Plexus WHD System

100DG 1 egaP dtL smetsyS naecO suxelP

Plexus Ocean Systems Ltd “TRT-S” Mudline Suspension System

GD-001

“TRT-S” Mudline Suspension System

GD-001

Published – 02/08/2001

Plexus Ocean Systems Ltd Page 2 GD001

Plexus Ocean Systems Ltd. “TRT-S” Mudline Suspension Systems

GD-001

Contents

1. INTRODUCTION ......................................................................................... 4

2. SUMMARY OF MAJOR ADVANTAGES .................................................... 5

3. SYSTEM DESCRIPTION............................................................................. 6 Surface Casing String Installation Methods ..................................................................................... 6 Annulus Washout - Telescopic Running Tool ................................................................................. 8 Hangers Forced Concentric and Parallel ........................................................................................ 10 Hanger Lockdown Facility............................................................................................................. 10 External Test Ports ......................................................................................................................... 10 Split Ring Landing Profile Design ................................................................................................. 11 Temporary Abandonment............................................................................................................... 13 TA Cap Retrieval ........................................................................................................................... 15 Designed for Tieback or Subsea Completion ................................................................................. 16 Mudline Annular Seals................................................................................................................... 17 Additional Hanger Options ............................................................................................................ 17 Dimensionally Designed for 15,000 psi ......................................................................................... 18

4. OPERATIONAL ADVANTAGES............................................................... 19

5. COST SAVING ANALYSIS....................................................................... 20

6. CONTACT DETAILS................................................................................. 21 PLEXUS OFFICES........................................................................................................................ 21


List of Drawings C100……………………………………………………………………………………………. Page 5 “TRT-S” Mudline System Advantages C001 ……………………………………………………………………………………………. Page 6 “TRT-S” Mudline System 30” x 20” x 13-3/8” x 9-5/8” Casing Programme with Running Tools installed. C110……………………………………………………………………………………………. Page 7 “TRT-S” Mudline System 30” x 20” x 13-3/8” x 9-5/8” with Plug Type TA Cap and Tieback Tools installed. C111……………………………………………………………………………………………. Page 8 “TRT-S” Mudline System – “TRT” Detail 30” x 20” x 13-3/8” x 9-5/8” Casing Programme showing 20” washout. C058…………………………………………………………………………………………….Page 11 Spilt Cage Landing Sequence C112…………………………………………………………………………………………….Page 12 Spilt Cage Design Advantages C107…………………………………………………………………………………………….Page 13 “TRT-S” Mudline System 30” x 20” x 13-3/8” x 9-5/8” with Through Bore TA Cap and Tieback Tools installed.

C103…………………………………………………………………………………………….Page 14 “TRT-S” Mudline System 30” x 20” x 13-3/8” x 9-5/8” with Plug type TA Cap, Running Tools / Tieback Tools shown.

C101…………………………………………………………………………………………….Page 15 “TRT-S” Mudline System vs Conventional System TA Cap Retrieval. C109…………………………………………………………………………………………….Page 17 “TRT-S” Mudline System 30” x 20” x 13-3/8” x 9-5/8” Casing Programme with Full Bore Annular Seal installed. C008…………………………………………………………………………………………….Page 18 “TRT-S” Mudline System High Pressure Running Tool configuration.


