Intro to December Focus: Land Seismic in Complex Basins

Welcome to this special issue of the RECORDER, with a focus on land seismic in complex basins which presents three papers on land acquisition, new recording equipment, acquisition planning, and resulting improvements in imaging and interpretation.

In the first focus article (Cableless Seismic Acquisition), Kendall discusses the various advantages and disadvantages of cableless seismic acquisition systems and compares the overall functionality of cableless systems to cabled systems. He also briefly reviews the various cableless systems and their similarities and differences. Most of these cableless seismic recording systems do not transfer data back to a central recording system and they do not transfer power to multiple stations though cables. The majority of them are autonomous with the data being recorded on flash memory at the station with a battery and sensor (geophone or accelerometer). Even though they are called “cableless” they typically use cables to connect the geophones and external batteries. They range from completely autonomous to being able to transfer data via some form of wireless transmission (WiFi, BlueTooth, multi-threaded (or mesh) RF, etc.).

In the second focus article (Imaging the Overturned Limb of a Footwall Syncline and its Impact on Exploration in Fold and Thrust Belts), Newson discusses the complexities associated with hydrocarbon exploration in the Western Canada Fold and Thrust Belt (WCFTB). For the last 70 years, WCFTB exploration has been aided by seismic imaging techniques providing an understanding of the deep structures. Even so, this process is still full of surprises as steep dips, fault repeats, detachments and poor coupling at the surface all contribute to obscuring a clear image of the subsurface.

In an effort to improve our understanding of the WCFTB, a seismic line (LOFF8) was shot across the Brazeau Thrust in the Alberta portion of the WCFTB. The LOFF8 seismic line is part of a unique experimental seismic program that was shot expressly to evaluate long offset, high intensity acquisition parameters.

The interpretations of the seismic line LOFF8 in time and depth are reviewed in this paper. The tools used for the integration of the surface and subsurface geological and geophysical data are described and a new deformation model is presented.

In the third focus article, (Land Seismic Acquisition Testing Strategies and Results – Southern Chad, Africa 2013-2015) Crook et al., discuss a seismic acquisition and testing program in Chad. The program involved acquiring four 3D surveys covering 1200 km2, 216 2D surveys covering 4500 km and 23 acquisition tests. The paper provides an overview of the seismic acquisition tests with a specific focus on tests designed to improve imaging in areas with subsurface laterites and near-surface scattering, which impede imaging. The paper focuses on two regions. The first region has near-surface laterites and only fair-to-good data quality and the second region has mixed laterite and laterite-free zones resulting in good-to-excellent data quality.