Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
7th May 2019, DEVEX
TONY PETERS
The Water-Oil Ratio (WOR)
WOR vs. Fractional Flow
WOR Decline Curve Analysis
WOR & Relative Permeability
WOR & IOR
WOR & Simulation Forecasting QC
WOR & Allocation
WOR & Redevelopment
OUTLINE
2
• Simple Analytical Tool
• Waterflood Developments (aquifer influx, water injection)
• WOR Plotlog WOR vs Cumulative Oil
• Standard Conditions
THE WATER-OIL RATIO (WOR)
𝑊𝑎𝑡𝑒𝑟 𝑂𝑖𝑙 𝑅𝑎𝑡𝑖𝑜(𝑊𝑂𝑅) =𝑊𝑎𝑡𝑒𝑟 𝑅𝑎𝑡𝑒 𝑏/𝑑
𝑂𝑖𝑙 𝑅𝑎𝑡𝑒 𝑏/𝑑
WOR Plot Key Components
• Post water breakthrough
• Initial rapid build – near well cone/cusp
• Turnover
• Post Turnover Trend
• to ultimate waterflood technical recovery for
development scheme (nominal, WOR100, 99%
w/c
• What happens post WOR not considered here
Scale Well, block, field, pipeline, basin, country
Reservoirs Majority – e.g. SS, chalk, fractured
Fluids All API’s so far developed in UKCS1
(Oil decline often flattens at high watercuts if liquid rates maintained to CoP)
4
2
2
3
3
4
1
5
5
Remaining mobile Oil @CoP
“SORW”
6
6
WOR – THE UPTURN
4
General perception that the WOR upturns at higher watercuts
Observation from simulation
Caused by simulation model boundary effects
Remove boundary effects, no upturn
Observed field upturns due to changes in reservoir hydrodynamic tilt (sweep).
e.g. reduced water injection, new offtake, etc.
PRESENTATION BASED ON DATA IN PUBLIC DOMAIN
5
Sourcehttps://data-ogauthority.opendata.arcgis.com/datasets/oga-field-production-points-pprs-wgs84*
* Data from some fields incomplete
Water-drive fields with
No gas injection (or no post turnover GI)
Wells allowed to produce with developing watercuts
Steady GOR
Recovery extrapolation <Mobile OIP
CANDIDATE FIELDS FOR WOR
6
Period of Post WBT
Optimization
E.G. BRENT PROVINCE*
7
Waterflood & aquifers (small)
Similar fluids
Platform & subsea
Multiple operators
Actively managed
<15% Recovery Dry
Similar WOR
*https://www.spe-uk.org/aberdeen/wp-content/uploads/2014/10/SPE-Simplified-Series-2014-11-01-Maximising-Waterflood-Recovery-Tony-Peters1.pdf
NON IDEAL CANDIDATES
8
Water & Gas Injection
Aquifer +Gas Cap
Active produced water management
Still suitable for selective application of WOR techniques• Well• Time
WOR VS. FRACTIONAL FLOW
9
WOR+ Extrapolates from lower recovery+ No knowledge of fluid properties required
WOR DECLINE CURVE ANALYSIS
10
Waterflood DCA key inputs for waterflood Fields• Liquid rate • Watercut development
WOR based DCA - Ideal for fields with fluctuating production histories Oil & Water Forecasts
E.G.
