W3V17 - Offshore - Handout

7/25/2019 W3V17 - Offshore - Handout

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Oil & Gas

From exploration to distribution

Week 3 V17 Offshore

Isabelle Rey-Fabret

W4V17 - Offshore p. 1

IFPEN - IFP School 2015 / TOTAL SA 2015 / IFP Training 2015


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Introduction

Offshore developments present specificities that we are going to explain during this lesson.

An important point that we may raise is : what are the critical factors to take into account in

order to choose the most adequate field architecture ? What can be the technical options ?

What are the critical factors to choose the field architecture ?

Offshore developments present specificities that we are going to explain during this lesson.

An important point that we may raise is : what are the critical factors to take into account in

order to choose the most adequate field architecture ? What can be the technical options ?

Selecting the development concept of an offshore field is related to all the parts of the field.

What will be the reservoir depletion strategy?Can the reservoir pressure be maintained?

How ?

Will the wells be subsea wells or surface wells? What will be the wells' trajectories? How

will they be drilled?

Will the support be fixed or floating? And how many of them will be needed for the

development of the field?

How many development phases will be needed? How will the production be stored and

exported?

Where will the living quarters for the people working on field be installed?

What can be the technical solutions ?

For each of these questions, different options exist.

In order to illustrate how to choose the best architecture, lets focus first on the reservoir

geometry criteria.

If the reservoir is deep and not wide, a fixed platform can be a good solution, and the well

heads will be located on the platform.

On the contrary, a wide reservoir will be produced with subsea wells, due to the big distance

between them and a net of flowlines will transport the fluid up to a floating system.

Lets now focus on the different offshore production supports. Their role is to provide a

stable and safe area to install equipment and to work.

Lets take a look at the platforms fixed on the sea bed, as the concrete platform, the steel

platform or the compliant tower. For all these structures, the well heads are installed on the

platform.

Such a choice allows easier well intervention and management.




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But when the water is too deep, such structures can no longer meet environmental

constraints. A floating unit is more adapted, such as a semi-submersible platform or the

Floating Production Storage and Offloading (FPSO).

As we can see on this picture below, the environmental conditions of work can drastically

differ from one region to another one, and are significant for the final choice of the futureoffshore production support.




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In the case of deep water, the specific technical challenges and risks are related to flow

assurance issues.

In fact, in these conditions of production, we can face low reservoir pressure and

temperature, and consequently lower well eruptivity.

Moreover, the temperature at the sea bed is low, flowlines are long and risers deep.Therefore, temperature and pressure conditions are favorable for deposits, and the fluid

encounters hydrodynamic issues, such as high pressure drops or slugging.



W3V17 - Offshore - Handout

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