Instructions - OFI Testing Equipment, Inc.

OFI Testing Equipment – 146-00 Instructions – Workover and Completion Fluids Test Kit Page 15 of 17
Calculation:
Mg ++ , mg/L =
(mL EDTA, Total Hardness – mL EDTA, Ca++) x 243
mL of Filtrate
POTASSIUM & POTASSIUM CHLORIDE
OFI Part No. 285-09
Centrifuge Method: > 5000 Milligrams per Liter KCl (1% KCl)
Potassium ion is used in drilling fluids to aid in the stabilization of shales and to control swelling clays. The accurate
determination of the potassium ion content is necessary to control the properties of the drilling fluid. This procedure is
used to measure the potassium ion content in mud filtrates at levels above 5000 milligrams per liter or 3.5 pounds per
barrel KCl. The procedure is most accurate in the range between 10,000 mg/L (2%) and 40,000 mg/L (8%) KCl and is
suspect below 10,000 mg/L (2%) KCl. Potassium is precipitated in a centrifuge tube as the perchlorate salt, and then the
precipitate volume is measured. The potassium ion content is then read from a prepared standard curve.
Equipment:
#153-21 Centrifuge Tube, Kolmer, 10 ml (2 supplied)
#153-25-2 *Centrifuge, Hand Crank, with dual head and shields
#153-38 Pipette, 5 ml x 1/10 ml, glass
Reagents:
#206-02 Distilled Water, 16 oz
#285-10 *Sodium Perchlorate sol'n, 16 oz (UN1502)
#285-11 Potassium Chloride sol'n (standard), 4 oz
Procedure - Generating a Standard Calibration Curve:
1. A standard calibration curve is required for each type of centrifuge. A minimum of three points or test
procedures (3.5, 10.5 & 17.5 pounds per barrel) is required to obtain an accurate graph.
2. Samples can be prepared by using the standard potassium chloride solution where 0.5 ml of standard
potassium chloride solution is equivalent to 3.5 pounds per barrel KCl.
3.5 ppb KCl = 1 % KCL = 5000 mg/L ≅ 0.5 ml standard KCl solution.
Therefore -
A. To obtain 3.5 ppb equivalent KCl or 1% KCl use 0.5 ml of standard potassium chloride.
B. To obtain 10.5 ppb equivalent KCl or 3% KCl use 1.5 ml of standard potassium chloride.
C. To obtain 17.5 ppb equivalent KCl or 5% KCl use 2.5 ml of standard potassium chloride
3. Dilute the samples in the centrifuge tube to the 7.0 ml mark with distilled water and agitate the mixture.
4. Add 3 ml of standard sodium perchlorate solution to each centrifuge tube and do not agitate.
5. Centrifuge at a constant speed of approximately 1800 revolutions per minute for one minute and read the
precipitate volume immediately. It will be necessary to counterbalance the centrifuge tube with another tube
and 10 ml of liquid of the same weight.
A fairly constant 1800 revolutions per minute can be obtained by determining the number of revolutions of the rotor per
each turn of the crank. Move the crank very slowly and count the number of revolutions of the rotor head during one turn
of the crank. For example, 15 revolutions of the rotor per one turn of the crank. Calculate the number of crank turns
required to obtain 1800 revolutions of the rotor head. In the example to obtain 1800 revolutions of the head would require
120 turns of the crank (1800/15). Thus the crank must be turned 120 times in one minute to obtain the rate of 1800
OFITE • 11302 Steeplecrest Dr. • Houston, TX 77065 USA • Phone (832) 320-7300 • http://www.ofite.com
Version 1.1
Date 03-04-03