The Comprehensive Application Research Of NMR Mud Logging In Jiangsu Oil Field

NMR mud logging have realized rock physics analysis from laboratory to drilling site, and have advantages of simplicity,rapidity,low requirement for sampling,ect. It also has great meaning to reservoir evaluation, direct field drilling and well completing test and discussion, and offers an effective technique and measure.This paper have introduced the theory of NMR logging, NMR relaxation mechanism and spectrum-decomposition method at first, and analyzed the method of SVD and SIRT in detail. The NMR measurement was influenced not only by the parameters of instrument measurements, but also the property of the samples, salinity and so. Making clear the influential factors can help to improve our analysis precision and evaluating level.NMR logging has special advances in distinguishing the movable and irreducible fluid. However, NMR logging cannot obtain these parameters directly, and we must calculate instead.T2cutoff is a very important value during this process, and the accurate aetermination of it is a key to evaluate reservoir. In this paper, we have analyzed the sensitivity of T2cutoff at first, and then, put forward a new method that making use of T2 geometric mean(T2g)to make sure T2cutoff, and checked out this new method by evaluating irreducible water saturation. The result proves that the method is feasible. At the end of this paper, we have discussed the applicability of the model in oil-bearing core that established by this method, and found that this model can perform a high accuracy when oil saturation is less than 30%,.But with the increasing of the oil saturation,the deviation of the model has increased,and the reasons is analyzed then.Generally speaking, we use two or three times measure means to obtain oil saturation (So) of NMR cuttings logging. However, because of the drill fluid's flushing, the cuttings'So usually lose seriously. Then, we must do some correction.NMR T2 distribution can reflect the percolation of pore structures well, and T2 distribution and mercury injection curve can change mutually. This paper uses T2 geometric mean (T2g) to calculate porosity exponent(m) in Archie's formulas.This way not only overcomes the drawback of complex reservoir constant selecting when we carry out reservoir evaluation, but also distinguishes the complex degree about reservoir's pore structure through the value of m. Finally, this paper uses many distinguishing methods, including all kinds of cross-plot which can reflect the properties of reservoir and characteristics of liquid, and selects 5 representative examples in Jiangsu oil field to carry out reservoir evaluation.The result is excellent.