Download NGWA Exam 80: Groundwater Well Construction and Development and more Exams Engineering in PDF only on Docsity!
NGWA exam 80 complete solutions.
National Groundwater Assocation
Water well defined - ANSWERDrilled, cored, bored, washed, dug, driven, jetted excavation, constructed for extracting groundwater.
Cable tool drill string - ANSWERSocket, jars, stem, and drill bit.
Drill String - ANSWEREntire column of string or drill pipe,drill collars, and accessories that transmit fluid and/or rotational power from Kelly(top head drive) to the drill collars and bit.
Rotary Drill string - ANSWERDrill bit, Drill collar (stabilizer), Drill pipe, Kelly (top head)
Porosity - ANSWERThe percentage of void spaces or holes in geologic formation. The amount of connected pore spaces
Barite - ANSWERbarium sulfate (BaSO4), a mineral used to increase the weight of drilling fluid (mud); its specific gravity is 4.
Air Rotary Drilling - ANSWERa method of rotary drilling that uses compressed air as the circulating medium; compressed air at high uphole velocity removes the cuttings
Surfactants - ANSWERImprove flushing of cuttings from bit. Used in air-based drilling to produce foam during well drilling, also well development to disaggregate clays
2.31 - ANSWERUnit of energy constant to overcome gravity. Head calculation 2.31 X 40psi = 92.4' of lift. 600' / 2.31 = 260psi
Well Development - ANSWERa procedure to facilitate the removal of fine solids and materials from the water-bearing zone of a water well to optimize production
Well Development Methods - ANSWERChemical, Over pumping, Rawhiding (Washing and backwashing), Mechanical Surging, Jetting, Air surging.
Over Pumping - ANSWERWell Development method; involves pumping well at a much higher rate than it will be pumped during well evacuation or sampling.
Rawhiding (washing and back washing) - ANSWERWell Development method, involves pumping water to the top of the well then allowing it to flow back through the intake of the pump, breaking up the bridge of sediments only around the pump intake.
Mechanical Surging - ANSWERWell Development method, involves attaching a surging block to the drill rod that fits well inside diameter, then dropping the block rapidly, forcing the water back up into the surrounding aquifer. In the recovery stroke water is lifted back into the well allowing fine sediments to flow from the aquifer.
Jetting - ANSWERWell Development method, involves attaching a surging block like tool with jetting nozzles, then with an external water pressure supply jet the water back into the well screen with in the well where it is most needed.
Air Surging - ANSWERWell Development method, involves injecting air into the borehole such that aerated slugs of water are lifted irregularly out the top of the well casing. Air pressure may be cycled on and off to create a surging action desirable in well development. Sufficient air pressure will result in a continuous flow of aerated water out the top of the well, removing sediment and fine particles from the borehole.
Chemical Well development - ANSWERWell Development method, involves using approved chemicals, to breakup mud cakes, and flush out gelled muds, used in conjunction with other methods. Chemical treatment can be used to break down drilling fluids, clays and polymers. Acids are often used for improving the yield in limestone, dolomite and other calcium carbonate formations.
Cable Tool Bailors - ANSWER-Flat Bottom (Open bailer)
-Dart Valve (Valve Bailer)
-Sand Pump (double valve)
Latch Jack - ANSWERa fishing tool with a "handle" on top, which is used to retrieve a bailer or similar object
Friction Socket - ANSWERa fishing tool used to recover a lost bit in the hole
Overshot - ANSWERa fishing tool attached to a wire line tool string, tubing, rods, or drill pipe that is lowered over the outside of a "fish" lost or stuck in the wellbore. A friction device in the overshot, usually a basket or a spiral grapple, firmly grips the fish, allowing it to be pulled from the hole.
Fishing Jars - ANSWERspecially designed jars for fishing operations. While cable tool drilling commonly run above the drill stem, fishing jars are commonly run below the stem and just above the fishing tool. Also termed long stroke jars.
Well Screen Size - ANSWERShould be slightly smaller than the sand or gravel to insure good well Development. Screen openings are selected on the basis of adopted standards to allow for water entry in ample quantities and with a minimum loss of head. In agricultural wells, slotted pipe is sometimes used as a screen
Cathead - ANSWERSmall spooled winch that draws works or hoisting drum, to one side of the swivel head to wind line when breaking or making up rod casing or pipe joints Slip Rope Drum
Wire Rope - ANSWERa cable composed of steel wires twisted around a central core of fiber to create a rope of great strength and considerable flexibility. Includes the right-lay line, left-lay line, and sand line (a type of right-lay cable).
-Left-lay cable is always for the drilling line on a cable tool rig so that the twisting motion of the cable does not cause the tools to unscrew.
Sand line - ANSWERRight-lay cable, a winch cable on the rig derrick that is used to move heavy objects (joints of drill pipe, larger bits, etc.) around near the rig; also called a cat line 2. a wire used to run a bailer, etc., down the hole and retrieve it
Drill line - ANSWERLeft-lay cable, the main line that goes from the mast down into the well, that drops down repeatedly hitting the earth, Spudder line
Rotary Table - ANSWERa component of a "table drive" drill rig through which the drill pipe and kelly bar passes. The kelly bar is temporarily attached to the rotary table with a table square. This attachment to the rotary table provides the rotational power to turn the drill pipe and bit assembly to penetrate the geologic formation
Rotary Top-head Drive - ANSWERa type of rig where the rotating force (torque) comes from a hydraulic drive head at the top of the drill pipe. A kelly is not required with top-head drive.
