Accelerating Production: Drivers
Aggressive budgeted 2014 production + Underperforming 2013 wells + Declining drilling/completion activity in Fayetteville
1
Accelerate production from existing and new wells
Casing Flow Casing Flow
Tubing Flow Tubing Flow
Concerns & Realized Impact
2
• High sand production through casing wing valves • Manpower requirements to check • Damage to wellhead • Significant environmental release • Complete loss of well control
EARLY WELLHEAD FAILURES 3 wells had washed VR pockets within 4 months 1 well had washed VR pockets within 1 month
Review of Previous Constraints on Flowback
• Max velocity out of a casing wing valve: 80 ft/s • Max sand production rate = 5 gal/hr sand • Sand knock-out released at ½ gal sand in 6 hr period
3
Predicting Erosion Rates w/ Sand Laden Fluids
Modeling Erosion Rates w/ Sand Laden Fluids 1. Computational Fluid Dynamics (CFD) 2. Semi-Empirical (blend of observation/theory) 3. Empirical (based on experimental data)
4
Simplest, correlations parallel theory, correction factors to best match experimental observations
Modified Salama Correlation – OTC 8898 • Developed as an alternative to API RP 14E • Accounts for impact of sand production • Tested and validated for pipe bends (applicable to erosion at B-section, 90’s, etc)
The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.
me
CVρ
= too simplified?
Modified Salama Equation for Erosion Rate
5
mim
sm
dSdWVEρ22
=
Where: E = erosion rate, mm/yr W = sand production rate, kg/day Vm = gas/liquid mixture velocity, m/s ds = diameter of sand particle, mm ρm = gas/liquid mixture density, kg/m3 Sm = geometry dependent constant di = inner diameter of flow path, mm
measured off sand separators assume ≈ Vg using API RP 14E Eq. 2.13 assume to be ~ 70 mesh exclusion size API RP 14E Eq. 2.15 use 5.5 for a bend/90° ID of B-section port, flowlines, etc
Salama, Mamdouh. OTC 8898: An Alternative to API 14E Erosional Velocity Limits for Sand Laden Fluids
Sm = 113 for straight pipe Sm = 5.5 for 90’s
PdTZQ
VVi
ggm 2
60=≈
( ) ( )( )( )TZGLRP
PSGGLRPSG gasliquidm +
+=
7.1987.212409
ρ
Modeling Erosion for Failure during Flowback
6
FAILU
RE PR
EDIC
TED
Impact of Sand Production & Velocity on Erosion
7
0 20
40 60
80 100 120 140 160
0
2
4
6
8
10
12
14
16
0 1 2
3 4
5 6
7 8
9
10 Flow Velocity through a
Single B-Section Port (ft/s)
Eros
ion
of B
-Sec
tion
Port
(mil/
hr)
Impact of Flow Velocity and Sand Production on Erosion
Sensitivity Analysis: B-section Erosion
• Parameter Assumptions – Constant flow temperature (80°F) – Diameter of sand = 0.0083 inches (~70 mesh size) – Sp Gr for sand = 2.65 – Steady flow velocity through diameter of interest – Constant water production (open as possible) – For a 90° elbow, Sm = 5.5 (per Salama) – Linear flowing pressure decline (400 psi → 200 psi)
• Failure Assumptions – Simulated 1 month flow (forced failure) – Condition for failure: 75 mil loss at the VR threads
(60% of thread height)
8
Results of Sensitivity Analysis
PROCEDURE • For varying flow velocities, a failure was forced
at 1 month flow time by varying sand production
RESULT • For a particular sand production, a maximum
allowable flow velocity is obtained
9
Applying the Sensitivity on the B-Section
10
Applying the Sensitivity on the B-Section
11
• Actual velocity ≈ Vg from API RP 14E Equation 2.13 • Max Allowed Velocity = Power law correlation from sensitivity analysis
which is a function of sand production
• Adoption of these limitations would require choking back the well and could noticeably impact obtained IP’s unless we increase flow diameter through the B-section, increase allowed erosion loss, or bulk up the area of concern
Results of Sensitivity Analysis for Flowlines
12
RESULT: New Constraints on Flowback
• Max velocity of 80 ft/s still upheld • Allowable velocity is a strong real-time function of
sand production and may be < 80 ft/s for higher sand production rates
• Restricted release of the sand separator based on sand production and flow-rate to protect the flowlines
• Reduction in early-life failures of the B-section • Reduction in flowline wash-outs following flowback
13
Continued Improvements
• August 2015 – Identified first B-section failure since the new guidelines were put in place back in March 2015
• Continue to see some flowline wash-outs, suggesting significant sand bypassing the sand separator (overestimated allowable velocity)
• Suggests a review of the sand separator design
14
Questions?
15
