Enhanced Oil Recovery and

Residual Oil Zone Studies at the

U.S. Geological Survey

P.D. Warwick and U.S. Geological Survey Enhanced Oil

Recovery and Carbon Dioxide Storage Assessment Team

2017 EOR Carbon Management Workshop – Midland, Texas

Part of the Annual CO2 Conference Week, December 4-7, 2017

U.S. Geological Survey

Department of the Interior1

Outline for Presentation

• Part 1: Current activities associated with

national carbon dioxide enhanced oil

recovery (CO2-EOR) assessment

• Part 2: Current investigations associated with

residual oil zones (ROZs)

• Summary

2

Part 1: Assessment of National CO2-EOR

and associated CO2 storage

• Requested by Congress in the Energy Independence and

Security Act

• Goals: 1) develop a probabilistic assessment methodology,

and 2) estimate the technically recoverable (pre-economic)

hydrocarbon potential using CO2-EOR within the United

States

• Benefit: CO2-EOR can increase recoverable hydrocarbon

production leading to incidental retention of CO2 while also

making available pore space for long-term storage of

anthropogenic CO2

3

Summary of USGS five step

probabilistic assessment

methodology for CO2-EOR

and associated CO2 storage

Primary data sources:

• IHS Energy Group (2011); IHS

Inc. (2012), and Nehring

Associates Inc. (2012)

• Other publicly available or

donated proprietary data sets

4

https://doi.org/10.3133/tm7C16

Carolus and others (2017)

5

Screening criteria

properties (units)Miscible flooding Transitional Immiscible flooding

API gravity of oil (°API) 1>25 22 > API ≤ 25 213 ≤ API ≤ 22

3Viscosity (cP) <10 <10 <10

4Minimum miscibility

pressure (psi)≤ fracture pressure – 400 ≤ fracture pressure – 400 Not applicable

Screening Criteria Eligible Reservoirs

1 National Petroleum Council (1984).

2 Hite (2006).

3 Andrei and others (2010).

4 To maintain a reasonable level of safety, the minimum miscibility pressure of candidate reservoirs must be at least 400 psi below

the reservoir fracture pressure. The 400 psi safety margin is an estimate of current industry practice.

Carolus and others (2017) 6

Other assumptions and conditions

• The candidate EOR reservoirs have these characteristics:

net pay >5 ft, permeability >3 mD, OOIP >5 MMbbls

(Attanasi, 2016)

• Residual oil zones and active EOR reservoirs are not

included

• Oil recovery and CO2 retention factors are modeled with the

CO2 Prophet reservoir simulator (Attanasi, 2017)

• About 3,700 reservoirs found to be amenable to miscible

CO2-EOR, with about 140 candidate reservoirs amenable to

immiscible CO2-EOR (Warwick and others, 2017)

7

https://doi.org/10.3133/sir20175062.

Verma, ed. (2017)

Describes methods

of estimating CO2-EOR

recovery factors

8

More than 3,700 reservoirs are miscible candidates for CO2-EOR

More than 140 reservoirs are immiscible candidates

NOGA = USGS National Oil and Gas Assessment

(see Beeman and others, 1996)

9

USGS CO2-EOR Assessment Status

• The geologic CO2-EOR assessment is

underway and about 90 percent complete

• The results will be compiled into a report,

with peer review beginning in 2018, and

publication expected in 2019

10

Part 2: USGS working definition

for residual oil zone:

• The residual oil zone (ROZ) is a naturally

occurring reservoir or part of a reservoir

where a mix of mobile water and

potentially producible hydrocarbons

remain

• The ROZ can be either found between a

conventional oil/water contact and an oil-

free water level, or can be a reservoir on

its own

11

• Not all reservoirs have a ROZ zone

• Location and extent of ROZs are not well defined

• Well log data usually does not extend into the ROZ

• ROZ production data are limited and often

commingled with conventional production

• Need production analogues to assess the technically

producible oil and gas from ROZs

• Need additional data to access the potential CO2

storage (via CO2-EOR) in ROZs

ROZ assessment challenges

and considerations

12

Part 2.1

ROZ well log study

East Seminole Field, Texas

Jacqueline Roueche

C. Özgen Karacan

13

ROZ well log study overview

Objectives:

