overview of slim hole drilling, what is slim hole drilling, advantages of slim hole drilling, disadvantages of slim hole drilling, opportunities of slim hole drilling, safety of personnel in slim hole drilling

1. Intro to Slim Hole Drilling
RAO Mubarak Ali
mubarik.ali43@yahoo.com
international member of
SPE 4353073

2. Overview
• Wells can now be safely and effectively drilled or sidetracked,
evaluated and completed in small diameters down to 4 1/8". The
resulting slim wells can provide a total well cost reduction of 30%.
At the same time, crew exposure, location size, cuttings and
waste mud volumes are drastically reduced.

3. Definition
• Definitions of slim holes vary from a well with 90% drilled with a
diameter of less than 7 inch to a well with 70% drilled with less
than 5 inch.
• A goal of slim hole, however it is defined, is the drilling of a well
with a diameter smaller than that used on conventional wells in
the area. The reduced diameter helps cut rig time and cost and
reduces the cost of the tubular.

4. Advantages
• Reduced well costs
Slim hole drilling with a small fit-for-purpose rig ensures lower costs of
• . day rate
• ·wellhead
• ·casing
• ·mud products
• ·location preparation
• ·logistics
• ·manpower
• ·waste disposal.
• Health and Safety Environment HSE
Slim hole drilling also results in substantial HSE benefits:
• ·Smaller location and camp
• ·Smaller crew reduces exposure
• ·Less logistic support required
• ·40-70% reduction in cuttings and waste mud.

5. Technical advantages
• Smaller mud volumes allow more efficient mud cleaning or use of
low solids (expensive) formate brines, resulting in a reduction in
formation impairment.
• Technical possibilities increased by ability to drill, evaluate and
complete through smaller casing strings.

6. Potential disadvantages
• High equivalent circulating densities (ECD) can limit mud weight
• Limit petro physical information obtained
• Limit completion options
• Limit production rates
• Limit potential for future sidetrack options

7. Disadvantages
• Early concerns about the robustness of well control procedures
originally proposed for continuous coring have now been resolved
in the light of field experience with improved computer-based
kick detection system (KDS) and minor modifications to traditional
well killing procedures.

8. Opportunities
• If the geology is sufficiently well understood, the cheaper drilling
method can be used to complement seismic exploration, by
providing a cheap series of throwaway wells with wireline logging,
occasional spot coring over the reservoir, and seismic check shots.
The slower, continuous coring method can be used where there
are substantial uncertainties over the geological model.

9. Safety of personnel
• Smaller wells mean smaller individual items of equipment and
tubular and a smaller total amount of material to be handled,
which reduces the total exposure of personnel. Smaller rigs
require smaller crews, and are easier to mechanise/automate
than bigger rigs because the range of tubular size to be handled is
smaller. They thus have the potential, in the longer term, of
reducing total exposure even further, though consideration must
also be given to the smaller dimensions of the workspace
available.

10. Thank you………