Surgil ESIA Report - Volume III - EKN

Surgil ESIA Report - Volume III
Appendix A.
Supplementary Project
Information
A.1.
Overview
The following section provides additional project information that is intended to supplement the project
description provided in Chapter 2 of Volume II. It provides further technical details of key upstream and
downstream (UGCC) component processes of the Project which have been used to inform the ESIA.
A.2.
A.2.1.
Upstream Component – Surgil Field
Well Design
Production wells will target production from the Surgil Field gas-condensate reserves contained within
Terrigenous deposits of the Middle Jurassic (J 2 ) and Upper Jurassic (J 3 ). Sixteen productive zones (seams)
are contained within these deposits (5 Upper Jurassic and 11 Middle Jurassic seams), in depths between
1,590 metres and 3,006 metres. The Surgil Field gas-condensate wells are a vertical design with a
maximum depth of 2,950 metres.
A.2.1.1. Well Casing
Wells are drilled in sequence through various geological strata. Once each well section of the hole is
drilled, well casing is installed in the hole to provide structural integrity to the wellbore, and where
necessary isolate any high pressure zones from each other and from the surface. Well casing is important
as it provides a conduit to allow hydrocarbons to be extracted without intermingling with other fluids and
formations. It is instrumental in preventing blowouts allowing the formation to be sealed in the event of a
‘blowout’. Deeper well sections are drilled once the previous section above is cased and this continues
until the gas-condensate production zone is reached.
The type of casing depends on the sub-surface characteristics of the well. Typically there are four different
types of casing. Table A.1 provides the casing design for a typical Surgil Field well, including a description
of the purpose of the different casing type.
254793/RGE/GEV/03/01/03/08/2011
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