Synthesis and Evaluation of High Temperature Weak Gel Viscosifier WG-1

A high temperature weak gel viscosifier WG-1 has been developed using inverse emulsion polymerization in an effort to satisfy the needs for high temperature deep wells and non-conventional wells.The optimum synthesis conditions were determined and key factors affecting the performance of WG-1 examined.Groups such as AMPS,DMAM and NVP are found in the molecular structure of WG-1 through SEM observation,and these groups are in spherical forms,with diameters between 0.1 μm and 1.8 μm.These data demonstrate that WG-1 has good thermal stability,salinity tolerance and superior thickening and gelling capacity.A 1.0% WG-1 solution,after aging at 200℃ for 16 h,had YP/PV ratio of 0.47 Pa/mPa·s,suitable for use at that temperature as a viscosifier and gelling agent.WG-1 solution retained enough viscosity and gel strengths after aging for 72 h at 170℃,meaning that it suffices the needs for operation at 170℃.WG-1 can be used in both fresh water and saltwater drilling fluids as viscosifier and filter loss reducer.After aging at 170℃,the filtration rate of fresh water base drilling fluid was reduced from 9.6 mL to 4.8 mL,and that of saturated water base drilling reduced from 8.8 mL to 3.2 mL,indicating that WG-1 can plug micro fractures and improve the quality of mud cakes,thereby reduce the filtration rate.