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To: Dave E. who wrote (4295)	8/25/1999 10:07:00 PM
From: Bearcatbob	Read Replies (1) \| Respond to of 15703

Dave and all, I have tried to read everything. However, I do not believe there is communication between the zones. If there was communication the pressures would be equal and we would not have the current problem. My understanding is that the top zone is at a higher pressure than the second. Therefore, in order to balance the top zone pressure with the mud column they have to overpressure the bottom zone - causing loss of fluid into the formation. I also seem to remember that the shale separating the zones was described as a seal cap of some type between the zones. Comments please. Bob

To: Dave E. who wrote (4295)	8/27/1999 3:43:00 PM
From: grayhairs	Respond to of 15703

Hi Dave, There are a few different ways that lost circulation can arise in a well. Excellent formation permeability (i.e. flow capacity) must be present for there to be lost circulation. The high permeability may be a consequence of fracturing, very large pore spaces in the "sand", or both. Also required is a formation pressure which is less than the downhole pressure exerted by the mud column. But, "differences in sand pressures" is not at a prerequisite for lost circulation. Lost circulation can and often does occur in reservoirs comprised of only 1 "sand". (Eg. Recall that the JV lost circulation in this well after having penetrated just the upper sand !!). Unfortunately, your idea about a temporary liner would not work to prevent lost circulation. Unless the liner were cemented in place there would always be mud flow behind the liner and lost circulation would still occur. If the liner were cemented to prevent that mud flow, then it would be there to stay and not "temporary". <<what else could they do to lessen difficulties if they reoccur?>> The Bellevue #1 well was a wildcat exploration well. The drilling program was established and engineered to test an exploration "concept" in a cost effective manner. That program was developed with all information available at the time and in the end, the discovery well has proven highly successful. The drilling programs of the current wells reflect information acquired from the discovery well. As the interpretation of the reservoir(s) change, we can expect further refinements to the drilling programs. <<Is this type of problem encountered very often and what does the size of the rig have to do with it - other than being able to drill a bigger hole?>> Lost circulation is a common problem. The size of the rig is not important to the problem of lost circulation, per se, but it can be important in terms of "drilling efficiency" when talking deep wells. That said, those are not exactly mickey mouse rigs on the Bellevue #1 and Cal Canal #1 sites, either !!! Have a great day. Later, grayhairs