Abstract:

In consideration of the high heterogeneity of carbonate reservoirs in the Wumishan Formation,the division criterion between reservoir and non-reservoir is taken,to some extent,as an important factor in evaluation of valuable thickness of a reservoir.Statistical data between residual oil Saturation and porosity in rock samples show that,they are generally in normal correlation and may probably reflect the oil abundance of the underground reservoir rocks,and just so,in 90% of non-petroliferous cores,the porosity is less than 2%,permeability less than 1mD.As the porosity and average size of pores are negatively correlated,it is revealed by capillary pressure curve that the porosity of the unpermeable samples is less than 2%(73%),and the average size of pores is more than 12.3φ(76%),the related throat diameter less than 0.21μm.According to electrical log,rocks with GR greater than 3μR/h,the porosity is only 1%,and the permeability is less than 1mD.Based on the measurement of downhole outflow and oil production test,wells with oil output less than 1t per day should be considered to non-reservoirs.The statistic results show that non-reservoirs'GR≥3μR/h,and NG>5.1con.u.So the authors suggest that porosity is 2%,permeability is 1mD and GR>3μR/h,NG>5.1 condition unit should be taken as the dividing criterion between reservoir and non-reservoir.