Once an area has been selected and the right to drill thereon has been obtained, actual drilling may begin. The most common method of drilling in use today is rotary drilling.
Onshore rigs are all similar. The most common arrangement for a land drilling rig is the cantilever mast (also called a jack-knife derrick ) which is assembled on the ground with large steel pins, then raised to the vertical position by the hoisting line, travelling block and drawworks. On the wellsite, the mast is usually set onto a substructure that is 8 to 40 feet high. Some have their masts permanently attached to a large truck to enhance their portability. They are used for moderately deep wells. Some land rigs can be moved by helicopter and are called heli-rigs . ADD NEW2: Standard Derricks - Four sided structures that must be assembled and disassembled when transporting. Portable Derricks - Telescoping and jackknife types. The telescoping derrick is raised and lowered in an extending and collapsing fashion and lowered in one piece, but may be disassembled to some degree after being lowered.
Barges are mobile, shallow draft, flat-bottom vessels equipped with a derrick, other necessary drilling equipment and accommodations. Tugboats usually tow them to the location with the derrick lying down. Once on location the lower hull is flooded until it rests on the bottom. The derrick is then raised and drilling operations are conducted with the barge in this position. After drilling is completed water is pumped out of the barge allowing it to be moved to the next location. Because of limited space on the drilling barge, utility barges are positioned alongside the barge rig and are used to: · Store materials · A container for cuttings that are dumped from the drilling barge
Suhannah-1 in Irian Jaya
Drilling tenders are usually non-self-propelled barges or semi-submersibles that are moored alongside a platform. They contain the quarters, mud pits, mud pumps, power generation, and other equipment needed to drill an offshore well. The only equipment on the platform is the derrick equipment consisting of the substructure, drillfloor, derrick and drawworks. Drilling tenders allow smaller, less costly platforms to be used for development projects. Self-erecting tenders carry their own derrick equipment set and has a crane capable of erecting it on the platform, thereby eliminating the cost associated with a separate derrick barge and related equipment.
Robray T-4. Note ILO unit on rig floor.
The offshore oil and gas industry celebrated its 50th birthday in 1997. The first offshore platform was installed off the coast of Louisiana in 1947 in just 6m of water. Today there are over 7,000 offshore platforms around the world in water depths up to 1,850m. Offshore platforms can be categorised according to whether they are rigid structures that extend all the way from above the water surface to the seabed (fixed-bottom platforms), or whether they float near the water surface. Platform costs rises very rapidly with water depth.
With the mobile self-elevating rig concept, one can drill in water depths of a hundred meters. While a jack-up is being towed to its site, its legs are raised. Once it reaches the drilling site, the legs are lowered onto the sea bed via toothed wheels. The wheels continue to turn even after the legs have reached the sea bottom, lifting the rig above sea level (“jacking up”). Jack-up rigs are very stable drilling platforms because they rest on the seabed and are not subjected to the heaving motion of the sea. Most jack-up rigs have three, four or five legs that are either vertical or slightly tilted for better stability. After the drilling is done, the legs are raised again and the platform can be towed off to another drill site. ADD jackup rig 1. n. [Drilling] 1434 A self-contained combination drilling rig and floating barge, fitted with long support legs that can be raised or lowered independently of each other. The jackup, as it is known informally, is towed onto location with its legs up and the barge section floating on the water. Upon arrival at the drilling location, the legs are jacked down onto the seafloor, preloaded to securely drive them into the seabottom, and then all three legs are jacked further down. Since the legs have been preloaded and will not penetrate the seafloor further, this jacking down of the legs has the effect of raising the jacking mechanism, which is attached to the barge and drilling package. In this manner, the entire barge and drilling structure are slowly raised above the water to a predetermined height above the water, so that wave, tidal and current loading acts only on the relatively small legs and not the bulky barge and drilling package.
Semi-submersible rigs or “ semis ” are floating drilling rigs that by means of a water ballasting system can be partially submerged so that the pontoons (lower hulls) are below the surface wave action during drilling operations (60-80 feet below the water line). They are supported by a number of vertical stabilizing columns (usually eight) which support an upper deck fitted with a derrick and associated drilling equipment. The upper deck is attached to the pontoons by large columns. They maintain their position by a series of anchors and mooring lines (most semis) or by dynamic positioning. They can operate in water depths of 20 ft to 2000 ft. Its operational depth is limited by mooring equipment and riser handling problems.
A drillship is a self-propelled ship capable of drilling in deep water up to 6000 ft + and offer greater mobility than either jack-up or semi-submersible rigs, but are not as stable when drilling. “Floaters” like the “semis”, they either are anchor-moored or dynamically positioned. Anchor-moored drillships are generally more limited in terms of water depth than dynamically positioned drillships. The drilling slot on a drillship is through the midsection of the vessel, its center of gravity. It is called a moon pool . The derrick mounted above it gives the drillship its distinctive appearance. Drillships typically have greater storage capacity than semi-submersible drilling rigs. This enables them to carry more supplies on board, which makes them better suited for drilling in remote locations. However, drillships are generally limited to calmer water conditions than those in which semi-submersibles can operate, and thus cannot compete as well as semi-submersibles in areas with harsh environments, such as the North Sea.
Keyway - The keyway is the opening on an inland barge or offshore jackup in which the drilling operations are performed.
Moonpool - The hole through a floater or semi-submersible structure is which the drilling operations are performed.
