Assessment of Oil and Gas Resources in the Vaca Muerta Shale,NeuquenBasin,Argentina

摘要

According to the 2015 Energy Information Administration(EIA)global assessment(EIA 2015),Argentinaranks third among countries in shale-gas resources and fourth in shale-oil resources.The Vaca Muertaformation in the Neuquen basin holds most of these resources.After the first EIA assessment of theseresources in 2011,there has been a huge increase in investment,given the interest of the Argentinegovernment to recover the energy autonomy it lost in the 1990s.The objectives of this study were to updateestimates of oil and gas reserves and resources with the four years of production data available,and toquantify the uncertainty in these estimates.The Vaca Muerta formation was subdivided into sub-areas based on the fluid type.The most appropriateproduction decline model was determined for each sub-area and coupled with Markov-Chain-Monte-Carlo(MCMC)methodology to analyze and forecast production of existing wells to calculate reserves.Theanalyses of individual wells in each sub-area were used to create probabilistic type-decline curves.Thesecurves were combined with the estimated acreage-per-well distributions and the remaining drillable areasper sub-area to estimate contingent and prospective resources.The difference between contingent andprospective resources was based on the distance from existing wells.As of January 2018,the total reserves(P90–P50–P10)for the Vaca Muerta shale in Argentina associatedwith existing wells are estimated to be 8.5–17.5–38.4 MMm~3 of oil and 9.5–27.2–74.6 Bm~3 of gas.Estimatedcontingent resources are 8.8–50.6–181.1 MMm~3 of oil and 2.6–16.4–51.5 Bm~3 of gas.Estimated prospectiveresources are 424–2,464–8,771 MMm~3 of oil and 211–1,279–3,483 Bm~3 of gas.Resources and reservesestimates were combined to estimate technically recoverable resources(TRR).The estimated TRR are 443–2533–8992 MMm~3 of oil and 223–1223–3609 Bm~3 of gas.The results of this work should provide a more reliable assessment of the reserves and resources in theArgentine Vaca Muerta shale than previous estimates based on volumetric methodologies and analogies.