Quebracho. An additive used extensively for thinning/dispersing to control low-shear-rate viscosity and thixotropy. It is a crystalline extract of the quebracho tree consisting mainly of tannic acid. See: thinner.
Quicklime. Calcium oxide, CaO. Used in certain oil-based drilling fluids to neutralize the organic acid.
Quiescence. The state of being quiet or at rest, being still. See: static.
Radial flow. Flow of a fluid outwardly in a 360 pattern. This describes the flow from a mechanical agitator in which fluid moves away from the axis of the impeller shaft (usually horizontally toward a mud tank wall). See: axial flow.
Radical. Two or more atoms behaving as a single chemical unit, that is, as an atom; for instance, sulfate and phosphate are nitrate are radicals.
Rate of penetration. The rate at which the drill bit penetrates the formation, expressed in lineal units of feet/minute. See: penetration rate.
Rate of shear. The change in velocity between two parallel layers divided by the distance between the layers. Shear rate has the units of reciprocal seconds (sec^-1). See: shear rate.
Raw drilling fluid. Drilling fluid, before dilution, that is to be processed by solids-removal equipment.
Rectangular screen. See: oblong mesh.
Reduced port. A valve whose bore size is less than the area of the pipe to which it is attached.
Removal section. The first section in the drilling-fluid system, consisting of a series of compartments and
solids-removal equipment to remove gas and undesirable solids.
Reserve pit. (1) An earthen pit used to store drilling waste in land drilling operations. (2) A section of a surface system used to store drilling fluid.
Resin. A semisolid or solid complex or amorphous mixture of organic compounds having no definite melting point or tendency to crystallize.
Resin may be a component of compounded materials that can be added to drilling fluids to impart special properties to the system, that is, wall cake, fluid loss, etc.
Resistivity. Resistivity is a characteristic electrical property of a material and is equal to the electrical resistance of a 1-meter cube of the material to passage of a 1-ampere electric current perpendicular to two parallel faces. The electrical resistance offered to the passage of a current is expressed in ohm-meters. It is the reciprocal conductivity. Freshwater muds are usually characterized by high resistivity; saltwater muds by low resistivity. See: conductivity.
Resistivity meter. An instrument for measuring the electrical resistivity of drilling fluids.
Retention time. The time any given particle of material is retained in a region, for example, the time a particle is actually on a screening surface, within a hydroclone, or within the bowl of a centrifuge.
Retort. An instrument used to distill oil, water, and other volatile material in a drilling fluid to determine oil, water, salt, and total solids contents in volume percentage. See: mud still, mini still, API RP 13B.
Reverse circulation. The method by which the normal flow of a drilling fluid is reversed by circulating down the annulus, then up and out the drill string. See: circulation.
Reynolds number. A dimensionless number, Re, that occurs in the theory of fluid dynamics. The Reynolds number for a fluid flowing through a cylindrical conductor is determined by the equation:
Re = DVρ/μ.
D=diameter
V=velocity
ρ=density
μ=viscosity
The number is important in fluid-hydraulics calculations for determining the type of fluid flow, that is, whether laminar or turbulent. The transitional range occurs approximately from 2000 to 3000. Below 2000, the flow is laminar; and above 3000, the flow is turbulent. See: fluid flow.
Rheology. The science that deals with deformation and flow of matter. See: viscosity, Bingham model, plastic viscosity, yield point, gel strength.
Rig pump. The reciprocating, positive displacement, high-pressure pump on a drilling rig used to circulate the hole. See: mud pump.
Rig shaker. Slang term for a shale shaker.
Rigid frame panel. One of the two main screen panel types, consisting of a rigid panel to which the screen or layers of screen are attached. The screen panel fastening device can be designed for fast panel replacement. See: hook-strip panel.
ROP. See: rate of penetration, penetration rate.
Rope discharge. The characteristic underflow of a
hydrocyclone so overloaded with separable solids that not all the separated solids can crowd out through the underflow opening (apex), causing those solids that can exit to form a slow moving, heavy, ropelike stream. Also referred to as ‘‘rope’’ or ‘‘rope underflow.’’
Rotary drilling. The method of drilling wells in which a drill bit attached to a drill string is rotated on the formation to be drilled. A fluid is circulated through the drill pipe to remove cuttings from the bottom of the hole, bring cuttings to the surface, and perform other functions. See: cable tool drilling.
Rotary mud separator (RMS). A centrifuge consisting of a perforated cylinder rotating inside of an outer cylinder housing. As drilling fluid flows outside of the perforated cylinder, only the very small particles pass through the perforations.
Round trip. See: trip.
rpm. Revolutions per minute.
