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Underbalanced Drilling

The Extreme Engineering™ XEM™ system offers superior performance in all underbalanced drilling applications

Clients can expect to find superior performance in the following underbalanced drilling environments:

Dry Air – This is also known as dusting. Here air compressors combined with a booster (which takes the head from the compressors and increases the pressure of the air, but does not increase the volume of air going down hole) are used. The only fluid injected into the well is a small amount of oil to reduce corrosion.

Mist – A small amount of foaming agent (soap) is added into the flow of air. Fine particles of water and foam in an atmosphere of air bring cuttings back to the surface.

Foam – A larger amount of foaming agent is added into the flow. Bubbles and slugs of bubbles in an atmosphere of mist bring cuttings back to the surface.

Stable foam – An even larger amount of foaming agent is added into the flow. This has the consistency of a shaving cream.

Airlift – Slugs and bubbles of air in a matrix of water, where soap can or cannot be added into the fluid flow of air.

Aerated Mud – Air or another gas is injected into the flow of drilling mud. Degassing units are required to remove air before it can be re-circulated.

Underbalanced wells have several advantages over conventional drilling including:

Eliminated Formation Damage – In a conventional well, drilling mud is forced into the formation in a process called invasion, which frequently causes formation damage – a decrease in the ability of the formation to transmit oil into the wellbore at a given pressure and flow rate. It may or may not be repairable. In underbalanced drilling, if the underbalanced state is maintained until the well becomes productive, invasion does not occur and formation damage can be completely avoided.

Increased Rate of Penetration (ROP) – With less pressure at the bottom of the wellbore, it is easier for the drill bit to cut and remove rock.

Reduction of Lost Circulation – Lost circulation is when drilling mud flows into the formation uncontrollably. Large amounts of mud can be lost before a proper mud cake forms, or the loss can continue indefinitely. If the well is drilled underbalanced, mud will not enter the formation and the problem can be avoided.

Differential Sticking is Eliminated – Differential sticking is when the drill pipe is pressed against the wellbore wall so that part of its circumference will see only reservoir pressure, while the rest will continue to be pushed by wellbore pressure. As a result the pipe becomes stuck to the wall, and can require thousands of pounds of force to remove, which may prove impossible. Because the reservoir pressure is greater than the wellbore pressure in underbalanced drilling, the pipe is pushed away from the walls, eliminating differential sticking.

Formation Damage – Some rock formation have a reactive tendency to water. When drill mud is used, the water in the drill mud reacts with the formation (mostly clay) and inherently causes formation damage (reduction in permeability and porosity) Use of underbalanced drilling can prevent this.

On occasion, we do see lower MTBF with the hostile environment of underbalanced drilling, mainly due to 3rd party inexperience. Shock from down hole conditions is the leading factor for EM failure. It is critical to monitor down-hole shock on real-time with a DymamX™ directional probe. If real time shock is monitored and kept within acceptable ranges, down-hole failures are virtually eliminated. It is important to weigh the risk associated with underbalanced down-hole conditions and to completely understand the environment. Once this is understood the XEM™ performance for this type of application is industry leading.