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Gas Lift Optimization at BP-Indonesia Dual String Gas Lift Well With Injection Pressure Operated Valve. By: Gatut Widianoko Weatherford Artificial Lift Systems. Abstract.

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Gas Lift Optimization at BP-IndonesiaDual String Gas Lift WellWith Injection Pressure Operated Valve

By: Gatut Widianoko

Weatherford Artificial Lift Systems


Abstract
Abstract

  • North West Java Oil (NWJO) field located offshore Indonesia is operated by BP. This mature oil field (discovered during 1970’s) has approximately 950 wells, and ninety percent (90%) are produced with dual gas lift systems. In thirty (30) years of production, the reservoir pressure has decline to an average between 500 – 600 psig at the mid-perforation depth (ranging from 3000 - 4000 ft TVD). Discharge pressure of lift gas is 680 psig at compressor station(s).

  • In June 2001, BP-Indonesia management made a decision to focus on optimizing their gas lift wells. After significant discussion, it was decided to take a non-conventional approach with respect to gas lifting dual wells by using Injection Pressure Operated valves (IPO’s).

  • Process Overview:

  • create effective optimization organization

  • design of dual gas lift utilizing IPO valves

  • experiences and solutions for eliminating “gas

  • robbing”.



Steps in gas lift optimization
Steps in Gas Lift Optimization

  • BP Management - focus on gas lift optimization

    • 90% of wells produced by dual gas lift

  • Optimization Team selected

  • Team reviews in-house (limited) gas lift expertise; decision made to contract gas lift services from Weatherford; GL engineer visits Jakarta office and NWJO field facilities

  • Optimization Team reviews report; proposals submitted Weatherford; further discussions held regarding project

  • Optimization Team contracts three (3) positions for implementation of NWJO project for 6 month period (including clause for additional 6 month extension)

  • Objectives determined and proper means of tracking or trending established; workable reports

  • Results of optimization reviewed weekly and monthly


Gas Lift Optimization –

Team Objectives

Identify problem wells or common well problems

Improving oil production rate

Optimizing gas injection

Reviewing well performance

Maximize overall potential

Stabilize oil production and gas injection


Contracted job titles

Contracted Job Titles

OFFICE JOB – Gas Lift Engineer

Gathering reservoir & production data

Reviewing gas lift performance & current GL design

Generating recommendations

WORKSHOP JOB – GLV Technician

Calibration and repair all gas lift equipment

Manage gas lift equipment inventory & inventory reports

FIELD JOB – Gas Lift Specialist

Installing, tuning & troubleshooting GL wells

Training company field operators (personnel)

Coordinate gas lift activities with field supervisor




Oil Gain Contribution by Field

Total oil gain = 3559 bopd


Diagnostic Tools

To optimize gas dual lift well, complete information is required:

  • Well Case History

  • Three-Pen Static Pressure Recorder

  • Daily Production Record

  • Flowing and Static Pressure Survey

  • Flowing and Static Temperature Survey

  • Echo Meter Survey

  • Well File (Drilling, Well Schematic)

  • Latest GLV Design Report

  • Setting Pressure Report

  • Wire Line Job Report


Well Review by Team

  • Old Oil Field with more than 30 years old

  • High FGOR with 1000 : 1 or more

  • Low PI with only about 1 – 3 blpd / psi

  • Low Production with about 200 - 500 blpd

  • Low Static Pressure with average ~ 600 psi

  • Limited Casing Pressure with ~ 600 psi only

  • Flowing Tubing Pressure is about 180 psi

  • Shallow well - reservoir depth ~ 3000 ft TVD

  • Limited data (SBHP and PI is normally unknown)

  • Old wells - may have leaking valve or tubing

  • Some gas lift valves installed 5-10 years ago


Dual gas lift design lessons learned
Dual Gas Lift Design – Lessons Learned

  • Enough Kick Off (KO) and Operating (OP) Pressure to reach deepest point of injection is required

  • Differential pressure between KO and OP is ~10% of casing pressure, (or at least 50psi) to cover all unloading valves of both strings are closed when surface casing pressure is set at OP

  • Use graphical method to select best point of injection of both strings and best draw down (200-300 psi) of both strings

  • Calculate by computer setting pressure Ptro; select best port sizes and gas injection rate required

  • All pressure settings (Ptro) of unloading valves for both strings must be selected according to surface closing pressure

  • Surface closing pressure of both strings must be at least 20 psi above OP, and 10 psi less than KO

  • Avoid “gas robbing” - depth point of injection of both strings must be close or equal; same thing in port size


Uxa 4s l well schematic
UXA-4S/L Well Schematic

REDESIGN WELL

Since mandrels were installed in well, optimization on this will be done by redesign.

Main job is how to determine best point of injection of both strings for optimum draw

down and to avoiding robbing.

To perform this job, gathering

complete information of both

strings is required.

Since SBHP data is old enough, and to ensure static pressure therefore SBHP survey is required to be performed.



Graphical method
Graphical Method

UXA – 4L

PRESSURE (psi)

500

1000

1500

FTP

CHP

0

D

E

P

T

H

Ft

T

V

D

0.1 p s I / ft

Casing Pressure

FL

1000

#1

Tubing

Pressure

#2

2000

#3

0.45 p s i / ft

#7

3000

Mid Perforation

FBHP

1200 p s i

4000



Computer program results uxa 4l
Computer Program Results (UXA – 4L)

NOTE: Third mandrel is designed with S/O, but existing #3 valve can not be pulled out, therefore #2 valve is opening and set with Ptro = 300 psi



Gain results after gas lift redesign
Gain Results After Gas Lift Redesign

Gas lift valves were calibrated in workshop, then installed; unloading of tubing strings was done with at least 650 psi as KO. After well unloaded, then gas injection rate was adjusted to maintain surface casing pressure at 640 psi, or OP. Following chart summarizes results after gas lift optimization:

OPERATING PRESSURE: 640 psi


Gain results after gas lift redesign1
Gain Results After Gas Lift Redesign

OPERATING PRESSURE: 640 psi

Well had been shut in since March 1996, and back on line March 2002 after gas lift redesign.



Total oil gains after well work at bp indonesia
Total Oil Gains After Well Work at BP-Indonesia

NOTE: Gas lift is the biggest contributor (70%) of the well work jobs, which resulted in oil gain at NWJO; BP-Indonesia


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