For example, Oriente Marine Group (OMG) works primarily in the Gulf of Paria and the Orinoco River Delta in Eastern Venezuela. The shallow waters allow the diving crews to work with surface-supplied air almost without bottom time limitations. The strong currents, along with zero visibility and quickly changing weather conditions due to the winds, create challenging conditions that have dramatic implications in the total effective bottom time during a particular job. The dive crews have procedures designed to take advantage of their slack and dead tide periods in order to accomplish the variety of tasks required by clients.

The crews use a number of tools to optimize the bottom time, including weather forecasts, precise tide and maritime charts, and even the experience of the local dive support vessel captains. Tidal currents and bad weather are factors that can be managed with precise information and work planning.

However, zero visibility is something that all divers have to live with. In order to be part of a successful diving team in these conditions, a diver must be more than comfortable working in complete darkness, which is not too difficult considering that most commercial diving activities are performed in very low visibility conditions.

Drilling activities in the Orinoco Delta and Gulf of Paria are performed primarily with shallow water jack-ups, swamp barges, and conventional shallow water drilling barges resting upon a flat carrier barge. The most common diving tasks are survey, sand bagging, piles recovery, pipeline routing, inspections, anchor recovery, and pipeline and cable lay. Underwater surveys are performed prior to the positioning of the drilling unit, with the job conducted from a small diving vessel. The predetermined area is first surveyed with regular methods (echosounding, side scan sonar, and sub-bottom profilers). Then the divers will carry a metallic rod and/or metal detector, walking the bottom in semi-circular patterns until the total area is covered. This diver's survey report is essential for the drilling unit positioning.

Sand bagging is one the most physically demanding tasks for the divers. The objective is to prevent serious scouring beneath the hull of the drilling unit or the basement barge, since they rest on the seabed when the unit is positioned and anchored (either with piles or anchors, according to the total size of the unit). This operation is performed around the clock to place the sandbags as fast as possible before the tidal currents create serious scouring on the most critical points of the hull (this varies according to the hull's shape and orientation of the unit with the main unidirectional tidal flows). Once the sand bags are placed, divers must keep a tight schedule of regular inspections to detect and repair further localized scouring processes.

Pile recovery is required whenever an anchoring pile is to be removed from the work site. Two methods are commonly used, underwater burning and extraction by vibration. In the first case, the whole job is the responsibility of the diving crew. The diver must ensure that the cut is made below the seabed at a predetermined depth established by the client and according to navigation regulations. When the pile is extracted using a hydraulic vibration hammer, the diving crew remains on standby in case of an underwater intervention requirement.

Pipeline routing and inspections are performed using the regular procedures employed in any offshore shallow water environment. However, pipes are always buried due to the high deposition rate of sediment. The divers must use a small air dredging system and metal detectors in order to track the pipe. Two categories of pipes are found: old abandoned pipelines from ancient oilfields, and recently installed pipelines that in some cases need to be inspected in very localized sections. Cable laying operations are favored by dive crews, since the natural burial of the cable is very fast. However, when the cable has to go ashore, the physical protections (often light concrete mattresses) are critical because of shallow waters and tide amplitude ranges. Diving work in these operations is simple and consistent: inspecting localized areas along the proposed route to verify any relevant information previously obtained by remote sensing, placing and securing the concrete mattresses, installing the I-tubes, and verifying the curve and cable elongation near the I-tubes.

On jobs using conventional shallow water drilling barges resting upon ballasted flat barges, anchoring is critical to secure the positioning of the unit in the precise well location. This often results in work for diving crews, since the marker buoy of the anchors can get ripped apart in bad weather and more often during supply vessel and tug boat maneuvers. In these cases, divers will be asked to locate the anchor and reinstall the marker buoy.

OMG follows the ADC Consensus Standards. For information on all things ADC, visit www.adc-usa.org.

Some of the following projects focus on the commercial diving aspects of offshore work, while some detail survey or decommissioning work. Still, all stress safety and environmental resposibility first, and are examples of the excellent work that goes on in offshore oil fields around the world every day.

