Enhancing Fluid Recovery in shales: Why Pores less than 10nm Matter
Unconventional reservoirs are present worldwide, and have added 7500Tscf and 418Billion stb of liquids to global resources by EIA estimates. The new prize is predicting the liquid yield and improving liquid recovery, with cyclic gas injection offering a route to a +60% increase in liquids. However, these are unconventional reservoirs, so some basic assumptions and mechanisms change. For a conventional reservoir we expect lighter fluid above denser fluid, for fluid samples to represent the fluid in the pores, and for lab measurements to apply in the reservoir. For an unconventional reservoir, the pore throat size becomes important. Small pore throats have low permeability, so the fluid type depends on local source maturity, with oil over gas, and lateral variations in a long horizontal well. The small pores impact the phase envelope, such that lab measurements of the phase envelope may not apply. The small pores also have a large surface area for adsorbed gas, so a fluid sample might not represent the actual composition. The Langmuir pressure for shales can be above 4000psi, taking the release of adsorbed gas into similar pressures as dewpoint for a condensate. The realisation that the adsorbed gas could be releasing methane into the free gas, changing the liquid yield above the dewpoint of the free gas, has allowed a history match of the unusual liquid yield behaviour. All content contained within this webinar is copyrighted by Greg Walker and its use and/or reproduction outside the portal requires express permission from Greg Walker.
