Water Well Driller flashcards
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31 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Annular velocity
- The upward speed of drilling fluid in the space between the drill pipe and borehole wall; it must exceed cuttings settling velocity to lift rock fragments out of the hole.
- Lost circulation
- A condition where drilling fluid escapes into a permeable or fractured formation instead of returning to the surface, causing falling fluid levels and reduced hole cleaning.
- Cable-tool drilling
- A percussion method in which a heavy bit is raised and dropped to crush rock; the hole is periodically bailed to remove cuttings and slurry.
- Rotary drilling
- A method using a rotating bit turned by a drill string, with circulating fluid or air removing cuttings; it is fast in consolidated rock and requires mud management.
- Filter pack sizing
- Gravel envelope placed around a screen, sized about four to six times the formation D50 for uniform sand, so formation fines pass while coarser particles are retained.
- Well screen open area
- The total slot or perforation area of a screen; it should be large enough to keep entrance velocity low and reduce head loss during pumping.
- Static water level
- The undisturbed water level in a well measured before pumping begins, reflecting the natural piezometric head of the aquifer at that location.
- Pumping water level
- The stabilized water level in a well while it is being pumped at a constant rate, lower than static level because of drawdown around the borehole.
- Drawdown
- The difference between static water level and pumping water level in a well, expressed in feet or meters; it grows with pumping rate and aquifer resistance.
- Specific capacity
- Pumping rate divided by drawdown, usually in gallons per minute per foot; a higher value indicates a more productive well or aquifer.
- Neat cement yield
- One 94-pound sack of neat cement mixed with water yields about 1.15 cubic feet of grout, used to compute sacks needed for annular sealing.
- Casing centralizer
- A device attached to casing that keeps it centered in the borehole, promoting a uniform grout annulus and reducing the risk of voids or channeling.
- Sieve analysis
- A laboratory test that determines the particle size distribution of formation samples; results guide screen slot size and filter pack gradation selection.
- Development
- The process of removing drilling mud and fines from the borehole and filter pack so the well produces clear water at maximum efficient yield.
- Artesian well
- A well in which the confined aquifer's potentiometric surface stands above the ground surface, so water flows without pumping when the well is completed.
- Grout placement
- Pumping cement or bentonite slurry from the bottom of the annulus upward through a tremie pipe to seal the casing and protect groundwater from surface contamination.
- Total dynamic head
- The sum of pumping lift, discharge pressure head, and friction losses in pipe and fittings; it defines the duty point a pump must meet at design flow.
- Pumping lift
- The vertical distance from the pumping water level in the well to the discharge point, one component of total dynamic head for pump selection.
- Brake horsepower formula
- Pump brake horsepower equals gallons per minute times total dynamic head in feet, divided by 3960, then divided by pump efficiency.
- Pump efficiency
- The ratio of water horsepower delivered to the brake horsepower input at a given flow and head; it varies across the pump curve and peaks near best efficiency point.
- Pump curve
- A graph of pump head versus flow rate; the operating point is where the pump curve intersects the system head curve.
- System head curve
- A plot of required head versus flow for the piping system, rising with flow because friction losses increase approximately with the square of flow.
- Best efficiency point
- The flow rate at which a pump operates at its highest efficiency; operating far from it increases vibration, wear, and power consumption.
- Submergence
- The depth of a pump intake below the pumping water level; insufficient submergence causes vortexing, air entry, and loss of prime or motor cooling.
- Check valve
- A one-way valve installed above a submersible pump that holds the water column when the pump stops and prevents backspin of the impellers.
- Drop pipe
- The vertical pipe carrying water from a submersible pump to the surface; its diameter affects friction loss, and undersizing reduces delivered flow.
- Pitless adapter
- A fitting that passes water through the casing below the frost line, allowing the discharge line to connect without a pit and protecting the well from surface water.
- Well seal
- A watertight cap at the top of the casing that seals around the drop pipe, wiring, and vent, preventing contamination and supporting the pump assembly.
- Voltage drop limit
- The maximum permitted voltage loss in motor supply conductors, commonly 5 percent at the motor terminals; excessive drop causes overheating and reduced starting torque.
- Three-phase rotation
- The direction a three-phase motor turns; swapping any two supply leads reverses rotation, so rotation must be verified before the pump is run.
- Amperage check
- Comparison of measured motor current with nameplate full-load amps; current above rating suggests overload, low voltage, or a worn pump.