摘要：The exploration and development of oil and gas fields gradually turned to low permeability reservoirs.Changes in reservoir petrophysical properties and pore fluid properties can cause varying degrees of reservoir sensitivity.Petrophysical properties and reservoir sensitivity are the core evaluation factors for the development of tight oil reservoirs,and they are directly related to the degree of oil and gas enrichment and development effects in the reservoir.In this paper,taking the Zhidan Oilfield in the Ordos Basin as an example,the petrophysical properties and reservoir sensitivity characteristics of tight oil reservoirs in the Upper Triassic were systematically analyzed.The research results show that the tight sandstones of the Chang 3,Chang 4+5 and Chang 6 oil reservoirs vary greatly in porosity and permeability,and the reservoir has strong heterogeneity.The average porosity of Chang 3,Chang 4+5 and Chang 6 Members are 9.96%,8.94% and 8.74%,and the average permeability is 6.69 mD,4.34 mD and 3.29 mD,respectively.There is a good positive correlation between rock porosity and permeability.We introduced a stress sensitivity evaluation parameter Rk (permeability relative damage rate) to describe the stress sensitivity of the target layer.The calculation results show that the Rk of Chang 3,Chang 4+5,and Chang 6 Members are mainly distributed between 0.2 and 0.25,and their stress sensitivity is in a moderately weak level.The average Rk of Chang 3,Chang 4+5 and Chang 6 Members are 0.231,0.234 and 0.237,respectively.Therefore,the stress sensitivity of Chang 6 is greater than Chang 4+5 and Chang 3 Members.This shows that the better the petrophysical properties of the reservoir,the weaker its stress sensitivity.
