PETE 406 - Underbalanced Drilling, UBD

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PETE 406 - Underbalanced Drilling, UBD

• Lesson 8
• Introduction
• Underbalanced Drilling Manual, UDM Chapter 1

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Introduction

• What is UBD
• Why drill underbalanced
• Techniques and Limitations
• Historical perspectives

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Text

• Underbalanced Drilling Manual, Gas Research
  Institute, GRI, Chicago, 1997.
• Can be purchased online from the SPE (61.50 for
  members), IADC, and other Petroleum publishing
  companies
• May be able to get it at the TAMU bookstore

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References

• A project Management Approach To Underbalanced
  Operations, Signa Engineering Corp., Houston,
  1998.
• Mudlite Air/Mist/Foam Hydraulics Model, Maurer
  Engineering Inc., Houston, 1988
• Selected papers and texts

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What is UBD

• Wellbore pressures intentionally maintained
  below formation pressure in the open hole
  section.
• Formation fluids flow into the well.

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Additional Definitions

• Flow (Live) operations
• wellbore pressures maintained below formation
  pressure and the well is intentionally allowed to
  flow during drilling or completion operations

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Additional Definitions, cont

• Gasified Fluid Operations (aerated fluid
  operated)
• Operations intentionally undertaken with a
  two-phase drilling fluid containing some form of
  gas mixed with a liquid phase.
• Gasified fluids normally do not contain a
  surfactant

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Additional Definitions, cont

• Foam Operations
• Operations intentionally undertaken with a
  two-phase drilling fluid containing some form of
  gas mixed with a liquid phase and tied together
  with a surfactant
• The liquid phase is continuous

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Additional Definitions, cont

• Mist Operations
• Intentionally drilling with a two-phase fluid
  having a gas as the continuous phase
• The liquid in this fluid system is suspended in
  the mixture as droplets

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Additional Definitions, cont

• Air Operations
• Intentionally drilling using a pure gas as the
  drilling fluid.
• The gas can be air, nitrogen, natural gas, or any
  combination of gases

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Additional Definitions, cont

• Mudcap Operations
• Operations undertaken when the annular pressure
  during flow drilling exceeds the safe pressure
  limit of the rotating control element.
• Mudcap operations are not underbalanced
  operation, but often are a result of drilling
  underbalanced and employ many of the same
  techniques and equipment

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Additional Definitions, cont

• Snubbing Operations
• An intentional operation that employs either a
  snubbing unit or coiled-tubing unit in order to
  operate at surface pressures that exceed the
  limits of rotating control elements such as
  rotating heads or rotating blowout preventers

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Additional Definitions, cont

• Coiled-tubing drilling
• Use of a continuous-spool of pipe to drill with
  instead of the conventional jointed drillpipe.
• CT units were originally designed to operate on
  live wells with surface pressure, without the
  requirement that the well be killed prior to
  entering the wellbore.

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Historical perspectives

• UBD operations are as old as the drilling
  industry
• First wells were drilled with cable tool
• Cable tool drilling was underbalanced

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Historical perspectives

• In 1866 a patent for air drilling was issued
• First recorded use of a gasified fluid was in
  West Texas in 1932

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Historical perspectives

• In 1938 mist was used by The Texas Company to
  drill in California.
• Natural gas was continuous phase and oil was the
  liquid phase

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Historical perspectives

• Interest dropped off using gas as a drilling
  fluid until the 1950s in
• Canada
• West and Central Texas
• Utah
• San Juan Basin of New Mexico

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Historical perspectives
Natural Gas drilling in West Texas
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Historical perspectives
Early Air Compressors used in air drilling
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Historical perspectives
In the 1960s, the U.S. Atomic Energy Commission
began to study the use of foams to clean
wellbores as large as 60 in diameter
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Historical perspectives

• Until the mid 1980s UBD was just a niche
  industry, and only utilized in certain areas
  around the world

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Historical perspectives
Mid 1980s Horizontal Drilling Became Fairly
Common (Plot is for three companies)
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Growth in Horizontal Drilling spurred the
resurgence in UBD (US operations)
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Until 1987 the maximum working pressure rating of
rotating heads was was 150-300 psi. RBOP was
developed with a working pressure of 1000 psi
Rotating control Devices
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More equipment development

• 1995 Varco-Shaffer introduced an RBOP with a
  rated to 3000 psi

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Closed loop system
Allows re-use of the drilling fluids in foam
systems environmentally friendly
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Nitrogen Generation System
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Electromagnetic MWD Tools
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Hollow Glass Spheres
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Factors leading to increased UBD

• Horizontal drilling
• Closed systems
• High-pressure rotating control devices
• Electromagnetic MWD systems
• HP HV compressors

• Increased availability of Nitrogen
• Better reservoir and rock strength analysis
• Improved Hydraulics analysis
• Percussion tools
• Ability to re-circulate fluids

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End of Lesson 8a