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天然气水合物稳定带下方游离气分布模式、气体含量及其对水合物富集成藏的指示是水合物研究中的难点,而利用振幅随偏移距变化(Amplitude Versus Offset,AVO)与岩石物理模型能够对游离气含量进行地震定量解释.我们对印度Krishna-Godavari(K-G)盆地的地震资料进行了叠前保幅处理,在测井数据和层位标定的基础上,基于等效介质岩石物理模型和AVO正演模拟定量估算了NGHP01-10A井的游离气饱和度,发现水合物下方的游离气饱和度与其分布模式有关.游离气呈均匀分布时饱和度为孔隙空间的0.3%~0.4%,而块状分布时为3%~4%,该结果与NGHP01-10D实测计算的泊松比交汇分析结果吻合很好.最后再根据干燥岩石骨架的泊松比反演结果进一步判断游离气分布为均匀分布,其饱和度为0.3%~0.4%.
Free gas distribution pattern, gas content and its indication of hydrate accumulation in gas hydrate stability zone are the difficulties in the study of hydrate. However, the use of Amplitude Versus Offset (AVO) and petrophysical model The seismic data of the Krishna-Godavari (KG) basin in India can be prestacked for amplitude preservation. Based on the logging data and horizon calibration, the seismic data of the Krishna-Godavari (KG) basin in India based on the equivalent petrophysical model And AVO forward modeling to quantitatively estimate the free gas saturation of NGHP01-10A well, it is found that the free gas saturation below the hydrate is related to its distribution pattern.The saturation of free gas is 0.3% ~ 0.4% of the pore space when it is evenly distributed, While the block distribution is 3% ~ 4%, which is in good agreement with the results of Poisson’s ratio calculated by NGHP01-10D.Finally, the distribution of free gas is further judged according to the results of Poisson’s ratio inversion of dry rock skeleton Uniform distribution, the saturation of 0.3% to 0.4%.