Final Presentation TOTAL

Bekapai Pipeline AnalysisPart One: BKP-SNP 12” Pipeline DepressurisationPart Two: BK-BP1 New Pipeline Design

Tahrizi Andana/13007045Chemical Engineering Programme of Study

Faculty of Industrial TechnologyBandung Institute of Technology

Outlines

2 - Reference, date, place

Part One: BKP-SNP 12” Pipeline Depressurisation Study

Part Two: BK-BP1 New Pipeline Design Analysis

Part One: BKP – SNP 12” Pipeline Depressurisation Study using Microsoft Excel and OLGA


Initial inventory (scf) and pressure (bar gauge) T


Background of Study: Depressurisation


Production stopped

To Flare

Certain pressure (atmospheric)

Method to prevent overpressure by relieving gas inventory in pipeline to the flare for gas combustion and disposal to the atmosphere

Two most important factors of depressuring gas: flare capacity and time efficiencyboth related to the gas outlet volumetric flow rate

Higher gas outlet flow rate

Lower depress timemore efficient

Higher risk of flare deterioration

advantage

disadvantage

Optimisation of depressurisation time and gas outlet rate needed to provide the most advantageous depressurisation system

To implement? MODELING OF DEPRESSURISATION SYSTEM

using and


Objectives and Methodology

Objectives for this present study are:

Learn how to make the depressurisation system model using manual calculation

through Microsoft Excel and another complex calculation through

Estimate the time required to depressurise Bekapai – Senipah 12” and 44 km pipeline

using hand calculation by Microsoft Excel and OLGA

Compare both calculation result to the depressurisation time empirical data

Several methods used in this study are:

Literature study by reading handbooks, articles, journals, and software manual

Basic calculation using Microsoft Excel as a hand calculation and OLGA software


Two calculations are provided: orifice flow model and valve flow model

Orifice Flow Model

Excel Modeling


Orifice characteristicsID = 4.5 in. = 114.3 mmCd = 0.84

Gas characteristic:k=1.25T=50 °CMW=20.00 kg/kmolPc=47.50 baraTc=215.09 K

Pipeline Char.:OD=314.8 mmID=304.8 mmL=44 km

Depress Cond.:P initial=10.7 bargP final=1.0 bargP increment=0.1 barg

A

L

G

O

R

I

T

H

M


Valve Flow Model


Valve characteristicsOpening=7%-21%Cg=15000Cf=34Valve Diameter=4.5 in.

Gas characteristic:k=1.25T=50 °CMW=20.00 kg/kmolPc=47.5 baraTc=215.09 K

Pipeline Char.:OD=314.8 mmID=304.8 mmL=44 km

Depress Cond.:P initial=10.7 bargP final=1.0 bargP increment=0.1 barg

A

L

G

O

R

I

T

H

M


OLGA Modeling

Case Description

Known Data & Assumptions

Case 1: Settle pressure of gas in pipelineAt a certain time, gas production stream and Senipah Node is closed Observing the settle pressureCase 2: Depressurisation of pipeline in Case 1 at the downstream (Senipah).Estimate time to depress initial pressure of gas inventory on the 1st case to final pressure = 1 bar gaugeCase 3: Depressurisation of pipeline due to the stopped source production.Estimate time to depress initial pressure to final pressure of 1 bar gauge after the source production is stopped

Initial standard volumetric flow rate = 15 MMSCFDInitial temperature = 50 °C (isothermal)Pipeline length = 44000 mPipeline inside diameter = 12 in.Pipeline thickness = 0.01 mPipeline roughness = 2.8e-5 mOrifice valve diameter = 4.5 in.Control valve gas sizing coefficient = 15000Pressure on arrival steady-state = 9 bar gaugePressure final transient = 0 bar gauge (atmospheric)

Pipe is divided into 100 segments

OLGA Model for Depressurisation


Main Finding: Excel vs. OLGA

Orifice Flow

Valve Flow

All cases are having same initial pressure of 10.7 bar gaugeInitial gas

standard outlet flow rate (MMscfd)

Time to reach 1 bar gauge (min) using Excel

Time to reach 1 bar gauge (min) using OLGA

5 666.21 667.8

10 333.10 341.4

15 222.07 241.2

All cases are having same initial pressure of 10.7 bar gaugeInitial gas

standard outlet flow rate (MMscfd)

Time to reach 1 bar gauge (min) using Excel

Time to reach 1 bar gauge (min) using OLGA

5 674.68 569.4

10 338.05 359.4

15 226.11 242.4

Orifice flow is preferable due

to the least error between Excel

and OLGA


Empirical Data

July 13th at 16.00 – 22.25: pigging activityGas flow rate = 3.8 MMscfd; departure pressure = 14.5 barg; arrival pressure = 3.5 barg

22.25 – 01.00: depressurisation activityFinal inventory = 1 barg, depress time = 2 h 35 min. (2.58 hrs)

By OLGA we obtain the actual departure pressure of 4.05 barg


Excel vs. OLGA re-runs

ParameterMethods

Excel OLGA

Initial Q outlet at

depress time = 2.58 h4.0 MMscfd 5.1 MMscfd

Depress time at initial

Q outlet = 3.8 MMscfd2.72 hours 3.38 hours

The sufficiently large error is obtained from both Excel and OLGA results!

