Rigless Through Tubing Cement job

Dear colleagues,
We’re planning a through tubing cement job which we’d like to have some feedback from the MY-Spread forum on how to best manage WOC and what to expect upon the WOC period.

To give you the context: 
• This cement job will be done through 3 ½” production tubing which is already installed. In the annulus we have 7” liner hanger on a 9 5/8” prod casing to surface. 
• This will be a rigless operation (thus only wireline-based ops). 
• The cement job requires to be integrity assessed with perforations in the tubing and pressure testing the cement in the annulus (thus the cement will be over displaced, to have a shallower TOC in the annulus and deeper TOC in the tubing). When we pressure test the annulus, we can assess the integrity of the cement by confirming no pressure response in the tubing side (or the other way around).
• For the cement job we see two opportunities: a "non-simplified" and a “simplified” method.
The “non-simplified” method would be to run on wireline a landing collar c/w dual float valve below and use the landing collar to land the cement darts (bottom and top) that separate the cement slurry from the seawater in the well and displacement seawater. Upon bumping the top plug the backpressure from the longer cement column in the annulus would be hold by the dual float valves whilst WOC.

The “simplified” method would be to not use a landing collar, but still use the cement darts. At the end of the displacement (volume control and pressure based) we would close the X-mas tree to hold the backpressure from the annulus. This is a situation quite like a “failed float” scenario during a casing cement job except that the darts are still able to travel upwards or downwards if pressure is not kept balanced (as we do not have a landing collar) whereas on a casing cement job with failed floats the cement plug may travel upwards (cement U-tubing into the casing) but not downwards as the plug will bump on the landing collar.
Waiting on cement w/could be done with the annulus vented and maintaining the final displacement pressure trapped in the tubing.

My question is only related to the WOC on the “simplified” method: 
• Other than maintaining the final displacement differential pressure until the cement develops sufficient compressive strength, are there any other ways to control / mitigate the thermal expansion effects whilst WOC with the X-mas tree closed? (we expect some 40 deg C heat up from end of displacement to stable conditions)
• Any shareable experience of having floats failure during a casing cement job and upon WOC whilst keeping back pressure finding the TOC above the shoe much shallower than expected (i.e. despite the back pressure kept in the tubing there is still some U-tubing effect)?
 

Looking forward for any feedback.
 

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