Presented ByDr. Youness El Fadili

January 31th 2016

Outline

Introduction

Objective

Critical rate definition

Theory and development of New model

Application and comparison of the New model

Experimental setup

Experimental results

Conclusion and Recommendations

What is Liquid Loading

3

CR

Loading

Intermitting

Loaded

Flowing

Pro

du

ctio

n R

ate

Time

Effects of Liquid Loading

Potential EUR 700 MMscf.Potential revenue $2.1MM

P&A candidate

Unstable production

Ga

s (M

scf/

d)

Ga

s (M

scf/

d)

TP

, C

P,

Psc

(psi

g)

Psc

(psi

g)

Potential EUR 234 MMscf. Potential revenue $0.71M.

Basis of Droplet Model

5

Force Balance

Drag

Gravity

Droplets fall at below critical velocity condition

Vertical Flow Patterns

𝑊𝑒 =𝜌𝑔 𝑑𝑝 𝑉𝑐

2

𝜎 × 𝑔𝑐

𝑞𝑐 =3.067 𝑃 𝐴 𝑉𝑐

𝑇 × 𝑍

𝑉𝑐 = 4

3 𝑔

l− 𝜌𝑔

𝜌𝑔 𝑑𝑝

𝐶𝑑

𝑉𝑐 = 1.593 𝜌𝑙 − 𝜌𝑔

𝜌𝑔2

𝜎

14

Droplet Model and its Evolution

30 Coleman

60 Turner

lbf/ft=6.852 10-5

dyne/cm

• Particle Terminal Velocity

• Critical Gas Velocity, ft/sec

• Critical Gas Rate MMscf/d

Particle Reynolds Number (NRep)

Cd

Modified Droplet Model, Horizontal Wells

Belfroid et al. (2008): Turner and Fiedler shape function

Veeken et al. (2009): observed rate and Turner Ratio, TR

where, a = -2.17 x 10-6, b = 3.09x10-3, and c = 1.02

𝑞𝑐 = 1 − 𝑏𝑄𝑇𝑢𝑟𝑛𝑒 𝑟 − 𝑏𝑄𝑇𝑢𝑟𝑛𝑒𝑟 − 1 2 + 4𝑎. 𝑐.𝑄𝑇𝑢𝑟𝑛𝑒𝑟

2 0.5

2𝑎.𝑄𝑇𝑢𝑟𝑛𝑒𝑟

𝑉𝑐 = 1.593 𝜌𝑙 − 𝜌𝑔

𝜌𝑔2

𝜎

14

× 𝑠𝑖𝑛 1.7𝜔

0.38

0.78

Horizontal Wells Geometry

Effect of Geometry on Flow

BUR 2

BUR 1

Liquid droplets entrained

in gas stream

Flow conduit

Liquid droplets

Fractional Energy Loss

y = 0.0406x0.7537

R² = 0.982

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90

(Vi2 -

Vb

2 )/V

i2

Angle of Impact (qi)

Jayaratne and Mason (1964)

Regression Curve

Maximum Limit

0.95

Fd,mup = Fd,befo re − Fd,after = (1 − 𝛼2)Fd,before

𝑉𝑏𝑉𝑐

= 𝛼 𝑜𝑟 𝑉𝑏 = 𝛼𝑉𝑐

𝑉𝑐2 − 𝑉𝑏

2

𝑉𝑐2

= 0.0406 ∗ 𝜃𝑖0.7537

Model Development

1. Determine the fractional energy loss

2. Calculate the restitution velocity

3. Makeup Drag

Fd,after =1

2𝑔𝑐𝑔𝐶𝑑𝐴𝑑(𝛼𝑉𝑐)2

hence,

Model Development Cont.

