Integrated Geoscience Reservoir optimisation packages reduce risk in the Permian Basin
Combining Geological Disciplines With Geophysical Analysis Helps Clients Better Understand Their Reservoirs.
The Permian basin is rich with opportunity, boasting half of all active oil rigs in the U.S. and currently producing about 45 percent of onshore oil production in the lower 48 states. The area has seen nearly a century of oil and gas production from more than 200,000 wells and notched up a lifetime output of nearly 50 billion BOE with few signs of slowing down soon.
The combination of multi-layered reservoirs and the recent decrease in exploration and development costs has brought a boom in activity to the region, with increased investment driving up acreage value. Companies are leveraging new technologies to exploit their assets cost-effectively. It used to be sufficient to just drill on a geometrical grid, but savvy operators are now using seismic reservoir characterization to create geologically supported reservoir models to design their drilling and completion programs and have turned their mature fields into ‘gold mines’.
The challenge in this area, as with most unconventional reservoirs, is the presence of thin layers. Seismic responses can be ambiguous, and interpreted as a single 30’ sand, three 10’ sands, or even one 50’ shaley sand. By integrating data from well logs, petrophysics, rock physics, geology, geochemistry, seismic data, interpretation and geostatistics, details can be visualized beyond the seismic bandwidth. CGG’s multi-client Reservoir Optimization Packages address the imaging and reservoir characterization challenges of shale and other unconventional reservoirs, using a holistic workflow to refine the stratigraphic framework and enhance understanding of the depositional setting, to review overall prospectivity in these plays.
A key step in the Reservoir Optimization Package workflow is to create a petrophysics and rock physics framework using basic well data. This framework can be extrapolated across the entire basin and has proven useful for calibrating client proprietary models, in particular for mineralogy, porosity and water saturation. Sets of sedimentological and elastic lithofacies are created from basic well logs and used to create a bridge between seismic and sedimentology. Input from CGG GeoConsulting’s RoqScan™ automated mineralogy system is used to validate several components of the workflow. After comparing the mineralogy results with RoqScan data, a stable model is created to generate shear sonic curves, which play a critical role in the subsequent geophysical and geomechanical modeling, and inversion projects. Finally, the lithofacies from the elastic logs are vetted against observations from the field and cores before being used for seismic inversion projects.
The geophysical interpretation phase includes:
- Using pre-stack AVO inversion to image key reservoir properties such as P Impedance, Vp/Vs, Density
- Deriving key reservoir properties of interest to engineers such as Brittleness, Porosity, Vqtz, etc.
- Using Bayesian inference to define and map reservoir facies
- Selecting relevant facies for probabilistic net pay analysis
- Determining reservoir anisotropy from a variety of methods including VVAZ, geometric attributes, spectral decomposition, discrete fracture analysis and anisotropic inversion
These procedures can be completed from both deterministic and geostatistical approaches and are performed using CGG GeoSoftware’s specially designed workflows.