CGG’s JumpStart programs are integrated multiclient geoscience projects designed to accelerate an industry understanding of petroleum systems and support exploration efforts. They are a new addition to an existing range of integrated geoscience products, which also includes Reservoir Optimization Packages, specifically designed for U.S. onshore reservoirs, and GeoSpec TerraCube regional projects, which are based on released legacy data. JumpStart programs complement the company’s existing multiclient library, including seismic surveys and Robertson Studies (Red Books).

When industry players explore a new area, collating all the available data can be challenging and time-consuming. Integrated geoscience programs provide a comprehensive, consistent resource of easily accessible data for evaluating petroleum systems, assimilating all the available data in a specific geographical area and framing it within a geological context. These programs enable clients to directly access the reviewed, validated, calibrated and interpreted datasets in one place in an accessible and ready-to-use format.

There are seven JumpStart programs nearing completion: in the northern North Sea, offshore Gabon, in the Timor Sea, offshore Australia, in the Gulf of Mexico and two offshore Brazil.

Major facets

The three major constituents of a JumpStart program are advanced multiclient seismic data; a validated, upgraded and ready-to-use well dataset; and a coherent interpretation and evaluation framework for the basin. Typical workflows start with a regional geological review, amalgamating all prior information and focusing on the main petroleum geology components such as the source rock, reservoir, charge, trap and migration pathways to provide holistic datasets that build a framework for interpretation of the seismic data, basin model-building and play fairway analysis.

Well data represent true samples of the Earth and, as such, are essential for calibration of geological models. A consistent petrophysical and stratigraphic review of the key available well data is undertaken to provide a robust chronostratigraphic framework for improved well ties and detailed understanding of the depositional systems. Where appropriate, wells are enhanced by new core and cuttings information, and biostratigraphic markers are used to help define consistent stratigraphic markers with consistent names and ages across the basin rationalized with the seismic markers to be interpreted. The creation of formation description logs based on quantitative analysis of wireline log data provides a consistent suite of interpretive logs calibrated to core data and laboratory measurements where possible. The number of wells reviewed varies widely depending on the maturity of the basin and the data-release policies in the area, from less than a dozen in some exploration areas to more than 100 in the Northern Viking Graben JumpStart program, for example.

This map shows the current JumpStart programs that are nearing completion. (Source: CGG Multi-Client and New Ventures).

 

Finding new information

Usually, adjustments to the previous interpretations are required since these did not benefit from the array of data for cross-validation and often contain many inconsistencies. In the Northern Viking Graben, some older sands were wrongly assigned to be part of the Agat Formation, but closer examination of the age and composition enabled them to be reassigned, and a better stratigraphic correlation was achieved between wells and seismic. Similarly, reexamination of the previous interpretation of wells in Mexico’s Encontrado JumpStart program has significantly changed the understanding of the basin, as discussed later. In Gabon, the reinterpretation of well data acquired through the pre-Aptian salt has revealed potential for an additional late syn-rift sand play to exist in the ultradeep offshore area, different from the one commonly known as the Gamba sandstone. These examples show how careful reexamination of the data with the benefit of advanced modern seismic and the integration of all the other available information can revolutionize industry understanding of the geology in some areas.

The updated well and geological information is used to calibrate the velocity model for imaging and quality control during seismic processing. Where possible prestack attributes and amplitude vs. offset (AVO) gather synthetics are generated from the well data and can be used to control the quality of AVO signature preservation throughout the seismic processing flow.

Where available or where acquired with the seismic, potential fields data are interpreted to help characterize the deep basin structures where seismic imaging reaches its limits and to provide regional linkage. Natural oil slicks on the sea surface are identified from interpretation of offshore satellite image data and integrated with the shallow seismic interpretation to provide highly valuable information about the presence and characteristics of the petroleum systems in place. On completion of seismic processing a structural and stratigraphic framework is interpreted using key horizons, and seismic attributes (pre- and post-stack and calibrated to well data where possible) are extracted to highlight reservoir facies and map the potential presence of hydrocarbon fluids.

The interpretation is used to form a framework for stratal slicing and exploration in the depositional domain. The 3-D horizons are used to flatten the seismic volume in the geological time domain to enable the mapping of lateral seismic facies variations along a constant depositional time slice, providing valuable information about potential reservoir and source rock distribution. Changes in rock facies induce subtle changes in the seismic wavelet bandwidth that are highlighted through spectral decomposition around three dominant frequencies. Stratal slicing provides a clear picture of lateral seismic facies and enables rapid evaluation of potential leads and prospects, significantly enhancing understanding of prospectivity and variations in reservoir quality.

Encontrado

The Encontrado program is a good example of the value of an integrated geoscience program. With the opening up of Mexican waters to the international E&P industry there has been a rapid surge in exploration, and extracting the useful information from the array of available data could prove time-consuming, especially for those not fully established in Mexico. Availability of consistent, coherent information from a single source can save valuable time and effort.

The Encontrado program consists of more than 38,000 sq km (14,672 sq miles) of seismic data, mostly recorded as wide-azimuth, that have been reprocessed using broadband and depth imaging technologies. All the available well data have been reinterpreted and upgraded, removing inconsistencies that may have been present in the existing well interpretation to create a consistent chrono- and lithostratigraphic scheme across the whole basin and tying it to the reprocessed seismic.

This revised interpretation has led to a reevaluation of the prospectivity of some areas. At least one well, drilled to test the Upper Wilcox Sandstone, is now considered not to have been drilled deep enough to penetrate this formation, leading to an incorrect downgrading of the area’s prospectivity. Only a few, if any, wells in the survey penetrated the Cretaceous, resulting in the program being extended to the U.S. Perdido region to incorporate a deeper well, enabling calibration at the Cretaceous level and verification of the new interpretation.

The stratal slices generated over Encontrado capture densely distributed high-sinuosity deepwater channels at unprecedented resolution. By looking at all the data in a paleogeographic context, it is possible to gain an indication of slope profiles, directions of travel and topographic barriers for depositional systems over time. This enables understanding of the interplay between basement structure and post/supra-salt structural development.

The review and reinterpretation of core data has led to the refinement of depositional process models, providing detailed understanding of the reservoir evolution. By carefully studying the core sedimentology it is possible to go well beyond the resolution limits of the seismic data and then back-propagate that understanding into the horizon and attribute analysis.

Integration of the seismic and well data with all the available geological and geophysical data delivers a coherent and comprehensive understanding of the basin. The aim is to create the best constrained and highest resolution geomodels possible to address the key petroleum systems questions that control prospectivity. Ready-to-use datasets and interpretation frameworks can help accelerate understanding of frontier and mature areas by reducing the time spent on further interpretations and analysis and increasing their accuracy, thereby allowing more time to be spent on the identification of new prospects and play models.