American Oil and Gas Reporter - January 2016 - 78

JANUARY 2016
strategies, and a drastically changed economic environment has made restimulation
an interesting option to improve production

and decrease capital expenditures to improve return on investment.
In the past few years, a dramatic in-

FIGURE 3

140

7,000

120

6,000

100

5,000

80

4,000

60

3,000

40

2,000

20

1,000

-

2010

2011

2012

2013

2014

2015

82

101

124

126

121

114

4,227

4,811

5,733

5,697

44

Avg EUR BOE

Avg Peak Rate

280

Well Count

Avg Perf Ft

50

54

731

1,273

5,270

54

52

1,732

51

1,924

5,464

0

695

First Production Year

FIGURE 4
Horizontal Well Type Curves by Grade
(Eagle Ford)
A
B
C
D
E
F
G
H
I
J

800
700
600

BOE/day 6:1

500
400
300
200
100
0

0

5

10

15

20

25
30
Months Produced

78 THE AMERICAN OIL & GAS REPORTER

35

40

45

50

55

Well Count and Avg Perf Length (ft)

EUR (MBOE) and Peak Rate (BOE)

Average EUR and Peak Rate
First Production Year for Eagle Ford Oil Window

crease in stage counts/frac density and
the volumes of fluid and proppant pumped
per lateral foot has made older, and-by
today's standards-insufficiently stimulated
wells and poor producers obvious candidates for refracturing. However, because
of insufficient data for restimulation performance, large-scale application may
not be feasible yet, despite the favorable
economics in the current price environment.
ROIs are inconsistent and most likely
related to candidate selection. Promising
wellbores have lower EURs compared
with surrounding wells, are completed in
areas of the play with generally higher
EURs, and show a significant increase in
gas-to-oil ratios over time. Other factors
to take into consideration are wellbore
and fracture stage spacing, reservoir thickness, the presence of faults and natural
fractures, and reservoir pressure.
Analysis of instantaneous shut-in pressures as well as microseismic data has
shown that refracs can stimulate new
reservoirs successfully and can contact
virgin reservoir pressure. However, finding
the optimum technique to restimulate a
well is a point of contention, mostly because of insufficient experience.
Depending on the original completion,
options for restimulation include various
diversion materials, cement squeezes and
reperforation, expandable casing and
reperforation, or pumping into the original
completion in one continuous operation.
Individual techniques show varying success, likely related to how effectively the
entire wellbore length can be restimulated.
Initial field data for diversion agents show
that the heel section appears to receive
most of the stimulation effort.
Nevertheless, today's dramatically reduced capital budgets strongly encourage
restimulation. It presents an opportunity
to collect data at a relatively lower cost
compared with a future environment
where wells have become mature and
are approaching the economic rate that
requires evaluating restimulation, but at
increased service costs as commodity
prices recover.
Refrac Opportunities
To get a sense of the potential refrac
opportunity (Figure 5), 1,500 Eagle Ford
wells were evaluated, all of which have
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