Oil & Gas Glossary 1.0

In drilling-fluid terminology, yield point means yield value (which see). Of the two terms, yield point is more common.

The yield value (commonly called "yield point") is the resistance to initial flow, or represents the stress required to start fluid movement. This resistance is due to electrical charges located on or near the surfaces of the particles. The values of the yield point and thixotropy, respectively, are measurements of the same fluid properties under dynamic and static states. The Bingham yield value, reported in lb/100 square feet, is determined by the direct-indicating viscometer by subtracting the plastic viscosity from the 300-rpm reading.

A dilatant, or inverted plastic, fluid is usually made up of a high concentration of well-dispersed solids that exhibits a nonlinear consistency curve passing through the origin. The apparent viscosity increases instantaneously with increasing rate of share. The yield point, as determined by conventional calculations from the direct-indicating viscometer readings, is negative; however, the true yield point is zero.

A term used to define the quality of a clay by describing the number of barrels of a given centipoise slurry that can be made from a ton of clay. Based on the yield, clays are classified as bentonite, high yield, low yield, etc., types of clays. Not related to yield value below. See API RP 13B for procedures.

A classification of commercial drilling-clay preparations having a yield of 35 to 40 barrels per ton and intermediate between bentonite and low-yield clays. Usually prepared by peptizing low-yield calcium montmorillonite clays or, in a few cases, by blending some bentonite with the peptized low yield clay

In drilling-fluid terminology, a chemical is any material that produces changes in the viscosity, yield point, gel strength, fluid loss, and surface tension.

Commercial clay chiefly of the calcium montmorillonite type and having a yield of approximately 15 barrels per ton.

Commercial clay chiefly of the calcium montmorillonite type and having a yield of approximately 15 barrels per ton.

An area or point above the point at which a tubular, such as drill pipe, is stuck in the wellbore.

Commonly called a "V-G meter." A rotational device powered by means of an electric motor or handcrank. Used to determine the apparent viscosity, plastic viscosity, yield point, and gel strengths of drilling fluids. See direct-reading viscometer

Commonly called a "V-G meter." The instrument is a rotational-type device powered by means of an electric motor or handcrank, and is used to determine the apparent viscosity, plastic viscosity, yield point, and gel strengths (all of which see) of drilling fluids. The usual speeds are 600 and 300 revolutions per minute. See API RP13B for operational procedures. Also see direct-indicating viscometer.

A given point at a certain temperature and pressure at which no more solid material will dissolve in a liquid.

The point marking the end of one stage of a process. In filtrate analysis, the endpoint is the point at which a particular result is achieved through titration.

That velocity at the transitional point between laminar and turbulent types of fluid flow. This point occurs in the transitional range of Reynolds numbers of approximately 2,000 to 3,000.

To pass from one point throughout a system and back to the starting point. For example, drilling fluid is circulated out of the suction pit, down the drill pipe and drill collars, out the bit, up the annulus, and back to the pits while drilling proceeds.

A clay to which an agent has been added to increase its initial yield

A squeeze cementing method in which a packer is set to form a seal between the working string (the pipe down which cement is pumped) and the casing. Another packer or a cement plug is set below the point to be squeeze-cemented. By setting packers, the squeeze point is isolated from the rest of the well. See packer, squeeze cementing.

A device run on wireline into the wellbore and inside the fishing string and fish to locate the area where a fish is stuck. When the drill string is pulled and turned, the electromagnetic fields of free pipe and stuck pipe differ. The free-point indicator is able to distinguish these differences, which are registered on a metering device at the surface.

The lowest internal pressure at which a failure (of pipe) will take place.

The yield of an oil or gas well; the branch of the industry that brings the oil and gas to the surface for sale. The phase of the petroleum industry that deals with bringing the well fluids to the surface and separating them and with storing, gauging, and otherwise preparing the product for pipeline. The amount of oil or gas produced in a given period.

1. a scale of pressure differences in which there is a uniform variation of pressure from point to point. For example, the pressure gradient of a column of water is about 0.433 pounds per square inch per foot (9.794 kilopascals per meter) of vertical elevation. The normal pressure gradient in a formation is equivalent to the pressure exerted at any given depth by a column of 10 percent salt water extending from that depth to the surface 0.465 pounds per square inch per foot or 10.518 kilopascals per meter).

Dissolved calcium ions in sufficient concentration to impart undesirable properties, such as flocculation, reduction in yield of bentonite, and increased fluid loss, in a drilling fluid. See also calcium carbonate, calcium sulfate, gypsum.

The greatest longitudinal stress that a metal can bear without tearing apart. A metal's tensile strength is greater than its yield strength.

The depth in the hole at which the tubing, casing, or drill pipe is stuck.

A device for measuring and recording the specific gravity of a gas or liquid passing a point of measurement.

A method for indicating hook load or force, read off rig's indicator; 1 point = 1,000 pounds

A bull plug or blind flange at the end of a tee to prevent erosion at a point where change in flow direction occurs.

A substance formed when two or more substances polymerize at the same time to yield a produce which is not a mixture of separate polymers but a complex having properties different from either polymer alone. See polymer. Examples are polyvinyl acetate-maleic anhydride copolymer (day extender and selective and selective flocculant), acrylamide-carboxylic and copolymer (total flocculant).

