Even as oil pricing continues its slow recovery, the need remains for improved drilling efficiency, particularly in unconventional shale developments in which well economics have now made profitability a reality. Operators looking to drive performance improvements in North American shale plays have a variety of solutions to choose from, but one of the best methods is drilling optimization using downhole data. National Oilwell Varco (NOV) has been using an optimization service—built around collecting and analyzing high-quality downhole data from BlackBox memory mode logging tools—to enable more efficient drilling in North American shale and beyond.

BlackBox tools use sensors to capture data on downhole events and parameters such as stick/slip, pressure, weight transfer, lateral vibration and torque reactions while drilling. The tool can be placed in a near-bit carrier sub, drillbit, bottomhole assembly (BHA) and/ or drillstring depending on the needs of the operator running the tool. The tool records data while downhole for post-run analysis by a drilling dynamics engineer. The benefit of this method is the engineer also has acquired surface data that—when combined with the downhole data obtained during the run—provide a comprehensive overview of what is occurring downhole. From this information, the operator can typically determine how drilling practices, BHA and drillstring configurations are affecting performance and reliability in its operation.

The integrated approach of bringing together surface and downhole data allows operators to more effectively choose components for their BHA and to design the full assembly better. Running the obtained post-run data through NOV’s proprietary algorithms identifies harmful vibration while evaluating the unique characteristics of formation lithology, which reveals to the driller that there could be a potential risk of dysfunction in any given section. This analysis is bolstered by measuring additional dynamic behaviors—such as torque and drag, mechanical- specific energy and helical buckling—to drive total understanding of the downhole drilling environment. Real-time remote monitoring rounds out the value of the service offering by providing technical expertise and updated rig conditions 24/7.

Permian Basin case study

NOV was approached by an independent operator working in the Permian Basin that wanted to verify it was drilling as efficiently as possible. The operator decided to run BlackBox units downhole on three wells to determine if the wells were, in fact, achieving maximum efficiency and ROP while identifying any performance-reducing drilling dysfunctions. NOV identified full-string stick/slip as an area of concern in the offset wells, leading to the recommendation of SoftSpeed II—a stick/slip prevention software that uses automated vibration dampening to mitigate torsional vibration and reduce stick/slip oscillations—to address the problem.

Implementing the software provided a major benefit to the operator, which drilled the next section using only two 12¼-in. bits. This saved the operator two bit trips, as the previous offset well had been completed with four bits, and even the best record for other wells was three bits. Also, the bit pulled from the new well was still in excellent condition, while bits from previous wells had been damaged. Despite the operator’s belief it had maximized ROP, implementing the recommended software and drilling parameter adjustments—determined after analyzing the BlackBox data—enabled a dramatic increase in efficiency. The offset well had been drilled to 1,504 m (4,935 ft) at an on-bottom ROP of 17 m/hr (56 ft/hr) in about 88.5 hours. Meanwhile, the new well—using the new parameters— was drilled for 1,773 m (5,817 ft) at an on-bottom ROP of 33.8 m/hr (111 ft/hr) in about 52.5 hours. The improvements saved the operator 36 on-bottom hours and increased ROP over the offset well by 98%.

Oklahoma case study

An independent operator in Oklahoma was experiencing torsional vibration in several shale wells, with energy loss at the bit leading to reductions in ROP and section intervals taking too long to drill. The operator initially decided to use the SoftSpeed II software to reduce or eliminate vibration, deploying the system in three 12¼-in. sections of its well to try to increase ROP and drilling efficiency. In the operator’s offset wells, vibration-induced ROP reductions led to costly delays in drilling time, with the operator drilling 2,498 m (8,196 ft) in 158 hours. While using the SoftSpeed II system, the operator was able to drill a longer interval of 2,549 m (8,365 ft) in 100 hours. ROP was improved from about 15.5 m/hr (51 ft/hr) to 25 m/hr (82 ft/hr) in this application, an increase of 61%.

In a unique application, the operator decided to run BlackBox tools to record torsional vibration levels at the bit to validate that the SoftSpeed II system was responsible for decreasing vibration levels and allowing a more efficient transfer of energy from the top drive to the bit. The downhole rpm recorded by the BlackBox tools closely matched the estimated BHA speed calculated by the SoftSpeed II system, validating the system’s model. When stick/slip was induced, heavy torque fluctuation was seen at the surface, with downhole data collected by the BlackBox tools confirming downhole rpm was fluctuating heavily. When the SoftSpeed II service was activated, the surface rpm fluctuations counteracted the torsional energy being transmitted up the drillstring, preventing the reflection of that energy—which would have been a driving force in causing stick/slip.

The result was a near-immediate decrease in both surface torque fl uctuation and downhole rpm fluctuation. The drilling records acquired by the BlackBox tools allowed NOV to confi rm for the operator that the SoftSpeed II service was indeed mitigating torsional vibration at the bit and enabling the rig to drill ahead for longer before pulling a bit. BlackBox data have been used to identify performance limiters and validate solutions in several other projects for other NOV technologies, including the FluidHammer performance drilling tool.

Conclusion

Shale projects will only continue to grow in importance as drilling activity rebounds, and the need for greater operational efficiencies in shale plays will remain a focus. Using drilling software and optimization services tailored to the unique needs of each operator ensures the solution cost-effectively addresses their specific challenges. Drillers in the future will be armed with more intelligent downhole data that enable continual improvement in BHA design and well planning, helping the industry to continue advancing.

Have a story idea for Shale Solutions? This feature highlights technologies and techniques that are helping shale players overcome their operating challenges. Submit your story ideas to Group Managing Editor Jo Ann Davy at jdavy@hartenergy.com.

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