11
Workflow• Choose WOR Match Period• Generate exponential type curve of WOR vs Cum Oil
WOR DECLINE CURVE ANALYSIS
WOR DECLINE CURVE ANALYSIS
12
Workflow• Choose WOR Match Period• Generate exponential type curve of WOR vs Cum Oil• Calculate Oil Rate
𝑂𝑖𝑙 𝑅𝑎𝑡𝑒 𝑏/𝑑 =𝐿𝑖𝑞𝑢𝑖𝑑 𝑅𝑎𝑡𝑒 𝑟𝑏/𝑑
(𝑊𝑎𝑡𝑒𝑟 𝑂𝑖𝑙 𝑅𝑎𝑡𝑖𝑜 ∗ 𝐵𝑤) + 𝐵𝑜
Bw – Water FVF rb/bblBo – Oil FVF rb/bbl
WOR DECLINE CURVE ANALYSIS
13
𝑂𝑖𝑙 𝑅𝑎𝑡𝑒 𝑏/𝑑 =𝐿𝑖𝑞𝑢𝑖𝑑 𝑅𝑎𝑡𝑒 𝑟𝑏/𝑑
(𝑊𝑎𝑡𝑒𝑟 𝑂𝑖𝑙 𝑅𝑎𝑡𝑖𝑜 ∗ 𝐵𝑤) + 𝐵𝑜
Workflow• Choose WOR Match Period• Generate exponential type curve of WOR vs Cum Oil• Calculate Oil Rate • Calculate Water Rate
𝑊𝑎𝑡𝑒𝑟 𝑅𝑎𝑡𝑒 𝑏/𝑑 = 𝑊𝑂𝑅 ∗ 𝑂𝑖𝑙 𝑅𝑎𝑡𝑒 𝑏/𝑑
WOR DECLINE CURVE ANALYSIS
14
𝑂𝑖𝑙 𝑅𝑎𝑡𝑒 𝑏/𝑑 =𝐿𝑖𝑞𝑢𝑖𝑑 𝑅𝑎𝑡𝑒 𝑟𝑏/𝑑
(𝑊𝑎𝑡𝑒𝑟 𝑂𝑖𝑙 𝑅𝑎𝑡𝑖𝑜 ∗ 𝐵𝑤) + 𝐵𝑜
Workflow• Choose WOR Match Period• Generate exponential type curve of WOR vs Cum Oil• Calculate Oil Rate • Calculate Water Rate• Repeat for DCA cum oil anchored at start of WOR match period
𝑊𝑎𝑡𝑒𝑟 𝑅𝑎𝑡𝑒 𝑏/𝑑 = 𝑊𝑂𝑅 ∗ 𝑂𝑖𝑙 𝑅𝑎𝑡𝑒 𝑏/𝑑
WOR DECLINE CURVE ANALYSIS
15
𝑂𝑖𝑙 𝑅𝑎𝑡𝑒 𝑏/𝑑 =𝐿𝑖𝑞𝑢𝑖𝑑 𝑅𝑎𝑡𝑒 𝑟𝑏/𝑑
(𝑊𝑎𝑡𝑒𝑟 𝑂𝑖𝑙 𝑅𝑎𝑡𝑖𝑜 ∗ 𝐵𝑤) + 𝐵𝑜
Workflow• Choose WOR Match Period• Generate exponential type curve of WOR vs Cum Oil• Calculate Oil from • Calculate Water from• Repeat for DCA cum oil anchored at start of WOR match period• Assess match quality • Refine
𝑊𝑎𝑡𝑒𝑟 𝑅𝑎𝑡𝑒 𝑏/𝑑 = 𝑊𝑂𝑅 ∗ 𝑂𝑖𝑙 𝑅𝑎𝑡𝑒 𝑏/𝑑
WOR DECLINE CURVE ANLYSIS
16
𝑂𝑖𝑙 𝑅𝑎𝑡𝑒 𝑏/𝑑 =𝐿𝑖𝑞𝑢𝑖𝑑 𝑅𝑎𝑡𝑒 𝑟𝑏/𝑑
(𝑊𝑎𝑡𝑒𝑟 𝑂𝑖𝑙 𝑅𝑎𝑡𝑖𝑜 ∗ 𝐵𝑤) + 𝐵𝑜
Workflow• Choose WOR Match Period• Generate exponential type curve of WOR vs Cum Oil• Calculate oil from • Calculate water from• Repeat for DCA cum oil anchored at start of WOR match period• Assess match quality • Refine• Forecast vs. liquid rate
• Compare forecasts with simulation model – informs whether simulation model is optimistic or pessimistic
𝑊𝑎𝑡𝑒𝑟 𝑅𝑎𝑡𝑒 𝑏/𝑑 = 𝑊𝑂𝑅 ∗ 𝑂𝑖𝑙 𝑅𝑎𝑡𝑒 𝑏/𝑑
Qo Forecast – low liquid rate
Qo Forecast – high liquid rate
Qw Forecast – high liquid rate
Qw Forecast – low liquid rate
WOR DECLINE CURVE ANALYSIS
17
Example #2Quieter WORDeclining Liquid Rate
WOR DECLINE CURVE ANALYSIS
18
Example#3
Whole Production History
DCA on Cone/Cusp
WOR Production Type Curve
WOR reflects field scale relative permeability
Captures impact of reservoir heterogeneity, gravity, Pc, wettability, on recovery efficiency
Relative permeability is a major uncertainty in reservoir simulation
Tendency to adjust relative permeability to achieve history match with a geological realization
Relative permeability can be generated from observed WOR
Allows reservoir engineer to fix relative permeability @start of history matching process.