Andrews Survey Busy in Europe and West Africa
During the past four years Andrews Survey has performed the majority of rig moves for Enterprise Oil in northwest European waters. The work has included continuous positioning support on the Ocean Guardian during the exploration and appraisal of the Pierce Field and for the exploration and development phases of the Corrib Field, west of Ireland, on the Sedco 711. Deepwater acoustic positioning services were also provided on the Jack Bates for an Enterprise Oil Exploration well located in 3,339 feet (1,018m) of water in Block UKCS 154/1, west of Orkney. The rig then moved to an adjacent block for Agip UK, where Andrews provided surface positioning and tug tracking services.

To assist the tow master with passage planning, admiralty charts in electronic format were provided on a large color monitor, with the real-time GPS position of the rig superimposed. Digitized field graphics information, such as the positions of existing pipelines and seabed structures from oil company data, can be displayed as a background to the real-time display of the rig and tug positions.

The use of an interactive telemetry system to provide graphic information both on the rig and associated anchor tugs made anchor deployment a more relaxed operation. In fact, the telemetry almost eliminated the need for continuous guidance with multiple AHTs via marine radio during the operations.

Turning to West Africa, Andrews Survey recently completed a pipeline corridor survey in Ghana. Andrews provided several different specialist survey teams working onshore and offshore from a proposed tanker mooring point, through the transition zone, and right up to the Tema Oil Refinery.

Vitol Energy needed to determine the optimum route for a new pipeline linking the refinery, 5km inland, with the tanker discharge point 7km offshore in the Gulf of Guinea.

Designed and directed by consultants JP Kenny Ltd, the survey sought information on topographic conditions and geotechnical parameters over the land section, together with a multidisciplinary survey of the offshore route. The consultants needed to define an area with suitable water depths and geotechnical characteristics for the location of a single point mooring (SPM) for tankers. Information on the seabed topography and soil conditions for the excavation of a pipeline trench were also part of the work scope. This would involve the acquisition of bathymetric, geophysical and geotechnical data.

The marine survey covered a 7km x 1km offshore corridor for the pipeline, a 2km square area for the SPM, and a large tanker turning area. In all, an area of around 36 square kilometers was surveyed.

On land, Andrews conducted a detailed topographic survey along the 5km x 30m corridor. This was supplemented by geotechnical data to depths of 6.5m. The proposed sampling schedule included boreholes with permeability testing to a maximum of 33 feet (10m) or until refusal at bedrock, trial pits to 10 feet (3m), and a soil resistivity survey of the area. In total, eight trial pit excavations and four boreholes (using a specially-adapted cable percussion rig) were completed.

For the offshore section Andrews equipped two local vessels, the Hope for hydrographic work close to shore and the Courage for the deeper areas and geotechnical operations. Some equipment was shipped by air, along with two 40-foot containers sent by sea from the UK. This enabled the Courage to be mobilized in neighboring Togo and fitted with all necessary hydrographic, geophysical, and geotechnical equipment for working offshore Ghana.

Survey lines were required at 50m grid intervals. Positioning was achieved using Andrews mobile RTK GPS systems with RTK control established by Andrews geodetic surveyors.

The coast of the Gulf of Guinea is an area littered with a considerable number of shipwrecks. Therefore the workscope also required a near-surface geophysical survey using side scan and magnetometers to identify seabed hazard features and obstructions with additional boxing-in around the wrecks.

Sub-bottom profiling provided sub-surface details to a depth of 33 feet (10m). Vibrocores and grab samples were obtained to determine seabed soil conditions, some of which were subjected to onboard tests for sulphate-reducing bacteria. In addition to the fieldwork, the laboratory testing and detailed interpretation and charting was completed by Andrews in the UK to the client's specifications.

Paroscientific Aids Maureen Decomissioning
In an incredibly challenging platform removal project, the Maureen was decommissioned last summer during a 60-hour operation. The Norwegian Geotechnical Institute (NGI) used ultra-high accuracy Digiquartz Pressure Transducers from Paroscientific, Inc., to monitor the critical lift-off of the platform from the bottom of the ocean.

