1915 - The Use of Mud-Ladened Water in Drilling Wells
A review of muds was presented in 1915 that covered both rotary and cable tool drilling was presented by I.N. Knapp at the AIME February meeting of that yearork. Knapp states that the;
“special object of these notes is to describe the mixing, testing, and use of mud-ladened water for rotary drilling in such a way as to make them helpful to the driller, the operator, or the engineer. in solving his own special drilling problems.”
The information imparted by Knapp was the result of experiences encountered in drilling through coastal plane formations. The land from which they drilled was about one foot above the mean tide level, which resulted in some flooding with the tidal flows. He used the hydraulic rotary drilling method using mud prepared on site from locally available clayey material. The use of high yield commercial clays was considered too expensive for routine drilling operations. He recommended a mud pit 20 by 30 feet and 3 feet high and a power driven mud mixer to prepare a thick mud. He stated that “a good mud will not settle in a week. Also, such a mud will not stick or freeze in a drill pipe if left in 24 hours.”
Knapp stated that; “at all times, the mud pressure at any point in the well must exceed the pressure in the strata penetrated at that point, thus excluding all gas, oil, and water as they are encountered.’ The use of the proper hydrostatic head was recognized as being very important. Knapp prepared his clay based mud system by weighing the slurry used to drill. Since there was no standard test for measuring mud weight he developed his own test, which is excerpted here.
“It is very difficult to judge whether any particular clayey material will make a suitable mud. The only sure way to know is to mix a sample of available material and try it. Mud can be best tested by weighing. I used a common market beam scale (without pan) having a capacity to weigh 50 lb. by ounces, and a common galvanized iron bucket in which to weigh the mud. Four equally
spaced ¼ inch holes were punched under the top rim to furnish level marks to fill to.
"The bucket is first hooked on under the beam, the poise brought to zero, and the whole balanced by counter-weighting. The bucket is then filled to the level holes with clear water and its weight taken and noted. It maybe, for instance,18lb. The poise is again placed at zero and more counter-weight added to balance the clear water. This water is then thrown out and the bucket filled with mud, and the poise, when balanced on the beam, will indicate the additional weight of the clayey material in suspension over that of the same volume of clear water. The bucket may be filled with mud as many times as desired and weighed without further adjustment. If the additional weight found at any time should be 6 lb. it would indicate the mixture weighed about 33 per cent. more than the same volume of clear water. If a good working mixture is found to be 5 lb. of additional weight per bucket of mud, and in drilling it increases to show 6 lb., clear water may be slowly added until the weight drops to 5 lb. or a little less."
The only other tests that Knapp proposed were two techniques to measure the sand content in the mud. The first was by dilution in the weight bucket and observing the amount of sand settled. The other was using a hand cranked sedimentation centrifuge with a saturated brine mixed with the mud. In both cases he recommended keeping the sand content at two percent or less.
The Use of Mud-Ladened Water in Drilling Wells I.N.KNAPP, ARDMORE, PA.
(New York Meeting, February 1915)
Published in Petroleum Transactions, AIME, Volume 52, 1916, pages 571-586.
Improved Methods of Deep Drilling in the Coalinga Oil Field, California
BY M. 1. LOMBARDI, SAN FRANCISCO, CAL. (AIME New York Meeting, February, 1915)
By the year 1915 the wells drilled in Coalinga oil field on the west side of California's San Joaquin Valley had reached depths greater than 4000 feet. Even though rotary drilling use was increasing in California, percussion drilling was used to obtain greater depths. Lombardy states:
"About the limit of rotary drilling to date in California seems to be the setting of the 10-in. string at 3,200 ft., although the rapid advance in rotary work during the past year secms to indicate that this depth may soon bc increased. It is my purpose now, however, to treat only of cabletool drilling."
The cable tool rigs, however, were equiped with a "standard circulator system." A diagram of a cable tool rig set up to run casing while continously circulating is shown here.
The fluid used in the standard circulator system is; "Mud- (clay) laden fluid is forced down through the pipe under pressure by pumps (ordinary rotary slush pumps) and returned on the outside of the pipe, carrying the drillings with it. This fluid is run through a flume and into a pit, as in rotary work, and its consistency is regulated as with the rotary."
"This mud-laden fluid presumably plasters up the walls of the hole, prevents sand and mud from running in and prevents caving. It is essential that circulation be interrupted as little as possible. Intermittent circulation seems to be worse than useless. The pipe is kept moving while drilling is in progress-i.e., without pulling out the tools ..."
Lombardy was also aware of the Hagan and Pollard work in Oklahoma and Louisianna about using higher specific gravity fluids to control pressures. He states:
"The mud-laden fluid as usually used has a specific gravity of about 1.40; therefore, its pressure in holding back artesian water, running sand, etc., is 1.4 times as much as clear water. I t is a well-known fact that this mud-laden fluid tends t o kill gas (see Technical Paper No. 66, U. S. Bureau o j Mines, Mud-laden Fluid Applied to Well Drilling), although it is the writer's opinion that the capillary action of water in sand has as much to do with holding back gas pressure as anything."
He does not report how the mud weight of 1.4 sg (11.7 lb/gal) was obtained. I assume it was drill solids buildup.