A wellhead is the component at the surface of an oil or gas well that provides the structural and pressure-containing interface for the drilling and production equipment.
20-426: The primary purpose of a wellhead is to provide the suspension point and pressure seals for the casing strings that run from the bottom of the hole sections to the surface pressure control equipment. While drilling the oil well, surface pressure control is provided by a blowout preventer (BOP). If the pressure is not contained during drilling operations by the column of drilling fluid , casings, wellhead, and BOP,
40-544: A subsea wellhead or mudline wellhead. The primary components of a wellhead system are: A wellhead serves numerous functions, some of which are: The oil industry specifications for wellhead systems (materials, dimensions, test procedures and pressure ratings etc.) are : In general well heads are five nominal ratings of wellheads: 2, 3, 5, 10 and 15 (×1000) psi working pressure. They have an operating temperature range of −50 to +250 degrees Fahrenheit. They are used in conjunction with ring type seal gaskets. In general
60-418: A mud motor, measurement while drilling (MWD) apparatus, stabilizers, and various specialty downhole tools. The drill stem includes the entire drill string, plus the kelly that imparts rotation and torque to the drill pipe at the top. See Drilling rig (petroleum) for a diagram of a drilling rig. Modern drill pipe is made from the welding of at least three separate pieces: box tool joint, pin tool joint, and
80-433: A red band. Drill pipe is a portion of the overall drill string. The drill string consists of both drill pipe and the bottom hole assembly (BHA), which is the tubular portion closest to the bit. The BHA will be made of thicker walled heavy weight drill pipe (HWDP) and drill collars, which have a larger outside diameter and provide weight to the drill bit and stiffness to the drilling assembly. Other BHA components can include
100-415: A well blowout could occur. When the well has been drilled, it is completed to provide an interface with the reservoir rock and a tubular conduit for the well fluids. The surface pressure control is provided by a Christmas tree , which is installed on top of the wellhead, with isolation valves and choke equipment to control the flow of well fluids during production. Wellheads are typically welded onto
120-426: Is held stationary while the tool joint is revolved at high RPMs. The tool joint is then firmly pressed onto the upset end of the tube while the tool joint is rotating. The heat and force during this interaction weld the two together. Once the "ram horns" or excess material is removed, the weld line can only be seen under a microscope. Inertia friction welding is the traditional proven method. Direct drive friction welding
140-646: Is manufactured in one piece with a female thread machined directly into one end.) Specification 5C3 of the American Petroleum Institute standardizes 14 casing sizes from 4.5 inches (11.43 cm) to 20 inches (50.80 cm) outside diameter ("OD"). This and related API documents also promulgate standards for the threaded end finish, the wall thickness (several are available in each size to satisfy various design parameters, and in fact are indirectly specified by standardized nominal weights per linear foot; thicker pipe obviously being heavier), and
160-403: Is run to protect or isolate formations adjacent to the wellbore. It is generally not possible to drill a well through all of the formations from surface (or the seabed) to the target depth in one hole-size section. For example, fresh-water-bearing zones (usually found only near the surface) must be protected soon after being penetrated. The well is therefore drilled in sections, with each section of
180-512: The Earth's crust , and also must be able to resist pressure differentials between inside and outside (or vice versa), and have sufficient strength to suspend the total weight of deeper components. For deep wells this requires tempered steel tubes that are expensive, and owners spend considerable efforts to reuse them after finishing a well. A used drill stem is inspected on site, or off location. Ultrasonic testing and modified instruments similar to
200-486: The spherometer are used at inspection sites to identify defects from metal fatigue , in order to preclude fracture of the drill stem during future wellboring. Drill pipe is most often considered premium class, which is 80% remaining body wall (RBW). After inspection determines that the RBW is below 80%, the pipe is considered to be Class 2 or "yellow band" pipe. Eventually the drill pipe will be graded as scrap and marked with