Toolpusher: The location supervisor for the drilling contractor. The toolpusher is usually a senior, experienced individual who has worked his way up through the ranks of the drilling crew positions. His job is largely administrative, including ensuring that the rig has sufficient materials, spare parts and skilled personnel to continue efficient operations. The toolpusher also serves as a trusted advisor to many personnel on the rigsite, including the operator's representative, the company man. Motorman The member of the rig crew responsible for maintenance of the engines. While all members of the rig crew help with major repairs, the motorman does routine preventive maintenance and minor repairs.
Roustabout Any unskilled manual laborer on the rigsite. A roustabout may be part of the drilling contractor's employee workforce, or may be on location temporarily for special operations. Roustabouts are commonly hired to ensure that the skilled personnel that run an expensive drilling rig are not distracted by peripheral tasks, ranging from cleaning up location to cleaning threads to digging trenches to scraping and painting rig components. Although roustabouts typically work long hard days, this type of work can lead to more steady employment on a rig crew.
The supervisor of the rig crew. The driller is responsible for the efficient operation of the rigsite as well as the safety of the crew and typically has many years of rigsite experience. Most drillers have worked their way up from other rigsite jobs. While the driller must know how to perform each of the jobs on the rig, his or her role is to supervise the work and control the major rig systems. The driller operates the pumps, drawworks, and rotary table via the drillers console-a control room of gauges, control levers, rheostats, and other pneumatic, hydraulic and electronic instrumentation. The driller also operates the drawworks brake using a long-handled lever. Hence, the driller is sometimes referred to as the person who is &quot;on the brake.&quot; Brakes: The mechanism on the drawworks than permits the driller to control the speed and motion of the drilling line and the drillstring, or the brake handle that the driller operates to control the brake mechanism.
One of the rig crew members who gets his name from the fact that he works on a platform attached to the derrick or mast, typically 85 ft [26 m] above the rig floor, during trips. On small land drilling crews, the derrickman is second in rank to the driller. Larger offshore crews may have an assistant driller between the derrickman and the driller. In a typical trip out of the hole (TOH), the derrickman wears a special safety harness that enables him to lean out from the work platform (called the monkeyboard) to reach the drillpipe in the center of the derrick or mast, throw a line around the pipe and pull it back into its storage location (the fingerboards) until it is time to run the pipe back into the well. In terms of skill, physical exertion and perceived danger, a derrickman has one of the most demanding jobs on the rig crew. Some modern drilling rigs have automated pipe-handling equipment such that the derrickman controls the machinery rather than physically handling the pipe. In an emergency, the derrickman can quickly reach the ground by an escape line often called the Geronimo line. The member of the drilling crew in charge of the mud-processing area during periods of circulation. The derrickman also measures mud density and conducts the Marsh funnel viscosity test on a regular basis when the mud is circulating in the hole. The derrickman reports to the toolpusher, but is instructed in detail by the mud engineer on what to add to the mud, how fast and how much. His other job is to handle pipe in the derrick while pulling out or running into the hole. The working platform approximately halfway up the derrick or mast in which the derrickman stores drillpipe and drill collars in an orderly fashion during trips out of the hole. The entire platform consists of a small section from which the derrickman works (called the monkeyboard), and several steel fingers with slots between them that keep the tops of the drillpipe in place.
A low-ranking member of the drilling crew. The roughneck usually performs semiskilled and unskilled manual labor that requires continual hard work in difficult conditions for many hours. After roughnecks understand how the rig operates and demonstrates their work ethic, they may be promoted to other positions in the crew.
Cac loai gian khoan
The Drilling Rig and Its Crew
Types of Rigs• Onshore or land rigs• Offshore rigs – Barges – Drilling Tenders – Platforms – Jack-ups – Semisubmersibles – Drillships
Land Rigs • Cantilever mast – most common arrangement • Portable mast – usually mounted on trucks that incorporate the hoisting machinery, engines and derrick as a single unit
Drilling Barges• Mobile, flat bottomed shallow draft vessels• Used for drilling in swampy or shallow coastal waters (8-20 ft) – West African river deltas, US Gulf Coast, Maracaibo, Kalimantan• Limited stability and can be used in very calm waters• Need utility barges because of limited storage space
Platforms• Fixed-bottom or rigid – rigid structures extend from the seabed to all the way above the surface of the water – Steel jacket or concrete gravity (CGS)• Floating – float near the water surface – Tension leg (TLP), Spar
Type of Platforms Type of Connection to Seabed Example PlatformFixed-bottom Piles Steel jacket Gravity Concrete Gravity Structure (CGS)Floating Tethers Tension Leg Platform (TLP) Catenary mooring lines Semi-submersible, Spar Single Point Mooring Ship-shaped vessel (FPSO) (SPM)
Semisubmersibles • Have a water ballasting system that can partially submerge its vertical stabilizing columns • Anchor-moored or dynamically positioned • Can operate in water depths of up to 6000 ft. • Operational depth limited by mooring equipment and riser handling capacity • Can work in harsh environments like the North Sea
A Word On Dynamic Positioning• Dynamic Positioning – is a technique used on floaters utilizing large computer-controlled on-board propulsion units (pitch propellers or “thrusters”) controlled by a satellite navigation system to maintain the position of a vessel with respect to a point on the seabed• Range of weather conditions is limited• Generally not used in water depths of less than 3000 ft• Because of large fuel consumption it is only economically feasible in the ff circumstances: – Frequent location changes are required – Anchor lengths required are excessive (>3000 ft)
Drillships • Capable of drilling in very deep water (>6000 ft) • Offer greater mobility than a “semi” or jack- up • Greater storage facilities • Anchor-moored or dynamically positioned • Limited to areas where wave action is not severe
Keyway• The keyway is the opening on an inland barge or offshore jackup in which the drilling operations are performed.
Moonpool• The hole through a floater or semi- submersible structure is which the drilling operations are performed.