Determination of the Rheological Parameters of Invert Emulsion Drilling Fluid in Real Time using Non-Linear Regression Technique

Rheological parameters are the key factor for hydraulic calculations and hole cleaning efficiency in the drilling operations. Rheological parameters include mud density, plastic viscosity, apparent viscosity, and yield point. Rheological parameters should be measured or estimated during the real operation to determine the actual equivalent mud circulation density, surge and swab pressures, hydraulic calculations, and hole cleaning efficiency. The mud rheological properties can be obtained from laboratory measurements. These measurement scan be divided into two types; the first one is simple testing such as mud density and Marsh funnel viscosity. The second set of experiments is the rheological properties measurements. Onsite, Marsh funnel viscosity and fluid density are measured frequently (every 10 to 20 minutes) to monitor the change of the drilling fluid properties while as the rheological properties are measured twice a day. In this paper a new model was developed to estimate the rheological parameters of invert emulsion-based drilling fluid using Marsh funnel viscosity and mud density. Multiple nonlinear regression technique was used to develop the new model. 6,000 data points from field measurements of the Marsh funnel viscosity, mud density, plastic viscosity, and yield point, were used in this study to develop the new model. The new model can be used to predict the following properties of the drilling fluid; viscometer readings at 300 and 600, plastic viscosity, yield point, apparent viscosity, power law index, and consistency index. All the previous parameters will be predicted using only Marsh funnel time and drilling fluid density. The developed models consists of six correlations that can be used to estimate the rheological properties with an average absolute error less than 4% and a correlation coefficient greater than 0.95 based on the Marsh funnel time and drilling fluid density. These correlations can be used to prepare the input parameters for hole cleaning and hydraulic calculations in real time. Applying this inexpensive technique will help drilling engineers predict any problem before it happens such as pipe sticking, sage issues, and loss of circulation