Performance control of high temperature and high density drilling fluid based on fractal grading theory

With the increase of drilling depth, the density of drilling fluid required also increases gradually. Increasing the density of drilling fluid by weighting material usually worsens the performance of drilling fluid. Based on the fractal principle and mathematical fractal, a fractal grading model suitable for the grading calculation of drilling fluid weighting materials was established, and the theoretical proportion of barite with different particle sizes was given. Through drilling fluid performance evaluation, filter cake analysis, oscillatory rheology measurement and circulation simulation, the influence of barite gradation on the rheology, filtration and sag stability of high -density drilling fluid was studied, and the influence of barite gradation on drilling fluid performance was dis-cussed. The results showed that the fractal grading model is suitable for the optimization of weighting materials of high-density drilling fluids, and the graded barite can improve the comprehensive performance of weighting drilling fluids.