“WELL PRODUCTION PERFORMANCE
ANALYSIS FOR UNCONVENTIONAL SHALE
GAS RESERVOIRS; A CONVENTIONAL
APPROACH”
FLORIN HATEGAN
Devon Canada Corporation
BACKGROUND
Shale Gas HZ Drilling, Multi-Stage Hydraulic Fracturing:
 Today is the norm throughout the industry
 Very High Drilling & Completion costs
 Performance Evaluation “complex” and controversial
 SUCCESS IS RESERVOIR SPECIFIC
 FIELD ANALOGIES CAN BE DANGEREOUS
 ABSTRACT CONCEPTS SUCH AS S.R.V., OR F.C.A.
WRONGLY USED AS DEFINING PARAMETERS
 IN-SITU RESERVOIR PARAMETERS SUCH AS PORE
PRESSURE AND PERMEABILITY ARE TO OFTEN
OVERLOOKED, OR IGNORED
PRESENTATION OVERVIEW
•
•
•
•
Introduction
Stimulated Reservoir Volume (SRV)
Linear Flow Spreadsheets
Analytical Model Construction
 Pseudo Steady State Equation Solution
 Reservoir Pressure
 Permeability or Flow Capacity
 Completion Skin
 Drainage Area and Shape
 Field Case Examples
• NORMALIZED SHALE GAS PRODUCTION PLOT
• In-Situ Testing for D&C Optimization
 Field Case Example
• Conclusions
INTRODUCTION
• PERFORMANCE EVALUATION
 SHALE GAS PRODUCTION CAN NOT BE ANALYZED BY
CONVENTIONAL METHODS (e.g. DARCY LAW)
 PRODUCTION PERFORMANCE IS MAINLY A FUNCTION OF
STIMULATED RESERVOIR VOLUME (SRV)
 USE OF “LINEAR FLOW” SPREADSHEETS
• CHALLENGE
 SHALE GAS PERFORMANCE CAN BE MODELLED ANALYTICALLY
USING PSEUDO STEADY-STATE SOLUTION
 ONLY 4 (Four) KEY FORECST PARAMETERS:
 Reservoir Pressure
 Matrix Permeability (In-Situ)
 Completion Skin
 Drainage Area & Shape per Stage (correlated to Pi, k & s’)
 ANALYTICAL MODEL = Superposition of Solutions for
Pseudo Steady-State Equation Applied to Individual Frac
Stages
Stimulated Reservoir Volume (SRV)
• The most talked about concept introduced after successful
HZ-MSF developments in the Barnett Shale and elsewhere
• Thousands of publications, articles and presentations on
this topic
• SRV may be over-rated or misunderstood
Stimulated Reservoir Volume (SRV)
• Microseismic Mapping
Stimulated Reservoir Volume (SRV)
• Integration of Microseismic into Reservoir Simulator
Stimulated Reservoir Volume (SRV)
• Integration of Microseismic into Reservoir Simulator
Stimulated Reservoir Volume (SRV)
• Integration of Microseismic into Reservoir Simulator
 SRV gridding and Ksrv distribution
Stimulated Reservoir Volume (SRV)
• IN-SITU SHALE GAS MATRIX CONFIGURATION:
 THIN SECTION
 MATRIX & NAT. FRACTURES
Stimulated Reservoir Volume (SRV)
• IN-SITU SHALE GAS MATRIX CONFIGURATION:
 THIN SECTION
 MATRIX, NO NAT. FRACTURES
Stimulated Reservoir Volume (SRV)
• MATRIX & NAT. FRACTURES
• MATRIX, NO NAT. FRACTURES
Stimulated Reservoir Volume (SRV)
• EVIDENCE OF SHALE MATRIX WITH NO IN-SITU NAT. FRACTURES:
Linear Flow Spreadsheets
Linear Flow Spreadsheets
WELL NAME HERE
WELL NAME HERE
6.0E+06
1000
WELL NAME HERE
10000
4.0E+06
900
5.0E+06
800
500
400
Rate
dm(p)/q
3.0E+06
Pressure
dm(p)/q
600
3.0E+06
1000
700
4.0E+06
2.0E+06
100
1.0E+06
2.0E+06
300
200
1.0E+06
10
100
0.0E+00
0.0E+00
1
10
100
10
20
30
40
10,000
0.0
0.5
1.0
Time
0
0
1,000
50
Daily Production
AOF
EHS
Test
Actual
Sqrt t
WELL NAME HERE
WELL NAME HERE
10,000
1.5
2.0
2.5
3.0
Cum (Bcf)
Fitted
tehs
WELL NAME HERE
1.0E-04
1.0E-05
3.0E+06
100
1.0E-06
dm(p)/q
Rate (Mcf/D)
q/dm(p)
1,000
2.0E+06
1.0E-07
1.0E+06
1.0E-08
0.0
10
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.5
1.0
1.5
2.0
Cum (Bcf)
2.5
3.0
1.0E+04
Cum (Bcf)
0
A ctual
Fitted
tehs
Actual
tehs
10
20
30
Sqrt t
40
50
60
Linear Flow Spreadsheets
• Input Data
• Results
ANALYTICAL MODEL
CONSTRUCTION
• Pseudo Steady-State Equation
 General
 Using Gas Pseudo-Pressure
ANALYTICAL MODEL
CONSTRUCTION
• Reservoir Pressure
Initial Reservoir Pressure (Pi)
 Pre-Frac Tests
Conventional FBU Tests
 As soon as possible after completion
 Watch balance of flow time and buildup time
 Requires long shut-ins (1 month +)
ANALYTICAL MODEL
