Nuclear Magnetic Resonance T1-T2 Maps Identification and Evaluation Method of Formation Oil in Oil-Emulsion Drilling Fluid
The real-time discovery and accurate evaluation of oil-bearing properties of formation are affected by oil-emulsion drilling fluid.However,the quantitative accuracy of identification methods such as chromatography,mass spectrometry and spectrum without background value is low.One-dimensional T2 nuclear magnetic resonance(NMR)method requires two analyses before and after the addition of relaxation reagents.For this reason,two-dimensional NMR T1-T2 method was adopted to test the oil-emulsion drilling fluid,brine with different salinity,three types of refined oil and five types of crude oil,and the interpretation chart of water,base oil and formation oil in the oil-emulsion drilling fluid was established.The evaluation model of formation oil content in the oil-emulsion drilling fluid was established by testing the oil-emulsion drilling fluid with different crude oil content.The lower detection limit of T1-T2 method was determined to be 200～750 mg/L by the test of white oil with different qualities.The interpretation chart and evaluation model were proved to be reliable by experimental simulation and actual drilling.Therefore,two-dimensional NMR T1-T2 maps can easily and clearly distinguish base oil and formation oil in oil-emulsion drilling fluid,and help realize the timely discovery and visual identification of oil-bearing properties of formation.
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