Mud, Mud, Mud. Liquid mud is the name of the game in the design of today's offshore service vessels. The drilling rigs not only want huge volumes of mud, but they want the vessels that serve them to be able to carry several different types of liquid mud. That means two or three separate piping and pumping systems to keep the mud from cross contamination. That also increases demands for automated control and alarm systems
, many of which utilize touch screen controls.
The rigs also need dry bulk cement, barite and other such products, so dry bulk tanks with 6,000 or so cu. ft. of capacity would be desired. Many rig owners would also like the vessels to carry methanol and, by the way, to be equipped with a dynamic positioning system rated to at least DP-1 (DP-2 would be better) by ABS so the liquid, bulk products and cargo can be offloaded in nearly any sea state.
Those are tall orders but the realities of supplying drilling rigs and platforms in deepwater.
In response to these design criteria, the offshore service vessel operators have develop vessels that can only be described as "Heavy Haulers."
A few recent deliveries have shown how the operators have stepped up to the plate to give the drillers what they want in a supply vessel.
"It's all about deadweight tonnage," said Roger White
VP of Edison Chouest Offshore (ECO), Galliano, La. a firm with over 100 advanced supply vessels and anchor handlers in the Gulf.
"That number tells all in our opinion since it is the true measure of how much weight a vessel can carry when it reaches its loadline," White added. "The length of a vessel is not a true reflection of its deadweight capacity anymore," White said.
Edison Chouest C-Leader Series
A new series of 280-ft. by 60-ft. by 24-ft. supply vessels proves White's point. ECO is building four of these vessels for charter to Shell Oil Company and a fifth boat for another client. While only 20 ft. longer than most large OSVs, its deadweight tonnage is 4,830 long tons...about 1,000 tons more than that of vessels only slightly shorter.
"The 280-ft. series of offshore supply vessels was purpose built by Edison Chouest as super efficient vessels able to carry multiple cargos in any sea condition short of hurricanes and serve multiple platforms on a single trip," said White.
The first vessel in the series…aptly named C-Leader went to work for Shell in February and the second vessel C- Legend was launched in March 2003 and will join the fleet in July. Two other vessels C-Liberty and C-Legacy will be completed in 2003.
This series of vessels was specifically designed to carry very high quantities of all liquid, bulk and deck cargo loads. For example liquid mud capacity is15,880 barrels, the largest quantity of liquid mud carried in a single vessel in the Gulf. In addition, the vessel can carry 359,720 gallons of fuel oil, 224,680 gallons of ballast, 32,100 gallons of potable water, 12,280 cubic ft. of dry bulk and the vessel even has dedicated tanks for 87,360 gallons of methanol. In the hull is a pair of anti-roll tanks with a capacity of 57,440 gallons of water. Another group of tanks in the hull are called "Service tanks." Number 11 in total, these tanks hold from 950 to 2,700 gallons of whatever the rig wants to offload and can be used to transport limited quantities of specialized liquids to the rig or platform.
On the 203-ft. by 50.5-ft. rear deck, the vessels can carry 2,700 long tons of cargo.
Propulsion power is via pair of Caterpillar 3608 engines, rated at 3,600 hp each. The engines drive both controllable pitch propellers and 1.2 MW shaft generators. Thrusters include a tunnel thruster and a swing down thruster at the bow and a tunnel thruster in the stern.
As expected, a vessel with twin bow thrusters has an advanced dynamic positioning system and the C-Leader has a DP-2 class system.
Tidewater Miss Jane Tide Series
Tidewater, Inc., New Orleans, La. the largest firm offering offshore vessel services has just completed the fourth of four 260-ft. by 60-ft. by 24.6-ft. platform supply vessels. All four have a deadweight capacity of 4,006 long tons.
Mud hauling capacity is 8,000 barrels in below deck tanks. "We have carried up to 10,000 barrels of mud with the addition of deck tanks," according to E. J. Hebert, manger of engineering for Tidewater.
Other below main deck capacities are also plentiful including 311,500 gallons of water, 342,300 gallons of fuel oil, 52,850 gallons of potable water and 11,220 cubic ft. of dry bulk. Main deck cargo capacity is 2,650 long tons.
These vessels use diesel electric propulsion. A quartet of Caterpillar 3516B engines drive KATO 1,800 kW generators producing all the power the vessel needs. For propulsion power two LIPS Z-Drives are each powered by three General Electric DC motors.
A drop down thruster and a tunnel thruster are in the bow. Since the vessel uses two 360-degree Z-Drives, no stern thrusters are need for the vessel to be fully DP-2 compliant.
"Redundancy is the key to this vessel," said Luis Sanders, assistant manager of new construction for Tidewater. "We have a great deal of redundancy in our power generation system and in thruster propulsion which is a key to operating in the harsh conditions found in deepwater," Sanders added.