1. Introduction

The Plexus "TRT-S" Mudline System represents a second-generation development of mudline suspension technology for use with adjustable Wellhead equipment. The system is specifically designed to facilitate the installation of Mudline Hangers whilst enabling spaceout in the adjustable Surface Wellhead. Furthermore, the Hanger configuration has been tailored to address various requirements for tieback completion or subsea conversion. The "TRT-S" system uses a Telescopic Running Tool, which can be retracted to expose washports in the Surface Casing Hanger for annulus washout purposes. The Telescopic Section of the Telescopic Running Tool is manipulated by the use of a drill-pipe deployed Torque Tool. This eliminates the need to rotate the Surface Casing Riser to effect washout, thereby allowing the Surface Casing String to be hung off in tension. The "TRT-S" feature simplifies space-out within the Adjustable Wellhead, allows the pre-installation of the Surface Casing Starting Head and eliminates the need to use an accurately spaced-out Butt-weld Sub within the Conductor. The "TRT-S" system offers all the features necessary to facilitate easy drilling of a mudline well. However, the major emphasis on design has been in providing a sound basis for future tieback conversion or subsea conversion. Our first aim has been to ensure that all the Mudline Hangers, once landed, are forced into a parallel pattern on a common centre line. By doing so, tieback operations can occur in a known configuration. Wherever possible, generous debris accommodation pockets have been provided to ensure that Mudline Hanger suspension and Tieback Tool engagement can be smoothly effected in an environment that is likely to be contaminated. Dual pre-alignment surfaces are used to minimise the risk of thread damage during Tieback Tool engagement and to protect the metal to metal seals that are provided for both the Running and Tieback Tools. To offer continuous control during drilling and completion operations the temporary abandonment system has been so configured that a TA Cap can be installed through the BOP prior to disconnection of the Intermediate Casing Riser and can subsequently be removed following re-installation and testing of the Tieback Wellhead. Plexus engineers for years have worked on the development of specialised mudline suspension equipment for 15,000 psi applications. The Plexus "TRT-S" system has been dimensionally designed and finite element analysed so that the standard system can be upgraded to full 15,000 psi use, by the substitution of standard materials with high strength corrosion resistant alloys and the re-location of the washports in the production Casing Hangers.


2. Summary of Major Advantages

C100

Tieback Tools andTA Cap Installed

Running ToolsInstalled


3. System Description

The "TRT-S" Mudline system is offered for the full range of casing programmes generally used in Jack-Up drilling operations. The system described in this document is configured for a 30" x 20" x 13-3/8" x 9-5/8" casing programme. The pertinent features of the system are described in more detail below. Surface Casing String Installation Methods The left-hand side of the drawing C001 shows the Surface Casing Mudline Hanger landed on a Butt-weld Sub. The right-hand side shows the configuration with the Surface Casing String installed in tension, ie on the top of the outer conductor. The following considerations apply when selecting the most appropriate installation method. Exploration Drilling In exploration applications, the operator may not know the precise distance between the ocean floor and Rotary Kelly Bushing prior to arrival on location. In this situation it is preferable to use a mudline system which enables the location of the Surface Casing Mudline Hanger to be independent of the setting depth of the Conductor. The configuration illustrated on the right-hand side of C001 shows the Surface Casing and Riser Section set in tension at a depth which can be precisely selected and which is measured against the top of the Conductor. The “TRT-S” Mudline System is designed to allow efficient washout of the Surface Casing Annulus without having to rotate the Riser Section, eliminating the need for a Butt-weld Sub.

C001

BUTTWELD SUB IN TENSION

P

Template Drilling

lexus Ocean Systems Ltd Page 7 GD001

In applications where tieback to several wells in a template system is planned, Plexus again recommend that the Surface Casing be cemented in tension, without using a Butt-weld Sub, as shown in C110. If Conductors are drilled and cemented, or even driven and drilled to locate a Butt-weld Sub at a pre-determined depth, then the agitation to neighbouring wells during drilling can cause cavities to be formed around and below the Conductors. It is known that under these conditions, individual Conductor slippage, or even the loss of the whole Template can occur. The Plexus “TRT-S” Mudline System allows the Surface Casing Mudline Hanger (the foundation stone for the subsequent tieback operation) to be set at a precise depth. In template drilling, the “TRT-S” System enables the Mudline Hangers in each Well to be placed at exactly the same level from RKB, by using identical Surface Riser lengths. This not only reduces cost during installation, but also facilitates tieback planning and implementation. Subsea Conversion For subsea conversion, Plexus recommends the use of a specialised Landing Housing to ensure that the distance from the Surface Casing Mudline Hanger to the Mudline Wellhead Conductor Housing is precisely controlled. The preferred installation method for a Conductor with a fixed landing shoulder is drilling and cementing. As subsea wells tend to be singular, there is no risk of disturbing neighbouring wells using this installation method.

