The frequency-weighted-exponential (FWE) function was designed to fit various asymmetric amplitude spectra by two parameters: symmetry index and bandwidth factor. A relation can be built between the FWE function and the Q-factor of media. When a source wavelet propagates in attenuating media, the FWE function is used to fit the amplitude spectra of the source and attenuated wavelet to obtain the symmetry indexes and bandwidth factors. After recalculating the bandwidth factors based on the average of the symmetry indexes, the Q-factor can be estimated by the decrease in the bandwidth factor between the source and attenuated wavelet. Compared with the existing commonly used methods, this method applies to various source wavelet types, and it has better tolerance to random noise. On this basis, we further evaluated an approach to invert the interval Q-factor from seismic reflection data. We used the FWE function to fit the local spectral contents of the interval seismic reflection data to obtain the symmetry indexes and bandwidth factors. After recalculating the bandwidth factors with the average of the symmetry indexes, the reciprocal of the bandwidth factor versus traveltime was linearly fit, and then the Q-factor can be calculated from the slope. This approach has high accuracy without having to correct for the tuning effect when the attenuation is high. It is suitable for different types of synthetic seismic traces and also produces good results in a field-data case study.

Most depth extrapolation schemes are based on a one-way wave equation, which possesses limited ability to provide the true amplitude values of reflectors that are highly important for amplitude-versus-offset inversion. After analysing the weaknesses of current migration methods and explaining the reason why wavefields cannot be extrapolated using the full-wave equation in the depth direction, a full-wave-equation migration method based on a new seismic acquisition system is proposed to provide accurately dynamic information of reflection interfaces for migration. In this new seismic acquisition system, double sensor data are provided to solve the acoustic wave equation in the depth domain accurately. To test the performance of recovering the true amplitudes of the full-wave-equation migration, we used a single shot gather and several multiple shot gathers produced by a 2-D numerical modelling technique to demonstrate that our methodology provides better estimated true amplitudes than that of the conventional Kirchhoff and reverse time migration algorithms through comparison of the amplitudes of the target reflectors with its theoretical reflection coefficients. Because double sensors are applied to implement the full-wave-equation migration, it is necessary to study the perfect distance between the double sensors to diminish the migration error for future practical exploration. Based on the application of the full-wave-equation migration method to the first set of actual seismic data collected from our double sensor acquisition system, our proposed method yields higher imaging quality than that of conventional methods. Numerical experiments and actual seismic data show that our proposed method has built a new bridge between true amplitude common-shot migration and full-wave-equation depth extrapolation.

To meet the requirement of true-amplitude migration and address the shortcomings of the classic one-way wave equations on the dynamic imaging, one-way true-amplitude wave equations were developed. Migration methods, based on the Taylor or other series approximation theory, are introduced to solve the one-way true-amplitude wave equations. This leads to the main weakness of one-way true-amplitude migration for imaging the complex or strong velocity — contrast media — the limited imaging angles. To deal with this issue, we apply a matrix decomposition method to accurately calculate the square-root operator and impose the boundary conditions of the one-way true-amplitude wave equations. Our migration method and the conventional one-way true-amplitude Fourier finite-difference (FFD) migration method are used by us to test and compare the imaging performance. The impulse responses in a strong velocity-contrast model prove that our migration method works for larger imaging angles than the one-way true-amplitude FFD method. The amplitude calculations in a strong-lateral velocity variation media with one reflector and in the Marmousi model demonstrate that our migration method provides better amplitude-preserving performance and offers higher structural imaging quality than the one-way true-amplitude FFD method. We also use field data to indicate the imaging enhancement and the feasibility of our method compared with the one-way true-amplitude FFD method. Our one-way true-amplitude migration method using matrix decomposition fully exploits the features of one-way true-amplitude wave equations with less approximation, and it is capable of producing more accurate amplitude estimations and potentially wider imaging angles.

The Hong-Che Fault Zone is one of the important oil and gas enrichment zones in the Junggar Basin, especially in the Carboniferous. In recent five years, it has been proven that the Carboniferous volcanic rock has 140 million tons of oil reserves, and has built the Carboniferous volcanic reservoir with a capacity of million tons. Practice has proven that the volcanic rocks in this area have great potential for oil and gas exploration and development. To date, Carboniferous volcanic reservoirs have been discovered in well areas such as Che 32, Che 47, Che 91, Chefeng 3, Che 210, and Che 471. The study of drilling, logging, and seismic data shows that the Carboniferous volcanic reservoirs in the Hong-Che Fault Zone are mainly distributed in the hanging wall of the fault zone, and oil and gas have mainly accumulated in the high part of the structure. The reservoirs are controlled by faults and lithofacies in the plane and are vertically distributed within 400 m from the top of the Carboniferous. The Carboniferous of the Hong-Che Fault Zone has experienced weathering leaching and has developed a weathering crust. The vertical zonation characteristics of the weathering crust at the top of the Carboniferous in the area of the Che 210 well are obvious. The soil layer, leached zone, disintegration zone, and parent rock developed from top to bottom. Among these reservoirs, the reservoirs with the best physical properties are mainly developed in the leached zone. Based on a comprehensive analysis of the Carboniferous oil and gas reservoirs in areas of the Chefeng 3 and Che 210 wells, it is believed that the formation of volcanic reservoirs in the Hong-Che Fault Zone was mainly controlled by structures and was also controlled by lithofacies, unconformity surfaces, and physical properties.