Mitigating Residual Cement Sheath In Liners Following Seawater Displacement

We recently performed a seawater displacement during a 4 ½” liner cement job on a long reach platform well. The 1,500ft liner was hung off on a hanger loaded with a single cement wiper plug, with the dart pumped down through a 4” x 5” DP tapered drillstring (S Shaped Well Profile) to ~19,000ft, to latch the plug in the hanger. The cement job went as planned and we recorded a positive plug bump at the expected strokes, however following the displacement we drifted the well on wireline to confirm access for the guns and held up around 200’ above the landing collar, leading to the requirement to perform a clean out run.

This was our 3rd seawater displacement which has saved considerable time/cost by negating the need to perform a clean-up and so far we have not experienced any issues. It is thought that the length of this well and the drill string transition has caused the dart to “flower” leading to possible fluid bypass. There are also other theories about incorrect line up’s and residual cement in surface lines possibly contributing to this.

The next well in our sequence calls for a 4,400ft horizontal 5 ½” liner which we intend to cement to the hanger and again displacement with seawater, we then need to run a 3 3/8” TCP gun string to depth and perforate. In order to mitigate any potential cement sheath which could potentially cause the guns to hold up, it has been suggested that we displace  the cement with a viscous pill in the liner, dosed with cement retarder (Sugar, citric or similar) to prevent any cement which may remain in the liner from setting up. The desire is to avoid the requirement to perform a tractor conveyed drift run due to the associated time and cost of this operation (which would erode the benefit of performing a seawater displacement).

Does anyone have any similar experience of these issues or the mitigations we are considering?

Thanks

Neil Deeney

5 Answer(s)

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