Study On The Performances Of Ca-bentonite Suspension For Water-Based Drilling Fluids With Enhanced And Extended Techniques

There are many problems in the application of bentonite in China,such as low resource utilization,backward product processing technology,and lack of high-level products.Based on bentonite in Xinjiang,Shaanxi and Hubei province,this paper studied the suspension performances of local bentonites and their enhanced techniques.According to the mineral characteristics of bentonite,improve the production technology of local enterprises.After testing,Zhaofeng bentonite had a low content of montmorillonite,only 37 wt%,in addition to 35 wt% of quartz.The drilling fluids of Zhaofeng bentonite was easy to settle and the apparent viscosity was very low.Testing showed that 4 wt% sodium carbonate could improve the suspension performances of Zhaofeng bentonite in water by modifying.The Zhaofeng bentonite was further modified with 0.4 wt% carboxymethylcellulose and 0.2 wt% polyacrylamide.The Zhaofeng OCMA standard bentonite was prepared directly.The apparent viscosity of Zhaofeng OCMA bentonite could reach to 20 mPa·s,the rest of the performance can reach the standard.The montmorillonite content of Dima bentonite was 58 wt%,and the quartz was only 6 wt%.There was a certain amount of magnesium ion in this bentonite.With 2.3% sodium carbonate,0.2 wt% sodium polyacrylate and 0.4 wt% carboxymethyl cellulose,Dima OCMA bentonite could be prepared at a cost of only 100 RMB/ton.After testing,the montmorillonite content of Qitai bentonite was 68wt%,and the bentonite could be used to prepare super viscosity bentonite(SVB).Testing showed that 0.8 wt% magnesium oxide and 4.5 wt% sodium carbonate as modifiers could greatly increase the apparent viscosity of Qitai bentonite in fresh water.Sodium carbonate plays a major role in reducing filtration loss of drilling fluids.Testing showed that,based on the modification of the inorganic mixture,1.2 wt% polyacrylamide could be used as a viscosifier,and 0.8wt% sodium polyacrylate was used as a rheology modifier to prepare Qitai SVB.The apparent viscosity of drilling fluids with 6.4 w/v% Qitai SVB could reach 64 mPa·s.Developing drilling fluids with good bentonite suspension stability in saline water-based muds is preferred for sufficient cutting carrying capacities,lower filtration loss.Testing has shown that xanthan gum could improve the rheological properties of bentonite in brine.The experiment proves that the temperature resistance of xanthan gum in water was insufficient.Borax was used as the cross-linking agent and sodium sulfite was used as the deoxidants.The modified xanthan gum can increase the temperature resistance of xanthan gum from 93 ℃ to 120 °C.Modified xanthan gum treated Qitai bentonite could prepare Qitai salt-tolerant bentonite(STB)could be prepared by 1wt% modified xanthan gum and Qitai bentonite,6.4 STB w/v% drilling fluids,and its apparent viscosity could reach 18 mPa·s.