Accelerating Production: Drivers

Aggressive budgeted 2014 production +  Underperforming 2013 wells +  Declining drilling/completion activity in Fayetteville

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Accelerate production from existing and new wells

Casing Flow Casing Flow

Tubing Flow Tubing Flow

Concerns & Realized Impact

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•  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

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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)

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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)

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me

CVρ

= too simplified?

Modified Salama Equation for Erosion Rate

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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

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FAILU

RE PR

EDIC

TED

Impact of Sand Production & Velocity on Erosion

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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)

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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

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Applying the Sensitivity on the B-Section

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Applying the Sensitivity on the B-Section

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•  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

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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

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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

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Questions?

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