Synthesis and Application of a Comb Polymer Filter Loss Reducer in Deep Well Saltwater Drilling Fluid

A comb polymer filter loss reducer, DMP-1, was synthesized through solution polymerization with allyl polyoxyethylene ether 400 (APEG400), acrylamide (AM), and 2-acrylamido-2-methyl propane sulfonic acid (AMPS). DMP-1 was developed in an effort to overcome the deficiencies of presently available high temperature salt-resistant filter loss reducers used in an environment with high salinity and divalent salts. The synthesized product was a viscous transparent liquid containing 30%DMP-1. Structure characterization of DMP-1 showed that APEG400, AMPS and AM all participated in the reaction to form the comb polymer and the polymerization was complete. Thermogravimetric analysis showed that DMP-1 decomposed at 320℃. Comparison of DMP-1 with the commonly used filter loss reducers such as DSP-2, Driscal D or PAMS601 showed that, after aging at 180℃, the percent reduction of the viscosity of DMP-1 was less than 42.0%, and the property of DMP-1 remained stable at 200℃. DMP-1 was resistant to salt contamination to saturation, and calcium contamination to 3%. These data indicate that DMP-1 works better in salt and calcium environment than the widely used high temperature salt-resistant filter loss reducers such as DSP-2. Application of DMP-1 in the 3rd interval (penetrating salt and gypsum formations) and the 4th interval (high temperature) of the well Tailai-201 and the well Yongxing-1 in Fuling area demonstrated that DMP-1 performed very well at high temperatures, high salinities and high calcium concentrations, effectively reducing the API filter loss of saltwater drilling fluids and calcium-treated drilling fluids, thereby ensuring the safety of drilling operation.