低渗透油藏驱油用缔合聚合物的合成及其油藏适应性研究

Synthesis of associative polymer for flooding in low permeability reservoir and its reservoir adaptability

针对长庆油田某区块中温高矿化度低渗透的油藏条件,设计合成了不同十二烷基烯丙基二溴化四甲基乙二铵(TDAD)含量的耐温抗盐型低相对分子质量(720.42×10^4~982.55×10^4)疏水缔合聚合物(HAWSP系列),通过红外光谱确认了聚合物分子结构,在该区块条件下考察了HAWSP系列的溶液性能和应用性能适应性,并在该区块现场开展矿场验证试验。结果表明,与抗盐部分水解聚丙烯酰胺HPAM相比,HAWSP系列具有更优的增黏性和相当的老化稳定性(60 d老化黏度保留率大于85%);在气测渗透率为50×10-3μm2的油藏条件下,缔合聚合物HAWSP-850在兼具良好注入性和传导性时,还能在4倍渗透率极差(低渗为25×10^-3μm^2)的非均质岩心中有更强的波及能力,可多提高采收率3.29个百分点。矿场试验表明,耐温抗盐低相对分子质量缔合聚合物的现场适应性较好,相比常规聚丙烯酰胺驱油体系,具有明显的降压增注提高采收率效果,在低渗油藏化学驱中具有重要的推广意义。

In view of the reservoir conditions in a block of Changqing Oilfield with medium temperature,high salinity and low permeability,different temperature-salt resistant associative polymers(HAWSP series)with low relative molecular weight(720.42×10^4~982.55×10^4)and different contents of dodecylallyl tetramethyl ethylene diammonium bromide(TDAD)have been designed and synthesized.Then the molecular structure of the polymer has been confirmed by infrared spectroscopy.Under the conditions of this block,the reservoir adaptability of HAWSP series involving solution properties and application performance have been studied,and the field test has been carried out in this block.The results show that,compared with the salt-resistant partially hydrolyzed polyacrylamide(HPAM),HAWSP series has better thickening capacity and similar aging stability(viscosity retention rate is greater than 85%after aging for 60 days).When the gas permeability is of 50×10-3μm2,the associative polymer HAWSP-850 not only exhibits good injectability and conductivity,but also could present stronger sweeping ability in heterogeneous core with a permeability contrast of 4 times(low permeability is of 25×10-3μm2),which can enhance the oil recovery by another 3.29 percentage points.Field tests show that the temperature-salt resistant associative polymer has better field adaptability.Compared with the conventional HPAM flooding system,it has a significant effect of reducing pressure and improving injection capacity and oil recovery.Associative polymer has important promotion significance of chemical flooding in low permeability reservoirs.