oa The Role of Non-Seismic Methods in ear-Surface Solutions: Applications of Seismic-Gravity Joint Inversion and Redatuming in South Rub Al-Khali, Saudi Arabia

Onshore seismic data from the Middle East are adversely affected by near surface and intermediate<br>depth velocity anomalies. The correct estimate of the near-surface velocity field is fundamental to<br>obtain reliable seismic images. Conventional velocity model building workflows based on refracted<br>arrivals (i.e. First Breaks - FB) fail to appropriately reconstruct the shallow velocity complexities in the<br>presence of large velocity inversions, sharp lateral velocity changes and noisy FB. In such cases, the<br>integration of seismic with additional geophysical measurements (i.e. gravity-EM) can solve the shallow<br>velocity modeling problem. Simultaneous Joint Inversion (JI) is an elegant and analytic method to<br>address geophysical data integration. It is implemented in this paper for velocity model building in<br>South Rub Al-Khali by taking advantage of the availability of high-resolution gravity data coincident<br>with the seismic acquisition. The analyzed 2D seismic lines are sampling different near-surface geologic<br>conditions such as dunes, sub-cropping carbonates and karsts. This corresponds to various degrees of<br>complexity in the near surface velocity field and related distortions introduced in the seismic image<br>when a conventional “statics” approach is used. An alternative approach to statics solutions is then<br>explored by simultaneous JI of FB and gravity data residuals for the shallow velocity and density fields.<br>Pre-stack wave-equation redatuming (WED) is then used to model and remove the effects of complex<br>velocity patterns from the seismic data. Various degrees of improvement are obtained with the<br>discussed workflow depending on the severity of the near-surface velocity complexities and shallow<br>geologic conditions. The analysis of the results allows to identify specific roles for non-seismic methods<br>for the solution of near surface problems in land seismic data processing.