/
Spotlight

PEMEX's Appetite for World-Leading Seismic Technology

Tue, 01/22/2013 - 12:46

When it comes to introducing the latest innovations in the world of marine seismic acquisition, Pemex has been a frontrunner in adopting world-leading technologies. 2009 marked the NOC’s first foray into wide-azimuth (WAZ) seismic marine surveys, and over the last few years the solution has been established in Mexico as a proven technology. The NOC has also worked with French geosciences company CGG, which first brought WAZ to Mexico, on a project that incorporates one of their latest seismic solutions, or BroadSeis, for marine seismic acquisition. This technology employs streamers with varying receiver depth from near to far o†sets to produce receiver ghost notch diversity, allowing the streamer to be towed deeper to improve the low-frequency signal-tonoise ratio without compromising the high frequencies.

BroadSeis provides clear images and details of the reservoir from its exceptionally sharp and clean wavelets without sidelobes. The broad bandwidths of BroadSeis also enhance imaging below di·cult to image geology and provides greater accuracy in seismic inversion from improved low frequencies.

Now, CGG is introducing a new technology to the Mexican market, known as StagSeis. Promoted as a “next generation” solution specifically designed for subsalt imaging, StagSeis is designed to reduce risk in exploration and production by providing high quality seismic imaging for areas where previous generation technologies cannot acquire targets due to complex overburdens. The technology was developed to help companies operating in the US Gulf of Mexico, where large wide-azimuth acquisition is extremely desirable but di·cult to attain due to sub-salt and sub-basalt. The solution can also be adapted to shallow waters, where ultra-long o†sets are not required, but wide-azimuth data is desirable.

StagSeis utilizes a multi-vessel acquisition configuration, which produces ultra-long o†sets of up to 20km, and full azimuth of up to 10km. The process is also compatible with BroadSeis, which adds extra frequency bandwidth, especially useful for deep imaging. Due to its staggered vessel configuration, it can provide wide-azimuth and ultra-long o†sets using a linear tow in two orthogonal passes. The linear tow brings with it many advantages, as it ensures that the fold, o†set, and azimuth distribution are consistent from bin to bin, providing a stable stack response. By combining long o†sets, full azimuths and broad bandwidths, StagSeis allows for better subsalt imaging by illuminating shadow zones and steep dips, improving noise and multiple attenuation. This leads to more accurate velocity models. It can provide more than six octaves of signal in conjunction with BroadSeis, with lower frequencies to improve deep imaging and to provide more quantitative inversion results. Data is immediately available after acquisition and the results are compatible with wide-azimuth processing technologies.

In Mexico, CGG sees the opportunity to develop existing 3D seismic surveys through time-lapse repeat surveys, also known as 4D surveys, in order to better characterize fields for development, and analyse the evolution of production. The only challenge in conducting further surveys is the infrastructure that has already been put in place: for this reason, in the Mexican case, 4D surveys will be easier to conduct in deepwater areas than in currently producing shallow water zones.