Proposed Steering Mechanism Reduces Tortuosity in Horizontal Wells
- Adam Wilson (JPT Special Publications Editor)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- November 2018
- Document Type
- Journal Paper
- 79 - 81
- 2018. Offshore Technology Conference
- 6 in the last 30 days
- 73 since 2007
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This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 28497, “Effect of the Rotary-Steerable-System Steering Mechanism on Wellbore Tortuosity in Horizontal Wells,” by Albaraa Alrushud, SPE, and Muntasar Mohammad, SPE, Baker Hughes, a GE Company, and Victor Oliveira, SPE, and Bader Zahrani, Saudi Aramco, prepared for the 2018 Offshore Technology Conference Asia, Kuala Lumpur, 20–23 March. The paper has not been peer reviewed. Copyright 2018 Offshore Technology Conference. Reproduced by permission.
This paper describes a new approach to evaluating the effectiveness of the rotary-steerable-system (RSS) steering mechanism on wellbore tortuosity in horizontal wells. Discussing the relative merits of a push-the-bit steering mechanism vs. a point-the-bit steering mechanism is an oversimplification; neither mechanism can deliver the wellbore quality the industry demands from RSS. The present study introduces the continuous proportional steering method (CPSM) and demonstrates how this mechanism can provide superior wellbore quality by reducing wellbore tortuosity.
For this study, 18 wells were chosen on the basis of geology, trajectory, and bottomhole assembly (BHA). The study focused on the horizontal 6⅛- and 5⅞-in. production sections, where the wellbore quality is more critical. These sections typically require minimum changes in inclination for reservoir navigation, and any tortuosity resulting from the steering mechanism can be identified easily.
The goal of this study is to evaluate the accuracy of RSS steering mechanisms available in the industry. The study was performed on wells drilled by different steering mechanisms yet logged by the same wireline service provider. Analysis of the wireline data shows that drilling with CPSM significantly reduces average tortuosity by 4 to 5 times, average dogleg severity (DLS) by 3 to 4 times, and average angle change (AAC) by 5 to 6 times. Results show that intervals drilled with CPSM are more continuous and smooth compared with push-the-bit and point-the-bit mechanisms.
Currently, three different steering mechanisms are considered, push-the-bit, point-the-bit, and CPSM systems.
In a typical push-the-bit steering mechanism, a force is formed against the wellbore side wall, causing the bit to push on the opposite side wall and leading to a direction change. The multiple pads mounted on the body of the RSS are activated one at a time by diverting some of the mud flow through a controller valve. The controller will orient the valve in the desired direction. Therefore, each pad that crosses against the valve will be activated, whereas the other pads will be deactivated. Consequently, the pads will go into a continuous cycle of opening and closing to meet the directional plan.Alternatively, a typical point-the-bit steering mechanism causes the bit direction to change relative to the rest of the tool by tilting the bit with an internal deflection running through the RSS.
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