The discovery of oil in the North Sea in the 1960s resulted in the construction and installation of large offshore structures needed to develop the newfound oil fields. The predominant structures installed in these deep waters are called "gravity-based structures" because they are held in place by their own weight. In addition, most of them have a shallow foundation skirt that penetrates the sediments on the seafloor during the installation process.

Gravity-based structures are constructed in coastal waters and fjords, then towed to the offshore sites and set on the seafloor to support the drilling and production equipment and living quarters on the deck. These enormous structures are unique because they can be refloated and reused.

One such structure, the 112,000-ton Maureen Alpha platform, located in the Maureen Field at the US Continental Shelf Block, contains the world's first large reusable platform. Maureen's production, drilling facilities, oil storage, and accommodations were all integrated into a single platform which was designed for refloat and reuse from the very beginning of the design phase. The complete platform is 784 feet (241m) high with three massive cylindrical tanks, each of which is 84 feet (26m) in diameter. These tanks hold 660,000 barrels of oil for storage.

Design work on Maureen started in 1978 following an extensive appraisal of the area around the field. Construction work began in 1979 in several yards in the UK and Europe. The Tripod Steel Gravity structure was built by Chicago Bridge and Iron at Hunterston on the west coast of Scotland. After completion, the dock was flooded and the TSG was towed to Loch Kishorn. With no added ballast, the towing draft was only 26m.

Maureen commenced production in late 1983 at around 80,000 barrels of oil per day, but the field was depleted by the end of 2000. Thus began the complex reverse process of removing the enormous structure.

On July 27, 2001, Maureen was successfully removed and towed to a fjord on the western coast of Norway for demobilization and possible reuse. The refloat methodology involved injecting high-pressure water under the tanks in the ocean to push them upward. While the tanks were moving upward, the water in the tanks was pumped to a tanker, which was carried to a nearby facility for disposal. The space in the tanks was then filled with inert gases to maintain their internal pressure.

The critical task in removal of a gravity-based structure is to control the breakaway, a term used to describe the structure's separation from the seabed and reversion to a floating structure. During this critical transition, it is necessary to monitor the first few millimeters of vertical movement accurately in order to properly control the deballasting operations.

The Norwegian Geotechnical Institute (NGI) was given the contract to design and deliver a monitoring system with the necessary accuracy for measuring the vertical position of the base of the structure relative to the seafloor. Based on their extensive experience with the use of heavy fluid leveling systems, NGI incorporated Paroscientific's ultra-accurate Digiquartz pressure sensors into its monitoring system.

The system consisted of a fluid-filled container connected by a 40m flexible hose to a Digiquartz pressure transmitter. The transmitter was mounted on a reference unit that served as a survey benchmark. During use, the fluid-filled container was attached to the base of the Maureen platform by divers, and the reference unit was set on the sea floor some distance from the platform. This system measured the vertical elevation of the platform with an accuracy of less than one millimeter at a water depth of 315 feet (96m).

After the platform was raised from the bottom of the ocean, it was towed to Aker Offshore decommissioning facilities in Stord, Norway. The whole operation was implemented in a safe, controlled, environmentally sensitive manner. The Digiquartz-equipped monitoring systems were recovered. The platform and the tanks have all been safely moored and will be completely cleaned before a decision is made for the future of the Maureen platform.

All the pipelines and umbilicals in the field have also been removed to shore. The only exception is the 24-inch oil loading pipeline, which has been cleaned and will remain buried along its 2.5km length.

Maureen is the only offshore structure in the world to receive the Royal Society for the Prevention of Accidents President's Award, which was given in March 2001 in recognition of the rig's strong safety culture and continued safety performance during the complex preparations for decommissioning. For more, visit www.paroscientific.com.

Webtool Answers the Call in the North Sea
Webtool recently developed four new concepts for Norway's Advanced Production and Loading (APL) to use on the Heidrun and YME North Sea oil fields. APL designs efficient solutions to transfer offshore oil to supertankers and has been instrumental in the development of the Submerged Turret Loading system (STL).

