An Experimental Investigation of Temperature and Aging Effects on Bentonite and Sepiolite Drilling Fluids
The selection and control of a suitable drilling fluid is necessary to successfully drill an oil and gas well. The rheological properties of drilling fluids vary with changes in conditions such as time and temperature. Slight changes in these conditions can cause unpredictable and significant changes in the mud’s properties. This makes it necessary to study the rheology of drilling fluids and how it is affected by these changes. At the rig sites, tests are carried out by the mud engineers to ensure that the properties of the drilling fluids are within the required limits. Similar tests were carried out at the laboratory in this work to determine the plastic viscosity, yield point, gel strength of mud samples at different conditions of ageing time, temperature and concentration of Xanthan gum (X.G) used as an additive. The Experiments carried out were grouped into three. The first was done with the aim to further explain how the Bentonite and Sepiolite water-based drilling fluids behaves after been aged for certain period. The second sets of experiments were conducted to investigate how the rheological properties of water-based Bentonite muds are affected by different concentration of xanthan gum added as an additive to improve the muds properties and the last sets of experiments were done to investigate the ageing effect on Bentonite mud treated with 250mg/L xanthan gum. Effects of temperature were also considered in these experiments with a 10℃ variation in the first group and 20℃ in the other two groups between readings from 20℃ to 60℃ . Results obtained indicated that Sepiolite water-based drilling fluid offers better plastic viscosity and yield point as compared to Bentonite water-based drilling fluids. It was also found that the viscosity and yield point of Sepiolite, Bentonite and treated Bentonite muds decreases with increase ageing time and temperature while the gel strength increases with ageing time but similarly decreases with increase in temperature. In the second group, results obtained indicated that plastic viscosity, yield point and gel strength increases as concentration of xanthan gum increases, all of which decreases with increase in temperature.