3.2.1. Key Questions and Related R&D Goals

The WGS Program targeted “tight” (low permeability) sandstone reservoirs in Western basins. Such reservoirs are often defined as gas bearing sandstone (which may or may not contain natural fractures) which exhibits an in situ permeability to gas of less than 0.10 millidarcy (mD).

Many “ultra tight” gas reservoirs may have in situ permeability as low as 0.001 mD. In addition to low permeability and porosity, these sands are often characterized by high water saturation and high clay content. At the time, even measuring these properties was a problem, as the recorded values could be highly sensitive to sampling procedures.

Standard core analysis techniques were not precise enough and logging tools and interpretation techniques were not refined enough to provide accurate measurements. The four major program elements and associated goals of the WGS Program were (Figure 3.2.1):

1. Resource Determination – The goal of this element was to reduce the uncertainty regarding the production and reserve potential of tight gas sands and direct priorities toward maximizing that potential.
2. Resource and Site Characterization – The goal of this element was to provide an accurate geologic understanding of specific local sites to guide the design of effective recovery technologies and thus improve overall resource estimates.
3. Research, Instrumentation and Modeling – The goal of this element was to develop the tools, procedures, measurements, concepts and models required to effectively recover gas from tight sands.
4. Production Technology Development – The goal here was to develop and test cost-effective means of recovering gas from Western U.S. tight sand formations.

Figure 3.2.1: Schematic of WGS Program Research Plan.

The objectives associated with these goals were as follows:

Resource Determination:

• Generate information sufficient to adequately characterize the geology of the priority basins.
• Construct geologic models to facilitate the advancement of production technology research and instrumentation development.
• Identify and quantify the in-place gas resource and based on current economics and technology assess the recoverable resource.

• Develop geologic understanding of the nature, amount and distribution of gas in western tight gas sands.
  
  

• Improve the quality of geologic diagnostic data.
• Improve the understanding of geologic controls on tight gas production.
• Improve methods of predicting reservoir performance.
• Improve methods of predicting, measuring and applying in situ stress data.
• Improve the understanding of hydraulic fracture fluid mechanics and fracture propagation.

• Apply and evaluate the application of hydraulic fracturing technology to tight gas reservoirs.
• Demonstrate the capability of fracturing to stimulate production from multiple sand lenses distant from the wellbore.
• Improve techniques for conducting multiple fractures from a single wellbore.
• Field test results of laboratory investigations into minimizing fracture fluid damage to the formation and proppant crushing.

• CER Corp. (core acquisition).
• CK GeoEnergy (out-crop studies).
• USGS (resource & reservoir characterization).

• Bartlesville Energy Technology Center-NIPER (fracture conductivity experiments, improved log interpretation).
• Sandia National Labs (Mine-back experiments, instrumentation development, logging tool development).
• Lawrence Livermore National Lab (models and instrumentation, in situ permeability measurement capability).
• Los Alamos National Lab (NMR log tool development).
• New Mexico Institute of Mining and Technology (rock property measurement).
• Institute of Gas Technology (in situ permeability measurement).
• Texas A&M University (improved log interpretation).
• University of Tulsa (proppant transport model).
• Terra Tek (proppant design R&D).

• Sandia National Laboratories (implement MWX field test site).