Well integrity in gas lift wells

Transkript

1 Well integrity in gas lift wells Claas van der Zwaag Petroleum Safety Authority Norway Well Regulators Meeting, Aberdeen November 17-18, of 18

2 Objectives Clarify technical safety aspects of gas lift wells Present results of a supervisory activity against several operators Demonstrate work wrt. administration of regulations, including modification of regulation Content Some background: gas lift, annular safety valves, production from gas lifted wells Experience with the regulations Other countries regulations, new NORSOK D-010 rev. 3 Proposal for a modification of regulation Special focus: gas lift valves 2 of 18

3 Background The risk and consequences of a blowout may be amplified in some gas-lifted wells by the large inventory of high pressure gas in the well Grasslok et al. (1992) Blowout Risk Analysis of Gas-Lift Completions, SPE Production Engineering, May After the Piper Alpha disaster the philosophy of isolating all hydrocarbons, tubing and annular, from the surface was adopted Leismer (1993) A System Approach to Annular Control for Total Well Safety, paper SPE Annular safety valves Safety valve for unintentional leakage of lift gas from annulus Part of the primary barrier against the reservoar. Sketch Annular Safety Valve Conventional gas lift 3 of 18

4 Gas lift on the NCS, numbers Total production from GL wells: appr bpd Upcoming GL-projects: Norne-Satelites (Urd), Alvheim 4 of 18

5 Gas lift on the NCS Production numbers document importance of gas lift as a method for artificial lift Used on fields with low reservoar energy and high water cuts in production Increased use of gas lift on NCS is expected 5 of 18

6 Regulations Facilities Regulation 53 on equipment for completion and controlled well flow sets requirements to use of annular safety valves in gas lifted wells. Regulations open for exemptions, exemptions require however formal application. Applications require evaluation of the non-conformance, risk analyses and description of compensating measures. 6 of 18

7 Experiences Over the last 3 years, the NPD has received a large number of applications for exemptions related to HMS-issues concerning annular safety valves (ASV) in gas lift wells. Risk-reducing completion alternatives prior to installation of ASV Operational problems related to ASV and risk-reducing solutions Operators have chosen different approaches to assess safety related issues 7 of 18

8 Core questions Does the large number of applications reflect a chronic problem? Are the given regulatory requirements attainable with the available technology? Should the regulations be adapted to the conditions set forward in the consents to the exemptions? Are the risk assessments presented by the operators reflecting risks properly? Invited to industry meeting 8 of 18

9 Response from operators Risks wrt. installation and workover of ASV contributes significantly to the total risk of conventional gas lift operations. ASV show insignificant risk reducing effect in subsea completions. The industry has identified and tested risk reducing measures that compensate for ASV. Regulations should avoid specific requirements wrt. ASV. Completion solutions should be evaluated based on QRA. 9 of 18

10 Risk with installation Risk analyses, factors Risk reducing effect of ASV Risk with workover when replacing failed ASV Example: Risk (PLL) over remaining field life Risks wrt. installation and use of ASV depend on: type of installation, platform, subsea type of operations, manning number of gas lift wells annular volumes and pressure conditions production volumes production phase and remaining reservoir energy other work (interventions, workovers) etc. 10 of 18

11 Compensating measures Different solutions with risk reducing effect Æ Wellhead design (reinforced double block valves, integrated check valves) Æ Test intervals Æ Deepset DHSV Æ Automatic blowdown systems Æ Dual string systems Æ Gascap gas lift 11 of 18

12 Other countries regulations USA Requirements for subsurface safety devices. Pipes or annuli that are in open connection to HC-bearing formations No specific requirements wrt. ASV. UK Analysis of major accident risks Well design and construction follow ALARP over the lifetime of the well Protective measures and risk assessments for fire and explosion, preventive actions wrt. uncontrolled releases of gas and accumulation of flammable substances No specific requirements wrt. ASV. Code of Federal Regulations, Title 30, Chap. II, 2001, Subchap. B, , Offshore Safety Case Regulations 1992, Reg. 8, Offshore Installations and Wells Regulations 1996, Reg 13(1) Offshore Installations (Prevention of fires and Explosions, and Emergency Response) Regulations 1995 (PFEER), Reg, 4(1), 5, 9(1) 12 of 18

