LINKING SEABED TO SURFACE

LINKING SEABED TO SURFACE

The use of HIGH PRESSURE JACKUP DRILLING RISERS for SUBSEA DEVELOPMENTS 2 High Pressure Jackup Drilling Riser

Contents Typical Jackup Well Configuration Typical Subsea Well Configuration High Pressure Jackup Riser System Configuration Typical High Pressure Jackup Drilling Riser Specification Preparation and Planning for the use of High Pressure Jackup Drilling Risers 3 High Pressure Jackup Drilling Riser

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 Are more typically drilled with a view to completion via a fixed platform 4 High Pressure Jackup Drilling Riser

Typical Jackup Drilling System Configuration 5 High Pressure Jackup Drilling Riser

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) Require 18 ¾ full bore access to allow casing hangers (etc) to be run/recovered 6 High Pressure Jackup Drilling Riser

Typical Semi-Submersible Drilling System Configuration Rig Floor Riser Sea Level BOP Hydraulic Wellhead Connector Subsea Wellhead Seabed 7 High Pressure Jackup Drilling Riser

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 Can be provided on a rental basis 8 High Pressure Jackup Drilling Riser

Typical Configuration Rig Floor BOP Tension Ring Riser Sea Level Hydraulic Wellhead Connector & XmasTree Subsea Wellhead Seabed 9 High Pressure Jackup Drilling Riser

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 A relatively high capacity hydraulic subsea hydraulic wellhead connector is typically necessary 10 High Pressure Jackup Drilling Riser

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 11 High Pressure Jackup Drilling Riser

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 deflections of the surface BOP are reduced to manageable proportions 12 High Pressure Jackup Drilling Riser

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 13 High Pressure Jackup Drilling Riser

Planning and Preparation for use of HPJDR (cont d) The effects of internal pressure must be accounted for 14 High Pressure Jackup Drilling Riser

Internal Riser Pressure BOP Rig Floor Tension Ring Riser Sea Level Hydraulic Wellhead Connector Subsea Wellhead Seabed 15 High Pressure Jackup Drilling Riser

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 employed Typically can be used up to 5,00psi internal working pressure 16 High Pressure Jackup Drilling Riser