The growing need to control costs and compress the decision-making time frame has become an ever-pressing issue in every E&P cycle. This means that the provision of seismic data must be carried out in a cost-effective way, with reduced turnaround time as well as operational and environmental exposure. Simultaneously, acquisition and processing should be accomplished without compromising the data quality required to overcome the technical challenges in a given area.
WesternGeco has achieved this by delivering higher volumes of seismic data of better quality at a lower cost through the development of technologies that deliver optimum subsurface illumination and imaging while incorporating efficiency-enabling features. These technologies rely on efficient algorithms, parallel workflows and innovative techniques that provide high-quality answer products to the customers in a timely manner.
A seismic survey acquisition project in the offshore Angoche basin illustrates how WesternGeco successfully implemented these technologies over the Mozambique 5th licensing round blocks. In addition, this survey also covers open acreage areas to be awarded in future licensing rounds. Data were required quickly to support short-term exploration decisions as well as higher-resolution studies for subsequent appraisal and development activity. The 15,000-sq-km (5,792-sq-mile) broadband multimeasurement towed-streamer seismic survey was acquired and processed onboard the acquisition vessel. The high-standard prestack time migration workflow included multimeasurement 3-D receiver deghosting and wavefield reconstruction.
A high-quality accelerated interpretation-ready image cube was produced onboard within four weeks of the last shot point. This volume became the basis for confident interpretation and exploration decisions. Further improvements are expected via subsequent onshore processing, including additional source deghosting and depth imaging, with the opportunity to revisit archived field products for future high-resolution reprocessing objectives.
Technologies accelerate the interpretation of seismic data
One of the technologies that speeds up the interpretation workflow is the eXchroma chromatic geology extraction technique, which offers structurally sharpened visualization of seismic data. It creates an environment and workflows that allow users to easily interpret 3-D seismic data and isolate important geologic details from seismic noise. This tool for the Petrel E&P software platform transforms 3-D seismic data cubes into a continuous color domain, allowing for stratigraphic interpretations and evaluation of lithology and pressure in a frontier basin where well logs are not available for calibration.
In a recently acquired survey in the Flemish Pass region offshore Canada, WesternGeco multiclient data provided a solution combining IsoMetrix marine isometric seismic technology data and image processing of the seismic cube to obtain information about the texture of stratigraphic horizons that show an impedance contrast. The resulting horizon images were interpreted for depositional environments, which in turn give new clues into lithology and pressure. Insight into depositional environments from interpreted 3-D seismic data benefits significantly from the broadband Isometrix data. The data were acquired with broad bandwidth for fine vertical resolution and with the combination of pressure and velocity sensors for nonaliased lateral reconstruction of the seismic wavefield.
Such 3-D seismic data offer sufficient resolution and data quality to enable color processing that yields horizon images of a quality similar to satellite images. The fundamental difference is that the color-processed seismic data can be generated on any lithostratigraphic horizon with an expression in the seismic impedance contrast. This allows depositional environments to be studied in the context of geologic time. The color-processed horizon images present a complete view of the depositional system—as far as it has been preserved in the subsurface—as opposed to sections that are available from outcrops of ancient strata.
These recent technological developments have greatly accelerated the interpretation of this Flemish Pass data, thus offering an insight into the structural evolution, geologic history and hydrocarbon potential of this frontier area.
To learn more about the WesternGeco 3-D seismic projects and fit-for-purpose technologies, please visit the Schlumberger booth, 903. A special lunch presentation, “Better, faster, cost-effective innovations for successful exploration in today’s market” will take place Tuesday, June 13, at 12:15.