𝑉𝑒𝑓𝑓 = 𝑉𝑐 + 𝑉𝑚𝑢𝑝

𝑉𝑚𝑢𝑝2 = (1 − 𝛼2)𝑉𝐶

2

𝑉𝑚𝑢𝑝 = 𝛽𝑉𝐶

𝛽 = (1 − 𝛼2)

where, b the effective velocity factor

𝑞𝑒𝑓𝑓 =3.067𝑃𝐴𝑉𝑒𝑓𝑓

𝑇𝑍

4. Makeup velocity

5. the effective velocity is:

6. Finally, the effective rate to keep the well from loading up is:

Example

It is desired to determine the effective gas rate for a horizontal well with the following

characteristics:

-Tubing pressure = 100 psi

-Temperature = 80 oF

-Tubing size = 2 7/8”

- Maximum BUR = 20 o/100 ft

- Water gravity1.07

- Gas gravity = 0.64

-Z factor = 0.95

-Surface tension= 60 dynes/cm

𝑉𝑏 = 0.78𝑉𝑐 ∴ 𝑉𝑔 → 0.78𝑉𝐶

𝑉𝑐2 − 𝑉𝑏

2

𝑉𝑐2

= 0.0406 ∗ 200.7537 = 0.388

Example

Determine the fractional energy loss

Calculate the restitution velocity

Makeup velocity

Makeup Drag

Thus, the effective velocity and rate to keep the well from loading up is:

1 −𝑉𝑏

2

𝑉𝑐2 = 0.388

Fd,mup = Fd,before − Fd,after = 0.392Fd,before

𝑉𝑒𝑓𝑓 = 1.6258𝑉𝑐

𝑉𝑒𝑓𝑓 = 35.47 𝑓𝑡/𝑠𝑒𝑐

𝑞𝑒𝑓𝑓 = 689 𝑀𝑠𝑐𝑓/𝑑

For comparison,

- Coleman rate is 425 Mscf/d

- Turner rate is 505 Mscf/d

Compressor Performance Analysis

3306 TAA Gas Rate in Mscf/d at different P discharge

Psuc @ Pd 1200 psi @ Pd 1100 psi @ Pd 1050 psi

60 650 650 650

50 546 550 550

50 657 650 647

40 550 520 517

40 619 625 629

16

3306 NA Gas Rate in Mscf/d at different P discharge

Psuc @ Pd 1200 psi @ Pd 1100 psi @ Pd 1050 psi

60 518 522 523

50 435 438 440

50 549 565 575

40 433 453 452

40 526 532 546

Spacer

400

450

500

550

600

650

700

60 50 50 40 40

Ga

s R

ate

(m

scf/

d)

Suction Pressure (psig)

3306 NA vs. TAA

@ Pd 1200 psi

@ Pd 1100 psi

@ Pd 1050 psi

@ Pd 1200 psi

@ Pd 1100 psi

@ Pd 1050 psi

600

700

800

900

1000

1100

1200

40 45 50 55 60 65

Ga

s R

ate

(m

scf/

d)

Suction Pressure (psig)

Volumetric Efficiency Comparison

'@ Pd 600 psi

'@ Pd 1050 psi

3306 TAA Gas Rate in Mscf/d at different P discharge

Psuc '@ Pd 600 psi '@ Pd 1050 psi

60 1121 650

50 983 647

40 805 629

- BPV: Back Pressure Valve. BV: Ball Valve MV: Motor Valve. CV: Check Valve. FRV: Fuel Recycle Valve. CTB: Central Tank Battery.

Experimental Setup

Formation

Bypass

CTB

Sales line MeterLP ~ 30 psi

Compressor

CV

Suction Controller Valve set at 40 psi

Liquids line from compressor scrubber to CTB

CV

MV 70 psi

CV

CV

FRV25 psi

Gas R

ecycle Lin

e

BPV

CV BV

BV

BV

BV

BV

BV

BV

Supply Gas

CV

BV 3 Phase Separator

BV

Injection Meter

Casing

Tubing

Byp

ass

Choke

3 Phase Test Separator with recycle line

Injection Gas Meter

3 Stages Dual Reciprocating Compressor: Front View

3 Stages Dual Reciprocating Compressor: Side View

Common Operational Issues

Causes Solutions

Max discharge- The volume of liquid accumulated in the wellbore is high.- Malfunctioning discharge valve.

- Reduce liquid volume in the well, i.e.swabbing, pushing fluid back to formation- Check the discharge valve for proper functioning.

Low suction

- Low gas supply to compressor. - Malfunctioning suction valve.- Suction line leak.

