AL Well Driller flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Cable-tool drilling
- A percussion drilling method that breaks rock with a heavy bit on a cable and removes cuttings with a bailer; suited to hard rock and boulder formations.
- Rotary mud drilling
- A method using a rotating bit and circulating drilling fluid, usually bentonite or polymer slurry, to cool the bit and carry cuttings to the surface.
- Air rotary drilling
- A rotary method using compressed air instead of mud to lift cuttings; fast in hard rock and useful where the formation yields little water.
- Reverse circulation
- A drilling method where fluid flows down the annulus and up through the drill pipe, giving rapid cuttings removal in large-diameter holes.
- Tricone roller bit
- A rotary bit with three rotating cones set with hard teeth or inserts; used for drilling hard rock and abrasive formations.
- Lost circulation
- The escape of drilling fluid into fractures or cavernous zones, reducing returns; treated by lowering fluid weight or adding lost-circulation material.
- Annular space
- The volume between the borehole wall and the outside of the casing, which is filled with grout, filter pack, or both.
- Filter pack sizing
- Gravel pack material is typically chosen so it is about four to five times the 50-percent retained size of the aquifer formation material.
- Well screen slot size
- Slots are sized so roughly 40 to 50 percent of the filter pack material passes through, retaining the rest to stabilize the pack.
- Sanitary seal
- A grout seal placed in the upper annular space from land surface to a required depth to block surface water and shallow contamination.
- Static water level
- The non-pumping water level in a well, measured after the water level has recovered and stabilized.
- Drawdown
- The difference between the static water level and the pumping water level in a well during pumping.
- Well development
- The process of removing drilling mud and fines from the filter pack and screen to increase yield and reduce sand production.
- Artesian well
- A well completed in a confined aquifer whose potentiometric surface stands above land surface, allowing the well to flow without pumping.
- Neat cement grout
- A cement-and-water grout without sand, giving high strength and low permeability for sealing the annular space around casing.
- Tremie placement
- Grouting from the bottom of the annular space upward through a pipe, displacing water and preventing voids or bridging.
- Centralizer
- A device attached to casing to keep it centered in the borehole so the annular space is uniform and grout fully surrounds the casing.
- Drive shoe
- A hardened ring attached to the bottom of casing that protects the casing edge and cuts a seat into bedrock during driving.
- Grout volume formula
- Volume equals pi times the difference of the squares of borehole and casing radii, times length, plus an allowance for lost circulation.
- Alabama driller license
- A credential required by the state before a person may drill or construct water wells in Alabama; obtained through the state licensing authority.
- Well completion report
- A required record filed after construction listing location, depth, diameter, casing and screen intervals, grout intervals, water levels, and formations.
- Abandoned well sealing
- An unusable well must be filled with grout or approved material to prevent contamination from moving between aquifers or reaching the surface.
- Well disinfection
- Treating a newly constructed well with a chlorine solution, commonly 50 to 200 ppm, held for a contact period before pumping to waste.
- Setback distance
- A required minimum separation between a new well and contamination sources such as septic systems or animal lots, set by state rule.
- Porosity
- The fraction of a rock or sediment volume that is void space, which determines how much water a formation can hold.
- Specific yield
- The drainable porosity of a formation, or the volume of water released from storage per unit volume of aquifer when the water table drops.
- Hydraulic conductivity
- A measure of a formation's ability to transmit water, appearing as K in Darcy's law and depending on both the medium and fluid.
- Transmissivity
- Hydraulic conductivity multiplied by saturated aquifer thickness; it describes the rate water flows through the full aquifer thickness.
- Darcy's law
- Discharge equals hydraulic conductivity times hydraulic gradient times cross-sectional area, expressed as Q = K i A.
- Specific capacity
- Well yield divided by drawdown, used as a practical measure of well performance and aquifer productivity.
- Cone of depression
- The drawdown shape around a pumping well that can capture nearby contamination or interfere with neighboring wells.
- Hardness in groundwater
- The concentration of dissolved calcium and magnesium, which causes scale and soap consumption and is common in carbonate aquifers.