Exploration and asset development can be challenging offshore West Africa. Legacy seismic datasets were not designed to deliver a holistic, basin-scale understanding of the petroleum systems along the West African margin. Reservoirs can be structurally complex with numerous intersecting faults and compartments. Conventional seismic images are often insufficient to delineate these structures, as the recorded acoustic data is frequently obscured by sea floor multiples and gas Clouds. In some countries, the pressures to use indigenous oil field services firms are intense and frequently mandated within the operators' development agreements.
Bulwark Services Limited and ION Geophyscical's GX Technology (GXT) Imaging Solutions group have undertaken a series of complex imaging projects in the offshore areas of the Niger Delta basin, Nigeria, through an existing joint Venture collaboration. Bulwark is a 100% indigenous company involved in geosciences services to the Nigerian E&P sector, and ION is a world-leading geophysical company based in the USA. This collaboration brings an in-depth knowledge of the geology of the Nigerian offshore, as well as provides the latest capabilities in data processing, converted wave imaging, advanced geophysical analysis, and data center management. The partners have been working together on several complex imaging projects, and the collaboration has brought new technology such as 3D SRME and Anisotropic Pre—Stack Depth Migration velocity model building to Nigeria for the first time.
More recently, Bulwark - ION/GXT have begun to image the early data from a multi-year seabed imaging project offshore Nigeria. The data for the survey were acquired using ION's VectorSeis Ocean seabed acquisition system although the project is ongoing and is hoped to be completed by this year ending, the results so far have been very promising. The improved bandwidth made possible by the VectorSeis sensor should lead to higher resolution images of potential reservoir targets. Deployment on the seabed appears to be reducing the problems often caused by seismic multiples, while the 4C data appears to be minimizing the signal attenuation that is normally caused by gas clouds.
According to Lucky Awobasivwe, Chief Executive Officer (CEO) Bulwark: "The JV collaboration has enabled us to offer the latest imaging techniques and has provided the Nigerian geoscientist in Bulwark Services Limited, access to the latest tools and expertise required to take on the most challenging geophysical projects in West Africa"
The Bulwark - ION/GXT collaboration is also currently working on a multi-year VectorSeis Ocean (VSO) program on both P-wave and converted wave (C-wave) imaging for an international major operator. This operator hoped to eliminate seabed multiple problems and improve the bandwidth of the recorded seismic data to better resolve thin bedding layers and delineate faults and compartments within the reservoir zones. In addition, the operator hoped that the c-wave data recorded by VSO would enable them to "see through" gas clouds. The VectorSeis Ocean platform, launched in 2004 has a proven track record of efficiently delivering highest resolution seismic data in the North Sea, the Caspian Sea, off the coasts of West Africa and Brazil, and in the Gulf of Mexico.
VSO II includes advanced capabilities that further improve the operational efficiency and further enhance VSO's health, safety, and environmental (HSE) advantages over conventional OBC systems. New features that enhance the core goals and unique elements of the VSO II platform include:
- A continuous recording capability that overcomes in data acquisition due to intermittent radio transmission in obstructed or congested areas
- Advanced diagnostic measurements and consolidated reporting tools that maximize productivity by streamlining maintenance and fault isolation and reduce the need to pull arrays on-board to troubleshoot problems
- An enhanced power delivery system that improves operational efficiency
VSO II remains a buoy-based system that eliminates the need for a dedicated vessel, thus reducing power needs, operational complexity, and the environmental footprint. Coupled with the Gator command and control system, VSO II automates and simplifies vessel navigation, spread positioning, data management, and QC across the seismic work-flow. Tim Rigsby, Senior Vice President of Strategic Initiatives at ION, added, "ION has been committed to accelerating and expanding the adoption of full-wave seabed imaging since launching VSO in 2004. We are pleased to introduce a number of enhancement in VSO II, designed to improve the operational safety and efficiency of seabed acquisition while providing the best data quality available on the market."