Underbalanced drilling equipment and techniques
- Baker Hughes INTEQ, Houston, TX (United States)
Underbalanced drilling usually takes place when the reservoir pressures have dropped substantially to levels below the hydrostatic pressure that is exerted by conventional water based drilling fluids. In a low pressure formation, fluids and solids invasion into the formation can be prevented by drilling at balanced or underbalanced conditions. A pressure overbalance during conventional drilling can cause significant fluid filtrate invasion and lost circulation; and it is known that fluid invasion into the formation can lead to formation damage, high mud costs, a need for expensive completions and well productivity impairment. Because underbalanced drilling creates a natural tendency for fluid/gas to flow from the formation to the borehole, successful underbalanced drilling depends upon the appropriate selection of circulating fluid. The use of a compressible fluid in the circulating system, referred to as air drilling, lowers the downhole pressure, allowing drilling into and beyond these sensitive formations. Other advantages include increased penetration rates, improved drill bit performance, and contamination-free drill solids for ready detection of hydrocarbons. This discussion of the various underbalanced applications, compressible fluid systems, and required drilling and surface equipment provides an overview of experience gained from successful and unsuccessful wells.
- OSTI ID:
- 170148
- Report Number(s):
- CONF-950116--; ISBN 0-7918-1288-X
- Country of Publication:
- United States
- Language:
- English
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