ABSTRACT

Current technology of acoustic logging has been limited to monopole and dipole sources and receivers. The shear wave can be accurately recorded with this technique but has inferior results in softer formations. A method is presented for acoustic logging with many times the power of conventional technology for improved depth of investigation, and improved signal in soft formations. The technique uses electromagnetic transmitters to generate a broad band width signal. The formation propagates a particular frequency depending on how hard or soft the rock. This insures that a strong first arrival of shear wave is identified by the receivers. In addition to monopole and dipole, quadrupole transmitters and receivers are used in the configuration for logging through casing, which is discussed. Log examples are presented for hard, soft, and very soft formations from monopole, dipole and quadrupole sources both in open hole and cased hole. Interpretive techniques are discussed and applied to this data for the evaluation of porosity, rock mechanical properties, fracture detection, fracture prediction, correlation to shear seismic data, and hydrocarbon indication in clastics.

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