Study Of NMR Core Experiment Variable T2 Cutoff Value And Application Study Of Reservoir Assessment

Variable T2 cutoff value of NMR logging is a very important parameter, change change T2 cutoff for determining reservoir parameters calculation, vital reservoir evaluation, this article is for rock Tarim Basin NMR experiments were analyzed to determine the dynamics of T2 cutoff. Get dynamic T2 cutoff to accurately calculate the movable porosity and permeability, irreducible water saturation and other important reservoir parameters, thereby to divide the reservoir, deliverability forecast.According to rock types, physical properties and quality of experimental data sources were studied using two methods T2 cutoff parameter method and form of law. Different lithologies, the paper is divided into clastic and carbonate rocks; experimental data according to different sources, the paper is divided into Geophysical Laboratory Tarim reservoir data and laboratory data Yangtze University. Press was good or bad, this article is divided into high porosity, low porosity. Before determining variable T2 cutoff value, this paper NMR irreducible water saturation with conventional core irreducible water saturation comparison, excluding the error is more than 10% of the rock sample points. Is the rock experimental T2 cutoff error is greater than 10% of the rock samples removed to ensure the accuracy becomes T2 cutoff research.Parametric method using magnetic resonance effective porosity, permeability, T2 geometric mean, comprehensive physical parameters to find the best correlation with T2 cutoff. Wherein the geometric mean T2 and T2 cutoff value the best correlation, correlation coefficient of 0.56. Among porosity of 12% for the sector into high porosity and low hole. The correlation coefficient of 0.69 with high porosity; the correlation coefficient was 0.28 lower hole. Description high and low porosity and pore established correlation significantly worse, illustrate the complexity of low porosity, affecting factors, the need for further classification of building relationships.Morphology is the analysis of each rock sample T2 spectrum shape, and T2 cutoff position on the T2 spectrum to determine the dynamics of T2 cutoff. Depending on the number of T2 peaks, we divided into singlet, doublet, triplet analysis. Unimodal T2 spectrum analysis according to different classified position on the T2 spectrum; according to two peak to peak position, size classification analysis bimodal T2 spectrum; triplet T2 spectrum based on three peaks peak position, size, and T2 spectrum valleys to classify the analysis position. T2 spectrum of different forms, with different methods to determine the variable T2 cutoff value.Wherein the method is superior shape parameter method, which eliminates the different logging instruments and laboratory instrument performance, measure the impact of different environments.T2 cutoff by the variable parameter method and the method to determine the form of movable calculate porosity, permeability, irreducible water saturation. These three reservoir parameters and coring data is corrected to determine a correction factor. Then movable to divide the porosity and permeability reservoir productivity prediction. In the movable porosity of 4% and 1% penetration limit, to divide the reservoir. Movable than 4% porosity, permeability greater than 1% of a class of the reservoir, the daily output of more than 10 parties; movable porosity of less than 4% penetration rate of less than 1% for the two types of reservoir, less than 10 cubic meters per day.