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FRACTURINGINTRODUCTION

FRACKING

• Most fracturing operations don’t have problems

• Some petroleum cannot be produced economically without fracturing

• Fracturing has been used since the 1940’s

• But, like any other operation, you can have problems

FRACTURING

FRACKING

• Not so hypothetical question:– Company B wants to sell their oilfield to

Company A

– You are an environmental specialist, working for Company A

– Your boss asks you to evaluate whether there are problems due to fracking

– What do you evaluate, to avoid buying a field with problems?

– If there’s “no baseline data,” how can you do your job?

– What, mechanically, causes the problems?

FRACTURING

FRACKING

• One way to handle it:– Watch several documentaries

online

– Quote a federal regulator who says fracking is fine

• Lisa Jackson even said there were no problems. And she’s a liberal, right?

– Quote the guy down the hall, who says “fracking has never caused a problem”

– Tell your boss everything is fine

– Buy the oilfield….

FRACTURING

FRACKING

• Buy the oilfield, everything’s fine…

•Except it isn’t fine, and you are about to get fired– Lisa Jackson and the guy down the

hall burst in and rescue you from getting fired

• Analysis would be a better idea– What do you evaluate, to avoid buying

a field with problems?

FRACTURING

WHAT IS FRACTURING?

• Injection of fluids under pressure to create or enlarge fractures in reservoir rocks

• Usually, sand (proppant) is also injected– Props the fractures open after pressure is

relieved

• Fractures become conduits for oil and gas to flow into the wellbore

MECHANICS OF FRACTURING

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WHAT IS PROPPANT?

• The frac will continue to make a fracture as long as you continue pumping. – Size of the fracture is proportional to how much fluid

you pump

• When the pumping stops, the frac will close.– Sand or some other type of “proppant” is added to the

frac fluid.

– Sand stays in the fracture and props it open.

– Oil and gas flow thru the permeable sand to the well.

FRACTURING

FRACKING

• “Conventional” = Sandstones, Limestones, Dolomites

• “Unconventional” = Shales

FRACTURING

George E. King, Apache Corp. SPE 152596

WELLBORE CONSTRUCTIONWE DRILL THE WELL, THEN WE “COMPLETE” IT

• Drilling and completion has some of the worst jargon in the oilfield

• We need to understand the lingo to do our jobs

• For this reason, there will be some slides that define a term that will be used in subsequent discussion.– These slides are not as “random” as they may seem.

DRILLING/COMPLETION JARGON

DRILLING

An annulus is a gap between two strings of pipe, or between the pipe and the open hole. The pipes have to be “one inside the other” or concentric in order to form an annulus.

Annulus - donut shaped space

It comes from the same root word as “annual,” as in annual growth rings on a tree.

Usually, you cannot see the annular space when you stand at the well.

ANNULUS

DRILLING

• The well must have a concentric pipe to circulate (there has to be some sort of annulus)

• You pump down the inside of the pipe, and let the fluid come back up around the outside of the pipe (the annulus, aka the “backside”)

• Fluids that are commonly pumped include “drilling mud” and “completion fluid”

CIRCULATION

DRILLING

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• The crew moves the rig to the location

• They drill a hole in the rocks hundreds or thousands of feet

– They “circulate” mud down the well to bring out cuttings, while simultaneously turning a bit to drill into the rocks

• They will run and cement at least one string of casing pipe

– Usually, there will be more than one

• The crew moves the rig to the next location

DRILLING

DRILLING WHY DO WE CEMENT?

• We have to keep the oil from coming up between the pipe and the hole

– If there are drinking water aquifers, they could be contaminated

• We want to control where produced fluids come from and where injected fluids go. (Zonal Isolation)

– If water disposal wells communicate with producers, you’ll be pumping the water in circles

DRILLING

Cementing CasingPERFORATING

• Assume we have a cemented well, and we are going to install a fraccompletion

• After we cement the casing in the well, the oil cannot get into the well, and fracfluid cannot get out into the formation

• We “perforate” holes in the pipe with explosive charges– Bullets shoot holes thru the pipe and

cement, and into the formation

COMPLETION

PERFORATING• Bullets shoot holes thru the pipe

and cement, and into the formation

• They can aim the perforating gun in a particular direction they are perforating so the frac will open against the minimum horizontal stress

PERFORATING VIDEOs

• First video: shaped charges

• Second video: blowing up just the primer cord, to loosen bolts on an old wellhead

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FRACTURING FRACTURING

FRACTURING

WHAT’S THE CONTROVERSY?

DIFFERENT FROM PRIOR “OIL BOOMS”

SHALE ZONE

Conventional oil and gas development wouldbe restricted to the anticlines shown in red anddark green. By contrast, shale development stretches across the countryside overlaying the“SHALE ZONE” layer.Towns have already been built – no way to keep development separate fromurban areas.

FRACTURING