Unique wellhead safety valve systems, to address issues with falling objects over surface lines

Alan Brodie PTC

Abstract

Session: New and Emerging Technology

Presentation Title: Unique wellhead safety valve systems, which address the concerns associated with falling objects over gas injection lines

Author / Presenter: Alan Brodie PTC

Abstract:

This presentation will describe a unique annulus safety valve system , which has been designed in response to concerns regarding the potential for the release of significant volumes of high pressure gas from the annulus of gas lifted wells, in the event falling objects damaged annulus lines.

The presentation will also describe the extreme test criteria the valves have satisfied and explain the HSE and operational benefits the system offers over the traditional annulus valve configurations. Finally derivatives of the system, that have been developed to facilitate automated management of the maximum allowable shut in pressures on the A B and C annuli will also be described along with a unique solution to the potential for a well integrity issue associated with damage to surface chemical injection lines .

Introduction

• Primary HSE risks associated gas lift

– What are they

– How to address them

• New modular actuated surface annulus safety valves

– Design objectives

– Solution delivered

– Performance

– Track record

– Derivatives

• Conclusions

The primary HSE risk introduced by gas lift

• The release of high pressure gas from the annulus

– Due to some disruption or failure of the

• Wellhead, Xmas tree or Surface lines

– The latter being the most likely

– Annulus volume can amount to several tonnes of gas

• Especially in deeper or HP gas lift applications

– Sufficient for a prolonged fire if ignited

– vs 2 -3 tonnes in surface lines

Addressing the primary HSE risk

• Possible mitigation options include:

– Dual completions

• Employing SCSSV’s in each string

– Downhole Annulus Safety Valves ( DH-ASV’s)

• These suffer from a number of potential drawbacks

– Some gas inventory above the safety valve still exists

– Additional completion complexity (and cost)

– Poor reliability track record

– Workover complexity

• Been argued

– Together adding more HSE risk than they eliminate

Traditional gas lifted wellhead configuration

• Biggest source of risk is falling objects

• Colliding with the annulus line and valves

• Creating a hydrocarbon release at the inlet to the wellhead

• Risk identified as significant by a number of major OPCO’s

• Especially re potential for dropped object damage

• Wellwork / Well bay ops

• Weather related

• Similar risks with chemical injection penetrations

• Usually just NPT connections

• Set inside wellhead VR profiles

Gas lift choke

Check valve

Gate valve

New surface annulus safety valve objectives

• Surface Annulus Safety Valve to:

– Form part of the primary well barrier envelope

• Same leak rate (0.1 scf/day) as permitted by packers / bridge plugs

– E.g. satisfying “V1 criteria“ : 20 cc/ 10 mins

• A check valve to close with 0 psi dp

– Address the concerns of conventional annulus safety valves

• Assure annulus isolation, even if damaged by falling object

• Eliminate potential for

– Seal face erosion

– Seat damage due to valve vibration and chattering

• Facilitate annulus bleed down to inflow test gas lift valves

Solution to challenges

• Required a complete valve design rethink

– Fresh sheet of paper

– First principles physics

– Common sense practicality

Surface Annulus Safety Valves (SAS)

• Uniquely designed

• To fit in wellhead VR profile

• Other unique features

– Spring Configuration

– Flow Path Geometry

– Materials and Coatings

– Temp rating -46 – 170 Deg C

– Actuator module option M-SAS

• Many unique advantages – Caters for chatter and vibration– A true metal / metal seal

• Uniquely V0 fire tested w gas– Superior erosional resistance– Caters for Joule Thomson effect– Valve held open in normal ops

• Further reducing wear and tear.

– In the event of a facilities ESD:• HP lift gas in flowlines will bleed

off to the annulus• HP gas in the annulus can be

bled to the facilities

– Gas lift inflow tests confirmed without temporary rig up

– Disconnects in event of impact• Leaving closed SAS in VR profile

M SAS performance

• Well Integrity and Reliability

– Vo (zero leak rate) option available

– Chatter and vibration free operation

– Fire tested with gas

– Unparalleled impurity resistance

– Full internal metal / metal seals

– Fail safe on accidental disconnection

– Actuated option increases reliability

• Operational efficiency

– Faster gas lift valve inflow testing

• Can save 1 -2 days downtime per well

M SAS valve system track record

• > 250 valves installed

– In use in GOM and N Sea

– To date , no premature failures or under performance

• Gas lifted wells with failed DH-ASV’s previously had to be closed in

– Awaiting workover

– Now permitted to remain on stream

• if M-SAS valves are installed

Derivatives (1)

• Chemical injection system surface safety valves

– Developed in response to concerns re chemical injection line integrity

– Potential for a hydrocarbon release via the chemical injection line

– Solution was to develop a M SAS - CIV

Derivatives (2)

• Maximum Allowable Annulus Surface Pressure (MAASP ) Mgt system

• System based around unique VR Plug sensors

– Continual annulus pressure and temperature measurement

– Data can be remotely monitored

• Via wireless (HART protocol) or wired link to control room

• Wireless module detaches safely under impact

– Annuli can be bled down automatically via M-SAS valves

• Before closing again to ensure well integrity is maintained

Wireless transmission moduleAnnulus

VR Profile

Pressure temperature module

wellhead

Conclusions

• A new safety system for gas lifted wells has been developed:

– Designed to be installed within the wellhead VR profile

– Actuated and held fully open throughout their life

• Therefore much more reliable if called upon in an ESD

• The actuator module is designed to detatch in the event of impact

– Leaving the check valve closed in the VR profile

– Have been thoroughly tested to the most stringent of standards

• Vo with gas / fire

• Now being used to maintain uptime in wells with failed DH-ASV’s

• Offer a real reduction in the major HSE risk associated with gas lifted wells

– Eliminating concerns re dropped objects damaging annulus lines

– Derivatives also solve other HSE risks

Feb. 1 - 5, 2010 2010 Gas-Lift Workshop 15

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Feb. 1 - 5, 2010 2010 Gas-Lift Workshop 16

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