The Synthesis and Evaluation of a Pentaerythritol-Based Hyperbranched Polymer Filter Loss Reducer

Filter loss reducers presently in use have some deficiencies such as great negative impact on mud rheology, poor high temperature resistance and poor salt contamination resistance etc. To overcome these deficiencies, a pentaerythritol-based hyperbranched polymer filter loss reducer PPAAN-1 was developed through radical polymerization with tetraallyl ether (PPTE, a polyene monomer with pentaerythritol as its core molecular structure), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), N-vinyl pyrrolidone (NVP) and acrylamide (AM) as raw material. Based on orthogonal experiment results, the effects of the concentration of the tetraallyl ether on the apparent viscosity of the filter loss reducer PPAAN-1 was also studied. The optimum synthesis condition of PPAAN-1 was finally determined as follows: concentration of PPTE = 17%, AMPS∶AM∶NVP = 2 ∶6∶1, reaction temperature=55 ℃, initiator (AIBN) concentration = 0.2%. In laboratory evaluation, the properties of PPAAN-1 were compared with Driscal and DrisTemp. PPAAN-1 has little effect on mud rheology, good thermal stability and good filtration control capacity. The thermal decomposition temperature of PPAAN-1 is 302.29 ℃. A 30% NaCl drilling fluid treated with 1% PPAAN-1 had API filtration rate (220 ℃) of 9.8 mL and HTHP (150 ℃) filtration rate of 18.5 mL. In high temperature high salinity conditions, PPAAN-1 can form a network structure and adsorb on the surfaces of the clay particles, thereby widening the range of the particle size distribution of clays in a drilling fluid, helping the drilling fluid form dense mud cakes, and reducing the filtration rate of the drilling fluid.