CONSTRUCTION
• Reservoir Pressure: 200 h Flow & 1 Mo BU
p* = 31330 kPaa
ANALYTICAL MODEL
CONSTRUCTION
• In-Situ Matrix Permeability & Total Completion Skin
 Most difficult to obtain
 Require recalibration with early time production data
 First step: km from initial FBU:
 Field example: SHALE 1 HZ-MSF 9 Stages
 Initial FBU Analysis: (kh)t = 1.9 mDm, s’ = - 4.41
 Divide (kh)t by net pay and nr. of frac stages: km = 0.0031 mD
ANALYTICAL MODEL
CONSTRUCTION
• Drainage Area and Shape
 Observed Strong Correlation between k and A
ANALYTICAL MODEL
CONSTRUCTION
• Drainage Area and Shape (Per Frac Stage)
 APPARENT EFFECTIVE DRAINAGE AREA
 Extrapolate to cover shale gas permeability range
 Drainage Shape: requires more work (L:W Ratio = 3:1)
ANALYTICAL MODEL
CONSTRUCTION
• ANALYTICAL MODEL = Superposition of Solutions for Pseudo
Steady-State Equation Applied to Individual Frac Stages
ANALYTICAL MODEL
CONSTRUCTION
• RECALIBRATE MATRIX PERM & SKIN
 km = 0.0015 mD
 s’ = - 5.2
Production History
28000
Legend
160
Tubing Pressure
Bottom Hole Pressure
Actual Gas Data
140
20000
120
16000
100
80
12000
Pressure (kPa)
HZ-MSF Model
History Match
180
30000
160
60
8000
140
40
Flow Press
120
Gas Rate
Syn Res Press, P is calculated
Syn Flow Press
0
0
10
20
30
40
50
60
70
80
100
20000
15000
80
90
60
10000
Time, days
40
5000
20
0
0
0
5
10
15
20
25
30
35
40
45
Time (d)
50
55
60
65
70
75
80
85
90
Pressure (kPa)
20
25000
Legend
4000
Rate (103m3/d)
Gas (103m3/d)
24000
ANALYTICAL MODEL
CONSTRUCTION
• ANALYTICAL MODEL (UPDATE):
ANALYTICAL MODEL
CONSTRUCTION
• ANALYTICAL MODEL & PRODUCTION UPDATE
ANALYTICAL MODEL
• ANALYTICAL MODELS & PRODUCTION UPDATES:
ANALYTICAL MODEL
• BARNETT SHALE Example
SHALE GAS
• SHALE GAS MODELS USING PSEUDO STEADY STATE SOLUTION
NORMALIZED SHALE GAS PRODUCTION
• SHALE GAS NORMALIZED PRODUCTION PLOT :
 DIVIDE TOTAL WELL PRODUCTION RATE BY:
Nr. Frac Stages (n)
Initial Pressure (Pi)
Flow Capacity (kh)
NORMALIZED SHALE GAS PRODUCTION
• SHALE GAS NORMALIZED PRODUCTION PLOT :
 Nr. Frac Stages (n), Initial Pressure (Pi) and Flow Capacity (kh)
NORMALIZED SHALE GAS PRODUCTION
• SHALE GAS NORMALIZED PRODUCTION PLOT :
 Nr. Frac Stages (n), Initial Pressure (Pi) and Flow Capacity (kh)
NORMALIZED SHALE GAS PRODUCTION
• SHALE GAS NORMALIZED PRODUCTION PLOT :
 Nr. Frac Stages (n), Initial Pressure (Pi) and Flow Capacity (kh)
NORMALIZED SHALE GAS PRODUCTION
• SHALE GAS NORMALIZED PRODUCTION PLOT :
 Nr. Frac Stages (n), Initial Pressure (Pi) and Flow Capacity (kh)
NORMALIZED SHALE GAS PRODUCTION
• SHALE GAS NORMALIZED PRODUCTION PLOT :
 Nr. Frac Stages (n), Initial Pressure (Pi) and Flow Capacity (kh)
IN-SITU SHALE GAS TESTING
• Several Testing Techniques Are Used To Test
Shale Gas Formations Prior Completion:
Diagnostic Fracture Injection Test (DFIT)
Wireline Formation Tests (RFT, MDT, CHDT…)
Perforation Inflow Diagnostic (PID)
IN-SITU SHALE GAS TESTING
• SHALE GAS PID TESTING:
 FIELD EXAMPLE (SHALE 1 – Vertical Well)
IN-SITU SHALE GAS TESTING
• SHALE GAS PID TESTING:
 FIELD EXAMPLE (SHALE 1 – Vertical Well)
IN-SITU SHALE GAS TESTING
• SHALE GAS PID TESTING: D&C OPTIMIZATION
CONCLUSIONS
1.
2.
3.
4.
5.
6.
Shale gas HZ-MSF well performance can be derived
using simple, “conventional” analytical models.
In-situ shale gas reservoir properties (Pi & k) and
shale “fabric” (presence of natural fractures) will
control the production performance of HZ-MSF wells
Misinterpretations of SRV will account for significant
overestimations of long-term cumulative production
HZ-MSF has a cumulative effect on well production by
adding in-situ FLOW CAPACITY and not by
“CREATING” better reservoir on a large areal extent
NORMALIZED PRODUCTION PER FRAC STAGE IS
ONE OF THE BEST TOOLS FOR D&C OPTIMIZATION
Pi & k for shale gas can be obtained using PID testing.
THANK YOU!