Thermochemical sulfate reduction, biodegradation make oil properties worse,whereas deasphalting by gas influx occuring in oil of Mesozoic and Cenozoic in Yaha area in Tarim basin can increase its API gravity and GOR,and decrease its viscosity.

• 热化学硫酸盐还原、生物降解作用使原油物性变差.；塔里木盆地牙哈地区中、新生界原油经气洗脱沥青；使原油密度、粘度降低；气/油比值增大；物性变好