The Heidrun project called for the removal of an STL loading buoy from the Heidrun oil field offshore Norway for minor modifications. This involved the cutting and gripping of eight high-tensile plastic-coated steel ropes using an ROV. To accomplish this, Webtool enlarged their existing 115mm cutter to 135mm. However, a more effective way of gripping the rope near the severed end through its tough plastic coating had to be developed. A standard over-center locking-type clamp would sink into the plastic coating beyond its locking range, possibly stripping the plastic off the end of the rope.

To solve the problem, Webtool designed an open tool that could be easily placed over the rope and hydraulically clamped by driving a spike through the plastic and into the spiral wound rope strands. At this point, the clamping jaws could be locked into position by winding down two locking screws driven by small hydraulic motors or externally turned eyes. The hydraulics could then be removed for hoisting. The design of the tool offered the advantages of light weight, low cost and wide range of capacity, but the main advantage was its ability to provide a positive mechanical lock to lift the rope near to its cut end. The practical application of the new design by Stolt Offshore personnel on-site was a complete success.

The YME Field project involved several tasks that were to be accomplished using an ROV. Given the adverse weather conditions in the North Sea, all aspects of the project had to be accomplished quickly and within a short weather window.

The first portion of the project was the removal of a 250mm flexible oil riser from a loading buoy. The conventional procedure in this type of operation is to cut the flange bolts which attach the oil riser to the buoy. In this particular project, the flange was positioned under the loading buoy, making access difficult. The decision was made to cut through the oil riser itself with a hydraulic guillotine. Webtool developed a very large version of their rope cutter to accomplish the job and once the tool's capability was demonstrated in the shop, the procedure was accomplished in one quick operation.

The second task was to cut and grip a 122mm spiral wound rope. Webtool's RCV135 could have been used to cut the spiral wound unsheathed ropes, but the problem was to prevent the unlaying of the rope down its entire length, forming an enormous steel "broom" which would be very difficult to salvage. Webtool developed a simple self-closing ROV-deployed latching clamp called the WRC120 to prevent this. The ROV maneuvered the clamp into position around the rope, closed the clamp, and used its manipulator to wind down the locking T-handle on the clamp.

The grippers that had been used on the Heidrun Field project were modified to lock down with hydraulic motors for the operator's convenience. This increased the lifting to 20 tons.

The final task to be accomplished by the ROV was to provide a means of lifting a 70-ton anchor shackle and chain with an automatic self-closing shackle. Webtool developed a self-closing shackle that could be reset, and which the ROV could easily trigger once the shackle was in position.

Since it is sometimes difficult for the ROV operator to accurately position a tool in one attempt, the shackle had to be easily reset if the operator missed. Additionally, the shackle was weight-balanced when open to allow for an easy aim. This could have been designed to operate hydraulically, but a dampened spring-loaded mechanism was chosen for its simplicity and low cost. The new design contributed to the quick and successful completion of the project.

On-site operations using the new tool designs in the YME Field were accomplished flawlessly by personnel from both APL and Oceaneering AS of Norway. Webtool, a division of Variators, Ltd., is located in Toronto, Canada. For more, visit www.webtool-subsea.com or call 416-234-8671.

Schleifring Slip Rings in South China Sea
To the casual observer, oil exploration pumps operating at the bottom of the South China Sea are as remote functionally as they are physically from the CT scanners in modern day health care facilities.

Engineers at Schleifring GmbH, however, know better. Their slip rings and fiber optic rotary joints are found wherever there is a need to transfer data, power and signals between rotating and stationary platforms.

Schleifring recently supplied one of the world's largest explosion-proof slip ring systems to an oil exploration vessel operating in the South China Sea. Part of the ship-board swivel stack system, Schleifring's Electrical Power Slip Ring (ESPR) transmits power to a pair of 1.5 MW oil pumps resting on the seabed. The swivel stack, encased in a waterproof housing, allows ship movement and rotation relative to the fixed pumps.

Nine silver-coated brass rings, with four silver-graphite brushes per ring, comprise the 3m, 7,500kg system. Rated voltage measures 10.5 kV; rated current is 150A. The main housing is rolled and welded out of saltwater-proof stainless steel and all parts are machined with oversized milling and lathe equipment.

