In his book “Oil Notes”, geologist Rick Bass describes the importance of logging operations. Only after completing a log run, the well can be properly classed as a success or a dry hole. That is why it is so surprising that wireline cables get stuck in the wellbore so often, with costly delays and sometimes loss of data as a result. It is even more surprising when one considers that there is a solution on the market. And that solution was developed by Guy Wheater from Gaia Earth (see the interview with Guy here).
But first, how does wireline cable get stuck?
There are two sticking categories. Cable keyseating is where the cable wears a slot in the formation which may then unleash a combination of sticking mechanisms, such as slot compression from borehole stress, slot swelling from reactive shales, mechanical binding from deep slots or differential sticking if the slot is permeable. Differential sticking may occur if the cable is in contact with mud-cake or permeable formation directly, or from loss zones. During a logging run, the abrasive action of cable or logging tools may damage the mud cake and induce sticking.
What can be done to prevent this from happening?
“Many operators’ wireline acquisition programmes are in the cable sticking risk envelope but they just don’t know it. An early risk assessment is invaluable since cable sticking can be predicted and avoided with 99% efficacy”, says Guy. “After more than 15 years of R&D, and ongoing modelling and monitoring of 1000s of hole-sections for our clients, we are very confident in our system. Furthermore, over 100 historical cable sticking and fishing post-mortems from around the world ensures our modelling is effective and dependable in a broad range of geological environments.”
And what if there is an elevated risk of cable sticking?
In wells with directional work and long open-hole sections, with weak to medium strength formations, or in wells with loss zones, overbalanced sands or fractured carbonates, there is an increased risk of cables getting stuck. To facilitate open-hole logging in these environments, Guy and his team at Gaia Earth Technologies developed the so-called wireline standoff tool. An array of standoffs can be attached to the wireline cable at pre-determined intervals. And this seemingly simple solution has proven to be highly effective on even the most challenging wells over the last 12 years, resulting in many days of saved rig time and GHG emissions.
