Ann: Hydrocarbon gas recovered & evaluation program forward plan, page-695

"So you don't think the need to increase the mud weight in the main borehole exaberated the washed out coals? "

It depends on the mode of failure causing the coals to wash out. If high mud weight is causing fracking of the coals then yes dropping mud weight might help. If the coals are thick and cleaty and prone to falling apart as they get drilled then a higher mud weight might slow the process.


"So will still be an issue in the sidetrack.during logging jobs you have done what methods have they used when this particular issue comes up? Is just avoiding them the only real method. I understand you have limited info to go on but curious what IVZ would be doing to possibly work around this issue. "

My experience has been that once you encounter washing out of thick (2m+) coal units in a well wiper trips may eventually knock the edge off the ledges enough to allow logging tools to get past or the trip may actually make the problem worse. Playing with mud weight generally doesnt help much from my experience. Shortening your logging tool strings can sometimes help. With the tools on wireline you can sometimes get the tools to turn which can cause the bottom of the tool to deflect off vertical enough to get past a ledge. You can add tool turner subs to a tool string to help with the latter. On TLC you don't have the option of turning the tool.