Bonanza! Your petroleum geologists have discovered an oil or gas deposit. Now you just have to get as much up as possible at the lowest possible cost. Part of the procedure is drilling production wells, usually done with the help of templates. Here is a basic introduction to what template drilling is, and why & how we do it.
The story starts below the sea
New challenges pave the way for new thinking and new technology. For the petroleum industry, Subsea production of oil and gas has brought us a lot of innovative solutions. The first subsea well saw the break of day in the Gulf of Mexico in 1961. Since then, much innovation has happened on the Norwegian Continental Shelf (NCS).
Template drilling stems from this time period. The drilling method has since been the only viable way to drill multiple wells (a batch) from a single location. (Hence the related term, «batch drilling»).
This reduces the footprint of the drilling operation on the surface and eliminates the need for multiple single well locations. The so-called template structure was used for the first time on the Statoil operated Tommeliten field in 1986.
Offshore template drilling is used for both surface and subsea installations. For land based operations «pad drilling» is a frequently used term.
How template drilling works
A template is used in order to easily tie in production from several wells. Consequently, the wells are closely spaced relative to each other.
The template is a steel frame with slots for each well and supporting legs. It is lowered down and anchored to the sea floor .
Sometimes the wells may be as close as 1.5 meters apart, center-to-center. It goes without saying that drilling vertical top holes is extremely important. Drilling into another well could render one or more slots unusable or at the very least require time and money to correct. You only have one chance!
From the template anything from 4 to 64 vertical top holes will be drilled through each slot, each one 100-200 meter deep . From the bottom of the top hole, the well bores will stretch in all directions into the reservoir.
> Read also: How to drill a vertical top hole
Batch drilling means doing several wells in one go. When you’re done with one well, move the rig using the anchors, DP or skid until you are positioned above the next slot. Drill a new top hole and repeat until the required number of well are finished.
Drilling an entire batch of top holes in one go saves time and money. However, drilling six or eight wells with the same BHA (Bottom Hole Assembly) has its challenges. Some components tend to wear out. The bit and the hole opener for example.
We have covered that topic in our previous blog posts «How to drill a vertical top hole» and «Hole openers: When your black gold is between a rock and a hard place», so check them out for more in depth coverage.