Diese Präsentation wurde erfolgreich gemeldet.
Wir verwenden Ihre LinkedIn Profilangaben und Informationen zu Ihren Aktivitäten, um Anzeigen zu personalisieren und Ihnen relevantere Inhalte anzuzeigen. Sie können Ihre Anzeigeneinstellungen jederzeit ändern.

Formation Damage

70 Aufrufe

Veröffentlicht am

DAMAGE ISSUES IMPACTING THE PRODUCTIVITY OF TIGHT GAS PRODUCING FORMATIONS; Formation Damage; Fracturing/Refracturing; Hydraulically Fractured; Tight Gas Reservoir; Economic Tight Gas Reservoir Production

Veröffentlicht in: Bildung
  • Als Erste(r) kommentieren

  • Gehören Sie zu den Ersten, denen das gefällt!

Formation Damage

  1. 1. FORMATION DAMAGE ISSUES IMPACTING THE PRODUCTIVITY OF TIGHT GAS PRODUCING FORMATIONS Prof. Dr. Hassan Z. Harraz Faculty of Sciences, Tanta University, Egypt October 9, 2019 hharraz2006@yahoo.com
  2. 2. Keywards:  Formation Damage; Fracturing/Refracturing; Hydraulically Fractured; Tight Gas Reservoir; Economic Tight Gas Reservoir Production
  3. 3. Outline of lecture  What is formation Damage  Definition of a tight gas reservoir  Conditions generally required for economic tight gas reservoir production  Common formation damage types occurring in tight gas reservoirs  Reducing formation damage in tight gas reservoirs
  4. 4. What is Formation Damage?  Any process causing a reduction in the inherent natural permeability of an oil or gas producing formation.  In Many cases the Exact cause of the damage is difficult to define-Another Good Definition of the Formation damage is:  The Impairment of the Unseen by the Inevitable, Resulting in an unknown reduction in the unquantifiable..!
  5. 5. What is a Tight Gas Reservoir?  Somewhat arbitrary classification  Often defined as a gas bearing sandstone or carbonate matrix (which may or may not contain natural fractures) which exhibits an in- situ permeability to gas of less than 0.10 mD  Many ‘ultra tight’ gas reservoirs may have in- situ permeability down to 0.001 mD
  6. 6. What Controls the Ability to Economically Produce Tight Gas Reserves?  Effective permeability  Initial saturation conditions  Size of effective sand face drainage area accessed by the completion  Reservoir pressure  Degree of liquid dropout from gas (rich vs. dry gas)
  7. 7. Capillary Equilibrium in Gas Reservoirs – High Perm Water Saturation Water Saturation CapillaryPressure-Psi RelativePermeability FWC
  8. 8. Capillary Equilibrium in Gas Reservoirs – LOW Perm Water Saturation Water Saturation CapillaryPressure-Psi RelativePermeability FWC
  9. 9. Generally if a Tight Gas Matrix is in Equilibrium With a Free Water Contact, Unless Very Large Vertical Relief is Present, Equilibrium Water Saturation Reduces Reserves and Permeability to Gas Below the Economic Limit for Production
  10. 10. Non - Capillary Equilibrium in Gas Reservoirs – LOW Perm Water Saturation Water Saturation CapillaryPressure-Psi RelativePermeability NO FWC
  11. 11. For Significant Reserves and Mobile Gas Production in Very Low Perm. Gas Reservoirs, a CAPILLARY SUBNORMAL Water Saturation Condition Usually Must Exist Water Gauge
  12. 12. Subnormally Water Saturated Tight Gas Reservoirs – What Are They  A gas reservoir in which the initial water saturation is less than that which would be achieved on a conventional drainage capillary pressure curve at the effective capillary gradient of the reservoir
  13. 13. Postulated Mechanism for Establishment of the Low Swi Condition Low Perm matrix Initially 100% Saturated with Water Gas Migration commences Pore system displaced to Capillary equilibrium swirr Pore System is isolated from Dynamic capillary contact With active recharge water Source (faulting, etc) Long Term Migration of Gas Slightly out of equilibrium with Reservoir results in Desiccation Of water saturation to subnormal value
  14. 14. Postulated Mechanism for Establishment of the Low Swi Condition  Low Perm. matrix Initially 100% Saturated with Water.  Gas Migration commences Pore system displaced to Capillary equilibrium Swirr  Pore System is isolated from Dynamic capillary contact With active recharge water Source (faulting, ..etc).  Long Term Migration of Gas Slightly out of equilibrium with Reservoir results in Desiccation of water saturation to subnormal value.
  15. 15. Postulated Mechanism for Establishment of the Low Swi Condition Results in unique combination of low perm. and low Swi
