Hole Stabilization Wall Building

An application for a U.S. patent, filed in 1887 by M.J. Chapman,* proposed "a stream of water and a quantity of plastic material, whereby the core formed in the casing will be washed out and an impervious wail be formed along the outside." He suggested clay, bran, grain, and cement. Here was another function of the drilling fluid: to plaster the wall of the hole and reduce caving tendencies.

Figure 2-2. Sweeny's rotary drill of 1866 had some features in common with rigs of today. (Courtesy of NL Baroid.)

During the 1890s many welis were drilled by the rotary method in Texas and Louisiana, where mud-making clays were common. Drillers became familiar with the use of mud as a means of hole stabilization ("wall building") in weak formations. Brantly's comprehensive History oj OH Well Drilling.2 in reviewing the developments of this period, makes no mention of the use of plastering agents other than clay.

Following the discovery of oil at Spindletop in 1901, drilling by the rotary method spread rapidly throughout the Gulf Coast and in California, The problem of unstable holes in poorly consolidated formations demanded attention.

Sufficient clay ("gumbo") usually was present in the cuttings from welis in the Gulf Coast to "make good mud."CJ In California, however, clays from surface deposits were often mixed with water to "plaster the walls."

Although most mud mixing was done with shovels by the crew, some auxiliary mixing devices were available (see Figure 2-3). Little attention was paid to the properties of the mud.10 The terms "heavy" and "thick" were used interchangeably.

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