Microbit Studies of the Effect of Fluid Properties And Hydraulics on Drilling Rate, II

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the 43rd Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Houston, Tex., Sept. 29-Oct. 2, 1968. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Microbit studies presented to the SPE of the AIME in 1966 (SPE 1520) showed that in one rock under fixed conditions of bit weight, rotary speed, and differential pressure, drilling rate could be expressed as a simple power function of mud flow properties and power function of mud flow properties and hydraulic parameters. A logical question arose: "Are these reported results general?" To resolve this question, the results of additional microbit studies are reported in this paper. These tests were conducted with bit weights 500 pounds less and greater than the original 1000 pounds test condition, rotary speeds of 150 rpm and 45 rpm in addition to the original 75 rpm value, and differential pressures of 0 and 50 psi in addition to the original 500 psi test condition. Tests were also run in Carthage marble as well as additional tests in the original Indiana limestone. Under all of these conditions, the original relationship of rate of penetration to fluid properties and hydraulics was unchanged. Changes in the various parameters caused changes in the drilling rate, but not in the effect of fluid properties and hydraulics. There was no detectable interaction between the variables, indicating that an equation of the form, can be satisfactorily used for calculating drilling rate. Introduction An earlier paper, "Microbit Studies of the Effect of Fluid Properties and Hydraulics on Drilling Rate" (SPE 1570, published in 1966), presented the results of a laboratory study indicating that drilling rate can be expressed as an exponential function of a pseudo Reynolds number involving flow rate, pseudo Reynolds number involving flow rate, nozzle size, and fluid viscosity and density. For non-Newtonian fluids, the "viscosity" is that at hole bottom, near bit-nozzle, shear rates. A relatively simple expression for drilling rate, can be used to cover the range of greatest variation—that is, for values of the Reynolds number between about 5 and 100.