Study On Logging Evaluation Method For Low Contrast Reservoir

With the development of oil and gas exploration,low contrast oil reservoirs have currently become a hot spot of exploration.The forming reasons of low contrast oil reservoirs are complex,and the contrast of oil and water logging is low,which brings great difficulty to log interpretation.Before the low contrast oil reservoirs only include low-resistivity oil layer,but with the development of technology,based on the study of the tight reservoir in the area of Daqingzi well,the results show that the response characteristics of tight reservoir and dry layer are very similar,and the qualitative identification is difficult,so the tight reservoir is also divided into low contrast oil reservoirs.Through the study of the formation mechanism of low-contrast oil reservoirs in the area of Daqingzi well,then a set of effective logging evaluation and recognition system was proposed.The paper briefly summarizes the geological characteristics of the study area,the mechanism for the formation of low contrast oil layer in the study area was clarified,carrying out researching the identification method,and the following conclusions were got:(1)The low resistivity reservoir is characterized by shallow lithology,high water saturation of the binding water,high salinity of the formation water and low amplitude,while the tight oil layer is greatly affected by compaction,carbonate cementation and pore structure.(2)low resistance oil layer is generally:medium and high value of acoustic,low density,low resistivity and oil,water layer resistivity difference is small.Tight oil layer is:low value of acoustic,high resistivity,oil layer and dry layer of physical properties and electrical characteristics have small differences.(3)Difference method of apparent natural potential,the overlap method of double porosity,the apparent formation water resistivity and the nuclear magnetic resonance method can effectively identify the low resistance oil layer;oil index method,resistivity overlap method,double water saturation overlap method and nuclear magnetic resonance method to identify the tight reservoir has a higher accuracy.(4)Archie formula,variable m value method,and Indonesian formula to calculate oil saturation and compare with actual production data has found that the oil saturation of the lowresistivity reservoir is calculated by using the Indonesian formula having got better results;tight oil reservoir prefers the variable m value method and get high accuracy.