• Estimate remaining oil in place of the ROZ

with the use of well logs and core data

• Develop a methodology that could be

applied to all sedimentary basins

• Identify and characterize the presence of

potential productive ROZs in basins of the

United States

14

With the use of well logs and core data:

• Identify one active CO2-EOR brownfield

for testing the methodology

• Identify the ROZ as a function of depth

• Predict remaining oil saturation in ROZ

15

East Seminole Field

Gaines County, TX

San Andres Formation

(Modified from Merrill and others, 2015)

16

Statistical techniques were used to identify patterns of association and relationships from the acquired core and log data

Core Data:

• Monte Carlo and triangular distribution

• Calculate probabilistic in-situ oil saturations

Well Logs:

• Neural network from raw log readings – training and testing

Combine Well Logs with Core Data:

• Identify main pay (MP) vs ROZ as function of depth

• Predict oil saturation from will logs without core data

Roueche and Karacan (in press) 17

Part 2.2

ROZ Carbonate Production

Analogues

West Carney Hunton Field

Hossein Jahediesfanjani

18

Map showing production locations from the Silurian-Devonian

Hunton Group and informal Misener sandstone of the Woodford

Shale, and Hunton Group thickness; contour interval is 250 feet.

(Modified from Gaswirth and Higley, 2014)

West Carney

Hunton Field

19

West Carney Hunton as a ROZ

• In the Hunton Formation, the original oil was displaced by aquifer water influx in geological times

• Some of the oil was displaced to shallower formations, while some remained trapped in the Hunton Formation

• The amount of trapped oil, which mostly remained in relatively tighter rock, is a function of porosity and homogeneity of the reservoir

• The matrix that contains low permeability is oil wet and hence the oil could not be displaced

(Kelkar, 2007) 20

West Carney Hunton Field Properties

RegionOil

SaturationWater

Saturation Porosity

Central West 0.48_ 0.52_ 0.045

Central East 0.486 0.513 0.045

East 0.382 0.617 0.067

West 0.279 0.72_ 0.079

(Kelkar, 2007)

West Carney Hunton Field

Representative wells with production data

(IHS Markit, Inc.)

21

Next steps:

IHS Markit, Inc. well

production data analysis

Part 2.3

Red Fork Sandstone

ROZ Analogue

Mt. Vernon Field

Lincoln County, OK

Jacqueline Roueche

22

Location of the Cherokee Platform

Province

Mount Vernon Field

Pennsylvanian

Cherokee Group

Red Fork sand production

Modified from

Drake and Others (2015)

23

Modified from Chernicky and Schad (2002)

Mount Vernon Field

24

Modified from Chernicky and Schad (2002)

Mount Vernon Field

25

Next steps:

IHS Markit, Inc.

well production

data analysis

Summary

• The USGS is conducting a probabilistic assessment of the

technically recoverable hydrocarbon potential using CO2-EOR within

the United States; expected publication in 2019

• Well log data need to be calibrated with core data to better define oil

and water saturations in ROZs

• Multiple challenges remain before ROZs can be assessed on

regional and national scales (see page 12)

• Regional reservoir hydrocarbon production and CO2 storage

analogues are needed to calibrate ROZ assessment estimates

26

U.S. Geological Survey Enhanced Oil

Recovery and Carbon Dioxide

Storage Assessment Team

Emil Attanasi

Madalyn Blondes

Sean Brennan

Marc Buursink

Colin Doolan

Joseph East

Philip Freeman

Hossein Jahediesfanjani

C. Özgen Karacan

Celeste Lohr

Matthew Merrill

Ricardo Olea

Jacqueline Roueche

Jenna Shelton

Ernie Slucher

Brian Varela

Mahendra Verma

Peter Warwick

27

`Utilization of Carbon and other Energy

Gases—Geologic Research and

Assessments Project

For more information contact:

Peter D. Warwick

pwarwick@usgs.gov

703-648-6469

Project Website

Selected Publications

http://go.usa.gov/8X8

http://go.usa.gov/xZDpz 28

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