海上时移地震中多道匹配的观测系统重复性研究

Matched multi-trace geometry repeatability for time lapse seismic

观测系统的重复性是时移地震的关键问题.而对于全面评价,多道重复性度量又是很有意义的.基于归一化均方根差异计算方法,地震多道数据的重复性一般为单道数据重复性的加权均方根.针对海上拖缆监测数据与基线数据多道匹配不确定的问题,采取了定向最佳匹配原则和失配虚拟技术方法.基于地震数据重复性与观测系统重复性的线性相关模型,研究了时移地震观测系统的多道加权均方根重复性特征.结合实际数据研究表明,基于面元的观测系统最佳定向匹配的多道加权均方根重复性基本反映全部观测系统的重复性和覆盖程度.

Time-lapse, or 4D, seismic technology is tool to monitor underground change for oil field maximum recovery or other purpose especially associated to human being activities. Repeatability is a key issue for time-lapse seismic and geometry repeatability is a fundamental element to essentially affect the repeatability. There were many practices to improve repeatability during data processing, but geometry repeatability needs to be acquired during monitor data acquisition phase. Theory and practice shows geometry has been determined in acquisition cannot be improved in processing. Thus, geometry repeatability analysis is important. Multi-trace geometry repeatability rises from practical situation. Multi-trace geometry repeatability is important for overall geometry repeatability evaluation. Forthgoers evaluate difference or repeatability of time-lapse seismic data by normalized rms difference （NRMS）. The definition of multi-trace repeatability can be derived from NRMS for time-lapse seismic/4D seismic data, showing that multi-trace repeatability is weighted RMS of all single traces. Noting that the uncertainty of the match between Monitor data and Baseline data and that probable data size difference between Monitor and Baseline, the repeatability of the best baseline-based match with imaginary data for mismatch was employed. Derived from forthgoersr researches, the linear model of relation between seismic data repeatability and geometry repeatability was established, and the weighted RMS geometry repeatability of the best baseline- based match with extrapolation for mismatch was obtained as the equivalent of the repeatability of the best baseline-based match with imaginary data for mismatch. The weighted coefficient is determined on the basis of NMO and its stretch. Application study was also conducted based on real data to demonstrate that the new geometry repeatability can be utilized to valuate geometry repeatability during 4D monitor seismic data acquisition. The application study showed that one display of the multi-trace geometry repeatability upon best baseline-based match with extrapolation for mismatch can indicate repeatability and effect of fold of coverage simultaneously. The calculation in application was simplified for speed improvement, which is not yet the main point in this article.