C110



Annulus Washout - Telescopic Running Tool It is essential that Casing Riser Strings can be easily disconnected at the mudline during well abandonment, and for this to take place, annulus washout procedures must operate efficiently. Most problems in this area occur with the Surface Casing annulus. Mudline Suspension Systems generally effect annulus washout by rotating the Running Tools to open washports. This procedure requires the casing below the Running Tool to be suspended on a shoulder within the Conductor. Such a shoulder cannot always be accurately positioned when Conductors are driven to refusal or even when drilling through a Template. In such cases, the Surface Casing String is cemented in tension and use is made of a cumbersome, inefficient and potentially ineffective system of washpipes to clean out the annulus. In circumstances where the Conductor can be accurately located and a Butt-weld Sub is used, the bending loads at the Mudline, often resulting from Riser misalignment, can impede rotation of the Running Tools. This can result in various problems such as thread or seal damage, failure to washout, failure to close washports after circulation or a stuck Running Tool. All of the above mentioned problems significantly increase well cost and have the potential to make future tiebacks problematic. The "TRT-S" Mudline System uses a Telescopic Running Tool, which can be opened and closed with an internal drill-string deployed Torque Tool. The Telescopic Section is housed between the Running Tool and the Hanger in what constitutes a stiff part of the Surface Casing String. The Telescopic Section is therefore not affected by the deflection forces normally present in the Riser. The manipulation of the Telescopic Section is thus virtually free of bending loads and requires minimal torque to rotate.

Telescopic Running

Tool

C111

Washout occurs below

interface

WASHPORTS OPEN

WASHPORTS CLOSED


Both the Telescopic Section and Running Tool have left-hand threads. This thread combination ensures that the Running Tool integrity is not compromised during operation of the Telescopic Section. (The Telescopic Section is checked on surface prior to being run and made-up hand tight; the right hand rotation required to open is thus low torque. The left hand rotation necessary to make the telescopic section up acts to tighten the Running Tool thus eliminating any back-off tendency during telescopic section closure). In order to optimise rig operational time the telescopic section can be manipulated with a Torque Tool which is part of the Cement Stinger assembly. This procedure can be implemented literally minutes after the completion of cementing operations. This advantage becomes apparent if unforeseen circumstances cause delay whilst the cement setting time approaches. In order to prevent debris build-up around the Running Tool the washports are located well below the Surface Hanger to Running Tool interface. This ensures a clean profile is left for any future tieback or well re-entry operations. The Intermediate and Production Mudline Hanger Running Tools utilise a conventional annulus washout system which requires rotation of the Casing Risers. After washout has been effected, a metal to metal Interface Seal can be energised. This is backed up by dual resilient seals. In the unlikely event that a Running Tool is disengaged during drilling operations, pre-alignment is provided to enable remote re-engagement of the left hand threads whilst protecting the interface seals.

C001



Hangers Forced Concentric and Parallel When utilising a Mudline Well for production applications, tieback procedures have to be effected. The feasibility of such procedures is greatly facilitated if the Mudline Hangers are arranged in a predictable configuration. To control the position of each Hanger, provisions have been made in the design of both shoulder type and split ring Hangers, to ensure that during landing both concentricity and parallel positioning is achieved. The Plexus "TRT-S" Mudline System provides such alignment for all hangers. The "TRT-S" Split Ring Hanger utilises a setting mechanism which prevents early release of the Split Ring, whilst also acting as a centraliser. Hanger Lockdown Facility For specific applications, lockdown facilities for the Mudline Hangers can be provided. This is particularly appropriate for wells where thermal expansion is a problem, such as HP/HT wells or wells converted to Subsea use. External Test Ports To facilitate hanger interface seal testing, all Running Tool seals are equipped with external Test Ports. Seal integrity can be verified prior to running an assembly. During onshore make-up of the Hangers and Running Tools these ports are used to eliminate the need for expensive and time consuming body tests, representing a considerable cost saving.

