Within Your Reservoir March 22, 2018 Stephen Whitaker Enhanced Oil - - PowerPoint PPT Presentation

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Within Your Reservoir March 22, 2018 Stephen Whitaker Enhanced Oil - - PowerPoint PPT Presentation

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Interwell Tracer Tests: Understanding Inter-Well Connectivity Within Your Reservoir March 22, 2018 Stephen Whitaker Enhanced Oil Recovery Institute 1 Agenda 1. Know Your Reservoir 2. General Properties of Interwell Tracers 3. Tracer

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Enhanced Oil Recovery Institute

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Interwell Tracer Tests: Understanding Inter-Well Connectivity Within Your Reservoir

March 22, 2018

Stephen Whitaker

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Agenda

  • 1. Know Your Reservoir
  • 2. General Properties of Interwell Tracers
  • 3. Tracer Project Design
  • 4. Injection and Sampling
  • 5. Data Analysis and Interpretation
  • 6. Examples of Interwell Tracer Surveys
  • 7. Remaining Oil Saturation Calculations
  • 8. Summary
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Two Rules for Being a Successful Oil & Gas Professional

  • 1 - You must excel at working with incomplete data sets
  • 2 -
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Know Your Reservoir

  • A key to maximizing recovery efficiency from any reservoir is

proper reservoir characterization (know your reservoir)

  • Data from logs and cores within a field do not provide the

necessary information to map the internal plumbing of the reservoir

  • Interwell tracer tests can greatly increase the understanding
  • f the reservoir architecture, which is needed to maximize

production

  • reservoir flow paths
  • heterogeneities
  • unswept areas of the reservoir

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Know Your Reservoir

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Example of Tracer Response with Uniform Sweep

  • Most operators assume that this is the case with each injection well
  • Very rare
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Know Your Reservoir

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An isopach of a traditional oil field with injector wells

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Know Your Reservoir

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An isopach of a traditional oil field with injector wells and producing wells

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Know Your Reservoir

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Inter-well tracers can determine the flow paths within the reservoir:

  • Measure breakthrough times
  • Identify thief zones
  • Identify existence of faults
  • Indicate extent of formation layering
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Know Your Reservoir

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and help indicate the locations of barriers to fluid flow

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Know Your Reservoir

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By measuring the amount of tracer recovered it is possible to quantify:

  • Swept Pore Volume
  • Sweep Efficiency
  • Approximate Remaining Oil
  • Conformance Gel treatment

volume estimations

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Such as identifying flow behavior prior to full-field planning and project scale-up

  • At the pilot stage of new flood projects
  • To evaluate specific injector-to-producer

flow connections

Breakthrough times allow the sources of high water-cuts or spurious gas:oil ratios to be determined

  • EOR studies

When evaluating various recovery mechanisms & different conformance treatments (e.g. polymer or chemical floods)

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When to use Interwell Tracers

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  • Inert chemicals that will follow

and behave as the water flowing through the reservoir:

  • Non-reactive and stable
  • No absorption or retardation with

the formation

  • Do not interact with hydrocarbons
  • Have very low detection limits

(parts per trillion)

  • Show minimal environmental

consequences

  • Cost-effective
  • Nearly 50 unique water tracers available

depending on reservoir conditions

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Properties of Waterflood Tracers

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  • Inert chemicals that will follow and behave as the

injected gas mixture flowing through the reservoir:

  • Non reactive chemical gas tracers used
  • Stable at reservoir conditions
  • No absorption onto reservoir rock
  • Should have vapor / liquid hydrocarbon

solubility properties as close to the injected gas as possible

  • Have very low detection limits (parts per trillion)
  • Show minimal environmental consequences
  • Cost-effective
  • About 20 unique gas tracers available

depending upon reservoir conditions

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Properties of Gasflood Tracers

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Tracer Project Design

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1. Project objectives 2. Tracer selection & compatibility testing 3. Tracer quantity calculation 4. Initial sampling regimen 5. Tracer injection and sampling 6. Analytical results 7. Data interpretation 8. Revise sampling regimen (if needed) 9. Evaluation of tracer data

  • 10. Historic match to fit tracer data
  • 11. Repeat tracer application if desired

Pre-Deployment Tracer Deployment Post-Deployment

Tracer Project Design

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Injection & Sampling

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Tracer analysis is able to measure very low detection levels (parts per trillion)

This means:

