Gamma ray model showing the higher values (shales) in darker browns and lower values (sands) in yellow. Data courtesy Rocky Mountain Oil Technology Center and the U.S. Department of Energy.
The unconventional shale reservoir has shown tremendous potential in the production of oil and gas in recent years. Companies are increasingly exploring oil fields for the commercial extraction prospect from these reservoirs. Unconventional reservoirs, however, require huge investments in complex technologies required for hydrocarbon recovery which makes the process of characterization extremely important.
Accurate analysis of the geological, petrophysical, and engineering data of the complex shale subsurface is crucial, considering the economic stake of the project. Interpretation through visualization of these complex unconventional shale reservoirs assists asset teams in making accurate decisions regarding production design and economic returns.
Unconventional Shale Reservoir Characteristics
Unconventional reservoirs mostly have shale as their dominant rock type. These reservoirs are often considered to be lithologically homogeneous. However, shale reservoirs can often contain complex lithologies including non-shale sub-facies such as micro-scale mineral grains and segmentations of silty sands and carbonates. These non-shale sub-facies have greater porosity potential. This porous zone embedded within the shale can indicate a potential pay zone. On the other hand, these intergranular spaces also indicate the potential presence of clay particles which can affect shale properties and formation. Along with it, the flow of hydrocarbon within the shale can also be limited depending upon the clay volume. Thus, unconventional reservoir characterization is an important step in gaining a complete understanding of the geological and lithological properties of the rock, including the shaly intervals, as well as the effect of such formations on the recovery process.
Various microseismic, seismic, and well log techniques can be used to collect data related to lithological, petrophysical, and geoscientific properties of the subsurface. Developing a correlation between these data can provide a deeper understanding of the key shale reservoir properties. Geologic mapping and analysis of this data can be utilized for determining production potential and reservoir development.
Need for Visualizing Shale Lithology
Visualization of complex shale lithology provides engineers and geoscientists with a unique understanding of shale properties, its effect on reservoir characteristics, and its future behavior and production. The data obtained through various seismic and logging tools and techniques can be integrated into a single geospatial platform to create a 3D geological model of the unconventional reservoir. The 3D visualization of complex shale lithology allows asset teams to:
- view shale formation and occurrence of faults and fractures for oil in place estimation
- Locate non-shale sub-facies
- Determine optimal placement zone for horizontal wells
- Design optimal well trajectory
- Interpret mineral distribution within the shale formation
- Optimize the frac job and proppant type
The geologic mapping of these unconventional reservoirs can be greatly simplified by incorporating all the available data into a single geospatial volume for 3D visualization and interpretation such as Coviz 4D.
CoViz 4D for Visualizing Complex Reservoir Characteristics
The efficient visualization through 3D modeling of petrophysical and geoscientific data is crucial for unconventional reservoir characterization. CoViz 4D provides an excellent platform for integrating and visualizing all available seismic, log, and core data. This provides an accurate understanding of the unconventional reservoir, shale lithologies, and its current and future production. Asset teams can efficiently examine variability in production by developing correlations among horizontal wells as well as comparing the current data with previous production data. With accurate analysis on hand, engineers can make informed decisions to maximize the economic potential of the reservoir.