Preliminary Methodology for a National Assessment of Technically Recoverable Oil Using the Carbon Dioxide-Enhanced Oil Recovery Process

Abstract

The U.S. Energy Independence and Security Act of 2007 authorized the U.S. Geological Survey (USGS) to prepare a national assessment of the potential volume of hydrocarbons recoverable by injection of carbon dioxide (CO₂) in known oil reservoirs. The implementation of CO₂ enhanced oil recovery (CO₂-EOR) techniques can increase the U.S. recoverable oil resource base and reduce CO₂ released to the atmosphere by storing the residual CO₂ in reservoir pore space vacated by produced oil. The USGS has developed an assessment methodology for estimating potential incremental technically recoverable oil resources that may be producible by implementing CO₂-EOR in reservoirs with appropriate depth, pressure, and oil composition for CO₂ injection. The methodology relies on a reservoir-level database that incorporates commercially available geologic and engineering data; play averages or province averages of reservoir data are used to populate incomplete records. This allows computation of an initial estimate of original oil in place (OOIP) for each reservoir. For each assessed play, USGS geologists evaluate probability distributions associated with estimates of average porosity and initial oil saturation for the largest reservoirs, and are responsible for evaluating EOR failure risk. Simulation is used to produce a probability distribution for the OOIP that has as its mean the database OOIP estimate. The resulting distribution is scaled and applied to the database point estimates of other EOR reservoir candidates in the play. Distributions of recovery factors are prepared based on EOR method (miscible or immiscible) and reservoir lithology. The distribution of incremental oil is computed by multiplying the appropriate probability distribution of recovery factors by the candidate reservoir distribution of OOIP. An estimate of the CO₂ remaining in the reservoir after the CO₂-EOR process is completed also is included in the methodology. Assessment results will be aggregated to the play, basin, region, and national levels. This assessment methodology has been tested and produced realistic results for the Permian Basin Horseshoe Atoll play comprising 84 reservoirs. Once the assessment methodology has been thoroughly reviewed by a panel of industry, academic, and other experts, the USGS plans to conduct a national assessment of incremental oil technically recoverable using the CO₂-EOR process.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015