Gas Well De-Watering Techniques Using Electric Submersible PumpsGas Well De-Watering Techniques Using Electric Submersible Pumps

J.W. Knight & B.L. Wilson

Baker Hughes Centrilift

J.W. Knight & B.L. Wilson

Baker Hughes Centrilift

Gas Well De-Watering Workshop, Denver, CO, USA

March 3-5, 2003

Presentation Outline

Introduction

Description of Technique

Case History

Conclusions

Introduction

high volume / low head apps (i.e., water wells, mine de-watering, surface liquid transfer)

low volume / high head apps (i.e., typical deep onshore U.S. oil wells)

high volume / high head apps (i.e., deep or extended reach offshore wells)

minimizing FBHPs (thus maximizing well inflow)

ESPs well suited for…

producing large quantities of water from significant depths (i.e., high volume / high head app)

potentially large volumes of gas which must be “handled”; thus annular separation usually key to success

setting the ESP system below perforations (sumping) in order to take advantage of annular gas/liquid separation

the need to significantly reduce FBHP

Gas Well De-watering can involve…

Recirculation System

• maximize well drawdown

• minimize gas interference

• improve motor cooling in low volume wells

• provide an alternative to slim-line equipment

• patent protected technology

Technique #1

“Original” Style Recirculation Tube

“Midland” Style Recirculation Tube

“Argentine” Style Recirculation Tube

Recirc Pump Head / Tube / “Cap”

Recirc Tube and Protective Clamp

Case History #1

Well Data Summary

Static pressure, psi 1,200

Producing GOR, scf/stb 6100

Water cut, % 93

Bottomhole temp, F 156

Oil gravity, API 43

Water gravity 1.03

Gas gravity 0.63

Casing size & weight 7-in., 23 lb.

Tubing size 3.5-in.

Perforated interval, ft TVD 7,528 – 7,767

Well depth, ft TVD 8,262

ESP Unit Comparison

Unit Pump Recirc pump Seal Motor

Pre-recirc 163 stg,

513-series, 4100 BFPD

N/A 400-series 450-series,

350 hp

(re-rate), with 5.5” shroud

Recirc 207 stg,

513-series, 6100 BFPD

9 stg,

513-series, 10000 BFPD w/ 64 ft recirc tube

513-series 562-series, 570 hp

0

1

2

3

4

5

6

7

Gas Oil Water

Pre-recircRecirc

Gas Prod., MMcfd

Oil Prod., BPD x 100

Water Prod., BPD x 1000

Note: estimated monthly oil & gas revenue increase = US $200K based on $18/bbl oil price and $2/Mcf gas price

Pre and Post-recirc Production

Shrouded ESP System

• not a new concept

• common arrangement when “sumping” unit

• also used above perfs in low flow scenarios

• relatively simple system w/ minimal hardware

• drawback – limits motor OD per given casing size

Technique #2

Case History #2

General field/reservoir/fluid data

Formation Name Upper Pennsylvanian

Rock Type Dolomite

Subsea Depth -3500’ SS to -4100’ SS

Porosity 4% to 30%

Permeability 2 md to 2000 md

Reservoir Pressure 900 psi to 1200 psi

Reservoir Temperature 140 F

Oil Gravity 40 API

Gas Gravity 0.65

Water Cut 80% to 98%

Hydraulic requirement

+/- 10000 BFPD

6938 ft. TDH

Delta pressure across pump = 3035 psi

7-in. versus 9.625-in. casing?

74 stage 3X tandem HC12500, ARC trim

513 seal double bag seal w/ HS shaft

836 hp 562 series motor w/ HS shaft

7-5/8” motor shroud

Instrumentation

Shrouded ESP system configuration

Results for two “Big-Holes”

Gas rates 2.5X higher than previous best 7” wells

Initial BWPD > 11,000

Economic Comparison 7 in. vs 9-5/8 in.

Parameter 7 in. casing 9-5/8 in. casing

CAPEX $1,500,000 $2,000,000

Monthly OPEX $20,000 $35,000

Avg Gas Rate 3500 MCFPD 5300 MCFPD

Avg Oil Rate 200 BOPD 350 BOPD

Avg Water Rate 3000 BWPD 5000 BWPD

AFIT ROR >100% >100%

AFIT NPV/I @ 10% 1.45 1.81

Capital/BOE $3.41/BOE $2.90/BOE

Inverted Injection ESP

• electric submersible pump system for de-watering gas wells

• inverted system to pump water through a packer into a lower disposal zone

• eliminate surface water disposal costs

• VSD required (normally)

• Centrilift system known as GasProTM

Technique #3

Case History #3

Gas well economics at unprecedented levels Gas price “Mean” predicted at $3.50 USD/MMSCF (Spear

& Associates) 1 MMSCF/day of incremental Production Incremental revenues $3,500 USD/d ($105,000 USD/month) ESP Cost estimated at $105,000 USD Work over/completion cost estimated or $105,000 USD Pay out estimated at 2 months Assumption is that 6 month pay out is the economic

threshold for project approval ESP’s now a cost effective de-watering method

Economic Overview

115 stage 450-series RA7 pump (700 BPD)

400-series expansion chamber

400-series thrust chamber

77 horsepower 450-series motor

Flow meter, check valve, on/off tool above packer

GasProTM System Configuration

– Stranded asset

– No production

– No revenue

– Well liquid loaded

– Casing not tied in

Before GasProTM

– Bookable reserves

– 3.85 MMcf/day gas

– $11,809 USD per day (@ US $3.07/Mcf)

– Well unloaded

– Casing tied into gathering system

After GasProTM

Conclusions

1. Electrical submersible pumps provide a viable gas well de-watering option, particularly at high Q/H requirements

2. All three “techniques” described have been successful for gas well de-watering

3. Sumping the ESP below perforations is oftentimes a key factor for success

4. Project economics can be quite favorable

References

1. SPE 75711 (for recirculation system case history)

2. SPE 77733 (for shrouded system case history),

3. SPE 37451 (for more info on recirculation system)

4. For more info on inverted ESP injection for gas well de-watering, see Hadaway and Oelke paper from 1996 ESP Workshop, Houston, TX, May 1-3

5. “Recirculation Pump For Electrical Submersible Pump System,” U.S. Patent No. 5,845,709 (1998), Mack, J.J. and Wilson, B.L.