air, fully laden Drill footprint on deck Drill height under A-frame Winch weight

6 m freight container 7 tonnes 2.4m by2.4m 5.8m 10 tonnes

DESIGN FEATURES Isolated from ship movement Retractable legs Structure - marine grade aluminiwn alloy Mechanisms - stainless steel and alloy Control and telemetry - fibre optic Dual redundancy on electric power Dual redundancy on fibre optic Suction feet for stability on sediments Pressure equalised electric motors Pressure equalised hydraulic system Release of drill string on sustained loss of power Thrusters for attitude control, repositioning

SENSORS Cameras with pan and tilt Sound transducer Bit weight, push core thrust Bit torque Attitude ( tilt, azimuth) Altimeter Water depth Weight distribution Hydraulic pressures Electric motor voltage, amps, temp. Position indicators Flushing water pressure, flow rate

Table 2 PROD Mkl Technical Specifications

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t--t-------~--


2330 Square ----------t~ Longyear HQ55HT

Ro ary Unit

51 2m Core Barrels

49 3m Drill Rods Maximum or 10 3m Casings Maximum with 35 Drill Rods

Figure 1 Plan view of PROD showing main components. Legs are retracted for container storage.

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2600 TILT

·~

Figure 2 Plan view of PROD with legs outslretched


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Figure 3 PROD being deployed at sea in Cockburn Sound, Western Australia

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