Tested at Schleifring facilities to withstand pressures as high as 20 bar and exposed to explosion-proof test EEx de II T3, the ESPR also offers quality assurance in accordance with DIN ISO 9001. This guarantees reliable performance under extreme conditions, such as found in the oil fields of the South China Sea.

Stolt Milestone at Girassol
TotalFinaElf recently announced first oil production from the Girassol field offshore Angola. Major contractor Stolt Offshore SA has worked on the unique field for four years, and recently reached a milestone.

The operator of the field is TotalFinaElf, with a 40 percent interest. Other minority partners are Esso Exploration Angola Limited, BP, Statoil, and Norsk Hydro. Girassol is being developed under a production sharing agreement with Sonangol, the national oil company of Angola.

Stolt Offshore has been involved in two parts of the development, first as the joint venture manager and 50/50 partner with Bouygues Offshore in the Mar Profundo Girassol joint venture, which built the world's largest floating production, storage and offloading vessel (FPSO). Second, Stolt acted as the joint venture manager and 66/33 partner with Bouygues Offshore in the Alto Mar Girassol joint venture that built and installed the subsea flowline bundles, riser towers, mooring, and offshore loading system for the field.

"The successful delivery of first oil from the Girassol field marks a very significant technology achievement, not only for the joint venture partners, but for the offshore construction industry as a whole," said Stolt Offshore CEO Bernard Vossier. "The challenges presented by this development were numerous, as the Girassol field involves the largest deepwater infrastructure ever to be installed in a water depth of 4,430 feet (1,350m). Some of the technologies that we have developed for this project are easily extendable to oil fields in water depths of 10,000 feet (3,000m). The experience that Stolt Offshore has gained, particularly in the installation phase of this project, is unique in our industry and will be of considerable value in tendering for and executing other deepwater projects."

Vossier says Stolt Offshore attained several industry firsts on the project, including:

• The Girassol FPSO is the largest such ship in the world, with a 42,000-ton hull supporting 24,000 tons of topsides designed to process 200,000 barrels of oil per day. It is equipped with a two-million-barrel storage capacity.
• Riser towers were developed for this project to provide the very demanding insulation requirements necessary to prevent heat loss of more than six degrees C from the produced oil between the wellheads and the FPSO. These towers, which contain a number of insulated rigid steel risers in a 1,300m long bundle, also provide efficiencies in the installation and tie-in of the large number of production risers that are required for a complex field development of this type.
• Stolt's remotely-operated MATIS subsea flowline connection system was used for the first time in this water depth to make both horizontal and vertical connections. This system uses robotically-installed standard API bolted flange connections, which provide superior flow assurance, mechanical and fatigue integrity, and cost efficiencies over other connectors.

"Despite the complexity of the technologies developed for the Girassol field," added Vossier, "we have been able to undertake successfully through Sonamet, our joint venture company with Sonangol, the majority of the complex fabrication work for the riser towers, offshore loading system and suction anchors in Angola. Our ability to fabricate high-quality components in Angola provides important local content for projects of this type and enables us to develop a skilled Angolese work force who will play an increasingly important part in the construction and maintenance of the deepwater oilfields off Angola in the years ahead."

On the other side of the globe, a Stolt Offshore dive crew claimed a new record dive depth for the North American region. The crew reached a depth of 945 feet (287m) with the American Constitution while working for Unocal on their East Breaks 160 A platform.

The job consisted of inspection and clearing of a J-tube, installation of a messenger cable, and jetting out of a path at the bell mouth in preparation for pulling a flowline and umbilical to the surface at a later date.

In the first stage of the job, the four-man dive crew was pressed to a depth of 650 feet (197m) for the initial clean out of the tube. On October 21, 2001, the dive team was then pressed to a storage depth of 900 feet (273m) for the final phase of clean out and jetting. This process of reaching the new storage depth took five hours to complete and an additional six hours of hold time for the divers to adjust to the 400 pounds-per-square-inch pressure that was being placed on their bodies.

