LINKING SEABED TO SURFACE

The use of

HIGH PRESSURE JACKUP DRILLING RISERS

for

Contents

• Typical Jackup Well Configuration

• Typical Subsea Well Configuration

• High Pressure Jackup Riser System Configuration

• Typical High Pressure Jackup Drilling Riser Specification

Typical Jackup Wells

• Are accessed using the Drilling Rig’s Surface BOP system

• Require multiple casing strings - along with a mudline suspension system, to be run into the well (from a surface wellhead) to provide the necessary pressure containment

• Typically require some form of “mudline conversion system”, to allow the use of subsea xmas trees

Typical Jackup

Drilling System

Configuration

Typical Subsea Wells

• Are accessed from a Semi-Submersible Drilling Unit

• Using a subsea BOP, and a Low Pressure Drilling Riser (with 18 ¾” full bore access)

• Utilise traditional 18 3/4” subsea wellhead systems, and xmas trees (typically provided by the likes of Vetco, Cameron, FMC, Dril-Quip, etc)

Typical

Semi-Submersible

Drilling System

Configuration

High Pressure Jackup Drilling Riser (HPJDR) Systems

• Provide a means of drilling, working over, and abandoning traditional subsea wells from a Jackup Drilling Unit (JDU)

• Typical main system components are:

• A hydraulic subsea wellhead connector at the lower end

• A length of riser pipe, that joins the subsea wellhead connector to the Surface BOP on the Jackup

• Allows full bore 18 ¾” drift access to subsea wellheads and xmas trees, for running casing hangers etc.

• Is straightforward to run and recover

Typical

Configuration

Typical HPJDR Riser Specification

• Comprises an assembly of 24” OD x 21” ID tubulars, each of 40 foot length (to allow easy drift of 18 ¾” diameter components)

• Tubulars are joined by the use of premium quality connectors – rig crews are familiar with their handling and make-up

• Majority of joints are typically of grade X65/X70

• Higher strength upper and lower riser transition (or stress) joints are normally required, typically of grade X80

Typical HPJDR Riser Specification (cont

’

d)

• A special joint is normally required towards the upper end, to allow an upward force to be applied by the Jackup’s tensioner system – to keep the riser system stable

• An umbilical and associated control systems are necessary to function the hydraulic subsea wellhead connector

• Guide arms can be provided to interface with the guide posts on the subsea equipment

Planning and Preparation for use of HPJDR

• The HPJDR is laterally unsupported other than at the seabed and the jackup

• Hence, in deeper water (circa 90 metres), there may be up to around 120 metres of riser “free-span”

• Tension normally has to be applied to the riser, from the rig’s systems, in order to ensure that:

• the system is stable

• the system can support the weight of the rig’s surface BOP

• deflections of the riser are reduced to manageable values, during drilling operations

• stresses in the riser system are maintained within acceptable limits

• the subsea hydraulic wellhead connector, and the subsea conductor is not overloaded

Planning and Preparation for use of HPJDR (cont

’

d)

• In order to ensure the system is acceptable, and define appropriate tensions, riser analysis is usually carried out

• The riser analysis typically comprises:

• Structural stability assessments

• Strength assessments (of the pipe, connectors and flanges, etc)

• Fatigue assessments (if the duration of proposed operations dictate)

• In cases where very high currents are anticipated or possible, it may be

necessary to consider the likelyhood of Vortex-Induced-Vibration, and possibly effect appropriate mitigating measures

• It is possible to define environmental operating envelopes, to reduce normal tension requirements

• Full running, retrieval and operating procedures are produced specific to each operation

Planning and Preparation for use of HPJDR (cont

’

d)

Internal

Riser

Pressure

In Conclusion

• High Pressure Drilling Risers are a viable means of drilling subsea wells from Jackups

• They can be employed (and have actually been used in the field) for drilling, workover and abandonment operations

• They allow 18 ¾” diameter, full bore access to subsea wellhead systems from a jackup

• They allow traditional subsea wellheads, xmas trees and completions to be accessed from Jackups, as well as Semi-Submersibles

• Can also be used for pre-drilling in the case of Platform Tieback applications, or where either a platform tieback, riser tieback or subsea completion may be