Research On High Temperature And High Density Water Based Drilling Fluid

With the development of exploration and exploitation of oil and gas resources to deep formation,more high temperature and high pressure formation will be drilled,and the demand for high temperature and high density water-based drilling fluid will gradually increase.High temperature and high density will bring many problems to drilling fluid,such as rheological deterioration,significant increase of filtrate loss,thickening of mud cake and so on,which will directly affect the well safety and drilling cost.Therefore,it is of great significance for the exploration and development of deep resources to study the high temperature and high density water-based drilling fluid system.This paper investigates and studies the influence and mechanism of high temperature and density on the performance of water-based drilling fluid,analyzes and summarizes the technical difficulties of high temperature and density drilling fluid and the technical countermeasures for performance control.The physical and chemical properties of micro manganese weighting agent and barite and their influence on drilling fluid are studied,and the existing formula of weighting agent proportion is improved.In this paper,a dispersant with high temperature resistance was synthesized.With Sepiolite and bentonite as slurry materials,a kind of high-temperature and high-density water-based drilling fluid with temperature resistance of 200?and density of 2.4g/cm3 was developed.The results show that.Micro manganese weighting agent has higher densit y,hardness and zeta potential than crystal,and has strong adsorption capacity and acid soluble characteristics.The average particle size of micro manganese particles is smaller than that of crystal,but the particle size distribution is narr ow.The experimental results show that the micro manganese weighted drilling fluid has better rheological properties and settlement stability than the crystal w eighted drilling fluid.Through theoretical calculation and laboratory experiment s,it is found that the comprehensive effect is better when the weight ratio of barite and micro manganese is 75:25.The dps-1 dispersant can improve the sta tic settling stability of the drilling fluid weighted by micro manganese,and the apparent viscosity reduction rate is about 19%.The best ratio of bentonite an d sepiolite is 3:1.The final formulation of high-temperature and high-density w ater-based drilling fluid is:clear water+1.5%sodium bentonite+0.5%sepiolite+0.25%Na₂CO₃+0.45%NaOH+0.2%KPAM+0.3%RHPT-2+1.5%KHm+5%SPNH+1%DPS-1+1.5%JM-1+weighting agent?75wt%barite+25wt%micro manganese,?=2.4g/cm³?.Compared with barite,micro manganese weighting agent is more suitable for weighting materials of high-density drilling fluid.By compounding with barite,the cost can be reduced and the comprehensive performance can be improved.Dps-1 dispersant can effectively reduce the heavy material settlement caused by clay and rock salt pollution of high-density drilling fluid aggravated by micro manganese,and the viscosity reduction effect is obvious.The addition of sepiolite can improve the thermal stability and suspension capacity of bentonite slurry,improve the rheological properties of bentonite slurry at high temperature,but increase the filtration.The final formulation of high temperature and high density water-based drilling fluid system has the characteristics of good rheology,filtration and wall building,high thermal stability and good settlement stability,meeting the drilling requirements of high temperature deep wells with well temperature of 200?and formation pressure coefficient of 2.4.