Underbalanced Equipment and Services

What is Underbalanced Drilling and Why Use It?

Underbalanced drilling is the intentional reduction of drilling fluid density to lower hydrostatic pressure in a wellbore so that it is lower than formation pore pressure.  Or, more simply put, underbalanced drilling maintains wellbore pressure below formation pressure while drilling.

Less Pressure, More Flow


Lower pressure in the wellbore encourages oil/gas flow, reducing formation damage.

Lower pressure in the wellbore increases the rate of penetration, prolongs bit life and increases flow.

Lower pressure means less fluid loss when drilling, resulting in reduced fluid maintenance costs, a decrease in lost circulation time, and less non-productive time.

In underbalanced reservoir drilling (UBD), the emphasis is on protecting the formation, particularly in low-pressure, depleted reservoirs. Encouraging the reservoir to flow while it is being drilled avoids creation of wellbore buildup and its associated negative impact on well productivity and reservoir recovery.  Lower pressure in the wellbore also increases ROP, prolongs bit life and prevents fluid loss into the formation, making differential sticking unlikely.  These benefits allow for enhanced production and reservoir recovery which increases the economic viability which results in quicker payouts for wells.


Our operations in West Texas have relied on air drilling for decades to get through hard fractured limestone formations quickly and without costly fluid losses.  Air drilling uses mist or foam as the drilling fluid, increasing ROP and lengthening bit life.




Advantages and Disadvantages of Underbalanced Drilling


Much Higher ROP While Drilling

Greatly Reduces Formation Damage While Drilling

Allows Drilling Through Severe Lost Circulation Zones

Numerous Geological and Pay Identification Benefits

    Normal Triple-Combo or Quad-Combo Can be Run

     Addition of Temperature Log Identifies Gas Flow Into Wellbore

        • Aides in Quickly Identifying Target Zones for Cement Calculations

        • Reduces Perforation Interval for Lower Costs

     High Quality Cuttings Which are Clean and Dry

Numerous Completion Benefits

    No Drilling Mud to Clean up From Formation or Fractures

        • Allows for Zones to be Quickly Tested

        • Less Cleanup Time During Flowback / Swab Testing

        • Decreased Rig / Testing Costs


Hazardous When Drilling High Pore Pressure Zones

Risk of Sticking When Encountering Formation Water

Possible Crooked Hold Due to High ROP

Increased Risk of Washouts

Viking Drilling, LLC consists of a team of management and drilling personal that have drilled hundreds of Underbalanced wells and have an excess of over 100 years of experience collectively in Underbalanced Drilling.  We are well positioned to provide expertise, in conjunction with our equipment and services, to Operators looking for value and experience from their partners.



Underbalanced Equipment


Mobile Air Drilling Packages


4 – 2560cfm/1500psi Mobile Air Drilling Packages each complete with the following components:

2 –  Primary Atlas Copco 1250/435 Compressors driven by QSX 15L Cummins Engines

   • Compressors are fitted with Separate Control and cooling systems that allow individual operation of each compressor

1 –  Primary PHT-2 Booster Compressor, driven by a QSM 11L Cummins Engine (400HP at 1800 rpm)

1 –  Trailer Mounted K & M 253 triplex mist pump driven by a A2000 Cummins Engine

Other features:

   •  3-Section Heat Exchanger (Precooler, Innercooler, Aftercooler)

   •   Electronic Control and Shutdown system for Driver and Compressor

   •   Manual Louvers on Cooler Sections for temperature control

   •   Fitted for Single or Two-Stages Operation

   •   Nitrogen manifold located between precooler and first stage inlet