On October 22, the diving bell was launched to 915 feet (278m), where the divers reached a bottom depth of 937 feet (284m) working on final clean-out.

The final phase of the project was jetting a path for the approach of the flow line and umbilical, during which all four divers reached their maximum working depth of 945 feet (287m).

The project was completed on October 23 by the Stolt Offshore crew without incident and ahead of schedule.

Abandonment from Oceaneering Vessels
The menu of subsea well intervention services is expanding with the development of diverless deepwater systems. Work previously consigned to semi-submersible drilling rigs is now being performed from mono-hulled multi-service vessels. Oceaneering International completed two such projects in 2001, completing a pair of plug and abandonment (P&A) projects from the decks of their Class 2 DP MSVs, Ocean Intervention and Ocean Intervention II.

Oceaneering assembled a dedicated P&A system package and technique, believing that such systems yield big savings for subsea clients. The proof arrived with P&A contracts for wells in depths of 463 feet (140m) and 832 feet (252m). Transporting the entire P&A spread at one time saved customers time and money. The single round trip for each job included recovery of the subsea tree and the well stub.

Current capabilities for jobs of this kind include working depths to 2,000 feet (600m) with eventual working depths to 10,000 feet (3,000m) envisioned.

Typically, the vessel arrives on location and then stabilizes its DP system. The underwater roughneck, the vessel's Hydra Millennium 150hp ROV, is then launched through the ROV moonpool to inspect the location and prepare for rigging the equipment stack. A tree cap recovery tool is lowered over the vessel side and transferred to a working winch line through a separate dedicated moonpool.

Oceaneering's proprietary Installation and Workover Control System (IWOCS) is submerged to depth for attachment by the ROV to a junction plate connected to the tree cap tool. Pressure testing will occur prior to the tree cap's release. The working equipment stack for gaining access to the well bore is staged on the vessel deck. Each stack varies with the differences in tree manufacturers' designs. Oceaneering's unique engineering and component design capabilities create smooth interfaces when the job-specific equipment stack is lowered and installed.

Once the stack is in place and tested, control of the well and the stack through the IWOCS begins. Dual circulation lines are lowered from the vessel and attached to the stack and the subsea tree utilizing large bore hot stabs. This facilitates the ability to squeeze the formation and spot the cement plugs. These same lines also circulate well fluids through the production tubing and the casing annulus.

The plugs are set in place at the location specified by the client. Once the plugs are placed and tested, the equipment stack is disconnected and recovered to the deck.

Next, the subsea tree can be disconnected and recovered to the vessel. The IWOCS again controls the required functions. The busy ROV pilot transforms into a rigger. The ROV collects a sling lowered from the vessel and attaches it to the subsea tree using specially-designed shackles. Once connected, a lifting winch line is attached and the load is transferred to it via the vessel's 60-ton A-frame. The tree is then recovered, spotted on the stern of the deck and seafastened in place.

The P&A process continues with testing the casing annulus for pressure. Subcontractor tools normally used on drilling rigs are employed with new purpose. The P&A package has a working false rotary deck that allows for running and recovering tubing and drill pipe. The tubing is severed below the SCSSVs and recovered to the surface, broken down into individual joints and secured in a pipe rack.

Next, drill pipe is run to stab into an easy-to-drill sliding valve installed by wireline for testing the casing annulus for pressure. If present, pressure can be circulated out or bull-headed into the formation depending upon the circumstances. The surface plug is then spotted using the drill pipe and the well stub is ready for recovery. The stub can be severed using explosives or cut using a subsea casing cutter.

Denso's Protective Coatings
Carbon steel is accepted as a cost-effective material of construction and is used in a multitude of areas in oil and gas exploration and production operations. When unprotected, it is subject to unacceptable corrosion losses, for example, from produced water and crude oil mixtures. One method of protection used in large vessels, e.g. Gravity Separation Vessels, is the application of a coating to the internal surfaces.

Deeper drilling and production often leads to higher temperatures of the well stream. An increasing number of pipelines are operating at temperatures above 100 degrees C. Adequate thermal insulation of the resultant high temperature crude during transportation requires an expensive pipe-in-pipe line.

