Abstract: [Objective] The platform area in the Tarim Basin contains enormous hydrocarbon resource potential in ultra-deep (>6000 m) carbonate reservoirs. Efficient exploration and development of these resources require breakthroughs in four key areas: prediction of the thickness of major source rocks, characterization of the distribution of strike-slip faults, prediction of high-quality ultra-deep reservoirs, and detection of ultra-deep hydrocarbon accumulations. However, the great burial depth and strong heterogeneity of the reservoirs, poor seismic source and receiver conditions associated with the extensive desert terrain, severe seismic attenuation, and the complex distribution of subsurface igneous intrusions result in low signal-to-noise ratios, poor resolution, and limited imaging accuracy of ultra-deep seismic data, thereby hindering reliable reservoir prediction. This study aims to establish a systematic seismic technology framework for the exploration of ultra-deep carbonate hydrocarbons in the platform area and to overcome these key technical challenges. [Methods] In response to the four major technical challenges, four core seismic technologies were developed. (1) Energy enhancement and noise attenuation technology, consisting of ghost-reflection-focusing source excitation, small-aperture square-array combined reception, weak-signal enhancement in the curvelet domain, and inverse scattering series method for interbed multiple suppression; (2) fidelity-preserving bandwidth extension technology, consisting of high-velocity-layer excitation, low-frequency geophone acquisition, and wavelet-based consistency correction using the recorded wavelet; (3) energy focusing and accurate positioning technology, consisting of 3D wide-azimuth, high-density, small-bin, long-offset seismic acquisition, refined migration-velocity modeling incorporating igneous intrusions such as volcanic rocks, detailed Q-field modeling, and Q-compensated reverse-time migration; and (4) seismic decoupling mapping technology, consisting of seismic decoupling mapping of strike-slip fault systems, source-rock thickness, ultra-deep reservoir properties, and ultra-deep fluid properties. [Results] The proposed seismic technology framework has achieved significant results in its application to the Tabei Depression. (1) Ultra-deep strike-slip faults have been transformed from weak and indistinct reflections into clearly identifiable seismic features, substantially improving fault interpretation; (2) the prediction error for the thickness of the major source rock, the Lower Cambrian Yu'ertusi Formation, has been constrained to within ±10 m; (3) the coincidence rate of predicted high-quality ultra-deep carbonate reservoirs exceeds 85%; and (4) the accuracy of ultra-deep hydrocarbon detection exceeds 80%. [Conclusion] These advances led to the discovery and efficient delineation of the Fuman ultra-deep giant oil and gas field in the Tabei Depression, with proved reserves reaching the billion-ton level and an ultra-deep oil and gas production base with an annual production capacity of approximately 5 million tons having been established.
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