Drilling Fluids - ANSWER1. a fluid that is circulated in rotary drilling to perform many downhole functions including carrying the cuttings of the borehole. The fluid, usually of water and clay or polymers along with or without chemical additives, is the most common drilling fluid (mud). Wells can also be drilled with air, with and without foamers and other additives, as a drilling fluid, and are often referred to as circulating fluid. 2. the medium that is circulated through the borehole in rotary drilling to perform many downhole functions including removing the cuttings from the borehole, cooling the bit, and stabilizing the hole. Drilling fluid can consist of a water-based fluid (mud) or compressed air (air). Water-based fluids typically consist of water, bentonite clay, and polymers. Other additives such as soda ash, sodium bicarbonate, lost circulation material, and barite may also be added to adjust the chemical or physical properties. Compressed air often has other additives injected into the air stream that may include water, foamers, polymers, or water-based drilling fluids.
Water Table - ANSWER1. the surface of a body of unconfined groundwater between the zone of saturation and the zone of aeration at which the pressure is equal to that of the atmosphere 2. that surface in an unconfined water body at which the pressure is atmospheric. It is defined by the levels at which water stands in wells that penetrate the water body just far enough to hold standing water.
Static Water Level - ANSWERthe distance measured from the established ground surface to the water surface in a well that is not being pumped (i.e., the well has been idle long enough to not be experiencing recovering water levels from a recent pumping event), under the nearby influence of pumping, or flowing under artesian pressure
Aquifer - ANSWERa geologic formation, group of formations, or part of a formation that contains sufficient saturated permeable material to yield economical quantities of water to wells and springs
Confined Aquifer - ANSWERan aquifer bounded above and below by less permeable materials, which causes the water in the aquifer to be under pressure greater than atmospheric pressure. Because of this pressure, the water level in a well completed in a confined aquifer will rise above the top of the aquifer.
occurs in adjacent wells. An aquifer test may be used to determine degree of hydraulic interconnection between different water-bearing units, as well as the recharge rate of a well.
Transmissivity - ANSWER1. the rate at which water is transmitted through a unit width of an aquifer under a unit hydraulic gradient. Transmissivity values are given in gallons per day through a vertical section of an aquifer one foot wide and extending the full saturated height of an aquifer under hydraulic gradient of 1 in the
Transmissibility - ANSWERthe rate of groundwater flow through saturated pore spaces or fractures (hydraulic conductivity) multiplied by the saturated aquifer thickness. The term has been replaced by "transmissivity."
Hydrological cycle - ANSWERthe continual circulation of water between the atmosphere, land, and sea by precipitation, evaporation, and transpiration
Evaporation - ANSWERthe process by which a substance changes from the liquid to the vapor state
Transpiration - ANSWERthe discharge of water vapor from the leaf surface by plants; usually this water is lost to the atmosphere and replaced by the transport of more water from the soil to the leaves through the roots and stem
Specific capacity - ANSWERthe rate of discharge of water from a well per unit of drawdown of the water level, commonly expressed in gpm/ft or m3/day/m, and that varies with the duration of discharge. Drawdown in relation to Well yield
Drawdown - ANSWERthe extent of lowering of the water surface in a well and water-bearing zone resulting from the discharge of water from a well or wells
Well Yield - ANSWERthe volume of water discharged from a well in gallons per minute or cubic meters per day
Storativity - ANSWERthe volume of water an aquifer releases from or takes into storage per unit surface area of the aquifer per unit change in head. It is equal to the product of specific storage and aquifer
thickness. In an unconfined aquifer, the storativity is equivalent to the specific yield. Also called storage coefficient.
Cone of depression - ANSWERa depression in the groundwater table or potentiometric surface that has the shape of an inverted cone and develops around a well from which water is being withdrawn. It defines the area of influence of a well
Hydraulic Head - ANSWERthe height of the free surface of a body of water above a given subsurface point.
Non-Porous Rock Fractures - ANSWER1. Creating crevices where water may be stored
2.May intersect with more permeable rock formation
Pore Spaces - ANSWERUsually occur between geological formations. Unconsolidated formations have many pore spaces
Granite stores water - ANSWERIn the crevices or fractures it also is stored in the interstitial space.
Geological Maps - ANSWERIndicate Consolidated and unconsolidated formation. And may give an analysis of where water may lie in fractures.
High Porosity - ANSWERMeans water or liquids flow fast through a material
Lower Porosity - ANSWERMeans that a liquid flows slowly through a material
Formation Sampling - ANSWERIs the surest way to determine what may lie under the soil surface. Samples are taken every 5' down to 200'
Climate Conditions - ANSWERAffect the availability of groundwater when precipitation levels decrease so will water levels
