“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
0.0E+00
1.0E+06
2.0E+06
3.0E+06
4.0E+06
5.0E+06
6.0E+06
0 10 20 30 40 50
Sqrt t
dm
(p)/
q
0
100
200
300
400
500
600
700
800
900
1000
Pre
ssu
re
WELL NAME HERE
10
100
1000
10000
1 10 100 1,000 10,000
Time
Rate
Daily Production AOF EHS Test
WELL NAME HERE
10
100
1,000
10,000
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Cum (Bcf)
Rate
(M
cf/
D)
Actual Fitted tehs
WELL NAME HERE
0.0E+00
1.0E+06
2.0E+06
3.0E+06
4.0E+06
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Cum (Bcf)
dm
(p)/
q
Actual Fitted tehs
WELL NAME HERE
1.0E+04
1.0E+06
2.0E+06
3.0E+06
0 10 20 30 40 50 60
Sqrt t
dm
(p)/
q
WELL NAME HERE
1.0E-08
1.0E-07
1.0E-06
1.0E-05
1.0E-04
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Cum (Bcf)
q/d
m(p
)
Actual tehs
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
20
40
60
80
100
120
140
160
Gas (
10
3m
3/d
)
0
4000
8000
12000
16000
20000
24000
28000
Pre
ssu
re (k
Pa)
0 10 20 30 40 50 60 70 80 90
Time, days
LegendTubing Pressure
Bottom Hole Pressure
Actual Gas Data
History Match
HZ-MSF Model
0
20
40
60
80
100
120
140
160
180R
ate
(10
3m
3/d
)
0
5000
10000
15000
20000
25000
30000
Pre
ssu
re (k
Pa)
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90
Time (d)
LegendFlow Press
Gas Rate
Syn Res Press, P is calculated
Syn Flow Press
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. Shale gas HZ-MSF well performance can be derived
using simple, “conventional” analytical models.
2. In-situ shale gas reservoir properties (Pi & k) and
shale “fabric” (presence of natural fractures) will
control the production performance of HZ-MSF wells
3. Misinterpretations of SRV will account for significant
overestimations of long-term cumulative production
4. 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
5. NORMALIZED PRODUCTION PER FRAC STAGE IS
ONE OF THE BEST TOOLS FOR D&C OPTIMIZATION
6. Pi & k for shale gas can be obtained using PID testing.
THANK YOU!
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