Gazelle Field Development

Technical Report, 2014
39 Pages, Grade: A


List of Contents



2.Key characteristics of Gazelle Field
2.1 Field description
2.2 Gazelle field information

3.Development considerations
3.1 System upgrade
3.2 Assumptions
3.3 Separation process
3.4 Flow scheme
3.5 Platform replacement (pipeline)
3.6 Complete system replacement

4.Flow Assurance

5.Economic analysis
5.1 OPEX
5.3 Cost option one
5.4 Cost option two
5.5 Cost option three

6.Development choice
6.1 Risk assessment

7.Development analysis
7.1 Comparisons
7.2 Technical risk
7.3 Advantages
7.4 Disadvantages

8.Decommissioning plan
8.1 Decommissioning technology
8.2 Decommissioning process
8.3 Key parameters



List Figures

Figure 1 – Field location

Figure 2 – PFD option one

Figure 3 – PFD option two

Figure 4 – PFD option three

Figure 5 – Hydrate formation

Figure 6 – Risk ranking

Figure 7 – Gazelle field

List of Tables

Table 1 – Petroleum Engineering

Table 2 – Flow assurance

Table 3 – Cost – concept one

Table 4 – Cost - concept two

Table 5 – Cost – concept three

Table 6 – Risk assessment

Table 7 – Wellhead alternative

Table 8 – TLP Alternative

Table 9 – Semisubmersible Alternative


Abbildung in dieser Leseprobe nicht enthalten


The Gazelle field is located offshore Kuwait in Iranian waters very close to Shat Al Arab. The field discovered with the initial exploration well in 1990. Oil production is via a steel piled jacket platform, and the export system is via FSO to a shuttle tanker. After a number of years of production, the oil rates have come off plateau with increasing amount of water cut. Field sensitivities require a new development of the Gazelle field.

According to the project brief, three field developments options were proposed such as:

- Refurbishment and upgrade of present system
- Replacement of the oil export via the FSO and
- Complete system replacement

The approach used to evaluate and recommend the most suitable development concept was based on

- Economics (technical costs)
- Flexibility (project implementation) and
- Abandonment strategies

2.Key Characteristics Gazelle field

Gazelle field sensitivities outlined in the following sections provides a development background.

2.1 Field description

The field is located offshore in 45 km to the nearest landfall, which is a desert remote region with very limited infrastructure. The water depth is 100 meters.

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Figure 1 – Gazelle Field location

The Gazelle field produces from two reservoirs – the Gazelle Upper and Gazelle Deep. For further details, please see the Table 1.

Table 1 – Petroleum engineering

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A pressure support will be required to enhance the recoverable reserves from the Gazelle Deep reservoir. Additional water injection wells are required in the lower bearing zone for pressure support.

2.2Gazelle Field Information

Gazelle production is via steel-jacketed platform in 100 meters water depth. Oil export is via FSU to a shuttle tanker. The field has been producing over 6 years and has come off plateau. The current production rates are around 75,000 bpd with water cut 15%. The process configuration in the Gazelle steel-jacketed platform consists of:

- Two 50% trains each two-stages of two-phase separation and a surge vessel to stabilise the crude oil to FSU and tanker specifications.
- Gas from HP separator and LP separators is compressed and conditioned for use as fuel gas. Gas from surge vessel plus any excess is flared.

The deck loadings and space availability at the Gazelle steel jacketed platform are very limited.

3.Development considerations

3.1System upgrade

The current separation system cannot handle the changes in the well stream, which uses gravity settling in the FSU tanks. Therefore, retrofitting the existing separation system in the Gazelle platform during the FSU refurbishment process technically proves to be a viable option.

The plan shall include the following:

- Upgrade of separation system
- FSU refurbishment
- Installation of new jack up platform (wellhead + water treatment/injection modules + gas injection and drilling module)


The integrated well caisson in the jack up shall contain slots for ten wells, risers and J-tubes [4]. The drilled platform wells shall be completed using a cantilever jack up drilling rig [4]. Workover on platform wells are of easy access. The drilling methodology used will follow the same trend for all field development options proposed.

3.3Separation process

The retrofit in the separation process consists in changing the existing separation trains from two-phase system to three-phase system; this option technically proves to be the best to handle initially the significant gross water cut at Gazelle platform. The gross liquids from three-stage separation are routed to the new jack up wellhead platform for further treatment. The platform is equipped with crude oil heat treaters (Tubular heaters), free water knockout drums (FWKO) and degassers.

3.4 Flow scheme

From wellhead to point of export, oil routes on a three-phase two-stage train separation system. The initial gross separation occurs in the HP separator, where gas is flashed to obtain a maximum liquid recovery. From HP separator the oil flows to LP separator and to oil surge vessel. Oil from surge vessel, which operates as a three-phase separator, flows to free water knockout drum (FWKO) for further water removal before passing through heater treaters and degasser vessel for final storage and offload via shuttle tanker.

Produced water from separator vessels routes to the water treatment unit (multiliner hydrocyclone vessel). The water is batch treated to meet the injection/disposal requirements. The oil rejected is recycled back to low-pressure separator. Degassing vessel is installed downstream of the multiliner hydrocyclone.

The gas out from separator vessels commingled passes through a scrubber before entering gas compressors. Compressed gas passes through a dehydration process before using for fuel and future re-injection purposes.

The economics associated to gas export are not feasible. The CAPEX to commission a gas export pipeline proves to be not very attractive worth to invest.

Figure – 2: PFD – Refurbish & upgrade

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3.5Platform replacement (pipeline)

This development option will consist of:

- New central processing platform (concrete)
- New wellhead platform with drilling rig and
- Oil export subsea pipeline from central processing platform

The following assumptions for this option includes the removal of existing Gazelle steel piled platform, and installation of a concrete gravity base CPP bridge linked to a wellhead platform with drilling capabilities.

From wellhead to point of export, the separation process will be via a three-phase three-stage system. The initial gross separation occurs in the HP separator. Downstream to HP separator a MP and LP separator increases the yield of liquid recovery. Oil leaving LP separator flows to an oil treater unit to stabilize the oil for storage in the base gravity tanks. The export of stabilized oil is via subsea pipeline.

Produced water from HP, MP and LP separators will be batch treated in the water treatment module prior to injection/disposal via wellhead platform. Conditioned gas from HP compressor is to use for fuel utilities purposes. Any excess gas is re-injected via dedicated gas disposal/lift wells.

Figure – 3: PFD – Replace Gazelle and pipeline

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3.6 Complete System Replacement

The development option will consist of:

- New central processing platform (piled)
- New wellhead platform (jack up) with drilling rig and
- FSU replacement and oil export via dedicated shuttle tanker

This option used the same process configuration of the previous development option, the only difference being that the oil exported is via a new FSU to a dedicated shuttle tanker.


Excerpt out of 39 pages


Gazelle Field Development
Robert Gordon University Aberdeen  (School of Engineering)
Master of Science Oil and Gas Engineering
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ISBN (Book)
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gazelle, field, development
Quote paper
Ataliba Miguel (Author), 2014, Gazelle Field Development, Munich, GRIN Verlag,


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