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This study summarizes the efforts taken to provide reliable structural delineations offshore the northern United Arab Emirates, an area where previous attempts failed to provide purposeful results. With the employment of latest acquisition and processing techniques, a new high-density full azimuth volume shows clear uplift over legacy results. Structures never detected before are imaged, contributing to the de-risking of future well placement. These results are indicative of the challenges when acquiring and processing seismic data in the Northern Emirates. The use of latest technologies was required to overcome several geophysical challenges, such as complex near surface, near-vertical thrust sequences and multiple faulting planes. All these elements contributed in generating extreme noise contamination, where a fast-varying geology with high dips made separation of primaries from noise one of the most difficult tasks. Key pre-imaging technologies such as near surface characterization, 5D regularization to radial symmetry, as well as a tomographic velocity model building approach with iterative inputs from interpreters have been fundamental to converge to a solid velocity model that allows for a reliable structural imaging. The work is particularly relevant for offshore exploration targets in the Northern Emirates, a region that has recently seen a growth in interest from local and international operators.

A 14,000 sq. km surface seismic survey was acquired onshore Abu Dhabi in recent years. With around 170 billion traces, it is the largest land survey shot in the UAE and one of the largest processed globally to date. We present here the methodology in processing this dataset to derive a high-resolution volume that surpasses benchmarks from previous exploration campaigns. A detailed near surface model and related statics have been derived using Data-driven Image-Based Statics (DIBS) workflow. Over twenty depth tomography iterations were required to reach structural continuity and guarantee well matching, with strong interaction between interpreters and processing team to define a geologically consistent model. Pre-imaging technologies such as surface wave modeling, 5D regularization to radial symmetry, Multiples prediction algorithms, as well as numerous iterations of multi-domain noise attenuation have been key to provide the desired level of Signal-to-Noise ratio and achieve high vertical resolution. The project is also part of a broader work that aims to cover the Abu Dhabi Emirate with high-density surface seismic. Hence, the survey was designed and processed to deliver seamless merge and continuity with neighbor sectors, for a total of 40,000 square kilometers of data. These efforts in seismic acquisition and processing have produced an accurate high-resolution volume that adds unprecedented levels of detail and a new geological understanding of key plays in the south-east regions of Abu Dhabi. This result has been achieved over established producing fields, as well as in new, unexplored areas. The outcome has been already proven accurate in the latest exploration campaigns and is currently being used as a benchmark to define possible new key targets.

Acquiring surface seismic data can be challenging in areas of intense human activities, due to presence of infrastructures (roads, houses, rigs), often leaving large gaps in the fold of coverage that can span over several kilometers. Modern interpolation algorithms can interpolate up to a certain extent, but quality of reconstructed seismic data diminishes as the acquisition gap increases. This is where vintage seismic acquisition can aid processing and imaging, especially if previous acquisition did not face the same surface obstacles. In this paper we will present how the legacy seismic survey has helped to fill in the data gaps of the new acquisition and produced improved seismic image. The new acquisition survey is part of the Mega 3D onshore effort undertaken by ADNOC, characterized by dense shot and receiver spacing with focus on full azimuth and broadband. Due to surface infrastructures, data could not be completely acquired leaving sizable gap in the target area. However, a legacy seismic acquisition undertaken in 2014 had access to such gap zones, as infrastructures were not present at the time. Legacy seismic data has been previously processed and imaged, however simple post-imaging merge would not be adequate as two datasets were processed using different workflows and imaging was done using different velocity models. In order to synchronize the two datasets, we have processed them in parallel. Data matching and merging were done before regularization. It has been regularized to radial geometry using 5D Matching Pursuit with Fourier Interpolation (MPFI). This has provided 12 well sampled azimuth sectors that went through surface consistent processing, multiple attenuation, and residual noise attenuation. Near surface model was built using data-driven image-based static (DIBS) while reflection tomography was used to build the anisotropic velocity model. Imaging was done using Pre-Stack Kirchhoff Depth Migration. Processing legacy survey from the beginning has helped to improve signal to noise ratio which assisted with data merging to not degrade the quality of the end image. Building one near surface model allowed both datasets to match well in time domain. Bringing datasets to the same level was an important condition before matching and merging. Amplitude and phase analysis have shown that both surveys are aligned quite well with minimal difference. Only the portion of the legacy survey that covers the gap was used in the regularization, allowing MPFI to reconstruct missing data. Regularized data went through surface multiple attenuation and further noise attenuation as preconditioning for migration. Final image that is created using both datasets has allowed target to be imaged better.

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