Z-Drives have become standard propulsion in the 15 or so new supply vessels Tidewater has built in the last three years and in the vessel currently under construction. Their wholly owned Quality Shipyards, LLC; Bollinger Shipyards and Bender Shipbuilding and Repair are involved in this building program.
Hornbeck Offshore Services 260-ft. Series
Hornbeck Offshore Services, Mandeville, La., boasts that they have the youngest fleet of supply boats in the Gulf of Mexico. Their vessels average 2.5 years old while 70 percent of the supply boat fleet is over 18 years old.
Hornbeck has built a series of five 190-ft. vessels, five 240-ft. vessels (with three still under construction) and four 260-ft. OSVs. LEEVAC Industries LLC, Jennings, built all of their 240-ft. vessels and two of the 260-ft. vessels La. Of the five 240-ft.ers built, two were finished as combination supply/ ROV support vessels for SonSub, Inc., Houston, Texas and one of the two 265-ft. vessels LEEVAC built was completed as a well stimulation vessel for BJ Services, Inc., Houston, Texas. Alabama Shipyard, Mobile, Ala, built the other two 265-ft. Hornbeck vessels.
Deadweight capacity of there 240's is 2,758 long tons while their larger 260's have over 3,700 long tons of deadweight carrying ability.
Their 260's can haul 10,450 barrels of bulk mud and 10,800 cubic ft. of dry bulk. Fuel oil capacity
tops out at 609,000 gallons if some of the tanks used for water or other materials are used for fuel oil. Normal fuel oil capacity is 148,300 gallons and rig water capacity is 413,000 gallons.
It is obvious that the new vessel being built for Edison Chouest, Tidewater and Hornbeck can hold significant quantities of the supplies rigs and platforms need most. They also can usually serve more than one platform at a time, increasing the efficiency of the vessels.
Delivering massive quantities of supplies is one aspect of what is happening in the Gulf. But speed of delivery is another part of the equation.
That is where the crew/supply boat comes in. With their massive horsepower and lightweight aluminum construction, the crew/supply boat has come into its own as a critical part of the fleet of an offshore supply company.
Tidewater recognized this last year when they decided to both buy existing and build new crew/supply boats. In fact they came up with an entirely new class of vessels, which they call the Fast Supply Boats. C&G Boatworks, Mobile, Ala. is building four 175-ft. crew/supply vessels for Tidewater with the first one delivered.
These vessels are the first ones to carry liquid mud in below deck tanks. So if you need 1,000 barrels of liquid mud delivered in a hurry (23 knots) rather than larger quantities delivered at 13 knots these vessels will no doubt serve this niche market.
The 175-ft. by 34-ft. by 14-ft. Vicki Tide has a deadweight capacity of 555 long tons.
Individual capacities include 33,900 gallons of fuel oil, 25,880 gallons of cargo water and 1000 barrels of liquid mud.
This is about 10 percent of the capacity of the giant supply boats discussed about, but speed does come with a price.
Deck cargo is 365 long tons on a 100-ft. by 29-ft. clear space.
Power to propel the vessel to 23 knots comes from four Cummins KT-50's each rated at 1800 hp. With the mud hauling ability of this vessel, the number of rig workers carried is reduced to 39 with a crew of 5. The vessel is rated at DP-1 by ABS.
There are still plenty of "typical" supply boats being built for the major operators. Tidewater is having four 162-ft. vessels built at Breaux Bay Craft and Breaux Brothers Enterprises (both companies located in the tiny town of Loreauville, La.) builds at least six crew/supply boats a year for Barry Graham and other operators. Breaux Brothers also builds safety/standby vessels and on occasion a passenger vessel or two in most years.
Boat operator giant Seacor Marine has two 170-ft. vessels and one 158-ft. vessel in the fab sheds at Neuville Boat Works, also in Loreauville.
Speaking of Seacor Marine, Gulf Craft, Patterson, La. (you guessed it…close to Loreauville) has a 175-ft. water jet powered crew/supply vessel for Seacor just delivered at the end of June. Behind that are three more vessels for Seacor…another 175-ft. boat and two 150-ft. vessels.
Gulf Craft also has a 175-ft. by 30-ft. high-speed catamaran ferry for Key West Shuttles, LLC for slated for November delivery. Gulf Craft started off the year by delivering the third of three 155-ft. crew/supply vessels to Trico Marine. The third vessel in the series Tennessee River is powered by five Cummins KTA-38's for a total horsepower of 6,750. Cummins also supplied the two gensets. A Wesmar hydraulic bow thruster is included in the package. A total of 78 seats are in the main deck cabin for rig crew. The total number of heavy haulers and fast haulers to be delivered this year is approximately 100 with a value well in excess of $1 billion. It is by far the largest workboat vessel construction market.