Abstract: The reservoir of Z1 oil group in W Oilfield has low resistance,high porosity and low permeability.The low resistivity of the reservoir was caused by many geological reasons.In this paper,for the reservoir characteristics of Z oil group,statistics of the reservoir of immobile water saturation has been done,and the genesis of high immobile water saturation in the Z1 oil group in the W Low resistivity reservoirs,as well as the relationship between the immobile water saturation and reservoir resistivity has also been studied.Through the study,in low resistivity layer segment of Z1 oil group,it is found that the main reasons forming a highly immobile water saturation are high levels of fine particles of the reservoir,Poor pore structure of reservoir,Slightly higher percentage of fine pore and throat volume,and the rock hydrophilic.The formation resistivity increases as immobile water saturation decreases.Therefore,high immobile water saturation is one of the important reasons affecting the low resistivity of the Z1 oil group in the W oil reservoir.