Imbibition Characteristics Of Tight Oil Reservoir In Jimusar Area

After fracturing of the tight oil reservoirs,Jimaosar Formation,in Lucaogou Formation of Xinjiang,huge amount of fracturing fluid will be absorbed and clogged by reservoir that leads to an unpleasant backflow rate.The low porosity,strong capillary force and powerful spontaneous imbibition of reservoirs have an important effect on oil production and enhanced oil recovery of Jimaosar Formation.But few people focused on the spontaneous imbibition of Jimaosar Formation yet and there is still many unknowns on its imbibition strength,wicking mechanism and influence factors.The technologies such as SEM and NMR was employed for analyzing the characteristics of Jimaosar Formation.In addition,spontaneous imbibition and fluid displacement experiments were conducted applying reservoir sample.The imbibition characteristics of the reservoir was obtained as well as the influence factors.The results are summarized as below:(1)The development of reservoir strata in Jimosar area,crude oil viscosity,salt lake environment,and high salinity of formation water are key factors of reservoirs spontaneous imbibition.(2)The porosity and permeability of targeting reservoirs were poor.The rock clay content have low proportion in the reservoir.The pore structure is complex and mainly consists of pores in the range of 0.01~1?m.These implicates the targeting reservoirs are typical tight oil reservoirs.(3)The reservoir core performed a strong imbibition ability and the anisotropy of the reservoir is large for the imbibition power of samples have differences.(4)The physical characteristics such as porosity and permeability have large impact on the imbibition of the reservoir.The cores with high content of layers have a large amount of absorption;the cores with cracks have greater infiltration rate and final absorption capacity than those of ordinary cores;the absorption of cores with cationic surfactants and KCl solution decreases and the infiltration rate decreases.(5)The absorption capacity of horizontal stratification can be about 30% higher than the vertical stratification,and bedding is an important seepage channel of the reservoir.(6)The low salinity could improve the oil recovery factor.This illustrated that it is practical to apply low salinity fluid for enhance oil recovery.