Underbalanced Drilling UBD

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Underbalanced Drilling (UBD)

• Lesson 1
• Introduction
• Chapter 1

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Introduction

• Course Syllabus
• Texts

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Introduction

• What is UBD
• Why Drill Underbalanced
• Techniques and Limitations
• Historical Perspectives

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Course Description

• This course provides an introduction and
  application of techniques that can be utilized in
  underbalanced drilling. It will cover topics
  such as BOP equipment, the types of drilling
  fluids used (air, mist foam, etc.), flow
  drilling, and mud cap drilling.

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Text

• Underbalanced Drilling Manual
• Gas Research Institute, GRI,
• Chicago, 1997.

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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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Instructor

• Dr. Jerome J. Schubert, PE, CPA
• Phone [phone]
• Office Richardson Rm 501K
• e-mail schubert_at_spindletop.tamu.edu

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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.
• Operations intentionally undertaken
  
  with a
  liquid drilling fluid system where the
  hydrostatic pressure exerted by the liquid column
  is below formation pore pressure such that the
  formation fluid is allowed to flow to the surface
  during the 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 is the continuous phase.

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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 UB 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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Why drill underbalanced?

• Increased Penetration Rate.
• Increased Bit Life.
• Minimized Lost Circulation.
• Minimize Differential Sticking.

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Why drill underbalanced?

• Reduced Formation Damage.
• Earlier Production.
• Reduced Stimulation Requirements.
• Improved Formation Evaluation.
• Environmental Benefits.

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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 were it showed a
  resurgence in
• Canada.
• West and Central Texas.
• Utah.
• San Juan Basin of New Mexico.

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Historical Perspectives
Typical of Nat Gas operations in New Mexico
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Historical Perspectives
Early Air Compressors used in air drilling
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Historical Perspectives
Natural Gas drilling in West Texas.
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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 from 45
feet as 2000 feet.
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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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Mid 1980s Horizontal Drilling Became Fairly
Common (Plot is for three companies)
No. of Wells
Year
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Growth in Horizontal Drilling Spurred the
Resurgence in UBD (US operations)
Mid 1980s Horizontal Drilling Became Fairly
Common (Plot is for three companies)
Total Lightweight Fluid Wells
Year
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• Until 1987 the maximum working pressure rating of
  rotating heads was 150-300 psi.
• RBOP was developed with a working pressure of
  1000 psi.

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Rotating Control Devices
RBOP-1000 psi (1987)
PCWD-3000 psi (1995)
RCH-2500 psi (1995)
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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.

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Factors Leading to Increased UBD

• Increased Availability of Nitrogen.
• Better Reservoir and Rock Strength
• Analysis.
• Improved Hydraulics Analysis.
• Percussion Tools.
• Ability to Re-Circulate Fluids.

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PETE 689 Underbalanced Drilling (UBD)
End of Lesson 1
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