- Increase supply gas by adding a recirculation line - Check the suction valve for proper functioning.- Check suction line for leaks- Add fuel recycle valve

22

Horizontal Wells Examples

Horizontal

Well 1

Horizontal

Well 2

Pro

duct

ion D

ata

qo (BO/d) 2.39 61.50

qw (BW/d) 19.52 2.00

qg (Mscf/d) 273 181

FTP (psia) 110 92

Tsurface (oF) 80 60

Tformation (oF) 223 130

OGR (bbls/MMscf) 3.3 90

WGR (bbls/MMscf) 27 3

WOR 8.18 0.03

Tubula

r D

ata

Tubing OD (in.) 2.875 2.875

d (in.) 2.441 2.441

Casing OD (in.) 5.5 7

Casing ID (in.) 4.892 6.276

Liner Top (ft) 12,950 8,177

Liner OD (in.) 3.5 4.5

Liner ID (in.) 2.992 4

Absolute roughness (in.) 0.0006 0.0006

Depth (ft) 12,863 8,306

Max BUR o/100 ft 12.34 18.34

PV

T

API 65 40

N2 Mol % 0 1.686

CO2 Mol % 0 0.843

H2S Mol % 0 0.003

Specific gas gravity 0.65 0.7

Specific water gravity gw 1.02 1.02

Specific oil gravity go 0.72 0.83

Identifying Critical Gas Rate: Horizontal Well 1

0

5

10

15

20

25

30

35

40

45

50

240

245

250

255

260

265

270

275

280

285

290

0 5 10 15 20 25 30 35 40

Inje

cte

d G

as

(Msc

f/d

), W

ate

r (B

WP

D)

Pro

du

ced

Ga

s (M

scf/

d)

Time (Days)

Gas (Mscf/d)

Injected Gas * 10

Water (BWPD)

Actual Lift Rate, Mscf/ d 730

Absolute Percent

Deviation, %

Coleman model Mscf/ d 455 38

Turner model, Mscf/ d 541 26

New Model, Mscf/ d 692 5

Belfroid model, Mscf/ d 495 32

Veeken model, Mscf/ d 579 21

Observed critical gas rates and percent deviation for horizontal well 1

Horizontal Well 1

26

40

45

50

55

60

65

70

400

450

500

550

600

650

700

750

800

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

To

tal

Flu

id (

BF

PD

)

To

tal

Ga

s (M

scf/

d)

Days

Total Gas (Mscf/d)

Fluid (BFPD)

Identifying Critical Gas Rate: Horizontal Well 2

Observed critical gas rates and percent deviation for horizontal well 2

27

Actual Lift Rate, Mscf/ d 684

Absolute Percent

Deviation, %

Coleman model Mscf/ d 404 41

Turner model, Mscf/ d 481 30

New Model, Mscf/ d 648 5

Belfroid model, Mscf/ d 506 26

Veeken model, Mscf/ d 512 25

Horizontal Well 2

Gradient

28

400

500

600

700

800

900

1000

1100

400

410

420

430

440

450

460

470

480

490

500

8:24:00 9:36:00 10:48:00 12:00:00 13:12:00 14:24:00 15:36:00 16:48:00 18:00:00

To

tal

Ga

s (M

scf/

d)

FB

HP

(p

sig

)

Time

FBHP (psig)

Total Gas (mscf/d)

650 to 720 Mscf/d rate yield lowest BHFP

Compressor

shut downs

Unstable BHP indicating

subcritical condition even at

rates proposed by other models

Don’t Set and Forget: Dynamic Operation

Don’t Set and Forget: Dynamic Operation

Conclusions & Recommendations

1. The new model accounts for the effects of wellbore geometry on liquid loading and predicts

the critical gas rate for horizontal and deviated wells.

2. Experimental work with 2 horizontal wells showed the new model prediction is within 5%

from actual.

3. Conventional vertical models should not be used for horizontal and deviated wells.

4. In vertical wells, the new model collapses to Coleman model.

5. The new model yields best results for gas rates less than 10,000 Mscf/d and for BUR’s

between 3o and 30o/100 ft.

6. Don’t set and forget. Optimization through surveillance with good automation setup.

References

Questions??

Youness El Fadili, Subhash Shah “A new model for predicting critical gas rate in horizontal and deviated wells”, Journal of Petroleum Science and Engineering, December 3rd 2016. http://dx.doi.org/10.1016/j.petrol.2016.11.038