Abu Dhabi Company for Onshore Oil Operations (ADCO) had a need for an exploration survey to delineate a low relief structure in onshore Abu Dhabi. The terrain is characterized by sand dunes of variable heights with some oilfield infrastructure, farms and conservation areas. ADCO tendered for a conventional survey but the successful bidder offered an economically attractive Single Sensor / Single Source (S4) option with the MD low frequency enhanced sweep. ADCO has tested some of the processing technology associated with S4 recording on vintage datasets and were keen to try them on a true S4 dataset.In particular it was very important that a good near surface model was obtained because of the low relief target. The use of the low frequency MD sweep, Shear Wave Inversion (SWI) and Simultaneous Joint Inversion (SJI) was an ideal approach to resolving the near surface model. There was an uphole program planned to calibrate the derived near surface model. The SWI volume was generated before the upholes were drilled so that any anomalies could be investigated.The crew with 50,000 channels mobilized and commenced operations on October 26th 2013 and completed the 604 Sq.km survey by December 25th. The survey consisted of 241,860 VP's and generated 3.5 billion traces. Despite this volume of data a field QC volume was generated on the crew utilizing a pre-defined velocity field developed in collaboration with ADCO and was delivered two days after the last shot. This volume was interpretable to guide the main processing team.Whilst the full processing and evaluation of the data is still ongoing, the early results have clearly shown that the S4 technique is ideally suited to acquisition in sand dune areas with infrastructure. This presentation outlines the details of this survey and the lessons learned.
Reservoir heterogeneties play important roles in reservoir description processes. It is therefore imperative to understand the source of uncertainties influencing structural and stratigraphic interpretations of reservoirs. An integrated reservoir, and seismic modeling study over an onshore giant field in Abu Dhabi came to the conclusion that 3D seismic is the most efficient approach to detect the reservoir heterogeneiy and structural uncertainties that are thought to be responsible for the irregular fluid flood front advance and consequently for the reservoir management problems. In preparation for a large vibroseis 3D seismic survey over the subject field, 2D and 3D field tests were carried out to determine optimum source energy distribution. Several versions of the 2D and 3D data were acquired with different source geometries and processed up to stack, migration and inversion (for 3D). The 2D test showed that in this area final data quality does not depend on vibroseis sweep length (i.e. source energy). A subsequent 3D test showed that final data quality is marginally dependent on dense source arrays, but is enhanced considerably using a finer areal distribution of source points. This could be used to improve the data quality and at the same time to reduce the cost of the subsequent production 3D survey.
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