The "Shoe Bond Test" is a confirmation of the placement and setting of the cement in the bottom of Shoe Joint to provide a potential explanation and indicate the potential remedy in case that the "Formation Integrity Test" or "Leak off Test" are lower than expected or lower than required for the next hole section to be drilled.
Failures of the placement or the placement or the setting of the cement inside "Shoe Track" can result from errors in the cement slurry mixing but are most often caused by errors along the sequence of pumping the slurry into the casing and displacing it out of it, including the potential of failures of the wiper rubber plug or plugs used or the failures to use them properly as well as not having provided for enough length or volume of "Shoe Track" or of water wetting washers and spacers.
For example, the practices of using a "Bottom Wiper Plug" ahead of the "Lead Cement Slurry and sufficient volume of water wetting spacing ahead of it can help to further prevent the potential a of "Wet Shoe" but are often avoided to save time, cost or just reduce job complexity. Using a too short of a "Shoe Joint" and single joint Shoe Track cand also save cost and rig time but are more prone to failures to achieve adequate "Shoe Bond". Longer Shoe Track (e.g.: two full R3 joints), good quality and large volume of water wetting weighted spacers and washes ahead of the cement slurry, Best chance to avoid a "Wet Shoe" would be when pumping lots of Washer and Spacer volumes and waiting until a small volume of the "Lead Slurry" is inside the casing to drop the "Bottom Wiper" and dropping the "Top Wiper" when still a small volume of "Tail Slurry" is still to be pumped (e.g.: the volume of the lines and the mixing tub); however, all these mitigations carry a cost that may not be justified for every case, considering the relevance of the "Leak off Test" or the required "Formation Integrity Test" for your particular well design.
I have also experienced cases of "Wet Shoe" or "Wet Shoe Track" or bad "Shoe Bond Test" when attempting to use the common practice to pressure test the casing integrity upon bumping of the "Top Wiper Plug" to save rig time, including a shortening of the waiting on cement time, or consideration of potential "cement Micro Annulus" caused when pressure testing the casing immediately before the drilling out of the Shoe Track.
These casing pressure tests conducted immediately before completely drilling out the bottom of the shoe track are great when you get "good" results but when they show a leak it is hard know if the pipe has a defect or damage or if it is a case a "Wet Shoe" because of bursting the top wiper plug or of folding of the rubber wipers or if these wipers had wore out while debris pushed down to the top of the float collar was preventing the nose of the top plug to seal against that surface. If a remedial cement job after a bad "Shoe Bond Test" fails to produce a solid pressure test of the casing you may need to consider a defect or damage somewhere up the pipe (e.g.: a poorly made up connection) which may be very costly to repair.
It is true that the procedure of the "Shoe Bond Test" is quite close to that of the "Leak Off Test" or the "Required Formation Integrity Test" to which the "Shoe Bond Test" is a complement; however, these other tests are to be performed after the drilling out of "Shoe" and some prefer that a short section of "Fresh Formation" is drilled before they are taken and the "Shoe Bond Test" has to be done after the drilling out of the "Wiper Plug" or "Wiper Plugs" but before drilling out the "Shoe".
These "Shoe Bond Tests" cost rig time and the information produced by then is only relevant when they show a cement job problem and when your well design requires a proof that a certain level of formation integrity is requires to drill the next section; so, you may skip them if there is no plan to later take "Leak off Test" or a "Formation integrity test"; furthermore, you could also consider to skip them even when planning a LOT or FIT when the cementing record shows that practices to prevent a "Wet Shoe" were used such as the use of at least two wiper plugs including a "Botton Wiper" and Top Wiper and the pumping of plenty washer and spacer volumes producing a good cement Job pumping pressure record including a solid "Bumping Pressure", that would not leak off. The "Shoe Bond Test" would show a "good result" as a solid pressure test holdng a value in excess of the expected LOT result and excess of the required FIT and "Wet Shoe" as leaking off pressure test that is often much lower than the expected LOT not because the formation where it is leaking too is weaker than expected but because it is showing a channel up out side the casing to a formation that may we a sand or shale that is shallower than the end of the pipe which vertical depth is assumed to calculate the "Frack Gradient" considered as the test result.
If mud cake along the channel outside the "Shoe Track" has been removed during the cement job and it connects up to a sand section the "Shoe Bond Test" may show leaking off at very low pressure tests only exceeding the formation pore pressure by a small margin and a costly remedial cement job may be required.
If the channel outside the Shoe Track only connects to shale or clay sections or more sandier sections which still hold a competent mud cake the "Shoe Bond Test" could show a "Wet Shoe" as a leaking pressure test when reaching pressures higher than a certain threshold after showing a few more solid tests at pressures only exceeding the pore pressure by smaller margins and in these cases the pressure reached in the more solid steps or to which the pressure fall chart slope breaks at the leaking steps may be enough for what is estimated required to drill the nect hole section and may be considered as sufficient to avoid a remedial cement job; considering that the effective formation integrity is likely better than calculated assuming the Vertical Depth of the end of the casing
Best regards,
Carlos R ESCUDERO
ESCUDERO.Carlos@Outlook.com+54(9-261) 707 4444 Argentina Mobile
+1(347) 837 7992 International Roaming
Original Message:
Sent: 3/14/2024 7:51:00 AM
From: Hans-Jacob Lund
Subject: RE: Requirement of Shoe Bond Test, FIT and/or LOT
If you perform a LOT, there is a way to determine if it is the formation or the cement that failed. There is an SPE paper I saw on the issue (sorry, don't have the paper number) that did a good job explaining the issue. I have never used it myself. If you have a significantly lower FIT on one well compared to the rest on a pad, I would assume it is the cement that is the problem. As far as well integrity, this may not be a problem: it may be a channel that goes up a little to a shale that is a little weaker. Regardless, you will need to use the measured FIT in your MAWOP calculations for that annulus.
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Hans-Jacob Lund
Principal Well Integrity Engineer
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Original Message:
Sent: 03-13-2024 10:38 PM
From: Sahir Inam
Subject: Requirement of Shoe Bond Test, FIT and/or LOT
Dear Loizzo,
Thank you very much for your response.
Basicaly we had a recent case where FIT failed at 1.22 SG against the planned 1.5 SG. The completion & WI engineer's concern was shoe bond failure however, drilling engineer has a different view, in his opinion the formation is incompetent. From your answer, if I correctly understood, probably we have used wrong assumption for the formation integrity? Although, this is 5th well, and all others had a higher FIT number (1.52-1.8 SG).
As I understand, to resolve this, we may perform both SBT and FIT separatly to confirm the shoe integrity in the first place (before drilling new formation), followed by the FIT (drilling few meters in to the new formation)? If this is not the right way of doing it, what alternate method industry uses.
Regards,
Sahir