13 NORSOK D-010, rev 3 august 2004 Kap 7.3 (c): En brønn bør kompletteres med ringromsikringsventil under følgende forutsetninger 1. Produksjonsringrommet er perforert ovenfor produksjonspakningen og brukes til produksjon eller injeksjon av hydrokarboner. 2. A-ringrommet brukes til gassløft og det finnes ingen annen kvalifisert barriereelement i primærbarrieren. 3. Risikoanalyser viser ikke akseptabel storulykkerisiko ved tap av brønnhode/sekundærbarrieren. Typical gaslift platform production well, kap of 18

14 Forslag til regelverksendring Ny tekst for Innretningsforskriften 53 om utstyr for komplettering og kontrollert brønnstrømning lyder: (2. ledd) Kompletteringsstrenger skal være utstyrt med nødvendige brønnsikringsventiler i strømningsrøret og produksjonsringrommet. Veiledningstekst: For å oppfylle kravene til ringromsikringsventiler skal det etableres barriereoversikter jfr. innretningsforskriftens 47 og utføres risikovurderinger av løsningen jfr. styringsforskriftens 14, 15. Innretningsforskrift 47om brønnbarrierer Styringsforskrift 14 om analyse av storulykkerisiko Styringsforskrift 15 om kvantitative risikoanalyser og beredskapsanalyser 14 of 18

15 Interpretation Annulus is used for production of hydrocarbons? No Annulus is used (only) for gas-lift No other qualified barrier-elements are or will be installed (deep-set SCSSV, or SCSSV plus qualified GLV No Yes Yes Risk of major accident is unacceptable without ASV Yes No ASV has positive influence on overall risk throughout well lifetime No Yes Annulus Safety Valve must be installed to obtain increased well-integrity and -safety Alternative completion solution OK 15 of 18

16 Barrierekrav, kvalifisering av gassløftventiler Gassløftventiler (GLV) som brukes som fullverdig barriereelement mot reservoaret må regnes som brønnsikringsventil (subsurface safety valve). GLV brukes i så tilfellet utover standardfunksjonen. Krav til kvalifisering jfr. innretningsforskriften 8 om kvalifisering og bruk av ny teknologi. Kvalifisering kreves for ulike GLV-typer og fabrikater. Krav til verifikasjon av ytelsen til brønnbarrierer jfr. innretningsforskriften 47 om brønnbarrierer NORSOK D-010: detaljkrav til brønnbarrierer. API RP 14B og ISO 10417: detaljkrav til operasjon og testing av brønnsikringsventiler. 16 of 18

17 Oppsummering/Konklusjon Innretningsforskriftens 53 foreslåes endret mht detaljkrav mot ringromsikringsventiler (ASV) Risikoanalyser viser at brønnsikkerheten ved komplettering og vedlikehold av gassløftbrønner med ringromsikringsventiler kan påvirkes i negativ retning under spesielle forhold. Ved komplettering av gassløftbrønner (konvensjonell) skal den ansvarlige (1) etablere barriereoversikter, (2) utføre risikoanalyser i forhold til storulykkesrisiko, (3) utføre risikoanalyser i forhold til andre kompletteringsalternativer. Petroleumstilsynet vil i tiden som kommer vurdere å øke innsatsen når det gjelder brønnsikkerhet i gassløftbrønner, spesielt i forbindelse med bemannede operasjoner og på flerbruksinnretninger. 17 of 18

18 Takk til F-Prosess/Ptil, F-Boring/Ptil Norske Shell, Statoil, ConocoPhillips Norge, Norsk Hydro, Esso, Pertra-DPT, BP 18 of 18