The Well / Aquifer Model (Initial Test Results) - 7
To simulate true field conditions, a "line drive" is created by
introducing water uniformly into the entire 5 ft by 12 ft face of the aquifer using
an entrance plenum. Aquifer material is prevented from entering the
water-filled plenum by removable steel grates covered with perforated stainless
steel sheets. Water enters the plenum through 8 in. diameter pipes located on
both ends of the model. The ribs and beams are drilled for free flow, allowing
unrestricted movement of water into the aquifer sand. Provision is also made
for placement of a selected gravel pack up to 6 in. thick between the aquifer and
well screen.
Water leaving the model through the well screen discharges into a
below-ground sump and flows through a mesh into a second sump, where it is pumped
through diatomaceous earth filters before returning into the model intake plenum.
Any coarse sand or gravel pack material discharged through the well settles into the
first sump.
The wedge-shaped prism design permits observation of the formation /
gravel pack interface as well as the screen interior. Viewing ports along one
side of the model reveal the aquifer and portions of the gravel pack. The viewing
ports are made of 16 in. diameter, 1 ¼ in. borosilicate glass.
Observation of aquifer flow lines can be studied utilizing these
viewing ports. Dye introduced into the aquifer material reveals flow lines
relevant to different screen/ aquifer designs. Tempered borosilicate glass
viewing windows permit observation of the inside of the test well screen, and
conventional photographic studies of the well screen and flow characteristics are
facilitated. The phenomenon of effective area of opening was first observed
through these viewing windows.
3.2.1 Pressure Head Measurement
New technology in the field of microelectronics was utilized to obtain
the multitude of pressure flow, and sand particle measurements necessary to evaluate
performance of the model well screen/ gravel pack/ aquifer combination. To
measure hydraulic head throughout he model, forty-four ¼ in. piezometer tubes
were placed in the aquifer and gravel pack in four horizontal planes, arranged
logarithmically from the well bore. Figure 4 shows the
location of the piezometers and their respective numbers as they are referred to in
the data.
Location of the piezometers is permanently fixed by taping them to
the rods and bottom of the frame. The ends of the piezometer tubes are covered
with a filter material to prevent formation from entering and clogging the line.
In addition to the 44 piezometers in the aquifer and gravel pack, a
45th piezometer is located in the well. Two additional piezometers are installed
in a venturi-type flow meter to provide data on the model flow rate. A rotating
valve (Scanivalve) combined with a solid state pressure transducer sequentially measures
the hydraulic head on each of the 47 ports.
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