Novel method for dipole shear wave remote detection azimuth discrimination

Key words:  dipole shear wave logging  remote detection technology  azimuth discrimination  experimental verification

Abstract:

The dipole shear wave remote detection instrument offers significant advantages such as low measurement frequency, wide frequency band, and a high signal-to-noise ratio. It can accurately characterize the attitude of geological structure near the borehole, making it especially effective in fracture-cavernous reservoirs and fault-controlled reservoirs of carbonate strata in northwest China, as well asin fault-fracture reservoirs of tight sandstone and shale strata in southwest China. However, realizing azimuth detection has been challenging due to the 180° azimuth uncertainty caused by the central symmetry of the dipolar source. To overcome this limitation, a novel method for azimuthal differentiation in dipole shear wave remote detection is proposed. Multi-component dipole data was acquired using dipole S wave remote detection logging tool with an asymmetric transmitters and receivers.The method involves conducting numerical simulations using finite differences and field tests. Additionally, a processing and interpretation software module is developed. The numerical simulations demonstrate that the method can selectively amplify the reflected shear wave amplitude of the reflector 's azimuth, enabling azimuth discrimination. Field test results align with the numerical simulations, confirming the method 's validity. This new approach provides robust support for azimuthal detection of geological anomalous bodies besides the well, as well as for the deployment of sidetracking wells and encrypted wells.