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综合利用了各种地震方法来估计位于委内瑞拉西南部的碳酸盐岩储层中的裂缝方位。具体方法包括:对沿三个不同方位采集的2D P-S数据作2D旋转方析,对同样三个方向的2D P-波数据作AVO分析,并对同一2D数据作NMO分析,同时还对在同一区块记录的3D P-波数据分别作3D方位AVO分析及NMO分析。 将几种方法的结果分别与在本区块4个不同位置由地层微扫描仪得到的测井数据求得的裂缝方位、最大水平应力的区域及局部测量值及穿过该区域的主断层的列线作了比较。 由P-S波数据求得的裂缝方位与最大水平应力的区域走势一致,并与在碳酸盐岩储层周围的井中得到的裂缝方位吻合。方位AVO分析得到的区域走势与P-S波数据分析结果相似,但分辨率要低些。由3D AVO分析推导出的裂缝方位的局部变化与构造的局部变化密切相关。相反,由于受多种因素(包括上覆地层的方位各向异性及横向非均质性)的影响,对3D P-波数据作方位NMO分析得到的方位与其他方法结果不同。目前断言哪种方法进行裂缝描述更适合、更可靠,尚为时过早,因为它取决于从局部地质条件到采集新资料所需的额外成本等因素。
Synthetic utilization of various seismic methods has been used to estimate the fracture orientation in carbonate reservoirs located in southwestern Venezuela. Specific methods include 2D 2D rotation analysis of 2D PS data acquired along three different orientations, AVO analysis of 2D P-wave data of the same three directions and NMO analysis of the same 2D data, Block recorded 3D P-wave data for 3D azimuth AVO analysis and NMO analysis. The results of several methods are respectively compared with the fracture orientation, the region of maximum horizontal stress and the local measured values obtained from the well logging data obtained by the formation micro-scanner at four different locations in the block, Column lines were compared. The fracture orientation obtained from the P-S wave data is consistent with the regional maximum horizontal stress and coincides with the fracture orientation obtained in the wells surrounding the carbonate reservoir. The regional trend of AVO analysis is similar to that of P-S wave data, but the resolution is lower. The local changes in fracture orientation derived from the 3D AVO analysis are closely related to the local changes in the structure. In contrast, azimuthal NMO analysis of 3D P-wave data results in different orientations than other methods due to the effects of many factors, including azimuthal anisotropy and lateral heterogeneity of the overburden. It is premature to assert which method of fracture characterization is more appropriate and reliable at present as it depends on factors such as the extra cost required from the local geological conditions to the acquisition of new data.