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Splitter wellhead & collision risk mitigation
22 August 2018


We are planning to drill adjacent wells within the same conductor pipe with splitter wellhead (2x wells in One CP). The conductor pipe might be angled (with a small angle under 10°).

As per vendor procedure, before drilling the first well (16in) a downhole guide is lowered in the second slot (of the same CP) to reserve the space for the next wells. Those DH guide are similar to big stabilizers with 15.67in OD.

Having the CP inclined imply that the relative position of the DH guide string and the 16in BHA at surface won't probably be the same downhole. The DH guide might lay on the low side or maybe not. This is exactly the uncertainty that increase the risk of  collision when drilling the second well.

Do you have any idea of a process to determine with precision the position of the BHA and the downhole guide relative to each other at the CP shoe depth? pip tag marker in the DH guide string and Azimuthal GR on the Drilling BHA?

The solution is perhaps very different from our proposition. Do you have any other options to solve our question?

Thank you in advance,


Documents uploaded by user:
Downhole guide-BHA position.docx
1 answer(s)
Drilling Superintendent
Total Posts: 20
Join Date: 31/10/07
in Malaysia we commonly run 2 in 1 system w/o the downhole separator/guide you talked about. What is commonly done here is to run a dummy string (normally flush jnts or skimmed down coupling) run to around the conductor shoe in the spare slot as a separator. The advantage is that it is simpler and also providing the ability to clean the annulus between conductor and the main csng strng to ensure no cement is above the conductor shoe.
This dummy string is later retrieved before drilling in the 2nd slot. As usual you may need a MoU as the separation factor between the wells may not fulfill your required SF. See paper OTC 24908 for further info on systems other than your downhole guide. These are old methods as far as I know not any longer used.
Posted by

Tony Mike Chembou

Drilling Engineer

Perenco - Oil and Gas

Total Posts: 6
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