【正文】 controllingThe principal ponents of a rig that perform these functions are shown in figure . The derrick supports the crown block and traveling block, which are operated via the drawworks and its drilling line. The kelly and swivel are connected to the drillstring and are suspended from the hook beneath the traveling block, allowing the kelly and drillstring to be turned by the rotary table. A drilling fluid circulation system pumps mud from the Figure The hoisting and rotating ponent’s of a rotary drilling rig. Courtesy EXLOG.pits through standpipe, hose, swivel, and drillstem, returning the mud and cuttings up the annulus and back to the pits. The blowout preventer (BOP) stack and its operating equipment allow the drilling crew to maintain control over subsurface pressures. A closer look at each of these basic functions and the equipment that is involved is given in the following.Hoisting (derrick, drawworks, blocks, and hook): The derrick, or mast, and the substructure it sits upon, support the weight of the drillstem and allow vertical movement of the suspended drillpipe. The substructure also supports the rig floor equipment and provides workspace for its operation. The drillstring must be removed from time to time。 rotating tension leg platformsAn example of the most mon piledsteel platform, with a drilling rig installed on its deck, is shown in figure . Drilling from these structures is not significantly different than other drilling operations.Although all of the drilling rigs mentioned vary quite a bit, depending on what sort of surface environment or stresses they are designed for, they still provide us with the ability to perform the four basic drilling functions discussed next.Figure A drilling rig mounted on a fixed offshore platform. Courtesy EXLOG Basic Drilling FunctionsThe four basic drilling functions are: caissontype monopod structures piledsteel platformss stability. Although the semi can operate in deeper water than a jackup, it is still limited by the capabilities of the mooring equipment and the “riser” (the conduit that connects the drill floor to the subsea equipment located at the borehole on the seafloor). These important items will be discussed in greater detail in section , Floating Drilling Equipment.Figure Semisubmersible drilling rigs. Courtesy EXLOG and Exxon.Drillships：Drillships are selfpropelled vessels capable of drilling in water depths of 18 to 6000 ft (5 to 1800 m) and are most often utilized for extremely deep water drilling at remote locations. A “floater” like the semisubmersible, a drillship must maintain its position at the drilling location by anchors and mooring lines, or by putercontrolled dynamic positioning equipment. A series of controllable pitch propellers, or “thrusters,” shift position and speed to maintain the ship over the wellbore. The drilling slot, or “moonpool,” is through the ship39。 structure rigsBarge Rig: The barge rig is most often a flatbottomed vessel with a shallow draft, equipped with a derrick and other necessary drilling equipment. It is usually towed to the location and then has its hull filled with water, which allows it to rest on the bottom, providing a solid support for drilling activities. Obviously, this type of rig is only used in relatively shallow, swampy areas such as the river deltas of West Africa, the inland waters of the Louisiana swamps, or the shallows of Lake Maricaibo, Venezuela. Barge rigs are generally capable of drilling in water depths of less than 12 ft (), or, in the case of a posted barge, perhaps to 20 ft ( m). A posted barge has a lower hull that rests on the bottom and an upper deck that is supported by posts from the lower hull.Submersible Rig: A submersible rig is a larger version of a posted barge, and is capable of working in water depths of 18 to 70 ft ( to m). Often the hull of a submersible rig will have steel floats or “bottles” that can be filled with water (ballasted) to help stabilize the vessel on bottom.Jackup Rig: The jackup rig is a selfelevating drilling rig, illustrated in figure , designed to operate in depths from 30 to 350 ft (9 to 107m). After being towed to the location (or in some cases being selfpropelled), the legs are lowered by electric or hydraulic jacks until they rest on the seabed and the deck is level, supported perhaps 60 ft (18 m) above the waves. Most jackup rigs have three to five legs that are either vertical or Figure A jackup drilling rig on location. Courtesy MarathonLe Tourneau Marine Company.slightly angled for stability. The legs may have steel feet, called “spud cans,” or they may be attached to a large steel mat. When moving to a location the legs are raised, high above the deck, creating a somewhat cumbersome vessel that must move at slow speeds and only in good weather. The derrick, or mast, on a jackup may be located over a drilling slot indented in one side of the structure, or the drill floor may be cantilevered over the side of the deck, allowing the rig to service wells on stationary platforms, or singlewell caissons, offshore.Semisubmersibic Rig: Unlike the other offshore vessels, the semisubmersible drilling rig does not rest on the seafloor. This rig is a floating deck supported by submerged pontoons and kept stationary by a series of anchors and mooring lines, and, in some cases, positionkeeping propellers (Figure ). “Semis” can either move under their own power or must be towed to their have a waterdepth operating range of 20 to 2000 ft (6 to 600 m), and differ from each other principally in their hull configuration and their number of stabilizing columns. Most types have a rectangular deck。 semisubmersible rigs submersible rigss horsepower, mud pump horsepower, and loadbearing capacity. The loadbearing capacity can be translated to a depth limitation depending on the size of the drillpipe. A few rigs are capable of drilling to depths of 30,000 ft (9144 m) and