What are Unconventional Resources?
Unconventional resources are hydrocarbon reservoirs that have low permeability and porosity and so are difficult to produce. Often enhanced recovery techniques, such as fracture stimulation or steam injection etc, must be performed, making the process more difficult than a conventional play.
|Worldwide hydrocarbon resources. Note conventional resources make up less than a third of the total.|
Examples of unconventional resources are:
- Tight Gas
- Coalbed Methane (CBM)
- Shale Gas
- Shale Oil
- Heavy Oil/Tar sands
- Methane Hydrates
Technical and engineering advances are now enabling companies to recover unconventional resources economically. For many unconventional gas plays, techniques to fracture the rock (also known as fracking) combined with horizontal drilling help the hydrocarbons from the reservoir flow more freely and profitably.
|FractAL identifies fracture density
Research has shown that seismic can be of value to engineers in several ways, and easily pays for itself by increasing the productivity of the wells drilled. CGG can provide a complete integrated seismic solution for all unconventional reservoirs, from feasibility studies and survey planning through acquisition and processing to reservoir studies and monitoring using microseismic and SeisMovie.
CGG is well positioned in the area of monitoring microseismic activities around these unconventional reservoirs, thanks in particular to our special relationships and partnerships with active members of this industry such as Magnitude.
Unconventional reservoirs tend to be massive and heterogeneous, but not clearly imaged on conventional seismic, requiring specialized techniques to characterize them, such as:
An example of the visualization of fracture swarms using AVAZ (amplitude versus azimuth analysis) around a very productive gas well in a tight gas reservoir in Wyoming. As fracture swarms in tight gas reservoirs often form vertical stacks, vertical wells can be drilled.
- AVO - can be used for estimation of geomechanical properties, lithology prediction and reservoir characterization.
- Fracture Characterization - fractures cause significant, measureable changes in 3D seismic data which appear as variations in seismic amplitudes (AVAz) and velocities (VVAz) with shot-receiver azimuth known as seismic azimuthal anisotropy.
- Orthorhombic PSTM - orthorhombic velocity modeling gives improved PSTM imaging below fractured overburdens, along with benefits for AVO and AVAz analysis.
- Multicomponent - can be used for stress analysis, fracture analysis and lithology predicition.
- Pore Pressure Prediction - to estimate pore pressure and fracture gradients, develop lithology dependent rock physics models, identify potential drilling hazards and improve well positioning.
- Stress Estimation - shows spatial variations in the stress regime that have important implications for field development, e.g. closure stress has been observed to vary by 30% over 1.5 km, the length of a horizontal well.
- Geomechanics - to monitor pressure and stress changes and indicate potential well bore instability.
- 4D Seismic - can be used to monitor production effects. The migration of steam injection through a reservoir can be continuously monitored for real-time production decisions using techniques such as SeisMovie.
CGG uses these techniques to investigate variations in P- and S-wave properties, which can be used in reservoir characterization to provide valuable information such as rock strength and stress state, in order to identify better targets for hydraulic fracturing, as well as the more conventional attributes such as fluidity, porosity, lithology and density etc. Our complete solutions can help companies plan field development and increase their success rate from horizontal drilling and fracturing.
CGG and our subsidiary Hampson-Russell have successfully applied our technologies to unconventional reservoirs in several areas of the world.