C001



Split Ring Landing Profile Design The Landing Profile for the Split Ring Hanger is designed with debris accommodation pockets in which contamination is dispersed during expansion of the Split Ring. This eliminates the need for a costly additional run with a landing profile clean out tool, as utilised in some systems. The Plexus Split Ring design also features dual concentricity – the Production Hanger is forced concentric by the Split Ring in two places. As well as ensuring concentricity, this ensures that the hanger is parallel to the Intermediate Casing Hanger, facilitating tie-back and allowing the use of an annular seal.

Split Cage being run through13-3/8" Hanger

Mating profile located Hanger landed and setin position C058

Dual Concentricity


One further advantage of the Split Ring is that it has been designed to collapse evenly, to ensure that landing shoulders are protected from damage during installation and to prevent premature setting. Other systems collapse such that the landing shoulders are the outermost part of the component as it is forced to collapse. Drawing C112 below demonstrates the advantage of the Plexus design over other systems.

Split Cage collapses evenly, ensuringlanding shoulders are protected

Split Cage collapses further at the bottom.This leaves teeth exposed and subject

to hang-up or damage

C112

PlexusSplit Cage

CompetitorSplit Cage

Bending stiffnessis equal above

and belowcompression point

Compression pointis below centre ofbending stiffness

SURFACE WELLHEADRISER


Temporary Abandonment When a Rig leaves its location the Casing Risers are disconnected. This leaves Mudline Hanger Profiles, designed to accept Production Equipment, exposed to the environment. Conventional systems use a number of plug type Temporary Abandonment Caps to plug the Well and to protect the Tieback Profiles. The Plexus "TRT-S" system offers a single annular Through Bore Temporary Abandonment Cap, which is installed in the Production Casing Hanger profile. The unit seals the Production Casing annulus only. The seal utilises an expandable resilient element that is activated by wedge action. The unit is engaged within the Production Casing Hanger with a stab type Threaded Ring and locks itself into the Intermediate Mudline Hanger with a Lock Sleeve activated by the downward motion of the TA Cap relative to the Production Casing Hanger. This locking action secures the Mudline Hangers in position and eliminates Casing rise. A "Jay"-Type Running Tool is designed to allow for testing of the Annular Seal, under the BOP's. The Through Bore TA Cap has been designed with full consideration of future tieback or well re-entry operations. The design allows the facility to first tieback the Intermediate Casing Riser prior to removing the Cap through the Tieback Wellhead after BOP nipple up has occurred. Another major advantage of the Through Bore TA Cap is that an inner tool string can be used for weight or guidance purposes. Operators with Tieback experience will know how essential this feature is during the re-establishment of outer Tieback Strings.

C107

Through Bore TACap

RUNNING TOOLS TIEBACK TOOLS


A plug type TA cap is available for operations where it is not feasible to plug the well by alternative methods. The Plexus “Plug Type Abandonment” cap seals the Production Casing Bore as well as the Production Casing Annulus. The Cap allows tieback of the Intermediate Casing riser prior to retrieval and it is also possible to separately establish pressure in either the Production Casing Bore or the Production Casing Annulus prior to the cap being removed. The "Plug Type Abandonment Cap" has a pressure balanced relief valve, which allows pressure monitoring or relief in both the annulus and the bore independently. In this mode the "TRT-S" Abandonment Cap can be effectively used as a tieback seal test tool for the Intermediate Casing Riser. The "TRT-S" Abandonment Cap is subsequently retrieved through the Tieback Wellhead. This procedure can be implemented under controlled conditions should pressure be found to be present under the Cap. Finally, similar to the "Through Bore TA Cap", the "Plug Type Abandonment Cap" is designed to lock the Mudline Hangers in position thereby preventing casing rise. During years of experience with tieback technology the Plexus team has learnt to appreciate the value of debris pockets. The "TRT-S" Abandonment Cap has been positioned so as to allow the settlement of debris on top of the Cap without interfering with the Intermediate Casing Riser Tieback procedure.

