Slim Hole Drilling

Definition - What does Slim Hole Drilling mean?

Slim Hole Drilling is a drilling technique which is used to develop a slim hole well. A Slim hole well is a type of gas or oil well whose borehole size is significantly smaller than the usual borehole size. It is generally less than 6 inches in diameter and 4 ¾ inches or less deep. It is drilled by E&P organizations. A slim hole well sets a perfect correlation between the well cost and the volume of rock drilled out. It goes with a notation that the cost of developing a gas or an oil well will reduce when less rock is extracted.

Petropedia explains Slim Hole Drilling

Drilling slim hole wells is the most commonly accepted engineering criteria these days within the E&P industry space. This is due to the fact that well development costs are reduced by 30% after following this drilling criteria. The small size diameter and shallow deepness has the following advantages:

  • Uses less material in well preparation.
  • Uses less rig hold time.
  • Increases the number of drillings at the same time.
  • Reduces waste mud volumes.
  • Uses less manpower.
  • Saves time in location preparation and many more advantages.

Some of the disadvantages of Slim hole drilled wells include:

  • ECD (Equivalent Circulating Density) is high which can limit mud weight.
  • It eliminates contingencies.
  • Geophysical information is limited.
  • Production will be for small rates.
  • It limits potential for sidetrack option.

Production rates of up to 50 mmscfd gas, 4000 bpd oil are achievable in many cases through 4 1/8 inch size borehole and 3 ½ inch liner. There are two technologies commonly used for drilling slim hole Wells, i.e., downsized conventional drilling and continuous coring method.

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