Enhances history matching workflow, improves quality of forecasts.
WOR & RELATIVE PERMEABILITY
19
Workflow – Spreadsheet Work
Fractional Flow (FW) & WOR generated from all production data
FW forecast from post turnover WOR extrapolation
FW post WOR turnover matched with corey curve – to 100% FW
Doesn’t match Pre WOR turnover FW
FW Pre WOR turnover matched on trial and error basis
Relative Permeability Curve Suitable to Forecast to 100% watercut
RELATIVE PERMABILITY FROM WOR
20
Corey Match
T&E
1
3
3
2
1
2
Corey Match
T&E
21
WOR – RELATIVE PERMEABILITY
Fine Grid Rel. Perm = 119 x 21 x 7
VS.
Coarse Grid Pseudo = 17 x 3 x 1
Fine Scale
Coarse with Corey Curve
Match to WOR Turnover
period only
Coarse, Corey +
T&E
• Match achieved first time with WOR generated pseudo relative permeability
A rel perm with excellent predictive capability
Utility in Material Balance/Integrated Production Models
22
WOR – RELATIVE PERMEABILITYAPPLIED TO FULL FIELD MODEL
Extrapolation from v low FW
Excellent match– first time
Careful selection of WOR extrapolation period
WOR & IOR
23
WOR Excellent@• Identifying changes in reservoir performance• Quantifying net impact of changes
E.G.Discernible change in WOR character at end of match Period. Coincides with:
• 1st 4D Seismic• 1St Horizontal Well
For observed liquid can calculate deltas
Approach suitable for any changes (+/-)
(WOR vs time often used for surveillance)
WOR & SIMULATION FORECAST QC
24
WOR plot a good reality check vs simulation model forecasts
E.G.Injector –producer pair, 100% VR200 md, varying KVKH
KV/KH1
0.10
25
KV/KH1
0.10
WOR & SIMULATION FORECAST QC
26
KV/KH1
0.10
WOR & SIMULATION FORECAST QC
27
KV/KH1
0.10
WOR & SIMULATION FORECAST QC
28
• Closer Look
WOR • Too flat, model optimistic past 70% watercut• Total Recovery > Mobile oil below top
perforation• Well draining more oil than it should
Subtle• Such artefacts difficult to eliminate• Can have significant impact on conclusions
re infill prospectivity
History Match with the DCA Forecast
WOR & SIMULATION FORECAST QCPROSPECT INTEGRITY
DATES01 SEP 2030 /
/WCONHIST‘P1' OPEN ORAT 500 5000 4* //
LTROWCONHIST+WCONPROD
e.g. – Two fields, shared flowline
WOR in each field changed
Production Performance ?
Reservoir Performance ?
Steady Pipeline (Meter ?) Level WOR
Potential allocation Issue
WOR DCA approach can help fill in the in the gaps in well test information
WOR & ALLOCATION
29
WOR & REDEVELOPMENT
30
• WOR plot can quantify the minimum amount of mobile oil left at CoP for development scheme• Volumes can be significant for large fields
Remaining mobile Oil @CoP
“SORW”
WOR & REDEVELOPMENT
31
• A number of fields have been redeveloped
• Partially resaturation
• Observation• Production trends back to historic WOR
trend
WOR can be a useful tool for redevelopment option screening
WOR & DEVELOPMENT SIZING
32
• Erratic Liquid Production History• 100 MMbbls+ Mobile oil at CoP
E.G.
WOR & DEVELOPMENT SIZING
33
• WOR DCA Forecasts vs Assumed Liquid Rate• Reserves profile (etc.) vs. redevelopment option
• Conservative • Resaturation not accounted for• No optimization• Compare with simulation results - when/if available• No account of modern technology
• ICV, HW, 4D, designer water
• Workflow Suitable @ all Levels• well , common drainage, field, licence, HUB etc
Define ultimate recovery early in field life for active development scheme O/W/G Profiles, quantification of target volumes for IOR schemes
Quantify net recovery benefits of changes to base
Improve simulation & integrated production models
Reality check simulation forecasts
Improve confidence in simulation model predictions – base + infill potential
Improve allocation
Quantify minimum amount of mobile oil remaining at CoP and generate conservative objective profiles for redevelopment option screening
All from production data
34
“PROBABLY THE BEST RESERVOIR ENGINEERING TOOL IN THE WORLD”
WOR SUMMARY
Thank You !
35