Wellbore Positioning While Drilling With LWD Measurements
- Benny Poedjono (Schlumberger) | Dozie Nwosu (Schlumberger) | Albert Martin (Schlumberger)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- Publication Date
- June 2019
- Document Type
- Journal Paper
- 450 - 465
- 2019. Society of Petrophysicists & Well Log Analysts
- 17 in the last 30 days
- 18 since 2007
- Show more detail
Driller’s depth has always been the reference measurement used when logging while drilling (LWD), calculated using the sum of pipe-strap measured while the pipe is on surface. However, environmental corrections must be applied to the driller’s depth to account for the dynamic changes the pipe undergoes while in the borehole. These include dynamic mechanical changes due to drilling activities, changes in the wellbore profile, torque, drag, friction factor, and temperature. They all result in LWD depth being shallower than the absolute depth.
Understanding the position objectives, assigning the depth uncertainty and environmental modeling to predict the magnitude of depth correction should be applied in advance, along with the surveying technique to be used. These are critical components in the prejob analysis to ensure the position objectives can be met prior to drilling.
Over the years, depth correction has successfully been run on several projects around the world. Environmental corrections were applied in various applications to improve the accuracy of the depth and demonstrate the significance of the correction for reservoir development. The intention of this paper is to raise awareness of the impact of LWD depth errors and existing approaches for correcting them. Case studies are presented to demonstrate the benefits derivable from applying depth corrections. In one case, the placement of the pressure and sample points provided the most accurate TVD possible. In another case, the corrected measurement enabled determination of where to set the casing depth to within the expected rat hole. Applying depth correction allows for accurate mapping of the geological markers, reservoir tops, sand continuity, and fluid contacts as well as for setting casing and other drilling applications in offshore deepwater and extended-reach drilling worldwide.
|File Size||16 MB||Number of Pages||16|