Automatic Measurement of Drilling Fluid and Drill-Cuttings Properties

Abstract

Summary To remotely control the drilling process, it is necessary to measure several drilling-fluid parameters automatically. This will increase objectivity of the measurements and make it possible to react to changes in real time. The current paper describes in detail the design for an integrated tool combination and the results of a full-size yard test of such a combined set of tools for measuring drilling-fluid parameters and formation properties automatically. Some of the automated tools have been tested on rigsite operations. Results from these individual tests are also presented. The automatic drilling-fluid analysis includes viscosity, fluid loss, electrical-stability (ES) measurements, and chemical properties such as pH. Full viscosity curves for the drilling fluid are measured using configurations and shear rates similar to those suggested by American Petroleum Institute (API) procedures. Because gel-formation curves and fluid-loss properties require some sort of controlled static periods, these measurements are made semicontinuously. However, they are automatic and can be measured as frequently as desired. An automatic system is included to measure the particle-size distribution (PSD), concentration, and morphology. Knowledge of these parameters is necessary, especially when drilling in depleted reservoirs where particles are added for increasing the wellbore strength. The produced-cuttings volume is measured. An automatic system is adapted that determines, with accuracy comparable to that of visual analysis, whether the particles separated at the shaker screens are drill cuttings or cavings produced by an unstable formation. The mineralogy of the cuttings is analyzed automatically using Raman spectroscopy, making it possible to evaluate continuously the different formations being drilled.