超高温低黏聚合物降滤失剂的研制及作用机理

针对深井、超深井中钻井液降滤失剂存在抗温、抗盐能力不足，对钻井液流变性影响大等难题。以2-丙烯酰胺-2-甲基丙磺酸（AMPS）、N，N-二甲基丙烯酰胺（DMAm）、N-乙烯基吡咯烷酮（NVP）、二甲基二烯丙基氯化铵（DMDAAC）为共聚单体，2，2-偶氮二（2-甲基丙基咪）二盐酸盐（AIBA）为链引发剂，通过使用链转移剂，制备了一种抗温达230℃，抗盐达20%的低分子量聚合物降滤失剂PANAD。采用正交实验法优化得到了降滤失剂的最优合成条件:单体物质的量之比DMAm:AMPS:DMDAAC:NVP=7:2:2.5:1，反应温度为65℃，引发剂加量为0.7%；利用一点法测得降滤失剂的特性黏数为58 mL/g。采用傅立叶红外光谱（FT-IR）和热重分析表征了其分子结构和热稳定性，结果表明，PANAD分子链热裂解温度高于314℃，具有良好热稳定性能。降滤失剂在水基钻井液中的滤失性能评价结果表明，PANAD抗温达230℃、降滤失性能优良，在加量为1%时，老化后淡水浆、20%盐水浆的中压滤失量分别为8.9、22.5 mL，淡水浆在180℃下高压滤失量为35.6 mL，优于国外同类产品Driscal D；在230℃老化前后，降滤失剂对钻井液流变性影响小，高温稳定性优良。最后，通过Zeta电位、吸附试验和SEM等测试分析了PANAD的降滤失机理。 

Preparation and Working Mechanisms of an Ultra-high Temperature Low Viscosity Polymer Filtrate Reducer

A low molecular weight polymer filtrate reducer PANAD was developed to overcome the disadvantages of conventional filtrate reducers use in deep and ultra-deep well drilling, such as poor stability at high temperatures, poor resistance to salt contamination and excessive impact on the rheology of drilling fluids. The PANAD was synthesized through chain transfer reaction with several monomers such as 2-acrylamide-2-methylpropanesulfonic acid (AMPS), N, N-dimethyl acrylamide (DMAM), N-vinyl pyrrolidone (NVP) and dimethyl diallyl ammonium chloride (DMDAAC). 2,2-azobis,2-methylpropylimid, dihydrochloride was used as chain initiator. PANAD functions normally at elevated temperatures,up to 230℃, and high salinity,up to 20% salt concentration). The optimum synthesis conditions determined by orthogonal experiment are as follows, molar ratio of DMAM:AMPS:DMDAAC:NVP=7:2:2.5:1, reaction temperature=65℃ and concentration of initiator=0.7%. The intrinsic viscosity of PANAD 58 mL/g, as determined by "one-point method". The molecular structure and thermal stability of PANAD, as characterized by FT-IR and thermalgravimetric analysis, showed that PANAD had excellent thermal stability, with its chain pyrolysis temperature of 314℃. Test of the filtration control performance of PANAD showed that PANAD worked normally in water base drilling fluids at a maximum temperature of 230℃. Aged fresh water base and 20% saltwater base drilling fluids treated with 1% PANAD had API filtration rate of 8.9 mL and 22.5 mL, respectively. Filtration rate of fresh water base drilling fluid at 180℃ was 35.6 mL, a better filtration control performance than Driscal D. PANAD has very weak effect on the rheology of the drilling fluid before and after aging at 230℃. The mechanisms of filtration control of PANAD was analyzed through zeta-potential measurement, adsorption test and SEM analysis.