Packer fluid. A fluid placed in the annulus between the tubing and casing above a packer. The hydrostatic pressure of the packer fluid is utilized to reduce the pressure differentials between the formation and the inside of the casing and across the packer.
Panel-mounted units. Shale shaker screens mounted to a rigid frame.
Parallel flow. See: laminar flow.
Particle. A discrete unit of solid material that may consist of a single grain or of any number of grains stuck together.
Particle size. Particle diameter expressed in microns. See: ESD, equivalent spherical diameter.
Particle size distribution. The volume classification of solid particles into each of the various size ranges as a percentage of the total solids of all sizes in a fluid sample.
Parts per million. The unit weight of solute per million unit weights of solution (solute plus solvent), corresponding to weight percentage.
The results of standard API titration of chloride hardness, etc., are correctly expressed in milligrams (mg) per liter but not in ppm. At low concentrations mg/L is about numerically equal to ppm. A correction for the solution specific gravity or density in g/ml must be made as follows:
ppm = (milligrams/liter)/solution density(grams/liter)
weight%= (milligrams/liter)/[10,000*solution density (grams/liter)]
weight%= [ppm]/[10,000]
Thus, 316,000 mg/L salt is commonly called 316,000 ppm, or 31.6%, which correctly should be 264,000 pprn and 26.4%, respectively.
Pay zone. A formation that contains oil and/or gas in commercial quantities.
Penetration rate. The rate at which the drill bit penetrates the formation, usually expressed in feet per hour or meters per hour. See: rate of penetration, ROP.
Peptization. An increased flocculation of clays caused by the addition of electrolytes or other chemical substances. See: deflocculation dispersion, high-yield clay.
Peptized clay. A clay to which an agent has been added to increase its initial yield. For example, soda ash is frequently added to calcium montmorillonite clay to increase the yield. See: high-yield clay.
Percent open area. Ratio of the area of the screen openings to the total area of the screen surface.
Percent separated curve. A plot of mass distributions of solids sizes discarded from a solids-separation device divided by the mass distributions of each size of solids fed to the device.
Perforated cylinder centrifuge. A mechanical centrifugal separator in which the rotating element is a perforated cylinder (the rotor) inside of and concentric with an outer stationary cylindrical case.
Perforated panel screen. A screen in which the backing plate used to
provide support to the screen cloths is a metal sheet with openings.
Perforated plate screen.
Shale shaker screens mounted on metal plates that have holes punched through.
Perforated rotor. The rotating inner cylinder of the perforated cylinder centrifuge. See: perforated cylinder centrifuge.
Permeability. Permeability is a measure of the ability of a formation to allow passage of a fluid. Unit of permeability is the darcy. See: darcy, porosity.
Pf. The phenolphthalein alkalinity of the filtrate is reported as the number of milliliters of 0.02 normal sulfuric acid required per milliliter of filtrate for the pH to reach the phenolphthalein endpoint, which is a pH of 8.3.
pH. The negative logarithm of the hydrogen ion concentration in gram ionic weights per liter. The pH range is numbered from 0 to 14, with 7 being neutral, and is an index of the acidity (below 7) or alkalinity (above 7) of the fluid. At a temperature of 70°F, a neutral pH is 7 or a hydrogen ion concentration of 10^-7. The neutral pH is a function of temperature. At higher elevated temperatures the neutral pH is lower. The pH of a solution offers valuable information as to the immediate acidity or alkalinity, in contrast to the total acidity or alkalinity, which may be determined by titratration.
Phosphate. Certain complex phosphates, commonly sodium tetraphosphate (Na6P4O13) and sodium acid pyrophosphate (SAPP, Na2H2P2O4), are used either as drilling-fluid thinners or for treatment of various forms of calcium and magnesium contamination.
Piggyback, -ing. The attachment of fine solids particles to the surface of larger solids particles due to surface attraction, fluid consistency, and particle concentration. This attachment phenomenon causes fine solids to be discharged from the screen that would normally pass through the screen.
Pill. A small volume of a special fluid slurry pumped through the drill string and normally placed in the annulus. See: slug.
Pilot testing. A method of predicting behavior of drilling-fluid systems by adding various chemicals to a small quantity of drilling fluid (usually 350 cc), then examining the results. One gram of an additive in 350 cc is equivalent to 1 lb/bbl.
Plastic flow. See: plastic fluid.
Plastic fluid. A complex, non-Newtonian fluid in which shear force is not proportional to shear rate. A definite pressure is required to start and maintain fluid movement. Plug flow is the initial flow type and only occurs in plastic fluids. Most drilling fluids are plastic fluids. The yield point, as determined by a direct-indicating viscometer, is in excess of zero.
Plastic viscosity. This is a measure of the internal resistance to fluid flow attributable to the concentration, type, and size of solids present in a given fluid and the viscosity of the continuous phase. This value, expressed in centipoise, is proportional to the slope of the shear stress/ shear rate curve determined in the region of laminar flow for materials whose properties are described by Bingham’s law of plastic flow. When using the direct-indicating viscometer, plastic viscosity is found by subtracting the 300-rpm reading from the 600-rpm reading. See: viscosity, yield point, API RP 13B.
Plasticity. The property possessed by some solids, particularly clays and clay slurries, of changing shape or flowing under applied stress without developing shear planes or fractures; that is, it deforms without breaking. Such bodies have yield points, and stress must be applied before movement begins. Beyond the yield point, the rate of movement is proportional to the stress applied, but movement ceases when the stress is removed. See: fluid.