C103

RUNNING TOOLS TIEBACK TOOLS

Plug Type TA Cap

TA Cap Retrieval As mentioned previously, both the Through Bore and Plug Type TA Caps have the facility to lock down the Production Hanger as a standard feature. This prevents movement of the Hangers if pressure builds up below the Cap. Conventional systems do not offer this, as is shown in drawing C101 below. One potentially disastrous scenario, which could occur if the TA Cap is not locked down, is shown. Pressure has built up in the bore. In the conventional system on the right, the lower cap will move upwards with casing rise, pressing on the upper cap with significant force. The resultant load on the threads of the upper cap make disengagement difficult if not impossible, so the well could be lost. In the “TRT-S” system, no hanger movement can occur, and any pressure build up, in either the bore or annulus, can be bled off in a controlled manner through the pressure balanced release valve.

Other SystemsPlexus "TRT-S" System

2 Feet

Pressure in the bore forces lowerCap against upper Cap, whichcould make retrieval impossible Eg: 5000 psi results in 200 kipscontact force between Caps

No movement asHanger is locked downby TA Cap. Pressurecan be released throughpressure balanced valvebefore Cap is retrieved


C101

11"

3"

7"6"5"4"

10"

8"9"

1"

5"

3"2"

4"

1"

9"10"11"

8"7"6"

2"DATUM

3 Feet

2 Feet

1 Foot

0

1 Foot

Plexus Ocean Systems Ltd Page 16

Designed for Tieback or Subsea Completion The Plexus "TRT-S" Mudline system uses a Riser Tieback method, which needs minimum rotation to effect engagement. The inner Casing Risers are connected with Stab-type Tieback Tools which use a Threaded Split Ring mechanism. In the case of the outer Tieback Riser, where optimum bending and tensile capacities are critical, the "TRT-S" Mudline system offers a fatigue resistant tapered threaded connection, which engages with 1-1/4 turns of right hand rotation. An FEA study can be made available to confirm suitability under specific fatigue loading conditions. In order to accurately control the recommended setting torque for each of the tieback connections internal torque profiles are provided for each tieback tool to allow use of a drill string deployed Torque Tool. To prevent cross threading during remote engagement, each tieback profile is provided with dual pre-alignment surfaces, thus protecting the thread profiles and preventing any damage occurring to the metal to metal Tieback Seals. To facilitate a successful tieback, the Plexus "TRT-S" Mudline system offers a number of redundant seal areas in the Tieback Profiles, which can be utilised should the primary seal areas be inadvertently damaged. For Subsea Wellhead conversions the "TRT-S" Mudline system can be specified with lockdown devices for each Mudline Hanger. A hydraulically tensioned Tieback Mechanism ensures that the Subsea Crossover Hangers are installed with positive downward load thus enabling the use of metal to metal Annular Seals.


R
EDUNDANTSEAL AREA
GD001

C110


Mudline Annular Seals For casing programmes where Surface Casing is omitted and the Intermediate Casing Riser is designed to contain full well pressure, the "TRT-S" Mudline system can be supplied with an Annular Seal which bridges the Production Casing and Intermediate String annulus, as shown in drawing C109. The annular seal is similar in design to the TA Caps, in that it provides single trip installation as well as positive lock-down for the Production Hanger. Additional Hanger Options To enable the operator to install an extra Casing String the Plexus "TRT-S" Mudline system offers the option of an additional Mudline Hanger Assembly, which can be installed directly below the Mudline Production Casing Hanger or at any other convenient location specified. The Running and Tieback Tools are designed with a tapered right hand thread, which sets a metal to metal interference seal.

