Drilling operations in the Komie area in northeastern British Columbia, Canada, can be tricky, and in the Fort Simpson shale formation, difficulties in achieving good build rates and sloughing shales can make operations even more problematic.

An operator planned a four-well pad, designing gas wells with 2,300-ft (700-m) surface holes followed by monobore horizontals with a total measured depth (MD) averaging 13,780 ft (4,200 m). Drilling the 311-mm surface holes accurately, as well as spacing them 23 ft (7 m) apart, was challenging. More drilling issues arose from downhole temperatures in an invert mud system, which can range from 230°F to 284°F (110°C to 140°C) in the lateral section, putting extra stress on the power sections of the positive displacement motors (PDMs).

Using its Geo-Pilot system, Halliburton delivered two 13,780-ft (4,200-m) MD monobore wells in 47.8 days versus the planned 75 days, saving the operator an estimated 27.2 days of rig time. (Graph courtesy of Halliburton)

The extra stress can result in heat failure and stator “chunking” of standard configuration PDMs, causing an increase in the amount of time required for the drilling process due to unplanned trips from downhole tool failures. The life of electronics contained within downhole tools such as MWD and LWD systems and rotary steerable tools can decrease exponentially with rising temperature. Tool reliability was critical to the success of demanding, high-temperature drilling applications given the inherent risk and associated technical challenges.

Many factors can contribute to the overall reliability in high temperature applications, and carefully monitored procedures must be applied when running in hole, initially starting with the drilling process, and throughout the entire hole section. In the case of PDMs, temperature also can create thermal expansion, affecting the mating fit between the motor stator and rotor beyond the specified operational limits of the particular motor type that can affect longevity and operational efficiency while drilling.

The client needed these wells drilled as quickly as possible and with minimal tortuosity to enable successful casing runs.

High-temperature solution
Drilling commenced on two wells in the Komie area. Halliburton used a vertical drilling system with a 9 5/8-in. GeoForce enhanced-performance range motor for the surface hole sections.A Geo-Pilot 7600 series rotary steerable system (RSS) was used for the first build, and a 6.75-in. Performance Plus SperryDrill motor was used to complete the build section. For the lateral section where higher temperatures were expected, a special oversize 6.75-in. PDM was used to helpaccommodate thermal expansion conditions the motor would encounter at that point.

The vertical drilling system is a self-correcting solution with an integrated high-output mud motor designed to automatically maintain a vertical well path at less than a 0.5-degree inclination.

Benefits to the project included improved ROP compared to maintaining vertically with conventional motors, reduced time for bit trips and remedial hole conditioning, tight inclination control to maintain the required spacing with close proximity to neighboring well bores, and improved success with running casing due to consistently high borehole quality.

The system was configured with a GeoForce even-wall enhanced-performance motor that significantly increased power output and reliability. The use of the Geo-Pilot RSS delivered unprecedented ROP and up to a 20% reduction in nonproductive time.

Using point-the-bit technology, the RSS precisely steered the well bore while continually rotating the drillstring. The tool build rate and direction were adjusted while on bottom drilling, making the RSS virtually invisible to the drilling operation. The system provided real-time continuous at-bit steering information and formation evaluation data to provide an accurate assessment of wellbore position.

Geo-Pilot and Halliburton’s MWD/LWD systems were fully integrated with the InSite data management system to provide a complete real-time drilling and formation evaluation service. Early warnings of trajectory and formation changes were provided by the at-bit inclination and optional at-bit gamma sensor that were beneficial to the overall drilling process. Three-dimensional “cruise control” software that allowed the Geo-Pilot tool to automatically maintain the desired well trajectory and correct any walk tendencies or abrupt formation changes also was employed.

