American Oil and Gas Reporter - April 2016 - 69

SpecialReport: Drilling Technology
well drilled a 2,700-foot lateral in 44
days.
"The Clinton is an extremely hard,
very abrasive formation to drill," he explains. "We have experimented with different drill bits and mud systems. This is
a productive formation, but because it is
so tight, we have been able to drain little
of the reservoir."
EnerVest has not drilled a well in the
East Canton Field since October, and
Lay says the company plans to keep its
horizontal program on pause until crude
oil prices recover. However, he indicates
the company is eager to resume drilling
in hopes of learning more about certain
completion variables-such as increased
sand concentrations and fluid load volumes-in the Clinton formation.
"We want to see if there will be
physical results if we change the parameters," Lay continues. "One of the biggest
questions is artificial lift. We have used
rod pumps, electric submersible pumps
and jet pumps, but what is the most efficient method that gives us the longest
run time? We have only scratched the
surface. We would love to see prices improve so we can continue to learn more."
Illinois Basin
As Jerry Robinson sees it, a lot of
people make a bad assumption when they
move into the Illinois Basin.
"It is a lot different," contends Robinson, who is technical manager for Franklin
Well Services, an independent full service
provider for acidizing, hydraulic fracturing,
cementing and drilling fluids in the Illinois
Basin, as well as Michigan, Ohio,
Louisiana and Mississippi. "Sure, most
of our wells are fairly shallow, but the
rock is very hard. In North Dakota, Texas
or the Rockies, the first 6,000 or 7,000
feet may be soft. In the Illinois Basin,
the first 150-200 feet are easy, and then
you hit hard rock. You have to pay attention."
Because of that, Illinois Basin operators have begun employing many shalestyle hydraulic fracturing techniques to
vertical wells in the conventional reservoirs across Illinois, Indiana and Kentucky, Robinson reports. Although the
Illinois Basin has a few deeper wells
that target the Knox and Trenton formations, he says, most of the area's wells
range from the Pennsylvanian Sands at
400 feet to the Warsaw, Fort Payne and
Trenton formations, which lie at depths
of 4,500-5,000 feet.

EnerVest is drilling horizontal Clinton formation wells between its existing vertical wells
and then using the same stimulation techniques to complete the laterals, but over 15-20
stages.

"Depths vary in this basin," Robinson
observes. "They go up and down from
the St. Louis Arch on the west to the
Cincinnati Arch on the east. The area
around Mount Vernon in southern Illinois,
as well as southern Kentucky and Tennessee, are the deepest parts of the basin."

In the last few years, Robinson says,
some Illinois Basin operators have started
using plug-and-perf fractures and zipper
fracturing. "Instead of starting at the toe
in a horizontal well, we start at the bottom
and work our way up with multiple frac
stages in these vertical wells," he illustrates.

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APRIL 2016 69

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American Oil and Gas Reporter - April 2016

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