The tendency of a metal bar or pipe to taper to a reduced diameter at some point when subjected to excessive longitudinal stress. See bottleneck.

The depth in the hole at which the drill stem, tubing, or casing is stuck.

A portion of cement placed at some point in the wellbore to seal it. See cementing.

An oil or gas well the production of which is so limited in relation to production costs that profit approaches the vanishing point.

Distance between well head and point to which fluid rises in the well.

A round cluster of hydrocarbon chains formed when the amount of surfactant in an aqueous solution reaches a critical point. The micelles are able to surround and dissolve droplets of water or oil, forming an emulsion.

A device used to measure the depth of a well or the depth at a specific point in a well (such as to the top of a liner or to a fish) by counting the turns of a calibrated wheel rolling on a wireline as it is lowered into or pulled out of the well.

A light, gaseous, flammable paraffinic hydrocarbon that has a boiling point of -25 degrees F and is the chief component of natural gas and an important basic hydrocarbon for petrochemical manufacture.

An immobile offshore structure from which development wells are drilled and produced. Platform rigs may be built of steel or concrete and may be either rigid or compliant. Rigid platform rigs, which rest on the seafloor, are the caisson-type platform, the concrete gravity platform, and the steel-jacket platform. Compliant platform rigs, which are used in deeper waters and yield to water and wind movements are the guyed-tower platform and the tension-leg platform.

A secondary-cementing operation in which a plug of cement is positioned at a specific point in the well and allowed to set.

The location of the bottom of a string of casing that is cemented in a well. Typically, a casing shoe is made up on the end of the casing at this point.

Abbreviation: the phenolphthalein alkalinity of the filtrate, reported as the number of milliliters of 0.02 Normal (N/50) acid required per milliliter of filtrate to reach the phenolphthalein end point.

Lease Automatic Custody Transfer, possible where measuring equipment installed at the point of transfer from lease to pipeline is so completely automated as not to require any manual activity or witnesses.

The operation during the drilling procedure at the point of drilling into the pay formation.

2. a point at which a photograph is made in a single-shot survey. See directional survey.

Semisolid or solid complex, amorphous mixture of organic compounds having no definite melting point or tendency to crystallize. Resins may be a component of compounded materials that can be added to drilling fluids to impart special properties to the system, to wall cake, etc.

A method for killing well pressure in which circulation is commenced immediately and mud weight is brought up in steps, or increments, usually a point at a time. Also called circulate-and-weight method.

A pressure-fight container (bomb) used to record the pressure in a well at a point opposite the producing formation

The point at which a formation will crack from pressure in the wellbore.

1. a tool placed on a drill collar near the bit that is used, depending on where it is placed, either to maintain a particular hole angle or to change the angle by controlling the location of the contact point between the hole and the collars. See packed-hole assembly.

A method of well completion in which a slotted or perforated liner, often wire-wrapped, is placed in the well and surrounded by gravel. If open hole, the well is sometimes enlarged by underreaming at the point where the gravel is packed. The mass of gravel excludes sand from the wellbore but allows continued production.

The methyl orange alkalinity of the filtrate, reported as the number of millimeters of 0.02 normal (n/50) acid required pr millimeter of filtrate to reach the methyl orange end point (pH 4.3).

A centrifugal device for removing very fine particles, or silt, from drilling fluids to keep the amount of solids in the fluid at the lowest possible point. Usually, the lower the solids content of mud, the faster is the rate of penetration. The desilter work on the same principle as a desander. Compare desander.

A method of killing a well in which the mud level in the pits is held constant while the choke size is reduced and the pump speed slowed. It is not effective, and therefore, is not recommended, because casing pressure increases to the point at which the formation fractures or casing ruptures, and control of the well is lost.

Intentional deviation of a wellbore from the vertical. Although wellbores are normally drilled vertically, it is sometimes necessary or advantageous to drill at an angle from the vertical. Controlled directional drilling makes is possible to reach subsurface areas laterally remote from the point where the bit enters the earth. It often involves the use of turbodrills, Dyna-Drills, whipstocks, or other deflecting rods.

Any cementing operation after the primary cementing operation. Secondary cementing includes a plug-back job, in which a plug of cement is positioned at a specific point in the well and allowed to set. Wells are plugged to shut off bottom water or to reduce the depth of the well for other reasons.

1. an automatic valve that opens or closes when an abnormal condition occurs (e.g., a pressure relief valve on a separator that opens if the pressure exceeds the set point, or the shutdown valve at the wellhead that closes if the line pressure becomes too high or too low).

A cast-iron or magnesium drillable tool consisting of a packing assembly and a back-pressure valve. It is used to close off the annular space between tubing or drill pipe and casing to allow the placement of cement or fluid through the tubing or drill pipe at any predetermined point behind the casing or liner, around the shoe, or into the open hole around the shoe.

The force exerted by a column of liquid expressed by the height of the liquid above the point at which the pressure is measured. Although "head" refers to distance or height, it is used to express pressure, since the force of the liquid column is directly proportional to its height. Also called head or hydrostatic head. Compare hydrostatic pressure.