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U.S.A., Ordovician carbonate reservoirs are the very important yet difficult targets in the oil and gas exploration and development of Tarim basin, western China. The main task (also main challenge) of seismic is to image and predict the storage spaces of carbonate reservoirs-the secondary dissolved caves, holes and fractures, which are buried in more than 6500m deep. The target formations are usually in very low signal-to-noise ratio due to the seismic attenuation and the caves and fractures are small and aligned in random directions. Narrow azimuth and conventional wide azimuth seismic fail to image and identify the fracturedcavernous reservoirs accurately, leading to many drilling failures. Here, the effects of some key acquisition parameters such as bin size, fold and aspect ratio on carbonate reservoirs imaging accuracy are carefully examined using seismic forward modeling and new analysis methods. A high-density full-azimuth seismic acquisition was carried out based on the above analysis and the results show that small bin size has the advantage to imaging the ultra-deep carbonate reservoirs and the fracture prediction results from full azimuth data well agree with that from imaging well logging data. A set of well drillings based on the full azimuth data have been proved to be successful.

We propose a theoretical scheme in a cold rubidium-87 (87Rb) atomic ensemble with a non-Hermitian optical structure, in which a lopsided optical diffraction grating can be realized just with the combination of single spatially periodic modulation and loop-phase. Parity-time (PT) symmetric and parity-time antisymmetric (APT) modulation can be switched by adjusting different relative phases of the applied beams. Both PT symmetry and PT antisymmetry in our system are robust to the amplitudes of coupling fields, which allows optical response to be modulated precisely without symmetry breaking. Our scheme shows some nontrivial optical properties, such as lopsided diffraction, single-order diffraction, asymmetric Dammam-like diffraction, etc. Our work will benefit the development of versatile non-Hermitian/asymmetric optical devices.

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