Page 318 - Drilling Technology in Nontechnical Language

Chapter 13 – DRILLING PROBLEMS AND SOLUTIONS 309

In general, several techniques should be useful in most loss situations
deeper in the well in smaller holes. Given in the order in which that they
should be attempted, these are as follows:

1. Decrease circulation rate for lower circulating pressures and
drill with controlled parameters to minimize annulus loading

with solids, which makes the fluid in the annulus heavier. The
losses may well decrease over a period of time (a few minutes to
a few hours). The severity of the loss may dictate whether this
is acceptable; for instance, with losses of over 60 bbl/hr using
expensive mud, the cost may be too high. Restricted replacement
mud supply may also preclude this, such as desert drilling with
limited water available. However, the circulation rate must
be sufficient to lift cuttings out of the well, or stuck pipe with

cuttings in the wellbore becomes likely.
2. Reduce mud density if possible by diluting the mud and
maximizing the use of solids control equipment.

3. Pump a 100 bbl lost circulation material pill with mixed fine,

medium, and coarse LCM. Place it across and above the loss
zone and observe the well. When the well becomes static,
start circulation cautiously, monitoring the active volume, and
resume drilling.
4. Add solids (LCM) to the whole active volume of mud to increase
plastering characteristics.

5. Severe or total losses can sometimes be cured by drilling ahead
slowly with reduced weight on bit. It is only an option if there
is a plentiful supply of water (such as on an offshore rig) and
mud chemicals.
Drilling with no returns is called blind drilling. It should not be
attempted if there is any chance of hydrocarbons being penetrated. The
circulation rate must be sufficiently high to lift cuttings away from the

BHA and up to the loss zone, where they may plug off the large pore
spaces or fractures. A general lower limit for annular velocity for blind
drilling is 50 ft/min.

Further action may include setting a barite plug (as described in
chapter 11), diesel oil bentonite plug, or cement plug (described later in this
chapter); setting an extra casing string; or plugging back and sidetracking

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