Experimental Simulation On Monitoring The Distribution Of Magnetic Proppant In Hydraulic Fracture

Microseism method is one of the most common fracture diagnostic methods in oil&gas field.In view of microseism method which cannot provide proppant distribution and effective fracture parameters,a diagnostic of hydraulic fracture method based on magnetic proppant can make up for these disadvantages in principle and this method has a better application potential.Therefore,a kind of magnetic proppant with high magnetic susceptibility,stable performance was prepared to use in the diagnostic of hydraulic fracture and its normal properties and magnetic properties were tested.Using experimental simulation method,the effectieveness of diagnostic of hydraulic fracture with magnetic proppant was elvaluated,providing the theoretical foundation for feasibility of engineering application.Nano-Fe₃O₄ particles was prepared by chemical co-precipitation method.The particle size and saturation magnetization intensity as the index,the optimizing the reaction conditions through orthogonal experiments:Fe²⁺/Fe³⁺ratio 1.5:2;reaction temperature 50?;reaction time 1h.X-ray diffraction?XRD?and scanning electron microscope?SEM?analysis indicated nano-Fe₃O₄ particles composition of high purity,smaller and narrow particle size distribution about 25nm;Hysteresis loop test showed that nano-Fe₃O₄ particles have the property of superparamagnetism with saturation magnetization 56emu/g.On the basis,magnetic proppant was prepared by alternating assembly method and the optimal experiment parameters were as follows:nano-Fe₃O₄ particles concentration 5wt.%;PDADMAC concentration 3wt.%;reaction pH 10;reaction temperature 60?;alternate assembly number 3.According to the performance of the magnetic proppant:crushing rate of magnetic proppant is a little lower than conventional ceramsite proppant;apparent density and volume density of Magnetic proppant is increased;magnetic proppant has the property of superparamagnetism.On the basis,design experimental device used in the simulation monitoring research of the magnetic proppant distribution.Simulation results showed that:measuring the magnetic signal,magnetometer angle along the direction of the magnetic field measurement effect is best;distribution of magnetic anomaly profile has five distinct characteristics,according to the different positions of magnetic anomaly profile,it is concluded that the magnetic proppant distribution and extension;distribution of magnetic anomaly gradient appeared law of more closer to magnetic proppant,value of gradient is bigger,according to the change of the magnetic anomaly gradient profile curve,the distribution of magnetic proppant could be obtained;with buried depth of magnetic proppant increased,the magnetic signal decreased,the shape of magnetic anomaly profile curve from the narrow and sharp became wide and flat;based on the contour map of magnetic anomaly obtained the distribution of different magnetic proppant shape,etc.