MODU Definitions

Rig Types

• Jackup
  • Jackups are mobile, self-elevating drilling platforms that are equipped with moveable legs. Jackups are towed to a drilling site by tug boats before the unit lowers its legs to the seabed and then jacks up the hull to elevate it above the sea level, after which drilling operations can begin. The units are used exclusively for shallow water exploration and production drilling
• Semi-submersible
  • A semi-submersible drilling rig is a floating drilling rig that is capable of working in water depths ranging from shallow through to ultra-deepwater. Semi-submersibles use a number of pontoons that are submerged beneath the water line to float and remain stable in a single location. The deck is positioned above the water line and sits on top of a number of columns that connect the hull to the submerged pontoons. Semi-submersibles offer an increased level of stability whilst drilling in comparison to drillships and are thus preferred for drilling in harsh environment regions
• Drillships
  • A drillship is ship-shaped vessel that has been equipped for drilling operations. The unit can be utilised for drilling operations in midwater to ultra-deepwater areas and are generally preferred for exploration drilling as the assets are self-propelled. Drillships are kept on station using dynamic positioning systems
• Tender assist drilling units (Tender/Semi-Tender)
  • Tender assist drilling units (TADs) allow drilling operations to be carried out on a fixed platform without the need for a permanent drilling package on the platform. The TAD is stationed next to the platform and its drilling package is lifted onto the platform. The TAD remains in place in order to provide power and other services that support the drilling operation. There are two different types of TADs, a tender rig and semi-tender, both units carry the same equipment but the semi-tender is capable of operating in deeper waters and harsher environments

Rig Generations

7 basic generations determined by delivery year and water depth characteristics

Semi-submersible rig generations:

• 1st Generation
  • Unit constructed from 1961 – 1972. Max water depth is N/A
• 2nd Generation
  • Unit constructed from 1973 – 1979. Max water depth is N/A
• 3rd Generation
  • Unit constructed from 1980 – 1985. Max water depth is N/A
• 4th Generation
  • Unit constructed from 1986 – 1997. Max water depth is N/A
• 5th Generation
  • Unit constructed from 1998 – 2004. Max water depth is N/A
• 6th Generation   
  • Unit constructed from 2005 onwards. Max water depth is 10,000ft
• 7th Generation
  • Unit constructed from 2015 onwards. Max water depth is 12,000ft

Drillship rig generations:

• 1st Generation
  • Unit constructed from 1961 – 1970. Water depth is N/A
• 2nd Generation
  • Unit constructed from 1971 – 1979. Water depth is N/A
• 3rd Generation
  • Unit constructed from 1980 – 1985. Water depth is N/A
• 4th Generation
  • Unit constructed from 1986 – 1997. Water depth is N/A
• 5th Generation
  • Unit constructed from 1998 – 2005. Water depth is N/A
• 6th Generation
  • Unit constructed from 2006 onwards. Max water depth is 10,000ft
• 7th Generation
  • Unit constructed from 2010 onwards. Max water depth is 12,000ft

Jackup rig types

Four jackup type categories

• High Specification
  • Water depth is 400ft+, with a hookload capacity of over 2,000kips
• Premium
  • Water depth is 350ft+, with a hookload capacity from 0 – 1,999kips
• Standard
  • Water depth is less than 350ft
• Mat Cantilever/Slot
  • Any jackup that does not have an Independent Leg Cantilever (ILC) sub-type

Sub type definitions

• Floating rigs
  • Midwater
  • Deepwater
  • Ultra-deepwater

• Jackups
  • Independent Leg Cantilever
  • Independent Leg Slot
  • Mat Cantilever
  • Mat Slot
  • Cantilever

Floating rig water depths

• Midwater
  • 4,000ft or less
• Deepwater
  • 4,001- 7,499ft
• Ultra-deepwater
  • 7,500ft and greater

Status Definitions

Data & Reports Definitions:

• Dayrate
  • The daily cost of contracting the asset
• Utilisation
  • Represents the number of units working compared to the units that are idle (displayed as a percentage)

Operating Status Definitions:

• Cold Stacked
  • Refers to a unit that has been ‘shut-down’ by the manager. All workers have been removed and the unit has been permanently stacked in a shipyard, harbour or offshore area
• Ready Stacked
  • Units that are currently idle but the crew are still employed on the rig and the unit is maintained in order to go to work when required
• Operational
  • The unit is currently under contract and performing drilling, intervention, accommodation or workover operations for the contractor
• Enroute
  • The unit is currently mobilising from one location to another
• Under Construction
  • The unit is in the construction phase and has been ordered by the rig owner
• Under Inspection/Repair/Maintenance
  • The unit is in the shipyard and minor work is being carried out. This status can refer to operator requested upgrades or SPS survey work
• Under Modification
  • The unit is undergoing a significant modification in the shipyard and parts of the unit are being replaced or upgraded

Marketed Rig Fleet Definition:

