Predicting Cumulative Production of Devonian Shale Gas ...
Transcript of Predicting Cumulative Production of Devonian Shale Gas ...
Predicting Cumulative Production Predicting Cumulative Production of Devonian Shale Gas Wells from of Devonian Shale Gas Wells from
Early Well Performance Data, Early Well Performance Data, Appalachian Basin of Eastern Appalachian Basin of Eastern
KentuckyKentuckyBrandon C. NuttallBrandon C. Nuttall
Kentucky Geological SurveyKentucky Geological SurveyWith contributions by Shannon DaughertyWith contributions by Shannon Daugherty
Eastern Section AAPG, Lexington, KentuckyEastern Section AAPG, Lexington, Kentucky1717--SepSep--20072007
Funding: National Coal Resources Data System, U. S. Geological Survey
A A ““shaleshale”” well well isis……??
•• Top Sunbury to Top Sunbury to top underlying top underlying carbonatescarbonates
SunburyBerea
Cleveland
Three Lick Bed
Upper Huron
Middle Huron
Lower Huron
Olentangy
Rhinestreet
Ohi
o
Early Performance DataEarly Performance Data
•• Well log and completion reportWell log and completion report–– Initial Open FlowInitial Open Flow–– Rock PressureRock Pressure
•• Monthly production Monthly production (805 KAR 1:180, KRS (805 KAR 1:180, KRS 353.205)353.205)–– Maximum monthly production (Maximum monthly production (McfMcf))–– First year cumulative productionFirst year cumulative production–– 5 year cumulative production5 year cumulative production
Data SetsData Sets
•• KGS online well completion dataKGS online well completion data–– Location, completions, IOF, RPLocation, completions, IOF, RP
•• Division of Oil and GasDivision of Oil and Gas–– Public production data by month (1997)Public production data by month (1997)
•• Gas Technology Institute (GRI)Gas Technology Institute (GRI)–– Historic, longHistoric, long--term production dataterm production data–– ProprietaryProprietary, available to members and , available to members and
contractorscontractors
Production Data SelectionProduction Data Selection
•• Completed since 1Completed since 1--JanJan--9797•• Devonian shale only (not commingled)Devonian shale only (not commingled)•• 60 or more months of non60 or more months of non--zero datazero data•• 310 wells310 wells
Initial Open Flow DataInitial Open Flow Data
•• Exhibits only Exhibits only weak trendsweak trends
•• No uniform No uniform method of method of acquiringacquiring
Reported Reported ““Rock PressureRock Pressure””
•• High and low High and low open flows open flows occur in areas occur in areas of both high of both high and low rock and low rock pressurepressure
Rock Pressure Rock Pressure vsvs IOFIOF
0
500
1000
1500
2000
0 200 400 600 800 1000
Rock Pressure (psi)
IOF
(Mcf
)
FiveFive--year Cumulative Productionyear Cumulative Production
•• Again, weak Again, weak trendstrends
•• Areas with Areas with higher and higher and lower lower production are production are often adjacentoften adjacent
Initial Open FlowInitial Open Flow
y = 0.0886x + 43.204R2 = 0.25
0
100
200
300
400
500
600
0 1000 2000 3000 4000 5000
IOF (Mcf)
5-ye
ar C
umul
ativ
e (M
Mcf
)
Correlation is statistically significant, but weak
GTI Cumulative ProductionGTI Cumulative Production
0%
25%
50%
75%
100%
0.0001 0.001 0.01 0.1 1 10
1 ye
ar
5 ye
ar10
yea
r25
yea
r50
yea
rBillion Cubic Feet
10 MMcf 692 MMcf
Proprietary data
Industry rule of thumb is 300 MMcf per well
Cumulative Gas ProductionCumulative Gas Production
0
0.5
1
1.5
2
2.5
3
0 10 20 30 40 50 60
Class 1Class 2Class 3Class 4
Years in Production
Bill
ion
Cub
ic F
eet
GTI data
Cumulative Production Over Cumulative Production Over TimeTime
y = 1.8887x + 7.0426R2 = 0.9278
0
200
400
600
800
1000
1200
0 100 200 300 400 500 600
Five-year (MMcf)
Ten-
year
(MM
cf)
GTI data
Public Production Data Public Production Data
0%
25%
50%
75%
100%
0.1 1 10 100 1000
Million cubic feet (MMcf)
35 MMcf
59 MMcf
98 MMcf
Type 1: Blue
Type 2: Green
Type 3: Yellow
Type 4: Red
Classes
Data from Kentucky Division of Oil and Gas
6 m
onth
s1
year
5 ye
ars
General Decline Model (General Decline Model (ArpsArps))
( )bi
it
tbD
qq 11+
=Hyperbolic:
Best fit parameters:qi – initial productionDi – nominal declineb – decline exponent
Special cases:
tDi
t ieqq =Exponential, b=0: Harmonic, b=1: ( )tD
qqi
it +=
1
SolvingSolvingExponential:
( ) ( ) tDqq iit += lnlnLeast squares
Hyperbolic:OptimizationLinear Programming
Both can easily be done with the built-in functions supplied with spreadsheets, but…
Best Case: Best Case: Textbook DataTextbook Data
Deplete free gas in fractures
Desorbs from fracture faces Desorption and
diffusion through shale matrix
Natural fracturing is key to production
Rule of thumb:Di ≈ -0.95 to -0.99
Many data sets have a “decline” (i.e., slope) that is not statistically different from 0 (no correlation).
Max production is the initial period
For exponential decline, Qi is often less than max production
For hyperbolic decline, Qi is often greater than max production
Basis of classification
25th percentile50th percentile
75th percentile
Public data from the Kentucky Division of Oil and Gas
Type DeclinesType Declines
0
50
100
150
200
0 12 24 36 48 60
Months
Type 1: 143MMcf Type 2: 78 MMcf Type 3: 46 MMcfType 4: 23 MMcf
Ave
rage
Mcf
/d
Five-year cumulative production in million cubic feet
ConclusionsConclusions•• Shale production data is messyShale production data is messy•• Decline curve analysis and reserves Decline curve analysis and reserves
projection is an artprojection is an art•• Maximum average daily production during Maximum average daily production during
the first 6 months is an adequate indicator of the first 6 months is an adequate indicator of future well performancefuture well performance
•• Best wells can be expected to make:Best wells can be expected to make:–– 20 20 MMcfMMcf in first yearin first year–– 100 100 MMcfMMcf after 5 yearsafter 5 years
ThanksThanks
•• www.uky.edu/kgswww.uky.edu/kgs•• [email protected]@uky.edu•• Oil and gas well search with production Oil and gas well search with production
datadata–– kgsweb.uky.edu/DataSearching/OilGas/OGSearch.aspkgsweb.uky.edu/DataSearching/OilGas/OGSearch.asp
•• Oil and gas well interactive mappingOil and gas well interactive mapping–– kgsmap.uky.edu/website/KGSGeology/viewer.aspkgsmap.uky.edu/website/KGSGeology/viewer.asp
•• Project web pageProject web page–– www.uky.edu/KGS/emsweb/devsh/production/index.htmwww.uky.edu/KGS/emsweb/devsh/production/index.htm