For example, see re-run curves below for first parameter


Recommendation

Excel

Strength: simple and efficient

Weakness: low in accuracy; too many assumptions used, such as zero pressure drop

Highly recommended for the fast prediction

OLGA

Strength: automatic, high in accuracy, and considering the pressure drop

Weakness: inefficient (due to too many inputs to be entered)

Highly recommended for the accurate and long-term prediction

Part Two: BK – BP1 New Pipeline Design Analysis



Background of Study: BK – BP1 New Pipeline

BK wells have been inactive since two years ago

From BK wells To Production Platform

sea surface

sea bed

Many studies are performed to revive the wells

The products are transported by three segments of pipeline

but the existing pipeline is unfit for service due to corrosion

THEREFORE:

A need to design the new pipeline

Regarding:

Low wellhead pressure (correlates ΔP and IPR)

Slugging effect and handling

Economy concern

Arrival pressure = 8 barg

Pipeline flow modeling is using OLGA to simulate the flow regime and pressure profile


Objective

Estimate the proper BK – BP1 pipeline diameter

Literature study from Prodem and OLGA user manual

Empirical data study from:

• BK platform annual prediction and composition data

• Future pipeline technical data

Methodology

Pipeline Design Data


Pipelines : 3 (two risers and one inclined pipe)Thickness : 9.52 mmCoatings : 50 mm concrete and 2 mm polypropyleneTemperature : 29 °C (ambient); 50 °C (arrival)Profile :

Downward riser height = 39 m

Upward riser height = 42 m

BK – BP1 distance = 1.9 km

Scenarios


Flow

Rates

Year

2010 2011 2012 2013

1st

Scenario

2nd

Scenario

1st

Scenario

2nd

Scenario

1st

Scenario

2nd

Scenario

1st

Scenario

2nd

Scenario

Oil (STBpd) 70.4 70.4 46.6 46.6 29.9 29.9 16.0 16.0

Gas (MMscfd) 1.3 4.1 1.3 4.1 1.3 2.4 1.3 1.3

Water (BWpd) 100 100 200 200 300 300 400 400

Annual prediction of well production rate data is divided into two prediction scenario, as shown on table below:

First scenario is predicting the gas rate would be equal year by year in a lower value than the second scenario

OLGA Results of First Scenario


Pipeline Types

(by Diameter)

Departure Pressure per year (barg)

2010 2011 2012 2013

2 in.-pipeline 18.796 19.117 19.613 20.231

3 in.-pipeline 10.078 10.189 10.305 10.406

4 in.-pipeline 8.644 8.699 8.770 8.846

6 in.-pipeline

(slugging)

Peak 10.1 Peak 10.2 Peak 10.2 Peak 11.0

Mid 8.2-8.72 Mid 8.3-9.1 Mid 8.4-9.25 Mid 8.6-9.4

Low 8.1 Low 8.1 Low 8.1 Low 8.1

8 in.-pipeline

(slugging)

Peak 10.6 Peak 10.9 Peak 11.1 Peak 11.1

Mid 8.4-9.0 Mid 8.5-9.35 Mid 8.5-9.75 Mid 8.4-10

Low 8.05 Low 8.05 Low 8.05 Low 8.05

OLGA Result of Second Scenario


Pipeline Types

(by Diameter)

Departure Pressure per year (barg)

2010 2011 2012 2013

2 in.-pipeline 50.80 53.83 33.130 20.231

3 in.-pipeline 21.277 22.022 13.818 10.406

4 in.-pipeline 12.170 12.095 9.710 8.846

6 in.-pipeline

(various)8.666 8.712

Peak 8.78 Peak 10.8

Mid 8.52 Mid 8.4-9.4

Low 8.4 Low 8.1

8 in.-pipeline

(various)8.200 8.231

Peak 9.8 Peak 11.2

Mid 8.3-9.2 Mid 8.4-10

Low 8.05 Low 8.05


Recommendation

The great design of BK – BP pipeline is in range of 4 – 8 in. but prefer in 6 or 8 inches if the existing slug catcher or vessels could handle all the slugs

Design would consider the pigging operation; 6 inches pipeline is preferable because of the suitable pig size availability


References

Emerson Process Management. 2001. Control Valve Handbook 3rd Edition. Iowa: Fisher Control International, Inc.

Richardson, S.M. and Saville. 1991. Blowdown of Pipelines. Aberdeen: Society of Petroleum Engineers

Parcol, S.p.A. Handbook for Control Valve Sizing. Italy

Datta, Arun. 2006. Process Engineering and Design Using Visual Basic. CRC Press, Taylor & Francis Group

AVCO Brochure

BK-2-SS Chromatography Analysis

O’Keefe Control Co.

OLGA 5.2.1 User Manual

Thank You


Exploration & Production

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