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Injection

  • Low tracer quantity
  • Portable equipment
  • No disruption to normal operations
  • No requirement to shut-in wells
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  • 1. Complete

paperwork

  • 2. Fill water

sample

  • 3. Or gas

sample

  • 4. Label sample
  • 5. Place sample

Into box

  • 6. Seal box
  • 7. Send box to

Tracerco

  • 3. Or gas

sample

  • 7. Send box to

tracer company

Sample Collection

Collecting samples and sending to the tracer company for analysis is simple, fast, and convenient

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  • Samples taken from producing wells at

regular intervals to measure tracer content

  • Samples taken more frequently

immediately after injection to catch matrix bypass events

  • Frequency dependent upon injection rates

& formation volume / quality, as well as the distance between injectors and producers

  • Special care is required to prevent sample

contamination during collection

  • For gas, CATS tubes (Capillary Adsorption

Tube Samplers) or onsite lab set-up an

  • ption if required to ship using constraints
  • Not necessary to analyze every sample

collected

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Sample Collection

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Sample Collection

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Data Analysis & Interpretation

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Data Analysis & Interpretation

Common response at producer to tracer injection

Tracer Concentration ppt Days Post Injection

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Data Analysis & Interpretation

Tracer Concentration ppt Days Post Injection

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Data Analysis & Interpretation

Tracer Concentration ppt Days Post Injection

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Data Analysis & Interpretation

Tracer Concentration ppt Days Post Injection

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Data Analysis & Interpretation

MRT is used to evaluate sweep efficiencies, heterogeneity, permeability, etc. Tracer Concentration ppt Days Post Injection

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Data Analysis & Interpretation

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Data Analysis & Interpretation

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Data Analysis & Interpretation

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Data Analysis & Interpretation: Commingled Zones

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Data Analysis & Interpretation: Commingled Zones

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Data Analysis & Interpretation: Commingled Zones

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Data Analysis & Interpretation: Commingled Zones

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Data Analysis & Interpretation: Commingled Zones

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Data Analysis & Interpretation: Commingled Zones

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Data Analysis & Interpretation: Commingled Zones

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Application Examples

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Case Studies: Waterflood Application

The Project:

An oil field operator wished to better understand communication pathways within an inverted nine-spot waterflood operation. This study was to establish:

  • Sweep efficiency of the field
  • Determine if there was preferential

flow direction

  • Resolve the problem of excessive

water production in several wells

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Case Studies: Waterflood Application

The Project:

An oil field operator wished to better understand communication pathways within an inverted nine-spot waterflood operation. This study was to establish:

  • Sweep efficiency of the field
  • Determine if there was preferential

flow direction

  • Resolve the problem of excessive

water production in several wells Tracers proved that there was preferential flow to the west-southwest

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Case Studies: Waterflood Application

Interpretation of Results

  • There is preferential flow to the west

and southwest

  • Several areas of the field have not

been swept

  • Flood can be improved by changing

pattern through recompletions or in- fill drilling

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Wyoming Case Study: Gas Flood

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Wyoming Case Study: Gas Flood

  • ~19 Injection wells
  • Unique gas tracer in each well
  • ~18 Producing wells
  • Breakthrough expected in hours or

days

  • Problems
  • Breakthrough of gas in several wells
  • Suspected poor sweep (fractures,

faults, varying reservoir quality)

  • Thinking of trying polymer
  • Objectives
  • Track preferential flow
  • Identify fractures/faults and other

factors that affect sweep

  • Identify wells for polymer

applications

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Depth: 7500’ Porosity: 15% Permeability: 50md

  • Sample collection started

within hours of injection due to expected breakthrough (BT) timing

  • Initial sample frequency on

an hourly basis and reduced

  • ver time
  • One or more tracers

produced in most wells

  • High connectivity identified

in 3 areas (circled)

Wyoming Case Study: Gas Flood

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Depth: 7500’ Porosity: 15% Permeability: 50md

  • Sample collection started

within 2 hours of injection due to expected breakthrough (BT) timing

  • Initial sample frequency on

an hourly basis and reduced

  • ver time
  • One or more tracers

produced in most wells

  • High connectivity identified

in 3 areas (circled)

  • Injectors 5, 7, 8, 11 and 18 identified as potential candidates for polymer trial.

Wyoming Case Study: Gas Flood

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Injectors 5 and 7.

