Abstract:
A high temperature salt-resistant viscosifier,BDV-200S,has been developed from 2-Acrylamido-2-methylpropane sulfonic acid (AMPS),acryl amide (AM) and another monomer X.Studies have been conducted on the molecular structures,molecular weights and distributions,and the thermal stability of BDV-200S molecules.Rheology and functioning stability at elevated temperatures were studied through high temperature rheological measurement,ratio of viscosity retention after aging at high temperature,suspension of barite in the aged muds treated with BDV-200S,and bottom-hole dynamic circulation simulation test etc.The performances of BDV-200S in solid-free drilling fluids at 120℃,150℃,and 180℃ were compared with those of the similar products.These studies reveal that the BDV-200S synthesized is the product designed.BDV-200S has a weight average molecular weight of about 2,000,000 which is distributed in a narrow range.After aging at 180℃ for 16 h,the BDV-200S solution still retained viscosity of greater than 45% of its original viscosity,and the color of the solution was still white.No barite settlement has been found of the solution,meaning that the suspending capacity of BDV-200S is satisfactory.A laboratory test simulating mud circulation in hole with bottom hole temperature of 180℃ indicated that the solution,after 4 cycles of circulation,still retained viscosity more than 50% of its original viscosity.In salt resistant performance testing,the viscosity of the saltwater increased with the concentration of BDV-200S in a linear relationship.Drilling fluids treated with BDV-200S has API filter loss of 5.0 mL,and HTHP filter loss of 19 mL at 150℃.The evaluation reveals that BDV-200S possesses a better performance than other similar products.