• Competitive Rigs
  • Units owned by national oil companies or working in ‘non-competitive’ areas are regarded as uncompetitive and are excluded from the marketed fleet

InfieldRigs Regions

InfieldRigs Detailed View Equipment Descriptions

• Derrick – The derrick is a lifting device composed of a tower, used for lifting and positioning the drill string and piping above the well bore and houses the top drive for turning the drill string whilst drilling the hole


• Top drive - The top drive is used to rotate the drill string throughout the drilling process. The top drive is a motor, suspended from the unit’s derrick; it turns the drill string by using mechanisms located in the top drive that is attached to the blocks. It is an alternative to a rotary table and preferred when drilling challenging extended reach and directional wells. The majority of drilling rigs now use top drives for the drilling process


• Rotary Table - A rotary table is a mechanical device used to provide rotational force to the drill string to facilitate the drilling process. Most recently manufactured rigs no longer feature rotary drives


• Drawworks - The primary function of the drawworks is to reel out and reel in the drilling line. The unit consists of a large-diameter steel spool, brakes, a power source and assorted auxiliary devices


• Moonpool - The moonpool is an opening in the base/floor of a drilling unit that gives access to the water below. Moonpool’s are generally found on floating drilling assets


• Gross Tonnage – Gross Tonnage (“GT”) relates to a unit’s overall internal volume.  GT is calculated based on the moulded volume of all enclosed spaces (from keel to funnel) of the unit and is used to determine things such as, a unit’s manning regulations, safety rules, registration fees and port dues


• Net Tonnage – Net Tonnage (“NT”) is a dimensions index calculated from the total moulded volume of the unit’s cargo spaces. Net Tonnage is not a measure of the weight of a unit; it is used to calculate the port duties for the unit


• Classification Society - A Classification society is a non-governmental organisation that establishes and maintains technical standards for the construction of ships and offshore structure


• Class Notation - Class notations are assigned to units in order to determine applicable rule requirements for assignment and retention of class


• Helideck ‘t-value’ – Refers to the maximum weight of aircraft the helideck is designed to accommodate


• Helideck ‘d-value’ – Refers to the size of the helideck to best represent the size of helicopter which it can accommodate


• Spudcan – Spudcan’s is a term used to describe the base cones found on the bottom of a jackup rig’s leg. The spudcan’s are mounted to the base of each individual leg and provide stability when the legs are deployed on the ocean floor


• Dual Activity Drilling - The system was pioneered by Transocean and allows a single derrick rig to perform parallel drilling operations in order to save time and cut costs


• Blowout Preventer (“BOP”) –There are two basic types of BOP – ram and annular BOPs. A number of annular and ram preventers are combined to form a BOP stack, which sits on top of a subsea well during the drilling process. These stacks can seal around drill pipe, casing or tubing and close over an open wellbore or cut through the drill string with steel shearing blades


• Cantilever – A Cantilever is a beam anchored at only one end, allowing for overhanging structures without external bracing. Cantilever systems are only applicable to jackup rigs. Jackups use the cantilever system to position the derrick over either a drilling platform or well for drilling operations. A classic cantilever can move longitudinally relative to the hull of a jackup. Whilst for transverse positioning of the drilling derrick, the drillfloor can subsequently be moved transversely relative to the cantilever structure


• Dual Gradient Drilling (“DGD”) – DGD is a variant of managed pressure drilling (“MPD”) that uses pressure gradients to manage pressure when drilling offshore. DGD employs two weights of drilling fluid, whilst conventional drilling uses a single fluid. DGD uses one fluid above the seabed and another below to more closely match the pressures presented by nature and helps to effectively eliminate water depth as a consideration in well design. DGD also allows drillers to react quickly to downhole pressure changes, which can enhance the safety and efficiency of deepwater drilling operations


• Mud pumps - A mud pump is a piston/plunger device designed to circulate drilling fluid down the drill string. The pump circulates the mud by pushing it down into the hole and then moving it back up again. Mud pumps are reciprocating pumps, meaning that they use oscillating pistons or plungers to displace the fluid. The "mud" used is drilling for oil consists of emulsified water or oil, clay and chemicals. For safety reasons, it is tailor-made to the particular chemical conditions of the drilling. Its purpose is to float rock cuttings out of the hole, clean the bottom of the hole and cool the drilling equipment. It also acts as the initial barrier in case of a blowout by resisting the pressure from any fluid within the rock that might enter the well. Most modern mud pumps are triplex-style pumps, which have three cylinders


• Variable deck load (“VDL”) – VDL refers to the carrying capacity of the rig. It is a measure of the deadweight (consumables and extracted product) the rig can hold. The higher the VDL, the more casings and pipe the unit may be able to hold. VDL includes any item of weight that is not included in the lightship of the basic vessel. Lightship weight includes the drawworks, mud pumps, rotary table, derrick, top drive, power plant & all items that cannot be readily lifted off the rig