Flow Drilling

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Lesson 17

• Flow Drilling
• Mudcap Drilling
• Snub Drilling
• Closed Systems
• Read UDM Chapter 2.8-2.11
• pages 2.180-2.219

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Flow Drilling

• Flow drilling refers to drilling operations in
  which the well is allowed to flow to surface
  while drilling.
• All UBD operations are really flow drilling
  operations, but the term is usually applied to
  drilling with a single phase mud, and no gas is
  injected except by the formation.

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Drilling fluid selection

• Density is determined by
• maximum pressure lt to formation pressure
• minimum pressure dictated by wellbore stability
• Pressure limitations of diverter and BOP equipment

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Surface Equipment
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Surface Equipment
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Surface Equipment
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Surface Equipment - RBOP
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Surface Equipment - RBOP sealing element
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Surface Equipment
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Sizing Flare line
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Sizing Flare line
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Sizing Flare line
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Sizing Flare line
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Surface Pits

• Primary Oil Separation Pit
• Secondary Oil Separation Pit
• Skimmer System Safety
• Drilling Fluid Pit
• Oil Transfer Tank

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Operating Procedures

• Mechanical objective is to control the well at
  the surface to maintain underbalanced conditions.
• Maximum tolerable surfaces pressures should be
  established before drilling starts.

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Mudcap Drilling

• Utilized with uncontrollable loss of circulation
  during flowdrilling operations.
• Higher pressures than can be safely handled with
  the rotating head or RBOP.
• Not necessarily underbalanced.

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Mudcap Drilling

• Driller loads the annulus with a relatively high
  density high viscosity mud and closes the choke
  with surface pressure maintained
• Drilling is then continued blind by pumping a
  clear non-damaging fluid down the drillstring
  through the bit and into the thief zone.

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Mudcap Drilling

• Applications
• Sustained surface pressures in excess of 2000 psi
• Sour oil and gas production
• Small diameter wellbores

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Mudcap drilling
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Fluid Volume Requirements
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Fluid Volume Requirements
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Fluid Volume Requirements

• Annular volumes will depend upon whether the
  operator desires continuous or periodic injection
  of annular fluids or whether a floating mudcap is
  to be used.

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Fluid Volume Requirements
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Fluid Volume Requirements
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Fluid Volume Requirements
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Snub Drilling

• UBD operation utilizing a snubbing unit or coiled
  tubing unit.
• Expense is justifiable if very high formation
  pressures are anticipated, and uncontrollable
  loss of circulation is expected.

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Closed Systems

• Refers to UBD operations with a specific surface
  system.
• A pressurized, four phase separator and a fully
  closed surface system, is used to handle the
  returned fluids.

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Fig. 2.70
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Fig. 2.71
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Fig. 2.72
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Other Surface Equipment

• Cuttings Filter
• Heater
• Degasser
• Flare Stack/Pit
• Production Tank
• Water Tank
• Solids Tank
• Instrumentation