Full Bore Annular Seal

C109

Plexus Ocean Systems Ltd Page 18

Dimensionally Designed for 15,000 psi Over many years Plexus have worked on the development of Mudline Systems for high temperature and high pressure applications. The Plexus Ocean Systems "TRT-S" Mudline system has been dimensionally configured and finite element analysed to enable the option of upgrading the system to full 15,000 psi service. This is achieved by substituting standard materials with high strength corrosion resistant alloys such as Inconel, and by relocating the washports to the Production Casing Hanger, if required, increasing hoop force resistance. In addition, the seal design utilised within the Plexus mudline systems can be classified as a genuine metal to metal 15,000 psi seal.

Standard Configuration

Washports in Running Tool

High Pressure Configuration

Washports in Hanger to increase

pressure rating

GD001

C008


4. Operational Advantages

• Surface Casing Riser annulus is washed without riser rotation.

• Washout procedure with Circulating Swage reduces time period between completion of cementing and starting of washout from hours to minutes.

• Surface Casing Mudline Hanger washports are located below the Running Tool interface.

• Pressure balanced cementing procedure eliminates risk of Casing collapse.

• Surface Casing does not require landing ring, ie set at surface in tension.

• Surface Wellhead Starter Head is pre-installed eliminating field welding.

• Running Tool to Hanger interface seal can be tested externally just prior to running through rotary table - Onshore body tests for Hanger are eliminated saving cost.

• Hanger/Running Tool assembly interface connections remain unused and protected prior to installation (no onshore testing with end caps is necessary).

• Dual concentricity places all Hangers on identical centre line facilitating tie-back.

• Split Cage design prevents accidental damage during installation.

• Split Cage run without the need to clean the receiving profile.

• Seal area is provided for production bore Annular Seal.

• Lock-down profile is provided for production Mudline Hanger.

• Single trip stab-type dual TA Cap.

• Dual stab-type TA Cap set prior to removal of BOP.

• Dual TA Cap retrieved after installation of Tie-back Wellhead under controlled conditions.

• Monitoring facility of production bore and annulus through TA cap valves.

• Isolated Tie-back Seal test capability.

• Separate Running (LH) and Tieback (RH) Threads.

Typical Systems do not offer many of the above features, some of which are critical to safe well operations.


5. Cost Saving Analysis

This analysis shows cost savings as a result of using Plexus “TRT-S” Mudline Suspension System over conventional mudline equipment during the drilling phase. Time related: • Surface Starting Head is preinstalled 4 hrs • Surface casing riser annulus washed without riser rotation 3 hrs • Split Cage landed without profile cleanout run 2 hrs • Single trip T/A and lock-down cap 2 hrs Total Hours Saved 11 hrs Total Time Related Savings (@ £ 80,000 per day rig rate) £ 36,667 Other savings: • Welding Starter Head (Personnel and Equipment) £ 2,000 • External test ports in Running Tools eliminate need to perform onshore body tests with end caps £ 3,000 Total Other Savings: £ 5,000 Grand Total Savings per Well: £ 41,667 Potential additional savings: In addition to the above savings, the Plexus “TRT-S” Mudline System offers features which facilitate subsequent tieback operations or sub-sea conversion procedures: • Dual alignment of Hangers ensures a known configuration. • Pre-alignment profiles prevent cross-threading. • Through Bore TA Cap enables the use of a drill pipe guide string to aid difficult

tieback. These features are difficult to quantify, but can be seen as ‘insurance’ against potential problems which may greatly impact the final cost of well completion.


6. Contact Details

PLEXUS OFFICES

Plexus Ocean Systems Ltd Unit 1, Ashley Base Pitmedden Road Dyce Aberdeen AB21 0DP Tel: +44 (1224) 774222 Fax: +44 (1224) 774333 E-mail: [email protected] Other Offices:

Plexus Ocean Systems Ltd Plexus House 1 Cromwell Place London SW7 2JE Tel: +44 (207) 589 8555 Fax: +44 (207) 589 8554 E-mail: [email protected]

Plexus Ocean Systems Inc Suite 120 1224 North Post Oak Road Houston Texas 77055 Tel: +1 (713) 686 5267 Fax: +1 (713) 686 0275 E-mail: [email protected]

Documents

Plexus WHD System