Negative Equipment LL with PGNiG

Copernicus (6608/1-1 S) – Production section

What happened:

The gas readings for the 12 ¼” was done very well, and the correlation was quite good between the stop in drilling and the total gas reading. A background on this is that if we have a break in drilling, and/or reduction in mud flow, this will result in less mud through the header box where the gas is released from the mud into the registration chamber where the gas reading is recorded.
The correlation between the stop in drilling / reduction in mud level and drop in gas reading levels, was good through the 12 ¼” section.

When changing the drilling regime with reduced flowrate for the 8 ½” drilling, it could be seen from 2160 m that the curve for the gas reading levels flattened, compared to the 12 ¼” section.
High importance is placed on accurate gas readings in the reservoir section.

A theory is that the mud loggers did not recalibrate the sensor on the header box for the change in section, meaning that the mud level could have been below a minimum level for which the registration chamber manages to extract the gas from the system to register the gas level.
This was contradicted by SLB as they were adamant in that they sent out experienced personnel and they would not do such a rookie mistake. It shall be noted that the offshore SLB data loggers were not informed by PGNiG geologists of this during the start of the 8 ½” section, however, experienced data loggers should see this themselves and report/fix it as well.

What was planned:

Gas reading on header box throughout drilling of 8 1/2″ section, Schlumberger Mud Loggers.

What was learned:

Ensure that the mud loggers know how and when to recalibrate the gas reading sensors when changing the fluid system and drilling parameters, going from one section to another.

They are also distracted by their focus on the sampling and evaluation during the reservoir drilling, which can allow for info to slip through. A solution that the onshore operations geologist did, was to change the scale of the logs, meaning that one could still “zoom in” and extract gas reading trends, although it is preferrable to have better readings to begin with.

What actions are required:

Learning to be incorporated into the DOPs as part of the pre-section checklist

What Was Done

Learning to be incorporated into the DOPs as part of the pre-section checklist