超稠油英文单词怎么说？

1.super viscous oil
2.super-dense oil
3.extra-heavy oil
例子：1.experimental study on super viscous oil wastewater treatment.（超稠油废水处理的实验研究）
2. the study on new techniques in exploitation for the super-dense oil.(超稠油开发新工艺研究 )
3.the development of deaquation technique for extra-heavy oil.(超稠油脱水工艺技术的开发)

thick oil