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Basic Knowledge
8.4 Fluid loss cell
  • Detailed description

1. The application of fluid loss cell
The fluid loss cell is designed and produced in accordance with the API specification. It is used to test the filtrate in 30min under the differential pressure of 6.9MPa.

2. The structure and character of fluid loss cell
The fluid loss cell is constitute的by the heat-kettle with thermostat, slurry cup, the upper and bottom cap, filter screen, air source, pressure instrument and air-guide tube. The pressure can’t exceed 8MPa and the temperature can’t exceed 260℃.
The measure method of fluid loss cell is not uniform completely with the downhole actual situation. The former is axial filtration of filtrate and the latter is vertical filtration of filtrate. Meanwhile, the actual situation of downhole fluid loss includes static fluid loss and dynamic fluid loss. The fluid loss measured by fluid loss cell is the static fluid loss. So it is just a relative data.

3. The operation procedure of fluid loss cell
a. Turn on the power, set the temperature parameter, and turn on the heater.
b. Beat the ventilation end cap gently (there is a scale on the cup well and the ventilation end is far away form the scale.), screw on tightly, and put it into the heater kettle.
c. Pre-heat the fluid loss cell to the set temperature. When the curing time of cement slurry in the atmospheric consistometer is about 19min, pick out the slurry cup, and converse it on the stand, unscrew the fluid loss end screw and put a measuring cylinder under it.
d. Pour the cement slurry into the cell up to the inner scale. Don’t be full in case the unsafe situation caused by the thermal expansion of cement slurry.  So the distance between the slurry level and support sieve should exceed 19mm.
e. Put the filter screen into the cell. Put the 60 mesh support screen upwards, screw on the fluid loss cell cap.
f. Put the slurry cell into the heat kettle, rotate it and ensure it is placed well. Connect the air-guide tube and the vent rob together.
g. Turn on the air source equipment; adjust the pressure to 6.9MPa, unscrew the vent rob valve widdershins about 90°, and then unscrew the fluid loss end valve clockwise about 180°. Start time when the fluid loss begins.
h. After 30 min, the experiment end, turn off the vent rob valve first and then turn off the air source valve. Turn on the air-guide tube, release the air in it, and then release the residual air on the slurry cell. Pick out the slurry cell, pour out the slurry and clean it.
i. Gather the filtrate and record it. If there is not gas channeling in 30 min, the fluid loss is double of the gather filtrate. If there is a gas channeling in 30min, calculate the fluid loss in accordance with the corresponding formulas. But the data calculated is a false data which should be recorded and explained.
j. Turn off the heater and power.

4. The maintenance of fluid loss cell
a. Clean the sieve and slurry cell completely, the valve on the cell cap should appear flow if it is connected to the water. Unscrew the valve, make sure there are no cement particles blacking the air hole.
b. Check if the sieve has hole or is damaged, and if the O-ring is damaged. If there is leakage on the valve, change the o-ring.

Attention matters

(1)The time from picking out the slurry from atmospheric consistometer to recording the fluid loss time should not longer than 2 min. the longer time is, the error probability is bigger.

(2)To the serious settlement slurry, the testing result is not correct.

(3)When dismantle the slurry cell after the experiment, make sure all the residual air is released, and prevent the slurry spilled out and hurt the experimenters.

(4)If the time of fluid loss is not come to 30min, the result has a bigger error, and the shorter the testing time is, the bigger the error is.