  • Both show high connectivity with
  • p6. Poor sweep with BT in day 1.
  • 37% of inj 7 tracer produced in p6
  • 25% of inj 5 tracer produced in p6

Inj 5 -Inj 7

6 5 7 4

Tracer Pulse Well #6

Wyoming Case Study: Gas Flood

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Injector 8

  • Connectivity to p10; 9% of tracer produced Day 1.
  • High tracer concentration early and brief pulse

indicating channeling through fracture or fault. Tracer not present in other nearby producers. Injector 11

  • 37% tracer produced in p10. BT Day 1.
  • Channeling and relatively poor sweep.

Injector 13

  • Communication with p10 detected. Effective sweep.

Wyoming Case Study: Gas Flood

Inj 8 Inj 11 Inj 13

Tracer Pulse Well #10

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Injector 18

  • Channeling and ineffective

sweep to p15

  • 35% tracer recovery in 6

days with BT day 1.

15 18

Inj 18

Tracer Pulse Well #15

Wyoming Case Study: Gas Flood

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Case Studies: CDG Pilot Flood

< 1,000 BO 1,000 – 5,000 BO 5,000 - 10,000 BO 10,000 - 20,000 BO 20,000-30,000 BO 30,000-40,000 BO 40,000-50,000 BO > 50,000 BO

Incremental Oil Production From Waterflood

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Case Studies: CDG Pilot Flood

Failed ASP Pilot

Reservoir had been under continuous waterflood for 65 years

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Four Injectors, 7 producers

Case Studies: CDG Pilot Flood

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ASP Pilot Wells

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Top of “D” zone Rate 700 BPD WHP 220 PSI Rate 225 BPD WHP 120 PSI Rate 228 – 741 BPD WHP 200 – 230 PSI

Griggs #131

0 100 200 300 400

Case Studies: CDG Pilot Flood

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RA Tracer survey shows injection fluids all going into one zone within perf’d interval

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 Reservoir had been continuously flooded since 1954  ASP Pilot project failed immediately to the east of the CDG Project area  CDG injection contemplated to improve sweep efficiency due to reservoir

heterogeneity (work on CDG pilot flood started early 2009)

 RA tracers indicated injectivity profiles must be modified to improve water-flood

  • r chemical-flood performance

 Interwell tracer survey was needed to help determine flow paths and degree of

heterogeneity

▪ Unique chemical tracers used in each of 4 injectors ▪ Potassium, Iodide, Thiocyanate, and Bromide  A rigid (MARCIT) gel treatment was designed and implemented to plug off thief

zones, based on results of interwell tracer survey, prior to injection of any CDG

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Case Studies: CDG Pilot Flood

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Case Studies: CDG Pilot Flood (Tracer Survey)

Sandstone Isopach > 18% Porosity

GH-6

Potassium tracer

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8 days 20 days

GH-6

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Case Studies: CDG Pilot Flood (Tracer Survey)

Sandstone Isopach > 18% Porosity

3 days

Iodide tracer

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1 day 13 days 58

HH-6A

0 250 ft 58

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Case Studies: CDG Pilot Flood (Tracer Survey)

Sandstone Isopach > 18% Porosity

15 days

GH-6

Thiocyanate tracer

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10 days 27 days 16 days 30 days 17 days 27 days ❖ Response @ # 52 (17 days) cannot be confirmed as the well had 2 SI days ❖ Response @ # 50 (30 days) cannot be confirmed—well had been SI for 2 days 59

II-6

13 days

0 250 ft

❖ Response @ # 52 (17 days) cannot be confirmed - well had been SI for 2 days ❖ Response @ # 50 (30 days) cannot be confirmed - well had been SI for 2 days

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Case Studies: CDG Pilot Flood (Tracer Survey)

Sandstone Isopach > 18% Porosity

GH-6 HH-6A

Bromide tracer

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“Thief” zone is no longer taking much fluid

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Case Studies: CDG Pilot Flood (Gel Treatment)

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Sandstone Isopach > 18% Porosity

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Case Studies: CDG Application

Inter-well Tracer Response 17 weeks after CDG Injection started

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Case Studies: CDG Application

10 20 30 40 50 60 70 200 400 600 800 1000 1200

9/3/09 9/10/09 9/17/09 9/24/09 10/1/09 10/8/09 10/15/09 10/22/09 10/29/09 11/5/09 11/12/09 11/19/09 11/26/09 12/3/09 12/10/09 12/17/09 12/24/09 12/31/09 1/7/10 1/14/10 1/21/10 1/28/10 2/4/10 2/11/10 2/18/10 2/25/10 3/4/10 3/11/10 3/18/10 3/25/10 4/1/10 4/8/10 4/15/10 4/22/10 4/29/10 5/6/10 5/13/10 5/20/10 5/27/10 6/3/10 6/10/10 6/17/10 6/24/10