The special oversize 6.75-in. PDM for the lateral section was used to help accommodate thermal expansion encountered in the build section. “The use of oversized motor combinations was a natural progression for Halliburton to enable us to get the correct rotor/stator fit once it was up to the proposed operating temperature,” said Jon Ball, senior Directional Drilling technical advisor for Halliburton. This created the correct clearance for optimal operation without compromising on performance. The SperryMet power unit metrology system was used to optimally mate rotors and stators together for motor operations at elevated temperatures. These motors were configured for high-temperature operation with a loose-fit rotor and stator setup that decreases once exposed to higher temperatures to produce optimum mating fit and performance. It also increases longevity, enabling the motor to stay in the hole for full bit runs without premature tripping.When running into the higher-temperature section of the well bore, periodic stops were made “staging in” to circulate until reduced temperature fluid was passed through the motor and MWD string, thereby maintaining a reduced circulating temperature under static hole conditions.

Positive reinforcement
Drilling the surface holes on both wells went well as far as hole deviation and ROP were concerned, with a plus/minus deviation rate of 0.2 to 0.5 degrees, respectively. ROP averaged approximately 213 ft/hr (65 m/hr), with an average bottomhole displacement of 6.5 ft (2 m) or less. Due to the fragile nature of parts of the surface hole section, some problems with lost circulation were experienced, negatively affecting the rig time to complete the sections. However, the operator was pleased with the performance of the vertical drilling system, as ROP and accuracy of the wellbore placement exceeded their expectations.

To achieve optimum performance in the 8.75-in. section of each well, the Geo-Pilot system was used with a PDC bit and a near-bit 221-mm sleeve stabilizer. This assembly delivered excellent ROP, averaging 180 to 196 ft/hr (55 to 60 m/hr) while ensuring a quality borehole free of kinks or tortuosity, which greatly reduced hole drag. This was a two-stage build section, with the first stage building to a 15-degree sail angle and the tool delivering 3.5-degrees/30-m build rates. The second stage of the build section used Sperry Drill Performance Plus motors for the higher-temperature build rates required in the problematic shale formation. This assembly averaged 131 to 148 ft/hr (40 to 45 m/hr) to the landing point. After tripping to install the special oversize motors required due to higher downhole temperatures, the rest of the wells were drilled to total depth.

“The maximum operating temperature for our standard Geo-Pilot tool is currently 150°C (302°F),” Ball said. The SOLAR Geo-Pilot XL RSS and SOLAR MWD/LWD systems with a special hardened, more durable package specifically designed to handle hostile drilling conditions and can operate in temperatures up to 347°F (175°C) and pressures up to 30,000 psi.

“The modeling and measuring aspect of this project enabled Halliburton to fully optimize the drilling process through real-time monitoring during the drilling process,” he said. In addition to real-time operations, Halliburton provided pre-run modeling for bottomhole assembly designs, which optimized the drilling assemblies in relation to both predicted performance and complete force analysis measurements, ensuring correct design. Pre-run hydraulics optimization also was completed to optimize hole cleaning capabilities and bit performance. The torsional efficiency monitoring system integrated on the Geo-Pilot system enabled Halliburton’s real-time advanced drilling technologies’ monitoring personnel based in Halliburton’s Nisku Real-Time Center in Alberta, Canada, to reduce or eliminate destructive downhole “stick/slip” and torsional vibration through optimal weight on bit and RPM adjustments, extending the tool life and reducing trips, which reduced overall drilling time.

Real-time value
Halliburton delivered two 13,780-ft (4,200-m) MD monobore wells in 47.8 days versus the planned 75 days, saving the operator an estimated 27.2 days of rig time.

Additional benefits provided by the Geo-Pilot system included its precise and rapid response to any commands that result in precise wellbore trajectory control in both build and horizontal sections and the high-quality borehole resulting from its point-the-bit technology, which minimizes torque and drag issues as well as issues during wellbore casing and completion operations.

Halliburton is continuing to develop technologies for extreme high-temperature environments with the recent introduction of the ExtremeHT-200 MWD/LWD systems, which can operate with tool temperatures to 392°F (200°C).