  16. 16. Subnormal Saturation Conditions  Generally a pre-requisite for an economic gas reservoir in ultra tight rock (<0.1 mD)  Increases reserves and gas permeability  Increases apparent salinity and suppresses Rw (proven by case studies)  Swi often difficult to precisely measure using conventional logging  Direct measurement via traced coring program common method used
  17. 17. Common Subnormally Saturated Formations in Western Canada  Deep basin area:  Paddy  Cadomin  Cadotte  Jean Marie  Montney  Rock Creek  Ostracod  Gething  Bluesky  Halfway  Doig  Cardium  Viking
  18. 18. Subnormal Initial Water Saturation Gas Reservoirs  USA  Powder River Basin  Green River Basin  DJ Basin  Permian Basin  Also documented in South America, Europe, Asia, Africa and Australia
  19. 19. Dominant Formation Damage Mechanisms in Tight Gas  Unless natural microfractures are present, almost all tight reservoirs must be fracture stimulated to obtain economic production rates.  In the case where fracture stimulation is required, classic formation damage associated with drilling is not normally problematic due to the radius of penetration of the fracture treatment
  20. 20. Exceptions – Tight Matrix With Enhanced Natural Permeability Conduits  Natural fractures  Interconnected vugular porosity  Possible deep invasion of whole drilling fluids  Possible application of UBD
  21. 21. Hydraulically Fractured Tight Gas Systems  High fracture conductivity essential (proppant crushing, embedment, residual gel/fracture fluid entrainment are issues).  Water or hydrocarbon based phase trapping a major source of matrix damage in the near fracture face area
  22. 22. Highway Analogy
  23. 23. Highway Analogy
  24. 24. Highway Analogy
  25. 25. Water Based Phase Trapping Water Saturation Water Saturation CapillaryPressureRelativePerm
  26. 26. Water Based Phase Trapping Water Saturation Water Saturation CapillaryPressureRelativePerm
  27. 27. Water Based Phase Trapping Water Saturation Water Saturation CapillaryPressureRelativePerm
  28. 28. Reducing Water Based Phase Trap Potential  Avoid use of water based fluids (OB, pure gas, etc).  Use surface tension reducing agents to reduce capillary pressure and trapping potential (mutual solvents, alcohols, etc).  Low fluid loss systems with rapid recovery times to minimize imbibition.  May also be an issue in some underbalanced operations.
  29. 29. Using Hydrocarbon Based Fluids in Reservoir Prone to Water Trapping  May still be the preferred method as relative volume of non wetting phase hydrocarbon which is trapped is often much less than water  Resulting damage is far less than if water based fluid had been used in the same situation in many cases
  30. 30. Hydrocarbon vs. Water Based Fluids in Low Perm., Low Swi Gas Reservoirs Total fluid saturation Relativepermeability
  31. 31. Hydrocarbon vs. Water Based Fluids in Low Perm, Low Swi Gas ReservoirsRelative permeability Total fluid saturation
  32. 32. Common Stimulation Treatments for Water Blocks  Dry gas injection (natural gas, CO2)  Mutual Solvent Injection (methanol, CO2)  Extended shut in time  Formation heat treatment  Direct penetration (Fracturing/Refracturing)  High drawdowns normally not effective
  33. 33. DJ Basin –Colorado Reservoir Parameters  Very fine grained sandstone  Depth – 2400 m  BHP = 20 MPa  kh = 1 – 4 mD-ft (0.3 – 1.2 mD-m)  Typical treatment  550,000 lbs (250 tonnes) in X-linked water  Post-frac production  50 mcf/day – 500 mcf/day Slide Courtesy of Calfrac
  34. 34. DJ Basin – J Sand Two Production Cycles Slide Courtesy of Calfrac
  35. 35. Common Stimulation Treatments for Hydrocarbon Blocks  High pressure lean gas injection (natural gas, nitrogen).  Lower pressure rich gas injection (CO2, ethane, propane, butane).  Mutual solvent (heavy alcohol) treatments.
  36. 36. Diagnosis of Problems and Evaluation of Most Effective Prevention or Stimulation Treatments  A variety of lab/core evaluation techniques exist to evaluate:  Water and hydrocarbon phase trap potential.  Interplay of reservoir pressure, invasion and drawdown effects.  Evaluation of optimum stimulation methods for existing damaged wells.  Evaluation of optimum drilling and completion methods in naturally fractured formations.
  37. 37. Lab Regain Perm Test Equipment
  38. 38. Conclusions  Tight gas reservoirs have a huge future potential for production.  Generally to be economic tight gas reservoirs are normally in a subnormal water saturation condition.  Fluid trapping tends to be a dominant damage mechanism for tight gas reservoirs.  Techniques exist to evaluate and minimize phase trapping problems and to stimulate existing damaged wells.

×