Plug flow. The movement of material as a unit without shearing within the mass. Plug flow is the first type of flow exhibited by a plastic fluid after overcoming the initial force required to produce flow. See: Bingham model, Newtonian fluid, laminar flow, turbulent flow.
Plugging. The wedging or jamming of openings in a screening surface by near-size particles, preventing passage of undersize particles and leading to the blinding of the screen. See: blinding, coating.
Pm. The phenolphthalein alkalinity of drilling fluid is reported as the number of milliliters of 0.02 normaI (N/50) sulfuric acid required per milliliter of drilling fluid for the pH to reach the phenolphthalein endpoint of 8.3.
Polyelectrolytes. Long-chain organic molecules possessing ionizable sites that when dissolved in water become charges.
Polymer. A substance formed when two or more molecules of the same kind are linked end to end into another compound having the same elements in the same
proportion but higher molecular weight and different physical properties, for example, paraformaldehyde.Polymers are used in drilling fluids to maintain viscosity and control fluid loss. See: copolymer.
Polyurethane. A high-performance elastomer polymer used in construction of hydrocyclones for its unique combination of physical properties, especially abrasion, toughness, and resiliency.
Pool. (1) The reservoir or pond of fluid, or slurry, formed inside the wall of hydrocyclones and centrifuges and in which classification or separation of solids occurs due to the settling effect of centrifugal force.(2) The reservoir or pond of fluid that can form on the feed end of an uphill shaker basket, a shaker basket with positive deck angle.
Poor boy degasser. See: gas buster, mud/gas separator.
Porosity. The volume of void space in a formation rock usually expressed as percentage of void volume per bulk volume.
Ports. The openings in a centrifuge for entry or exit of materials. Usually applied in connection with a descriptive term, that is, feed ports, overflow ports, etc.
Positive deck angle. The angle of adjustment to a screen deck that causes the screened solids to travel ‘‘uphill’’ to reach the discharge end of the screen surface. This so-called uphill travel increases the fluid throughput of a screen but also shortens the life of a screen. See: negative deck angle.
Possum belly. The compartment on a shale shaker into which the flowline discharges, and from the drilling fluid is fed, either to the screens or to a succeeding tank. See: back tank, mud box.
Potassium. One of the alkali metal elements with a valence of 1 and an atomic weight of approximately 39. Potassium compounds, most commonly potassium hydroxide (KOH), are sometimes added to drilling fluids to impart special properties, usually inhibition.
Potential separation curve. A distribution curve of sizes determined by the optical image analysis for separation potential.
Pound equivalent. A laboratory unit used in pilot testing. One gram of a material added to 350 ml of fluid is equivalent to 1 lb of material added to one barrel. See: barrel, barrel equivalent.
ppm: Parts per million. See: parts per million.
Precipitate. Material that separates out of solution or slurry as a solid.
Precipitation of solids in a drilling fluid may follow flocculation or coagulation.
Preformed foam. Foam formed at the drill bit (obsolete).
Prehydration tank. A tank used to hydrate materials (such as bentonite, polymers, etc.) that require a long time (hours to days) to hydrate fully and disperse before being added to the drilling fluid. See: premix system.
Premix system. A compartment used to mix materials (such as bentonite, polymers, etc.) that require time to hydrate or disperse fully before they are added to the drilling
fluid. See: prehydration tank.
Preservative. Any material used to prevent starch or any other organic substance from fermenting via bacterial action. A common preservative is paraformaldehyde. See: fermentation.
Pressure drop. See: friction loss, pressure loss.
Pressure head. Pressure within a system equal to the pressure exerted by an equivalent height of fluid (expressed in feet or meters). See: head, hydrostatic head, centrifugal pump.
Pressure loss. The pressure lost in a pipeline or annulus due to the velocity of the liquid in the pipeline, the properties of the fluid, the condition of the pipe wall, and the configuration of the pipe. See: friction loss, pressure drop.
Pressure surge. A sudden, usually brief increase in pressure. When pipe or casing is run into a hole too rapidly or the drill string is set in the slips too quickly, an increase in the hydrostatic pressure results due to pressure surge which may be great enough to create lost circulation. See: ECD, annular pressure loss.
Pressurization. The process of supplying an enclosure with a protective gas with or without continuous flow at sufficient pressure to prevent the entrance of a flammable gas or vapor, a combustible dust, or an ignitable fiber.
Pretensioned screen. A screen cloth that is bonded to a frame or backing plate with proper tension applied prior to its installation on a shaker. See: backing plate, perforated panel screen.
Progressive gel. A condition wherein the 10-min gel strength is greater than the initial gel strength. Opposite of flat gel. See: flat gel, zerozero
gel.
Pseudoplastic fluid. A complex non-Newtonian fluid that does not possess thixotropy. A pressure or force in excess of zero will start fluid flow. The apparent viscosity or consistency decreases instantaneously with increasing rate of shear until at a given point the viscosity becomes constant. The yield point as determined by direct-indicating viscometer is positive, the same as in Bingham plastic fluids. However, the true yield point is zero. An example pseudoplastic fluid is guar gum in fresh- or saltwater. See: viscosity, Bingham model, plastic viscosity, yield point, gel strength.
Purging. The process of supplying an enclosure with a protective gas at a sufficient flow and positive pressure to reduce the concentration of any flammable gas or vapor initially present to an acceptable level.
