According to Annex B of the API 13B-1 (ISO 10414-1) some drilling fluids tend to develop excessive shear strength under static conditions, especially at downhole temperatures. Excessive shear strength results in high pump pressures and loss of circulation. High shear strength can also cause difficulties in logging, perforating and other downhole operations.
The MUDTEST Shearometers may be used to determine this tendency and to estimate the extent to which the drilling fluid will develop excessive shear strength.
Two types of Shearometers are available:
Light drilling fluids can be tested using the Shearometer Kit. It consists of a stainless-steel sample cup with a graduated scale positioned vertically in the center of the cup base and two hollow shear tubes. The sample cup is filled with drilling mud on top of which the shear tube is placed. Depending on the shear strength, the hollow tube sinks into the mud. The results are read directly from a calibrated scale. The scale measures gel strength in lbs./100ft².
High gel strength fluids can be tested using the Shearometer Tube with weight support that is used together with a set of weights to conduct a shear-strength measurement. The test is made using a static-aged mud sample left at high temperature for several hours. Aging temperatures are selected to be near the estimated bottom-hole temperature of the well. MUDTEST aging cells meeting these pressure and temperature requirements are required. The Shearometer Tube is placed on the surface of the gelled mud and weights are applied until the tube sinks to a marked depth. The applied weight indicates shear strength of the mud sample.
The MUDTEST Shearometer complies with the requirements of API RP 13B-1 or the corresponding international standard ISO 10414 for field testing of drilling fluids.
|Shear Tube, 5 g||8050.00.00001|
|Shearometer with weight support 20 g||8050.10.00000|
|Weight Support, 20 g||8050.10.00002|
|Weight Set, 10 mg - 50 mg||8050.10.00003|