220-442: The 135 ksi of the tube. They generally are stiffer than the tube, increasing the likelihood of fatigue failure at the junction. The lower SMYS on the connection increases the fatigue resistance. Higher strength steels are typically harder and more brittle, making them more susceptible to cracking and subsequent stress crack propagation. Tubes and tool joints are welded using rotary inertia or direct drive friction welding . The tube
SECTION 10
#1732792954289240-406: The casing-liner overlap zone.) Depending on the conditions encountered (e.g., zones of differing formation pressure gradients), three or four casing strings may be required to reach the target depth. The cost of the casing can constitute 20-30% of the total cost of the well , and failure can be catastrophic. Great care must therefore be taken when designing an economic casing programme that will meet
260-401: The first string of casing, which has been cemented in place during drilling operations, to form an integral structure of the well. In exploration wells that are later abandoned, the wellhead may be recovered for refurbishment and re-use. Offshore, where a wellhead is located on the production platform it is called a surface wellhead , and if located beneath the water then it is referred to as
280-553: The requirements of the well. Drill pipe Drill pipe , is hollow, thin-walled, steel or aluminium alloy piping that is used on drilling rigs . It is hollow to allow drilling fluid to be pumped down the hole through the bit and back up the annulus . It comes in a variety of sizes, strengths, and wall thicknesses, but is typically 27 to 32 feet in length (Range 2). Longer lengths, up to 45 feet, exist (Range 3). Drill stems must be designed to transfer drilling torque for combined lengths that often exceed several miles down into
300-950: The strength and certain chemical characteristics of the steel material. Several material strengths—termed "Grades" and ranging from 40,000 pounds per square inch (276 MPa) to 150,000 pounds per square inch (1,034 MPa) minimum yield strength—are available for most combinations of OD and wall thickness to meet various design needs. Finally, the API publications provide performance minimums for longitudinal strength ("joint strength") as well as resistance to internal (bursting) and external (collapsing) pressure differentials. A typical piece of casing might be described as 9-5/8" 53.5# P-110 LT&C Rg 3: specifying OD, weight per foot (53.5 lbm/ft thus 0.545-inch wall thickness and 8.535-inch inside diameter), steel strength (110,000 psi yield strength), end finish ("Long Threaded and Coupled"), and approximate length ("Range 3" usually runs between 40 and 42 feet). Casing
320-405: The surface, being hung instead from a liner hanger set inside of the previous casing string but usually within about 300 feet (91 m) of its bottom. Other than the obvious cost savings, the liner installation allows larger drill pipe or production tubing to be used in the upper portions of the well. (A disadvantage is the occasional difficulty in effecting a pressure seal by squeeze cementing
340-452: The tube then goes through a heat treating process. Drill pipe steel is commonly quenched and tempered to achieve high yield strengths (135 ksi is a common tube yield strength). The tool joints (connectors) are also received by the manufacturer as green tubes. After a quench and temper heat treat, the tool joints are cut into box (female) and pin (male) threads. Tool joints are commonly 120 ksi Specified Minimum Yield Strength (SMYS), rather than
360-433: The tube. The green tubes are received by the drill pipe manufacturer from the steel mill. The ends of the tubes are then upset to increase the cross-sectional area of the ends. The tube end may be externally upset (EU), internally upset (IU), or internally and externally upset (IEU). Standard max upset dimensions are specified in API 5DP, but the exact dimensions of the upset are proprietary to the manufacturer. After upsetting,
380-422: The well being sealed off by lining the inside of the borehole with steel pipe, known as casing, and filling the annular space (or at least the lower portion) between this casing string and the borehole wall with cement. Then drilling commences on the subsequent hole section, necessarily with a smaller bit diameter that will pass through the newly installed casing. A liner is a casing string that does not extend to
400-491: The yield strength of the materials range from 36000 to 75000 psi. Casing string In drilling technology, casing string is a long section of connected oilfield pipe that is lowered into a wellbore and cemented. The purpose of the casing pipe is as follows: The pipe segments (called "joints") are typically about 40 feet (12 m) in length, male threaded on each end and connected with short lengths of double-female threaded pipe called couplings. (Some specialty casing
#288711