Barrels Oil Produced & Oil Cut Total Fluid Bbls

W Griggs Lease CDG Flood Weekly Averages

Fluid Injected Total Fluid Produced Oil Oil Cut %

Pre-CDG Flood Weekly Average from 8 producers was 18.2 BO / 1008 BW (1.8% oil-cut)

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Remaining Oil Saturation Calculations

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  • Use partitioning and

non-partitioning tracers

  • Both tracers added to injection at same

time

  • During transit between wells,
  • Partitioning (passive) tracer moves only

with the water

  • Non-partitioning tracer interacts with

residual oil, thus altering its progress

Remaining Oil Saturation Calculations

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Benefits:

  • Non-intrusive
  • Provides measurement of oil

saturation in the region between injectors and producers instead of only near the well bore

  • Tests can be run during normal
  • peration
  • No loss in production
  • Assumes that tracers contact

immobile oil along flow-paths

  • f watered-out zones between

wells

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Partitioning Tracers

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Ideal candidates have the following properties:

  • Relatively mature flooded reservoir
  • Injector to producer spacing is relatively close to

enable results in a reasonable time period

  • Need to know that well pairs are communicating
  • Sweep efficiency should be reasonable
  • Only Sorw (residual oil saturation to water) will

be measured and NOT unswept zones

  • Production well must be able to lift fluids to surface
  • Formation should be reasonably homogeneous –

allows for relatively easy interpretation of key positions along the tracer graphs

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Partitioning Tracers

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Prior to using passive and partitioning tracers the following measurements should be carried out:

  • Laboratory based crushed core retention and retardation tests

using clean and residual-oil-saturated core

  • Partition coefficient testing at reservoir conditions
  • Analytical compatibility
  • Required data
  • Core sample or access to similar rock
  • Produced oil from field
  • Gas sample from the field or gas composition
  • Formation / produced water close to study area
  • Injection water from injector close to study area (if water is re-injected)

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Partitioning Tracers

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0 30 60 90 120 150 180 250 200 150 100 50 0.0 Tracer Response Days after injection So = Tp – Tw Tp + (K-1)Tw = 34% = 34 - 22 34 + (1.06-1)22

Partitioning Tracers: Sampling & Analysis

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Discussion & Conclusion

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  • Interwell tracer surveys are a powerful tool in determining ways of maximizing

recovery efficiencies in IOR and EOR projects

  • One of best direct tools to understand fluid movement within a reservoir
  • Provide information on:
  • Breakthrough times
  • Communication pathways
  • Thief zones, natural fractures, faults
  • Formation layers
  • Identify sources of excess water
  • Problem injectors
  • Quantification of
  • Injected fluid distribution
  • Swept pore volume
  • Sweep efficiency
  • Reservoir geometry (including flow capacity and storage capacity)

Summary

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Companies: Interwell Tracer Surveys

  • Chemical Flooding Technologies, LLC: www.chemicalfloodingtechnologies.com

24431 E. 61st Street, Suite 850, Tulsa, OK 74136 (918) 743-7575

  • Chemical Tracers, Inc: http://www.chemtracers.com

Headquarters: 1814 Steele, Laramie, WY 82070 (307) 742-0418

  • Core Lab (Spectraflood): www.corelab.com

Headquarters: 6510 W. Sam Houston Pkwy. N., Houston, TX 77041 Contact: David Chastain, Manager Interwell Tracer Services David.Chastain@corelab.com (713) 328-2393 office; (281) 352-4697 mobile

  • Tracerco: www.tracerco.com

Headquarters: 4106 New West Dr., Pasadena, TX 77507 Utah: 2698 S. Redwood Rd, Ste. T., West Valley City, UT 84119 KC Oren; KC@GeoStarSolutions.com (303) 249-9965

  • Tracer Technologies International (subsidiary of Chemical Flooding Technologies):

sales@tracer-tech.com

26800 Fargo Ave # B, Cleveland, OH 44146 (216) 464-9300

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Thank You

Questions and Comments:

Stephen Whitaker, Senior Geologist

swhitak2@uwyo.edu Office 307-315-6446

Lon Whitman, Petroleum Engineer & Outreach Manager

eoribiz@uwyo.edu Office 307-315-6450

www.eoriwyoming.org

Enhanced Oil Recovery Institute