Study On The Influence Of Drill Collar Waves In The Exploration Of Fractured Reservoir Using An Impulse Source

With the deepening of oil and gas exploitation and development,people have gradually shifted the goal of exploitation to the cracks that control the distribution of oil and natural gas.In recent years,the sound wave depth detection technology based on plasma impulse sound source has a very significant advantage for detecting cracks,but the plasma impulse sound source is a monopole sound source,which must eliminate the interference of the collar waves propagating along the drill collar when logging while drilling.In order to reduce the interference of collar waves,this article first studied the influence of different formations,different sound source frequencies and borehole size on the amplitude of collar waves.The results show that the best excitation frequency of the impulse sound source is 8k Hz when detecting in fast and slow formations.At this time,the impact of the collar waves on the reflected longitudinal wave is minimal.At the same time,the size of the borehole will affect the amplitude of the indirect collar wave reflected from the borehole wall,which will cause the amplitude of the collar waves to decrease first and then increase with the increase of the borehole diameter.Secondly,four methods of restraining collar waves were analyzed,and the analysis showed that only two methods,groove cutting and physical calibration,were feasible when using impulse sound source to detect formation.The physical calibration method was used to simulate the restraining of collar waves,which proved that the longitudinal wave velocity of formation could be extracted by this method when using impulse sound source to detect formation.Finally,the influence of grooving method to suppress collar waves on the detection of fractures with different shapes and different fillings was simulated by finite element method.The results show that the grooving can affect the Stoneley wave,the reflected Stoneley wave and the reflected compressional wave in different degrees,and the grooving can change with the change of the detected object,so the fixed compensation formula cannot be used to compensate.Therefore,the choice of grooving to remove the collar waves in the exploration of fractured reservoir will inevitably bring unpredictable errors,and the physical calibration method is an effective solution after establishing the corresponding physical model by studying various factors that affect the excitation amplitude of the collar waves.