The History of Mud Testing

Jan 18, 2011

Marie Brannon

Before Baroid offered commercial mud testing services to the petroleum industry, mud men experimented with various techniques to test drilling fluids

Drilling mud was first tested for commercial purposes by the Baroid Division of the National Lead Company in 1929 in Houston, Texas. They also produced the first commercial mud testing products. Before 1929 drillers dug clay out of any nearby bank or used native earth.

From Mud Buckets to Precise Instrumentation

Between the discovery of Spindletop in 1901 and the appearance of Baroid in 1928, there were nearly three decades of rotary drilling. The old-timers tested their mud by “rule of thumb”. They knew two kinds of mud: thick and thin. New workers learned from the veterans how to pick up a handful and determine just the right thickness needed.

By 1913, drillers were aware of gelation. Since the well was often shut down for lunch break or other delays, the mud would gel during the break, and the workers called this “getting logy”. They discovered that if they started the pumps occasionally during shutdowns, it would keep the circulation free.

They also could tell if the mud was gas-cut by observing the froth or foam in the mud pit. During the winter of 1913, the Bureau of Mines conducted the first engineering studies by sending J.A. Pollard and A.G. Heggem to Oklahoma oil fields to test the properties of drilling mud. The resulting report was published in 1916 and holds the distinction of being the first ever technical bulletin on the subject.

In early field tests, samples of clay were mixed by hand in an ordinary wash basin. Circulation tests were made by adding two quarts of red paint into the drill pipe at the surface and timing the period required for the color to appear in the mud pit. One record of such a test provided a time of two hours and 33 minutes for circulation in a hole that was slightly more than 3,300 feet deep.

Heavy Drilling Muds

Early on, researchers discovered that all “thick” muds did not weigh the same. It was believed that heavier muds could be useful in drilling against gas pressures, so the California Department of Petroleum and Gas conducted some tests with five-quart containers.

These were calibrated so that one gallon fluid would fill exactly 4/5 of the inside and was marked with a ridge. They also had scales that would accurately record weights up to 30 pounds showing a difference in just one ounce. This was the prototype for the first piece of mud-testing equipment ever produced, by Baroid in 1929.

Between 1917 and 1922, when college degrees were first awarded in the field of Petroleum Engineering, mud testing began to receive serious attention from both scholars and manufacturers. The specific gravity (weight) of drilling mud was tested using oilfield hydrometers that were adapted for this use.

Several different terms and scales were used to express results, including pounds per cubic foot or pounds per gallon. They also developed a specific gravity scale. In 1921, petroleum geologist Dorsey Hager said “Mud-laden fluid has a specific gravity of from 1.15 to 1.3, and weighs from 72 to 81 pounds, as against 62.5 pounds per cubic foot of water. It exerts a pressure of 0.499 to 0.564 pounds per square inch, as against 0.434 for pure water”.

Gradually, oil men realized that not only weight but viscosity should be considered. Standard Oil Company of California engineers used a McMichael viscometer to test mud. It measured the friction of a liquid against a disc suspended from a calibrated wire, in a cup of liquid which was rotating at a constant speed. The ancestor of the Marsh funnel was the Engler viscometer, originally developed by Dr. Charles Engler in Germany in 1884 for use in the railroad industry.

Testing the Viscosity of Drilling Mud

Various rotary viscometers were also in use to test the viscosity of oil. The Napier and Cockrell types were early predecessors of the Stormer, Fann and Baroid devices. Napier and Cockrell apparatus was in use for more than fifty years and utilized paddle wheels revolving in oil or other fluids. There is no record that these were used to test mud, but they were described in oil engineering texts of the time and may have been used in this manner.

In 1930, Baroid introduced the first mud bucket and scale as a test instrument. These were given away as free samples, but by 1934 they began to equip vehicles for field testing. These cars carried a Marsh funnel, a Stormer viscometer, a portable mixer, an electric hot plate, screens, graduates, a Mudwate Hydrometer, a Wulff pH tester, a balance, and a mortar and pestle. Around 1936 they added a mud balance that had been developed by Phil Jones of the Union Oil Company of California.

References:

“The History of Mud Testing”, Baroid News Bulletin October 1960

Shale Shakers and Drilling Fluid Systems, by American Association of Drilling Engineers, Gulf Publishing Company, 1999

Oil Field Practice, by Dorsey Hager, McGraw-Hill, 1921

Read more at Suite101: The History of Mud Testing