油气藏的多物理、多尺度探测方法和理论研究

Elastic wave (including seismic and sonic wave) and electromagnetic wave measurements are the most effective exploration methods for deep hydrocarbon reservoirs, but both have their own advantages and disadvantages: Elastic wave methods have higher vertical resolution, but are difficult to distinguish oil from water zones; electromagnetic methods, on the other hand, can readily distinguish oil/gas from water, although their resolution is lower. Therefore, developing a joint inversion method to combine these measurements can significantly improve the precision of hydrocarbon reservoir exploration. This project will investigate the joint inverse scattering methods to combine elastic wave and electromagnetic wave measurements for hydrocarbon exploration; it will incorporate large-scale yet lower resolution surface survey methods with small-scale but higher-resolution sonic and electromagnetic well logging measurements, as well as the intermediate-scale well-to-surface and well-to-well measurements. The challenges in developing such a multiphysics, multiscale joint inversion technology include: strong nonlinearity, high degree of non-uniqueness or ill-posedness, and high complexity in high-frequency field solutions. This project will utilize the petrophysical relationships and structural relationships to link elastic wave measurements with electromagnetic measurements in the development of the mathematical model on the joint inverse scattering; the forward problem solution technology will be based on a highly effective multiscale domain decomposition method; multifrequency, multiphysics data will be utilized to alleviate the nonlinearity and under-determinacy of the inverse scattering problem. The joint inverse scattering of elastic wave and electromagnetic waves will directly provide the information of oil/gas saturation in the porous medium, thus is highly valuable for the exploration of deep hydrocarbon reservoirs and for secondary recovery. .This special grant for one year is the preliminary project for the above full project.

弹性波（包括地震波、声波）和电磁波测量是油气勘探最有效的物探方法，各有优劣且互为补充：弹性波测量法垂向分辨率高，但难于区分油、水区域；电磁波测量法分辨率较低，但油、水区分能力强。因此，研究两者的联合反演方法可极大地提高深层油气勘探的准确度。本项目将结合大尺度、低分辨率的地表勘探，小尺度、高分辨率的声波、电磁测井，以及中尺度的井对地测量和井对井测量，用以研究基于弹性波、电磁波数据联合逆散射的物探新理论和新方法。需要解决的挑战性问题有：强非线性、高度病态性及高频场求解的海量计算等。本项目将引入岩性关系、结构关系,建立弹性波和电磁波的耦合方程，并发展联合逆散射的数学模型；研究发展多尺度区域分解法实现多物理耦合方程正问题的高效求解；在此基础上,采用多频率、多物理数据来减小逆散射的非线性和不适定性。联合弹性波-电磁波逆散射方法可直接得到孔隙介质的油气饱和度信息，对深层油气勘探、二次开采具有极大价值。.本专项项目是上述“重点项目”的预研部分,研究时间为一年。

油气勘探中弹性波(包括地震波和声波)和电磁波测量是最有效的物探方法, 弹性波测量具有高分辨率，而电磁测量容易区分含水区与含油区，两种方法各有优劣且相互补充。本项目结合大尺度、低分辨率的地表勘探，小尺度、高分辨率的声波、电磁测井，以及中尺度的井对地测量和井对井测量, 引入岩性关系、结构关系,建立弹性波和电磁波的耦合方程，并发展联合逆散射的数学模型；研究发展多尺度区域分解法实现多物理场耦合方程正问题的高效求解，并有效地解决强非线性、高度病态性及海量数据计算问题。最终基于弹性波、电磁波特性开发一个集地震、电磁及测井数据为一体的多物理、多尺度的全波反演平台，更加精细、准确的描述油气藏结构及孔隙介质的油气饱和度信息。. 本专项项目是上述“重点项目”的预研部分,研究时间为一年。其主要内容是研究弹性波正演的新方法和新理论，并针对正演问题的计算速度等性能改进算法，提高完美匹配层的吸收效果以解决地震波的独立逆散射问题；通过正问题的数值模拟及实验验证确定正向求解器的精度与效率，推广地震波正演方法在实际勘探工程的应用。对于电磁波反演问题，运用探地雷达的试验数据加以验证，并将算法应用于地下目标探测，提高算法的效率。项目组在计划的研究方向上做了深入研究，特别对弹性波时域伪谱(PSTD)及有限差分(FDTD)方法在各向异性介质及自由表面地形等环境中的正演求解算法有了新的认识，并对 SPECFEM3D 软件做了初步的分析和调试，为下一步发展高精度矢量谱元方法做基础，以期融合有限元适应任意复杂介质模型的韧性和时域谱元法(SETD)的精度，从而高效求解弹性波正演问题。项目的研究不仅提升弹性波在非均匀有限差分中吸收边界条件精确、高效的求解能力，以指导改进算法的性能;且对电磁波各向异性介质区域分解法中的分界面上利用迭代法计算耦合矩阵，发展了正问题求解的高效算法并实现快速计算。