لوصف الحالة البيولوجية لتقييم الحالة التي تبيع العلم لكم 29453984-Injection-Well-Problems.ppt
- 1. WELL INTERVENTION PRODUCTIVITY SCHOOL Nov 2001 CORROSION Production Related Problems • Are numerous (!) and included: – water – corrosion – wax precipitation – asphaltene precipitation – hydrates – Hydrogen sulphide – fines migration – phase-related permeability reduction – stress-induced permeability change – scale – emulsions – gas production REMEMBER PREVENTION IS BETTER THAN CURE
- 2. WELL INTERVENTION PRODUCTIVITY SCHOOL Nov 2001 CORROSION • How can we handle produced water more effectively? • Water Production and its effects on profitability Production Related Problems - Water How to recognise production related damage Rapid decline due to production related damage- productivity might be restored by regular stimulation treatments (not always successful, dependent on interval length and cause of damage). Years of Production Production Rate, stb/day 6000 4000 2000 0 0 1 2 3 4 Production Rate, stb/day Years of Production 6000 4000 2000 0 0 1 2 3 4 Natural decline due to drop in reservoir pressure- no production related damage.
- 3. WELL INTERVENTION PRODUCTIVITY SCHOOL Nov 2001 CORROSION Production Related Problems - Water • Main culprit of production related damage Some or all of the above problems may occur at the same time! P r o d u c t io n W e l l WATER PRODUCTION It causes loss of lift energy extra treatment expense corrosion scale formation hydrates emulsions wells to be choked back due to facilities constraints
- 4. WELL INTERVENTION PRODUCTIVITY SCHOOL Nov 2001 CORROSION Production Related Problems - Water • Corrosion considerably increases the cost to well productivity Increased roughness, hence bigger friction drops and lower rates. Potential for formation/screens/perforation plugging during bullheading or injection. Difficulty in running intervention tools (especially in ERD wells). Difficult to set reliable plugs for gas/water/ sand control. Well has to be shut-in/loss of production/ injection until workover. May be impossible to plug tubing and isolate reservoir, therefore well may require killing by bullheading with potential for permanent formation damage. Water/gas/sand production loss in oil production. May require well abandonment or a sidetrack. Limited corrosion of tubing Corrosion of injection pipework, pumping equipment etc. Extensive corrosion downhole e.g. Holes in production tubing e.g. Parting of tubing e.g. Failure of liner e.g. Failure of casing Increasing Corrosion
- 5. WELL INTERVENTION PRODUCTIVITY SCHOOL Nov 2001 CORROSION Not normally a problem with the right metallurgy Not normally a problem with the right completion metallurgy Production Related Problems - Corrosion • CO2 – Combines with water to form Carbonic Acid – Pitting • H2S – Sulphide stress cracking – Hydrogen embrittlement • Completion and Intervention fluids – Oxygen – Microbiologically induced corrosion. • Acids – Severe corrosion without inhibitor – May also react with sulphides to form H2S – may require sulphide scavenger • Solids – Erosion – Or erosion-corrosion – Monitor rates and if need be choke back
- 6. WELL INTERVENTION PRODUCTIVITY SCHOOL Nov 2001 CORROSION Water Injection - Source • Seawater – Quality varies with location, depth and time (e.g. algal blooms)). – Monitoring may be required. • River water - – clearly the water quality will vary with location and time. • Aquifer water - many fields use dedicated water production wells. – The water may be fresh (with or without oxygen) – Saline (again with or without oxygen). – Contaminants may be introduced by extraction (e.g. if gas lift is used to lift the water). • Produced water - – Oxygen free at the wellhead. – The water may also contain dissolved salts, oil carryover, dissolved gas or produced solids. – Once separated from the oil, the water may also pick up oxygen.
- 7. WELL INTERVENTION PRODUCTIVITY SCHOOL Nov 2001 CORROSION Water Injection Treatment • Bacteria – beware of bugs in your water – can plug pore throats – can cause H2S • Corrosion (oxygen control) – major problem for many injectors – maintain O2 levels below 30 ppb – many workovers required because of this Injection pump(s) Water injection wells Oxygen removal (eg. gas stripper) Ineffective removal e.g. inadequate gas rate Oxygen introduced through seals Oxygen introduced through leaky flanges Corrosion by overdosing oxygen scavenger or poor deployment
- 8. WELL INTERVENTION PRODUCTIVITY SCHOOL Nov 2001 CORROSION Corrosion - Water Injectors
- 9. WELL INTERVENTION PRODUCTIVITY SCHOOL Nov 2001 CORROSION Oxygen Control - The Reality Any oxygen above threshold - even for very short durations causes corrosion - and over long time period 1 2 3 4 5 6 Time (days)
- 10. WELL INTERVENTION PRODUCTIVITY SCHOOL Nov 2001 CORROSION Corrosion Monitoring • Examination of recovered intervention toolstrings • Detection of dissolved iron • Finding a leak! (beware!) • Corrosion probes (at surface) • Corrosion logs (beware!)
- 11. WELL INTERVENTION PRODUCTIVITY SCHOOL Nov 2001 CORROSION Intervention In Water Injectors • Avoid? • Wireline or toolstrings can score semi-protective films • Wireline or toolstrings can damage plastic coatings - especially at connections • Coil? • Use nylon roller stem • Avoid burrs and sharp edges run at normal rather than reduced speeds - for slickline - reduced speed for braided cable - why?
- 12. WELL INTERVENTION PRODUCTIVITY SCHOOL Nov 2001 CORROSION corrosion in tubing exacerbated by erosion from wireline operators. REMOVAL OF “PROTECTIVE” FILM Corrosion - Best Practices • Adopt corrosion management strategy • Be aware of corrosion • Involve contractors in planning • Develop maintenance programs, measure corrosion • Consider dedicated corrosion engineer • Read relevant literature • Use your eyes! - report corrosion • Design your completion to minimise corrosion • Ensure inhibitors are compatible with materials and the reservoir! • If tubing corrosion is suspected, DO NOT bullhead fluids in the formation