API RP 13M pdf download Recommended Practice for the Measurement of Viscous Properties of Completion Fluids ANSI/API Recommended Practice 13M First Edition, July 2004 Identical to ISO 13503-1: 2003
Rotor and bob shall be properly aligned.All parts in contact with the fluid shall be at the same temperature asthe fuid. Use of the standard cup provided by the manufacturer is recommended. Other vessels may be used, however the vertical space between the bottom of the bob and bottom of the vessel shall be at least 13 mm(0,50 in).
The non-crosslinked fluid sample to be tested shall be representative of the fluid as a whole,and airentrainment shall be minimal. After being placed in the viscometer, the fluid is strred for 10 s to 15 s at thehighest shear rate for which a measurement is to be made. Viscosity measurements should be made fromlowest to the highest shear rate.Record the average reading 20 s after reading is stabilized at each shear rate.
ln order to convert a reading in revolutions per minute to shear rate, use the following formula:
1 rlmin = 1,704 s-1
Viscometric calculations shall be performed according to the manufacturer’s specified procedure.For rheological calculations,see Clause 9.
126.96.36.199 Pressurized concentric-cylinder viscometer2), to measure the viscous and rheological propertiesof completion fluids at elevated temperatures.
Pressurization minimizes the effect of entrained air on measured parameters and allows measurements to bemade at temperatures above the atmospheric boiling point of the sample.Multiple-point measurements maybe suitable for determining the rheological parameters of fluids.
Any pressurized concentric-cylinder viscometer with the dimensions shown in Figure 3 may be used.188.8.131.52.1 Calibration
Measure the temperature of the fluid being tested according to the manufacturer’s specified procedure whichshall be traceable to a national/international standard such as ISO,ASTM, DIN, or equivalent.
Measure the rotor or sleeve speed according to the manufacturer’s specified tachometer calibration procedurewhich shall be traceable to a national/international standard such as iSO,ASTM, DIN, or equivalent.
Use one of the following calibration methods:
Verify system using a standardized Newtonian calibration fluid traceable to a national/internationalstandard such as iso,ASTM,DIN or equivalent.A calibration oil viscosity shall be selected toencompass the shear rate/shear stress envelope to be evaluated.The calibration shall be conducted atambient pressure.
NOTE While the compressibility of aqueous fluids are not significantly affected by the pressure, some calibrationoils. in particular silicone oils, are affected by pressure.
b) alternative torque-only calibration
Measure according to the manufacturer’s specified calibration procedure (e.g. hanging weight)whichshall be traceable to a national/international standard such as ISO, ASTM, DiN, or equivalent.
Pre-heat thermal bath (if equipped) to test temperature. All temperatures in this document refer to actualtemperature of the fluid.
The following procedures shall be followed.a)Loading, pressurizing and heating the fluid
Load the fluid to be evaluated into the viscometer immediately after the last component is addedaccording to mixing procedure.Place 52 cm3 of fluid in the viscometer.This volume is sufficient to fullycover the bob. Pressurize the system with nitrogen to a minimum of 2,75 MPa (400 psi) and immediatelystart shearing at 100 s-1.When shearing of the fluid starts, define the elapsed time as zero (t = 0) andbegin heating the fluid.All actions in this paragraph shall be completed within 45 s.
Optionally, for an ambient-temperature shear ramp [described in 184.108.40.206.2 b), elapsed time is defined aszero (t = 0) immediately after completing this ramp, and fluid heating is begun.
At 20 min elapsed time,the fluid temperature shall be no lower than 5 % below (base = 0 °C) and nohigher than 3 °C(+ 5 °F) above the desired test temperature. In addition, at 30 min elapsed time, and forthe remainder of the test, the fluid temperature shall be within ± 3 °C(±5 °F) of the test temperature.
b)Application of shear rate ramps
The fluid shall be sheared at a constant 100 s-1 initially and between shear rate ramps.
The time reported for each shear rate ramp is the total time elapsed when the ramp begins. Starting att = 20 min, shear rate ramps shall begin every 15 min up to t=2 h 5 min. Beginning at t=2 h 35 min andcontinuing up to 4 h 5 min, ramps shall begin every 30 min.After 4 h 5 min, the time elapsed when rampsbegin is at the discretion of the operator, however these shall be reported.
The specified shear rates for all shear rate ramps are 25 s-1,50 s-1,75 s-1 and 100 s-1. The shear ratesduring a ramp shall occur in the sequence specified，however the sequence of rates may be eithermonotonically increasing or decreasing.Following each change in shear rate, the fluid shall be allowed toequilibrate for 25 s.This is followed by 5 s of data collection.Each new shear rate shall be attained within thefirst 5 s after completing data collection at the previous shear rate.When a sequence of increasing shear ratesis used, a 40-s equilibration period shall be allowed before collecting data at 25 s-1.Then proceed asdescribed above.Table 1 shows the viscometer speed, in revolutions per minute, corresponding to eachshear rate based on the specified viscometer geometry.