Research And Application Of NMR In Measurement Of Reservoir Physical

NMR analysis is to measure the nuclear magnetic resonance signal of the core sample by making use of characteristics that nuclear magnetic resonance occurs in hydrogen atom under a extra magnetic field, and to obtain porosity, permeability, oil saturation ,movable fluid saturation and other geological parameters.This technology overcomes the shortage of high cost and long test time of the conventional log interpretation and indoor core analysis,which has advantages of low usage, short time,low cost, accessing to many parameters, and high accuracy.the research and application of NMR can provide reliable and timely data to guide on-site drilling ,which has profound significance.Combined with conventional core analysis, this paper had verified the correctness of the measurement of porosity,permeability,oil saturation and other reservoir physical properties using NMR;combinating low permeability core data, NMR permeability formula of low permeability reservoir is improved by lots of calculation and fitting the formula coefficients, which has better feasibility for low permeability reservoir.Using nuclear magnetic resonance, the relationship among movable fluid ,porosity and permeability of sealed coring rock samples is valued in Ansai area in Changqing Oilfield.The results show that the movable fluid saturation is the key physical parameters in the evaluation of low permeability oil field .therefore, the potential of low-permeability oil field should not be evaluated directly by reservoir evaluation methods used in high-permeability , but should consider moving fluid .Based on deeply analysis of factors affecting NMR, experimental studies are carried out on influncing factors of NMR.The results show that:rock sample should be timely and representative.Concentration of Mn 2+ and soaking time have great impact on the oil saturation measurements ; oil and water signals can be distinguish at 20000 mg/L of Mn 2+ and 24 hours soaking time.Take sealed rock samples of Changqing Oilfield for example, combing core displacement experiments, the characteristics of water displacing oil and oil displacing water are studied by NMR on different types of wetting core samples.Take L well of Wuli Bay area in Changqing Oilfield for example,by application of NMR logging method, based on analysis of physical characteristics of reservoir, physical property of formation are evaluatioed qualitatively and quantitatively; based on movable fuild saturation and oil saturation, flooding zones are also valued combining with the fluorescent logging and rock wetting, based on the above evaluation and combining well testing, interpretation criteria and interpretation chart are established, which have a good results in practical application.