20Jan00 Darcy-enheten og forkortelser Spørsmål Spørsmålet er om en skal bruke forkortelsen d eller D for enheten 1 Darcy (eller darcy) og om en skal bruke md eller mD for milliDarcy (eller millidarcy). Ifølge SPE Publication Style Guide så skal enheten skrives helt ut med darcy og ikke forkortes. Eksempelvis skal det hete at reservoaret har en permeabilitet på 2 darcy. Dette kan også skrives som 2000 md. SPE vil altså at en skal bruke md som forkortelse på millidarcy. Dette er vist nedenfor fra SPE sin hjemmeside, se darcy og millidarcy. Denne konvensjonen stemmer ikke med det som ellers brukes i SI-systemet for andre enheter. For eksempel brukes forkortelsen N for Newton og det heter mN for milliNewton. Det faller kanskje naturlig å bruke stor N fordi det dreier seg om navnet på en person (Newton). I boken til L.P. Dake, "Fundamentals of Reservoir Engineering" brukes D og mD. Denne boken er utgitt på Elsevier forlag i Nederland. I et internt Statoilnotat om målesystemer brukes Darcy (D) og mD. Nedenfor, i utdrag fra Encyclopædia Britannica, så er enheten betegnet med darcy. Hva gjør vi så? Jeg vil forsøke å holde meg til konvensjonen i Dake sin bok. Det vil si å bruke D og mD. Men når jeg skriver SPE-papers så må jeg bruke darcy og md. -------------------------------------------------- Fra SPE sin hjemmeside http://www.spe.org/journals/styleguide/abbrevs.html 4.3.10 The following lists abbreviations for common oilfield units of measure. barrels of oil per day -- BOPD [m3/d oil] barrels of water per day -- BWPD [m3/d water] barrels per day -- B/D [m3/d] barrels per minute -- bbl/min [m3/s] billion cubic feet -- Bcf [109 m3] billion cubic feet per day -- Bcf/D [109 m3/d] cubic feet per barrel -- ft3/bbl [m3/m3] cubic feet per day -- ft3/D [m3/d] cubic feet per minute -- ft3/min [m3/s] cubic feet per pound mass -- ft3/lbm [m3/kg] cubic feet per second -- ft3/sec [m3/s] darcy -- spell out dead-weight ton -- DWT [Mg] feet per minute -- ft/min [m/s] feet per second -- ft/sec [m/s] foot-pound -- ft-lbf [J] gallons per minute -- gal/min [m3/s] gallons per day -- gal/D [m3/d] gram -- g horsepower-hour -- hp-hr [J] inches per second -- in./sec [cm/s] kilopond (1,000 lbf) -- lbf [N] kips per square inch -- ksi [Pa] mho per meter -- mho/m [S/m] millidarcy -- md million electron volts -- MeV [MJ] mils per year -- mil/yr [m/a] ohm -- pound per cubic foot -- lbm/ft3 [kg/m3] pound per gallon -- lbm/gal [kg/m3] reservoir barrel -- res bbl [res m3] reservoir barrel per day -- RB/D [res m3/d] square feet -- ft2 [m2] square mile -- sq mile [km2] standard cubic feet per day -- scf/D [std m3/d] standard cubic foot -- scf [std m3] stock-tank barrel -- STB [stock-tank m3] stock-tank barrels per day -- STB/D [stock-tank m3/d] stoke -- St [m 2/s] trillion cubic feet -- Tcf [1012 m3] Fra Encyclopædia Britannica http://www.britannica.com/ Darcy, Henri-Philibert-Gaspard b. June 10, 1803, Dijon, France d. Jan. 3, 1858, Paris French hydraulic engineer who first derived the equation (now known as Darcy's law) that governs the laminar (nonturbulent) flow of fluids in homogeneous, porous media and who thereby established the theoretical foundation of groundwater hydrology. After studying in Paris, Darcy returned to his native city of Dijon, where he was entrusted with the design and construction of the municipal water supply system. During the course of this work, he conducted experiments on pipe flow and demonstrated that resistance to flow depended on the surface roughness of the pipe material, which previously had not been considered a factor. Planning to use the technique of water purification by filtration through sand, he also studied cases in which the pipe was filled with sand. From the data gathered, he derived the law that bears his name. The darcy is the standard unit of permeability. Darcy's law mathematical relationship discovered (1856) by the French engineer Henri Darcy that governs the flow of groundwater through granular media or the flow of other fluids through permeable material, such as petroleum through sandstone or limestone. As the basic relationship from which many sophisticated theoretical and practical derivations have been devised, it has become the foundation for quantitative work in the field of groundwater flow. One of the most useful derivations from the formula, which can be used to calculate the amount of water flowing through a given cross-sectional area of an aquifer, equates the discharge to the product of the cross-sectional area through which the discharge occurs, the hydraulic gradient (the change in head for a unit of length), and a coefficient of permeability. Symbolically, Qd = PIA, in which Qd is the discharge water in gallons per day; P is the coefficient of permeability in gallons per day per square foot; I is the hydraulic gradient in foot of head per foot of length; and A is the cross-sectional area through which the discharge occurs. permeability capacity of a porous material for transmitting a fluid; it is expressed as the velocity with which a fluid of specified viscosity, under the influence of a given pressure, passes through a sample having a certain cross section and thickness. Permeability is largely dependent on the size and shape of the pores in the substance and, in granular materials such as sedimentary rocks, by the size, shape, and packing arrangement of the grains. The standard unit of permeability is the darcy, equivalent to the passage of one cubic centimetre of fluid (having a viscosity of one centipoise) per second through a sample one square centimetre in cross-sectional area under a pressure of one atmosphere per centimetre of thickness.