用于岩性预测的地震方法

SEISMIC METHOD FOR LITHOLOGY PREDICTION

南海西部石油公司计算中心

Computer Cent re of Petroleum Corporation, Western S. China Sea

本文讨论了一种适用于海上岩性预测的地震方法。在精细处理海上地震资料的基础上,采用两步子波反褶积把CDP道集处理为相对反射系数道集;然后做三点共偏移距叠加,拾取预测层相对反射系数随偏移距变化的数据,经归一化处理后作为Zoeppritz方程中纵波反射系数的实测值;再根据地震信息提供的层速度、密度等参数计算理论值。当实测值与理论值达到最佳逼近时,通过两步精度控制进行迭代逼近,估算介质的泊松比,并在相邻预测点进行统计综合,取其最佳值。利用修正后的Gassaway岩性量板,在某海区进行多例的岩性预测,成功率达75％以上。

In this paper, a teachnigue was developed for predicting lithology in offshore seismic exploration. On the basis of fine processing for the data from such exploration,the COP gather could be transferred to the gather of reflectivity by using the 2 - step wavelet deconvolution. Then, carrying out the 3 - point common offset stack, extracting the information about the relative reflectivity of the layer predicted tarsus the offset. After normalization, such reflectivity will be taken as the measured value of the P-wave reflectivity used in the Zoeppritz’s equation. The theoretical value was obtained from the information such as the interval velocity, the density of the rock, etc. by calculation. The optimal value was obtained from iteration by 2-step accuracy controlling, the Poisson’s ratio estimation for the medium, and the statistical integration at the adjacent measuring points on condition that the optimal approximation between the measured value and the theoretical value was reached. By using the Gassaway lithology template modified,lithology prediction for offshore seismic data was made and the hit-rate is up to more than 75%.