Kind of a dumb question about drilling unconventionals

[yimc]

I have noticed that many oilcos tend to drill unconventional wells and run 4 1/2" casing. While this keeps the cost of the drilling program down, I do hear of multiple problems when trying to produce these wells. For example, landing a rod pump to about 70 degrees as opposed to running it to 90 degrees.

A small ESP might do better, but the 4 1/2" diameter limits ESP's from playing in this area due to pump + cable clearance.

So my dumb question is; what is the cost difference in drilling a well to say 7500 feet MD (say 4500 feet TVD) and running 5 1/2" casing to TD vs 4 1/2" casing?

 

[zdas04]

Compared to rod wear, damaged cables, worn tubing? NOTHING. Every time a client suggests drilling 4-1/2 (or even 5-1/2, I want 7-inch and in the really deep horizontals I want 9-5/8) I haul out my "you are saving pennies to force yourself to spend $100 bills" speech. I win about half the time. Get fired the other half. Both are great outcomes (either way I don't have to deal with lifting 4-1/2 inch casing in a deviated 6,000 ft well again).

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist

 

[yimc]

Priceless response David, it certainly matches my observations also.

If you have some firm numbers on how much the drilling department saves on this type of decision, I would appreciate it. My calculations show about 200 000 dollars over the drilling and completions, but that money is easily made back in not doing a bunch of workovers and repairs.

I simply can't understand oilcos short-sighted rationale on this, but I may very well be missing something.

 

[zdas04]

I don't, but when I told a drilling manager that the cost of bigger casing was less than he was spending mud-drilling into a coal seam and cementing the coal in a CBM well (75% mud loss, cement requirement twice topsetting to coal), he didn't disagree. I've spent a fair bit of time with drillers to make sure that when we got the well we could produce it. Every time I've found stupid "little" crap that they didn't need to spend money on and that little crap was more money than we added by going to 7-inch. The conversation is worth while, drillers assumptions are often invalid.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist