页岩油地层固井用改性铝酸盐水泥的水化行为及性能

Hydration Behavior and Properties of Modified aluminate Cement for Well Cementing in Shale Oil Formation

页岩油原位转化的资源潜力巨大,属于中国油气的战略性替代资源。但是,低成熟度页岩油在原位转化过程中极端高温会导致固井水泥石强度衰退。系统研究了改性材料六偏磷酸钠对铝酸盐水泥水化行为及在650℃高温环境下应用性能的影响规律,并对其宏观性能和微观结构进行了深入探究。低场核磁共振分析测试技术显示,改性材料六偏磷酸钠对铝酸盐水泥初期水化行为存在较为显著延缓作用,且可有效改善其流变性能。50℃环境下,掺入六偏磷酸钠能显著降低铝酸盐水泥石的渗透率,但对强度提升不明显;650℃处理后,掺入5%六偏磷酸钠的改性铝酸盐水泥石的抗压强度最高为47.19 MPa。铝酸盐水泥石在650℃处理前后水化产物发生明显转化,主要是C3AH6和AH3转化为C12A7和CA,其中,C3AH6和AH3主要在180~400℃期间发生热分解。同时,压汞孔径分布显示,净浆铝酸盐水泥石以及5%六偏磷酸钠改性铝酸盐水泥石孔径范围主要分布在100~1000 nm之间,且两种类型水泥石高温650℃处理后由于晶型的转化均导致孔隙明显增大。

The resource potential of in-situ conversion of shale oil is enormous,and it is a strategic replacement resource for China’s oil and gas industry.However,extreme high temperatures under low maturity shale oil in-situ conversion conditions can lead to a decline in the strength of hardened cement.The influence of modified material sodium hexametaphosphate on the hydration behavior of aluminate cement and the application performance of cement slurry at the high temperature environment of 650℃was systematically studied,and its macro performance and microstructure were deeply explored.low field nuclear magnetic resonance analysis and testing technology showed that the sodium hexametaphosphate had a significant retarding effect on the initial hydration behavior of aluminate cement and could effectively improve its rheological properties.In addition,at the temperature of 50℃,addition of sodium hexametaphosphate could significantly reduce the permeability of hardened aluminate cement,at the same time,which had no significant impact on the strength.After treatment at the temperature of 650℃,the maximum compressive strength of was 47.19 MPa by adding 5%sodium hexametaphosphate to modify hardened aluminate cement.Simultaneously,before and after treatment at 650℃,the hydration products of aluminate cement slurry underwent significant transformation,the C3AH6 and AH3 converted into C12A7 and CA mainly.C3AH6 and AH3 underwent thermal decomposition mainly during the period of 180—400℃.the pore size distribution of mercury intrusion showed that the pore size range of clean hardened aluminate cement and 5%sodium hexametaphosphate modified hardened aluminate cement was mainly between 100 and 1000 nm,and the pore size of both types of cement stones increased due to the transformation of crystal form after high-temperature treatment at the temperature of 650℃.