Oil & Gas Vertical, 15. 01.2013
UniQ technology, developed by WesternGeco (Schlumberger) a couple of years ago, is the most advanced land seismic acquisition system. UniQ is capable of acquiring up to 200,000 live channels of seismic data at any density or required step change in land seismic imaging. Such a system significantly guarantees efficient noise removal when processing data. After the completion of infield data processing, the signal-to-noise ratio is dramatically increased, while the imaging resolution is improved. Therefore, infield data acquired using the UniQ system, guaranteeing a high resolution level that is unsurpassed, can address land seismic challenges even in challenging noise environments and in areas with complex geologies. The advanced tools and methodology by which the land seismic signal and noise are acquired, recorded, and processed significantly improve efficiency when compared to standard seismic surveys. The seismic data thus acquired are used to assess the fluid saturation level of the fields being examined.
Most oil companies that initially aim at reducing the costs of land seismic surveys stick to traditional exploration workflows that are sufficient for specific geological exploration tasks, but such methods do not contribute to further development of the resource base.
However, detailed reservoir surveys and the reliability of interpretation largely depend upon the acquired seismic data and the quality of data processing. Therefore, WesternGeco (Schlumberger) developed and launched UniQ, a unique seismic data acquiring and processing technology that dramatically improves the resolution, accuracy and completeness of seismic data for field/reservoir characterization projects (and the assessment of the fluid saturation data) and the efficiency of subsequent drilling operations.
UniQ has been used by leading overseas oil and gas companies in areas with complex geologies and in isolated, aging fields where traditional seismic acquisition technologies turned out to be inefficient. After the technology was introduced in Saudi Arabia, it was used by SaudiAramco and other oil and gas companies for the completion of almost all seismic projects. UniQ is currently used by field seismic crews worldwide, from Alaska to Australia. In particular, one of WesternGeco’s field crews operating in Kuwait uses up to 200,000 live channels for 3D seismic acquisition, covering an area of several thousands square kilometers, or nearly half the country.
Architecture and Advantages
UniQ is an integrated land seismic acquisition and processing system that guarantees the greatest level of efficiency and the highest resolution.
Special point receivers are used for data acquisition. The source base is maximally reduced as a result of a reduction in the number of sources by replacing groups of vibroseis sources with single, more powerful, and heavier vibroseis sources, or by switching from a linear to an areal configuration. A signal registered by point receivers is recorded on separate seismogram traces for further digital processing.
It is widely known that most noise waves registered by traditional, standard linear seismic receivers cause a noise cone at a PP step (distance between receivers) = 50 m, or even at a PP step = 25 m. Such noise cannot be removed using standard tools. UniQ significantly increases the point density and reduces the PP step. Thus, the minimal distance between receivers enables the separation of wave field components. Moreover, the unevenness of the reservoir surface is considered, while noise is removed before grouping seismic traces. Grouping at a PP step = 25 or 50 m makes the signal stable after removing such key noise as basic microstatic, surface and Rayleigh waves, industrial noise, etc.
Moreover, grouping exercises or a variable PP step facilitate the formation of infield data packages for specific tasks. Grouping exercises at a 12.5 m interval appear useful for detailed, near-surface section analysis, the definition of hidden karst zones, the minimization of the relic everfrost effect and steep-dip subsurface imaging. Grouping at a 25-50 m interval may be used for deeper or shallower horizons.
Properties and Specifications
A virtually unlimited number of live channels is a key advantage offered by UniQ. The system can support from several tens up to 200,000 live channels simultaneously, and guarantees a far more powerful data exchange when compared to conventional ЗD seismic acquisition tools.
In addition to bypassing various obstacles, the networking configuration of a seismic acquisition system with individual IP addresses assigned to each point receiver enables automatic redirection of the data stream between modules in the event of a connection failure.
The spacing layout of land receivers may be different. The only restriction is the maximal linear distance between two receivers. If areal grouping is required, areal distribution methods are used, either the linear grouping of point receivers or several parallel receiving lines.
The possibility of adjusting/reducing the spacing interval (up to 2.5 х 2.5 m if required) is another key advantage of the system compared with conventional units. There is no aliasing effect when point receivers are used for seismic acquisition.
In addition to providing an improved surveillance system and innovative methods of seismic data acquisition (instead of suppression, surface noise waves are registered at a high resolution and subsequently removed), UniQ is based upon a new generation of field acquisition tools that enable a dramatic extension of the initial seismic data range.
Field seismic data acquired by UniQ are processed using algorithms and methods that guarantee the efficient suppression of registered noise, a high output signal-to-noise ratio, and an extended frequency range. The last property improves the correlation of the seismic data and drilling specifications, and as a rule, the acoustic and dynamic inversion.
Finally, the adjusted static data and the interval range between point receivers before grouping guarantees a maximal signal-to-noise ratio and bandwidth.
Summarizing all that has been stated above, we can draw the conclusion that UniQ is the most integrated, most advanced, and least expensive technology, which significantly improves efficiency when prospecting new fields and creating detailed field appraisals. Moreover, the technology has neither regional nor climatic restrictions upon application. It is maximally flexible and adjustable for various geologies, field properties, environmental conditions and organizational issues.
Application in Russia
UniQ is expected to be initially applied in the Russian Federation in Eastern Siberia. In Summer 2012, the Gazprom Neft Company and Geotech Holding JSC, the holder of the rights to use the technology in Russia, signed an agreement for using UniQ during land seismic acquisition within the Vakunaisk prospecting area in the Irkutsk Region. In accordance with this agreement, land seismic acquisition operations will be performed on an area of 1,125 km2.
The application of UniQ technology on the Vakunaisk prospecting area is expected to result in a precise seismic data cube. A detailed analysis of the high-resolution data will address challenges related to its complex geologies and identify those producing horizons having promising collection properties.
This area was thoughtfully selected because of a combination of various restrictions that complicate the identification of drilling locations. For instance, in addition to the trappean magmatism typical of the region, the area is characterized by a complex block structure with a significant vertical and lateral drop in the facies composition of its productive layers and their collection properties.
Schlumberger will provide comprehensive technological support for project implementation (in the framework of a strategic partnership). Training for Russian seismic specialists will be arranged at the Schlumberger Training Centre in the United Arab Emirates. Schlumberger’s experts will supervise field seismic operations during the first season. The contractor is currently making all preliminary arrangements for further on-site UniQ deployment.