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Journal

Issue 38, November 2011

FAQ: BAKER HUGHES COIL TRAK™ SYSTEM

According to our query, the most innovative and interesting equipment among the bottomhole assemblies (BHA) for CTD applications for now is the Baker Hughes’ CoilTrak™ system. That is why we suggested the Company experts to answer the questions of “CTT” readers. Please send your new questions about new equipment to cttimes@cttimes.org.

What types of services does Baker Hughes offer to producing and servicing companies for directional drilling of laterals? How is Baker Hughes advancing CTD applications in Russia and CIS countries? What is the outlook for CTD projects in Russia and CIS countries?

Baker Hughes provides many services throughout Russia and CIS countries. Drawing on its many years of directional drilling experience and more than 15 years of coiled tubing (CT) experience and leadership in closed-loop drilling systems, Baker Hughes has engineered the CoilTrak™ service, a state-of-the-art drilling and evaluation bottomhole assembly (BHA) for CTD applications. CoilTrak, an advanced directional drilling system, precisely positions the wellbore within the productive reservoir using CTD. Its unique downhole sensors provide real-time measurement and interpretation of the drilling environment, allowing for rapid decision-making and subsequent actions.

CTD in general is more challenging than conventional drilling and its success depends on effectively integrating surface and subsurface services and disciplines. A shortage of experienced CT directional drilling (CTDD) personnel has been a barrier to CTDD growth. This has been recognized and is being addressed through development programs and the introduction of the most appropriate technology.

Baker Hughes offers training to clients in Russia in drilling and reservoir placement techniques for optimal lateral placement. As a result, there are clients within Russia that are running CoilTrak BHA on a daily basis on multiple CTD rigs with excellent results.

At present, the CTD market is set for rapid growth in Russia, Mexico, and the Middle East. Several large projects are being considered where re-entry and infill drilling using CT will be introduced to giant mature fields where a large number of existing wells are production-impaired. In many cases, the producing reservoir was damaged or originally completed sub-optimally. CTD using CoilTrak allows for sidetracking deeper and closer to the producing interval and bypasses disturbed or damaged zones, precisely repositioning the wellbore in the most productive aspect. Underbalanced CTD can overcome many risks inherent to conventional drilling (e.g., fluid losses; drilling depleted zones; stuck pipe scenarios; and hydrogen sulfide environments).

Whether accessing bypassed, or unswept, pools of oil and gas from mature fields, or tapping as yet undeveloped unconventional reservoirs, CTD is emerging as a highly desirable, economically viable option.

Growing emphasis on mature field redevelopment and low-cost reservoir access is also driving the increased demand for new-generation hybrid CTD rigs, such as coil over top drive. The enhanced mobility and state-of-the-art automation features enable operations in a variety of applications (e.g., underbalanced, managed pressure, or overbalanced scenarios). Several companies have made significant investment to develop CTD rig technology and have built a new generation of CTD rigs that address current and future market needs, especially for Russia, Mexico, the Middle East and the U.S.

How does maintenance of the directional drilling system compare with standard drilling systems? What types of maintenance can be done in-situ?

CoilTrak BHA adheres to Baker Hughes’ standard maintenance procedures. The system’s high level of reliability is demonstrated by a record-breaking 12 days continuous multilateral drilling of more than 4,267 m (14,000 ft) of additional reservoir exposure from a single motherbore. CoilTrak drilled more than 103,632 m (340,000 ft) in 40 re-entries to reverse production decline and revitalize an otherwise uneconomic depleted gas field.

Because of its modular design, CoilTrak can be maintained without the associated equipment normally required for larger assemblies, resulting in a smaller rig footprint. To assist maintenance in remote locations, a Mobile Maintenance Unit (MMU) capable of on-site maintenance can be deployed, Maintenance on CoilTrak is recommended at standard intervals of 200 hours, and mud motors’ recommendations

are application-specific (e.g., 80 to 150 hours on an overbalanced application).

What is the life expectancy of the directional drilling system, and what are some of the determining factors?

The elements that determine the maintenance and life expectancy of the equipment include downhole conditions, such as temperature, formation type (drilling abrasive formations), drilling fluid compatibility/selection, and underbalanced and/or overbalanced drilling application. These factors are considered by Baker Hughes during pre-job planning with the client and a specific schedule is recommended for

each application, ensuring maximum reliability and durability in the most challenging drilling environments.

What are the components of the CoilTrak directional drilling system? Have specific or reoccurring failures been identified? If so, how are these failures avoided or overcome?

The basic components of the CoilTrak drilling system are:

Power & Communication Module (P&C) – modulates the power supply via electric-line (conventional mud-pulse option is also available) and is the system control unit; the P&C has an integrated casing collar locator (CCL).
Electrical Disconnect & Circulation Module (EDC) – a multi-cycle circulation sub that allows increased circulation when open and acts to divert flow from the bit. It is the primary CT recovery mode with a separate computer controlled disconnect option, leaving a standard GS fishing profile.
Directional Gamma Sub (DGS) – contains the directional and survey package; also houses the Gamma module for geological formation response.
Hydraulic Orientor Tool (HOT) – module enables infinite real-time control of the tool face while drilling through 400° rotation (200° left or right) using bi-directional one-degree incremental control with the click of a mouse. It overcomes the reactive torque of the motor and enhances wellbore placement accuracy.

Additional modules also available are:

Ultra-slim Multiple Propagation Resistivity (USMPR) for formation evaluation;
GyroTrak for vertical well kick off and drilling module;
Dynamic Pressure Sub (DPS) which has downhole weight-on-bit;
Annular / Bore pressure and VSS (vibration monitoring), which also allows the real-time monitoring of Equivalent Circulating Density (ECD) – essential for monitoring hole cleaning and downhole formation pressures;
Rib Steer Motor System (RSM) to extend CT reach when drilling; reducing tortuosity and drills a smoother wellbore (straighter, with less torque and drag).

After more than 15 years development, CoilTrak modules are extremely reliable and not prone to any “specific or reoccurring” failure. The use of the Drilling Performance System module in real time assists in reducing mud motor stalls and increases bit optimization by enabling smoother weight-to-bit transfer.

Is special servicing, calibration or equipment required before each running operation? What special requirements to CT units exist when using directional drilling system?

The drilling modules are all serviced and calibrated before arriving on location. The computer software available in the field allows diagnostic checks to be performed on location. The CTD control cabin has no special requirements. Additional real-time drilling screens are installed for the CT driller’s information, and a remote computer set-up with Baker Hughes directional driller ensures good lines of communication during wiper trips or for changes while drilling.

Are there specific requirements, different from standard ones, for the recommended drilling mud cleaning while using the directional drilling system?

No, standard mud cleaning systems and shaker screens are acceptable. Mud solids content monitoring is done as normal during the drilling phase.

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