Insight into skywave theory and breakthrough applications in resource exploration

Skywave refers to the electromagnetic wave reflected or refracted from the ionosphere and propagate in the form of a guided wave between the ionosphere and the Earth's surface. Since the skywave can propagate over large distances, it has been widely used in long-distance communication. This paper explores and demonstrates the feasibility of skywave for deep resource and energy exploration at depths up to 10 km. Theoretical and technical advancements were accomplished in furthering the skywave applications. A new solution method based on Green's function has been developed to study skywave propagation in a fully coupled lithosphere-air-ionosphere full space model. The model allows one, for the first time, to study skywave distribution characteristics in the lithosphere containing inhomogeneity such as ore deposits or oil and gas reservoirs. This model also lays a foundation for skywave data processing and interpretation. On a parallel line, we have developed a multi-channel, broadband, low-noise, portable data acquisition system suitable for receiving skywave signals. Using the skywave field excited by a high-power fixed source located in the central China, actual field surveys have been carried out in some areas in China including the Biyang depression of Henan Province. The initial results appear encouraging – The interpreted resistivity models prove to be consistent with those of seismic exploration and known geological information, and the exploration cost is only about 1/4 to 1/10 of seismic surveys. These initial successful applications of the skywave theory lay a solid foundation for further verification of the new method.

Seismic prediction of lithofacies heterogeneity in paleogene hetaoyuan shale play, Biyang depression, China

Shale lithofacies identification and prediction are of great importance for the successful shale gas and oil exploration. Based on the well and seismic fine calibration, extraction, and optimization of seismic attributes, root mean square (RMS) amplitude analysis is used to predict the spatial–temporal distribution of various lithofacies in the fifth organic-matter-rich interval, and the prediction results are confirmed by the logging data and geological background. The results indicate that in the early expansion system tract, dolomitic shale and calcareous shale were widely developed and argillaceous shale, silty shale, and argillaceous siltstone only developed in the periphery of deep depression. With the lake level rising, argillaceous shale and calcareous shale were well-developed, and argillaceous shale interbedded with silty shale or argillaceous siltstone developed in deep or semi-deep lake. In the late expansion system tract, argillaceous shale was widely deposited in the deepest sag; calcareous shale presented in eastern sag with belt distribution.