Application of a Torsional Impact Hammer to Improve Drilling Efficiency
- Carl Aron Deen (Ulterra Drilling Technologies) | Ryan Joseph Wedel (Ulterra Drilling Technologies) | Abhijeet Nayan (Ulterra Drilling Technologies) | Shaun Keith Mathison (Ulterra) | Greg Hightower (Ulterra Drilling Technologies)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 30 October-2 November, Denver, Colorado, USA
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 1.12.2 Logging While Drilling, 1.10 Drilling Equipment, 1.2.5 Drilling vibration management, 1.11 Drilling Fluids and Materials, 4.1.5 Processing Equipment, 1.4.1 BHA Design, 1.5.1 Bit Design, 4.1.2 Separation and Treating, 1.6 Drilling Operations, 1.6.1 Drilling Operation Management, 1.6.2 Technical Limit Drilling, 1.12.1 Measurement While Drilling, 1.4.4 Drill string dynamics, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.5 Drill Bits
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Several phenomena that negatively affect drilling efficiency are still commonly observed in practice. These phenomena can often be linked directly to the high torque required for a PDC bit to aggressively shear formation, and the difficulty of effectively transmitting such torque consistently to the bit. In highly transitional or conglomerate formations, the depth of cut and subsequent torque required for the bit to continuously shear formation fluctuates greatly, leading to the buildup and release of torsional energy in the drill string, commonly known as stick/slip. High speeds and vibration during the slip phase, combined with the heterogeneous and/or hard nature of the environment can cause damage to PDC cutters and other drill string components, resulting in reduced bit and tool life as well as poor rate of penetration (ROP).
A proprietary torsional impact hammer was tested in applications in Western Oklahoma and in the Southeast Arabian Peninsula where drilling efficiency was believed to be much lower than the theoretical limit. These applications were identified by high cost per foot drilling with roller cone and diamond impregnated bits, as well as known and expected high vibrations accompanying unsuccessful and inconsistent PDC testing. The case studies reveal the strengths and weaknesses of applying such a solution, and introduce a discussion on selection of applications where this solution is advisable. The balance of this paper will also describe how this solution has reduced drilling costs and changed the economics of drilling applications in Western Oklahoma and the Southeastern Arabian Peninsula over the course of the cases studied.
Improving drilling efficiency (i.e. lowering the overall cost of drilling) is always a goal of operators and service companies. Increasing the speed of drilling is a good tactic because most costs are time based. Creation of a wellbore requires the destruction and removal of rock, which requires energy. The speed at which a wellbore can be created depends largely on the efficiency by which available energy can be used to that end. There are two parts to this problem, how to most efficiently fail the rock and how to most efficiently convert the available energy into the proper mode for failing the rock.
Shearing with a PDC bit is currently the most efficient mechanism available to fail the rock, which requires energy to be available in the form of torque. However, the ?torsional capacitance? of the drill string often allows for a cycle of torsional energy being stored and released—a phenomena better known as stick/slip. Should the threshold strengths of the materials used be overcome before the formation fails, the bit and its components can be catastrophically damaged. Also, the violent release of energy, usually in the form of coupled modes of vibration, during the slip phase can just as easily result in damage to the bit and cutters.
As the case studies presented show, a torsional hammer, converting hydraulic energy to instantaneous torque, can reduce the tendency for stick/slip to initiate. In addition, the authors believe it can improve on the efficiency of the traditional shearing rock failure mechanism.
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