Bulwark Data Processing centre is primarily established in Nigeria to offer a high tech state-of-the-art imaging solutions to the E & P in Nigeria. To actualize this dream, we formed a JV with GX Technology Corporation, a world leading imaging company, for technology transfer to local staff. At the moment, Bulwark Services Limited is the only Nigerian Company which has a fully operational seismic data processing centre.
Pre-processing - Conventional
Our pre-processing algorithms are focused on the analysis and suppression of noise, including seismic interference, swell noise and multiples. Also, the Pre-processing activities at the Bulwark/ION-GXT centre are designed to especially meet the needs of high-end, detailed and superior quality data conditioning and imaging. The primary focus is to create an assembly of main processing tools that are necessary in today's difficult-to-image subsurface geology.
Performing operations on our cluster-based parallel processing environments, means that we can execute our time processing routines within the same efficient environment as our imaging. Algorithms are developed and continually upgraded upon challenges, to focus on the analysis and suppression of noise, including; seismic interference, swell noise and multiples.
We also offer specialized pre-processing services such as apex-shifted multiple attenuation, 2D/3D surface related multiple elimination high resolution radon demultiple, beam radon demultiple. We also offer specialized pre-processing techniques of shear-leakage removal and high-end mirror sum dual sensor summation on multicomponent data.
Bulwark in collaboration with ION/GXT provides seismic data processing (2D/3D), with the objective of producing as clear an image of the geology as possible.
Bulwark's technology supports your toughest geologic challenges by offering multiple isotropic and anisotropic tomography solutions depending on geologic challenge: narrow azimuth (NAZ), wide azimuth (WAZ), multi-azimuth (MAZ), parametric and general move out tomography.
Q-Tomography and Q-Migration
Q tomography leverages pre-stack migrated common image gathers for estimating Q attenuation, as Q field estimates are often unstable. The Q tomography has a choice of two industry best practices, frequency-based calculations (log spectral ratio and centroid frequency shift) to provide a deterministic correction based on either specific horizons or generalized moveout picks to confidently estimate attenuative travel time. From there a deterministic model of attenuation
can be built by back projecting the compensated horizons and picks along raypaths derived from the 3D velocity model. This robust Q tomography approach is designed to deal with spatially variant effects and works in concert with our suite of time/space variant 3D Q migrations.
Bulwark offers a full suite of pre-stack migrations that are enabled with Q parameter support including: Kirchoff, Beam, and Reverse Time Migration. The Q migration propagators have been efficiently designed for visco-acoustic medium effects that take into account the spatial variations of Q within the subsurface and yield a higher fidelity image.
AZIM and OVT PreSTM
Unless properly accounted for in seismic imaging, the effects of anisotropy can significantly degrade the seismic image. One form of anisotropy that is common in nearly all 3D WAZ data from land and hard rock marine basins is horizontal transverse isotropy (HTI). Bulwark's approach to addressing HTI in wide azimuth seismic data is built on two foundational technologies: Non-sectored azimuthal velocity analysis (AZIM) and offset vector tiling (OVT).
WiBand Deghosting and Advance pre-processing
The industry is seeing a significant uptake of broadband technologies to deliver a full range of frequencies required for high fidelity/site-update images and accurate uantitative results from inversion. In marine data, for example, the problem of ghost notches generally limits frequency bandwidth and data resolution. Acquisition based de-ghosting solutions are expensive and do not address the ghost notch issue for data acquired by traditional towed streamers.
WiBand de-ghosting and processing tackles both the source and receiver ghosts to recover the full spectrum of towed streamer data with effectiveness approaching an acquisition solution, but at a far lower cost. WiBand solution delivers improved resolution and clarity while providing more robust inversions and ties to well data - "The ground truth".
WiBand technology can be utilized for flat or variable - depth streamers, new data acquisitions and the reprocessing of conventionally acquired or legacy data. The technology greatly improves seismic interpretation through improved fault definition, horizon delineation, and attribute analysis, allowing E&P companies to make more accurate decisions in exploration and reservoir development. ION has extensive experience in broadband technologies with almost 10 projects.
Velocity Model Building
From the 3D migration standpoint, in Bulwark we offer Kirchhoff preSTM, Kirchhoff preSDM, and several wavefield extrapolation (WE) preSDM algorithms. The main focus of Bulwark Services Limited is to be Nigeria’s leader in pre-stack time and depth imaging. The heart of our time imaging is true and relative amplitude processing, essential for fulfilling the needs of AVO, 4D and advanced imaging solutions. Our noise removal modules are AVO consistent, avoiding statistical, deterministic processing that could adversely and irreparably damage the data in terms of the ability to preserve information content.
For model building, we offer two varieties of tomographic inversion (a layer based scheme using preSTM finite-offset picks and a gridded scheme using preSDM finite-offset picks) in addition to preSDM CRP scanning and model perturbation image scanning techniques. We also take anisotropy into account if we have sufficient well control in our velocity model building.
Anisotropic Model Building and Anisotropic Migration
In presence of thick anisotropic layers, the migration operator has to be adapted to accommodate distortions in the data. Common assumption: the medium is characterized as VTI with the Thompsen’s parameter ɛ and δ, or TTI; the anisotropic velocity expressed as function of the tilting angle of the axis of symmetry with vertical. However, in practicality, anisotropic media in most cases presents variations between well velocities and seismic velocities (well velocities are usually slower than seismic velocities); hence the seismic depths are generally greater than the well depths for a positive δ.
Furthermore, to resolve this, we migrate anisotropically by taking into account the deviation between well and seismic velocities via the (epsilon & delta) parameters. In this case, we use the well velocities or interval velocity estimates derived from Vnmo after scaling by delta, in conjunction with the (epsilon & delta) parameters in the migration. In the model building route for anisotropic migration, we thus scale the seismic velocities with the delta parameter to bring them into line with the range of well velocities. Bulwark Services Limited has a strong and diverse experience in imaging complex anisotropic media.
Full Wave Form Inversion (FWI)
FWI requires a lot of attention, and the starting point is very important. To enhance proper definition of the geobody, we use tomography update to improve the migrated image for our client’s satisfaction. FWI is suitable in resolving shallow velocity anomalies and greatly improves the match between the field data and model data.
AVO and Inversion
While traditional AVO (amplitude variation with offset) methods are well known industry standards, Bulwark has developed next-generation AVO tools and approaches. Building on the solid foundation of our AZIM anisotropic processing method, we developed a new technique that extends the utility and application of the technique - WAVO (wavelet-based AVO).
Reverse Time Migration
Traps against steeply dipping geology can be extremely prolific and capable of being drained with relatively few high-rate wells. However, current migration methods face limitations in the presence of complex, steeply dipping reflectors such as those found on salt flanks. Reverse time migration (RTM) overcomes these constraints, enabling structures with dips greater than 90 degrees to be properly imaged.
- Benefits RTM Offering
- Provides an alternative approach to migration with fewer compromises
- Images both the steep sides of salt bodies and underneath them, regardless of the dip and rugosity at the top
- Reduces project turnaround time
- Yields more accurate models that significantly improve the final sub-salt image