Maintaining verticality in today’s challenging drilling applications is of critical concern. The vertical section is increasingly important in anti-collision situations, as well as in extended reach directional wells where weight transfer through tortuous vertical sections can make the difference in calling Target Depth (TD) early of not. Excessive dogleg severity compromises well completion and adds costs that erode the profitability of operations and ultimately production of the well. To date, a limited number of options have been available, with low cost, low performance systems at one end of the scale and high cost, high performance systems at the other. Every day we are looking at more unconventional reserves and tighter budgets to work within. To align with these goals, we must find a solution that provides the quality performance through a technology that fits today’s fiscal demands as well. Conventional vertical drilling approaches such as control drilling, drilling with bent housing motors, and rotary steerable systems have notable drawbacks. Poor performance and efficiency on the low end and exorbitant cost on the high end push us to a new solution. A technology is now commercially available that provides all the performance of the higher cost Rotary Steerable System (RSS) while offering a better economic position for operators. With this new technology, borehole quality no longer has to be sacrificed for cost. The technology is fully autonomous and recent performance data shows that a major operator has utilized this technology for a reduction in costs of over 20% versus conventional technology while providing comparable rates of penetration and borehole quality.
The challenges involved in maintaining a truly vertical wellbore in the vertical section result in significant losses in drilling efficiency, raising the cost to reach the final target. The increasing complexity of modern drilling programs frequently require extended lateral and horizontal sections to be drilled to allow for production through multiple pay zones. As the reach of these wells is extended further each year, the importance of maintaining a truly straight and vertical top section becomes more critical, but modern solutions to this challenge are either inefficient or prohibitively expensive. A more financially viable solution must be provided for the drilling industry to continue the pursuit of hydrocarbons in these applications.Ensuring that the vertical section of the well is as straight and true as possible is vital in today's drilling operations. This will reduce the frictional forces as much as possible, allowing the driller to more effectively provide Weight on the Bit (WOB) to penetrate the formation. Natural variations in the earth, such as tendencies in the formation caused by layers that are deposited at an angle to the surface or random deposits of hard rock, can push the bit off of its true vertical trajectory, which then require corrections to steer the bit and drill string back on a true vertical course. The curves or kinks created by correcting the drift of the bit create additional points of contact with the wellbore wall by increasing the tortuosity of the vertical section.Unfortunately, the solutions to maintaining true verticality and a straight bore are limited. Controlled drilling is slow and limited in terms of performance, while bent housing motors can correct deviation, but result in increased tortuosity. Rotary Steerable Systems (RSS) offer excellent performance, but are expensive to run both in terms of daily cost and the increased risk of Lost in Hole (LIH) charges.The industry has taken a new step in the evolution of this technology by creating a tool that combines the quality and speed of an RSS system with the economics of a bent housing motor solution. By focusing on simple mechanical and electrical design features, this tool has driven down the cost required to supply RSS performance while maintaining the same high standards. By combining the field proven design elements from a number of existing technologies such as motors and Measurements While Drilling and Logging While Drilling equipment, a robust and reliable system has been developed which not only provides drilling correction in vertical sections, but also provides the real time surveys that are required to keep the well on course. This system is fully autonomous providing an economical solution that will deliver a high quality vertical wellbore while reducing the cost per foot of the well.A major independent oil company estimates they would increase adoption of RSS technology from 5% of their wells to 70% if a product could be offered with a 50% reduced cost. This paper will detail a new system that is being used...
The challenges involved in maintaining straight and truly vertical bores in the vertical section of the well continue to plague the drilling industry. These challenges result in massive losses in drilling efficiency, and subsequently excessive costs associated with complications caused by "corkscrew" wells. Increasingly complex drilling programs are being designed, often involving extended lateral and horizontal sections to be drilled to optimize production through multiple payzones. As the reach of these wells is extended further each year, the importance of maintaining a truly straight and vertical top section becomes more and more critical. The deeper the well and the deviated reach extends, the more difficult it becomes to move the drill string through the well bore and continue drilling ahead to target. The vertical section of the well has a particularly high impact in these wells as the weight that is transferred though this section must be efficiently transferred down the well bore in order to effectively provide weight on the bit to penetrate the formation and continue to drill ahead. As the drill string drills ahead vertically, natural variations in the earth or tendencies in the formation caused by formation layers that are deposited at an angle to the surface or random deposits of hard rock can push the bit off of its true vertical trajectory. When this occurs, a correction must be made to steer the bit and drill string back on course for true vertical. The more curves or kinks created by correcting the drift of the bit, the more points of contact exist through the vertical section. The number of deviations and corrections in a well is often referred to as its tortuosity. These points of contact each have a frictional impact on the drill string and ultimately result in increased levels of torque and drag. These forces ultimately hinder the drilling process by interfering with the transfer of weight through the vertical section to the drill string below as well as causing a resistance to the rotation of the drill string.
Previously, few options existed for the complex directional challenges. Drillers either needed to rely on multiple Bottom Hole Assemblies (BHAs) or use expensive drive systems, which resulted in increased operational cost and limited drilling flexibility. This novel Downhole Adjustable Motor (hereafter referred to as downhole adjustable motor or the motor) described in the paper addresses these limitations by enabling the driller to change the motor bend in real-time downhole. In addition, the motor can deliver up to 1,000 horsepower (HP) at the bit during rotary drilling—the highest power in its size range. This paper will review how, even in harsh drilling applications, the downhole adjustable motor has proven to save trips, increase bit life, reduce lateral vibrations and stick-slip, and allow for drilling optimization to increase Rate of Penetration (ROP) and decrease overall drill time. Whether for drilling contracts or lump-sum turnkey projects, the directional drilling industry benefits from this new technology's ability to improve drilling economics while increasing safety by reducing drillpipe tripping and additional BHA handling.
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