Numerical Simulation Study Of Isolator Properties Of Composite Structural Acoustic Isolator With Logging While Drilling

Acoustic Logging while drilling(LWD)technology is widely used in offshore drilling operations.Monopole source is often used in formation P-wave measurement,however,monopole can excite the drill mode waves propagating along the drill collar,affecting the measurement of longitudinal waves.In order to eliminate the effects of drill collar mode wave.In this paper,Composite structural acoustic isolator is designed on the basis of a single structure acoustic isolator.The structure consists of non-magnetic drill collar steel and rubber,adopts a double-cycle grooved structure.This paper mainly study the mechanical properties and isolator properties of this type of composite structural acoustic isolator under different geometric parameters and isolator properties under different environmental conditions.First,a single structural acoustic isolator was studied.A single structural acoustic isolator model was established to simulate the isolator properties of the isolator.Secondly,the mechanical properties of composite structural acoustic isolator were studied.The mechanical model of the composite structural acoustic isolator is established,calculating and analyzing the mechanical strength of composite structural acoustic isolator,connection thread strength and mechanical strength under different geometric parameters.The calculation results show that the mechanical strength of the composite structural acoustic isolator meets the design needs.Finally,isolator properties of composite structural acoustic isolators were studied.The paper deduces curves of groove structure theoretically and calculates the pass-band and stop-band of the Composite structural acoustic isolator with different geometrical parameters.ANSYS simulation results show: the isolator properties of the composite structural acoustic isolator of the rubber inner wall is better than the lead inner wall;the depth of the inner groove and the radius of the outer groove increase,isolator properties becomes better;circular arc radius of inner grooves has no effect on the time delay and has little effect on the isolator properties;the center spacing of grooves or the width different inner grooves increases,acoustic Attenuation performance of composite structural acoustic isolator is enhanced,and the delay time is basically unchanged.Fluid-structure interaction simulation results show that the external environment has no effect on the time delay of the composite structural acoustic isolator,but the acoustic attenuation of the acoustic isolator under the mud environment is greater.