Location of Lost Circulation Zone Dilemma

Lost Circulation is one of the major drilling problem geologists and drilling engineer’s struggling it while drilling a well for both oil/gas and groundwater. If a very porous, cavernous or highly fractured zone is encountered while drilling; an excessive amount of drilling mud is lost to that zone during lost circulation. The zone is called a thief or lost circulation zone. In this case I’ll explain dilemma I faced while drilling groundwater well in North Sinai, Egypt we expecting the aquifer at 1200m. Within drilling community North Sinai distinguishing by repetitive Lost Circulation. I joking with my colleagues we need to invent (Lost Circulation Preventer) instead of (Plow out Preventer). That lead me to design Excell worksheet to make cement job calculation easy work, because I think every repetitive work should has a system to make it done.

The following table is the important data about lost circulation zones:



Depth(m)


Lithology/comment

Fromto
372404Dolomite, brown color very hard
404417Dolomite [lost circulation] [already cemented]
417435Dolomite, brown to dark color, very hard
435442Missed sample [lost circulation] [already cemented]
746828White Limestone with grey argillaceous limestone
829-Missed sample [lost circulation]


Note: All samples are ditch

 caption="Sketch explained the situation of lost zones"

Sketch explained the situation of lost zones


I measured the well static at 62m after the mud filled the loss and become stable.

So we have 2 losses zone!

It’s high risk to use wireline logging in open hole well like that to determine which zone is the thief.

where is lost circulation zone ?!

How can I know that the previous cemented interval not cracked or reopened? Drilling Engineers here decided to close the previous cemented interval with cement plug and test if it’s work or not! if not they will close the bottom with another cement job. I’m not involved on coast estimation, but I think the company loses a lot of money in a case like this.

Comments

  1. Jim Andersen27/07/2011, 15:17

    If you regained circulation following the first loss circulation zone its most likely the second zone however there may be other zones that you dont know about too. Loss of circulation is also caused by heavy mud weight when mud is full drilled solids. A good mud system is important in the removal of solids or the driller needs to continually waste and mix new mud to keep the weight to spec. Often times drillers will speed up penetration to fill the drinking zone with cuttings that works in regaing circulation. Fast penetration can also speed the loss of circulation.

    Why are you not drilling this interval reverse air or reverse circulation? The lithology that you describe may be sufficiently competant to maintain open hole without mud. Fractured dolomite may require some dredging but the lithologic sample quality and ability to evaulate flow zones, water quality and the ability to perform advanced water filled borehole logging techniques make reverse air drilling a great choice for the drilling of water supply wells.

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  2. Thank you for the useful tips to struggling losses zones. Actually we don't have reverse circulation equipment at this well. We cemented the loss zones and this well become more stable but, I was searching for a technique or low coast method applicable for that dilemma instead of cementing jobs.

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