Denso developed a high temperature resistant, modified epoxy-based coating specifically for the above-mentioned applications and submitted it for testing. Many organic coatings have been tried at high temperature and pressure, but most suffer from severe blistering called explosive decompression failure.

A major oil company requested a series of immersion soak tests at 130 degrees C, with subsequent depressurisations. A candidate formulation was tested according to the following conditions in a specially designed autoclave:

• The test fluid was a crude oil and synthetic produced water mixture, continuously agitated in a 40:60 ratio at 130 degrees C.
• The aqueous solution chemistry was produced as an equilibrium state with gas containing hydrogen sulphide and carbon dioxide at 50 ppm and two mol percent, respectively.
• The test pressure was 30 bars, which was achieved by an overpressure of methane, and with periodic controlled depressurization.
• The test pieces were made up on 100mm to 150mm blasted mild steel plates and the coating applied at 750 microns minimum dft.

In order to test resistance to blowdown, the vessel was depressurized to just above atmospheric pressure twice, initially after 12 days exposure and finally after a total exposure period of one month. The depressurization rate was controlled and targeted at a full pressure drop from 30 bar to three bar in 10 minutes. Sample weight change during testing was also monitored, since this can provide a useful indicator of coating degradation in liquid environments.

The test results showed no evidence of decompression blistering. In addition, the gravimetric data at the end of the test period indicates good performance in the high temperature and aggressive test conditions.

More recently, another major oil company initiated a project to perform a pre-qualification test regime in a pressurized vessel holding seawater at 180 degrees C and 30 bar pressure. Again, the object was to determine if the spray grade formulation indicated above is suitable for external corrosion protection at a depth of 1,000 feet (300m).

The exposure program was three months in an autoclave at 30 bar hydrostatic pressure. The coating dry film thickness was 750 to 1,000 microns dft. The samples were first inspected after one month, and in this test the pressure was released gradually to reduce the effects of explosive decompression. After inspection and coatings measurements, the samples were replaced. After three months, they were removed.

The results indicated no loss of adhesion at the scribe area, and no cracking or softening of the coating on the main flat part of the samples or along the edges of the coupons. Destructive investigation of the coating indicated very good coating integrity and adhesion. The coating thickness varied from 700 to 1,000 microns. Measured reduction in the coating thickness (seven microns based on 12 measurement points) was considered to be an insignificant change. The chemical resistance to high temperature water (180 degrees C and 30 bar pressure) was shown to be very good.

Olympian Effort by Cns
Having gained an international reputation in the telecommunications sector laying and burying fiber optic cable in deepwaters, Cns was keen to break into the energy sector. The company recently completed its first installation support contract.

Originally setup to offer high quality project engineering in subsea construction to the oil and gas industry, Cns quickly discovered that the collective oil and gas experience of its people could be effectively used in the telecommunications sector. At that time there was a real demand within the telecom industry, and Cns soon became a recognized player in that sector.

Coflexip Stena Offshore (CSO) contracted Cns to carry out survey support work and cable plow assist operations in the North Sea last October. Using the Hi-Pap Acoustic Tracking System, Cns deployed the Highland Fortress survey vessel to provide positional monitoring for the CSO cable plow during power cable installation operations near pipelines between Shell's Auk and Fulmar platforms.

The Olympian T2 was used to perform an "as buried" survey along the route. The cable burial system, manufactured by Perry Slingsby Systems with design intervention from Cns, is able to bury cable deeper and in stronger soil conditions than other vehicle on the market. It can also be launched and recovered in harsher environmental conditions than the normal operating parameters of other burial spreads. This capability increases the operational window and reduces costs for the individual projects undertaken.

"The success of the Olympian T in the telecommunications cable market has led us into the oil and gas market," says Cns Managing Director John Sinclair. "We are now prepared to undertake umbilical and power cable burial work, as well as small diameter flexible and rigid flowline burial work along with the associated engineering."

However, Cns believes that as fiber optic cabling is playing an increasing role in the oil and gas sector with the communications required for smaller satellite fields, their expertise in telecommunications will be very welcome to the major oil and gas operators.