PBIOS - October 2018 - 155

stages of deposition (post-Grayburg)
starved out the deeper-water organics
while earlier stages (Clearfork and
Abo/Wichita Albany) had all the organics
needed, but offered more limited expanses
of reservoir-quality carbonate shelves.
One of the haunting questions for any
resource play is why certain areas are
more prone to successful wells than
others. Taking a dual approach is best,
which consists of using simple regional
statistics to individually characterize areas,
and then test against good scientific
reasons for the observed variability.
For example, is the predictability and
presence of the entrained gas a key? Is
the degree of natural waterflood sweep a
key? What could one look to for optimizing
the areas for high grading and optimally
selecting the best landing depths for maximizing the oil cuts?

FIGURE 4
Growth of Oil and Gas Production and Number
of San Andres Horizontal Wells
35,000

600
137% Growth in 18 mos.

25,000

500

20,000

400

15,000

300

10,000

200

5,000

100

0
Jan-12

Jan-13

Jan-14

Jan-15

Jan-16

Jan-17

Jan-18

# of Producing Wells

Daily Oil (bbl/d) and Gas (Mcf/d)

30,000

700
Oil (bbl/d)
Gas (Mcf/d)
# Wells (Rt Scale)

0
Jan-19

Mo-Yr

San Andres Statistics
Looking at the statistical status and
emergent trends in the play, Figure 4
charts oil and gas production from horizontal San Andres wells from the first
wells in 2012 to mid-2018. Note the
130+ percent increase in average daily
oil production from 18 months ago. Table
2 summarizes the current status of the
play in the key six-county region and in
terms of the number of wells, average
daily and cumulative oil and gas production, and gas-to-oil ratio.
One can draw several conclusions

from the study. The horizontal San Andres
play has grown from producing no oil in
early 2012 to producing 35,000 barrels
of oil and 32 million cubic feet of gas a
day as of May 2018 (six years). The play
has amassed over 27 million barrels of
crude oil. The latest annual growth rate
is 37 percent for the number of wells
drilled, 40 percent for average daily oil,
and 60 percent for cumulative oil.
The play has spread out geographically
to a regional one with significant well investments in six counties. Andrews County

started first, but Yoakum County now
leads the way with 37 percent of the wells
(compared with 34 percent for Andrews).
Gaines County, Tx., is coming on fast
with 16 percent of wells (76) after having
52 wells only six months ago.
There are two categories of gas-to-oil
ratios for the San Andres ROZ wells:
Andrews and Gaines counties with 500
cubic feet per barrel, while the other four
counties average over 1,200 cubic feet.
Curve-fitting production versus time suggests that many wells (using a standard

TABLE 2
Horizontal San Andres Play Statistics (Through July 2018)
Yoakum

Andrews

Gaines

Cochran

Lea

Ector

6-Counties

36.3%

36.0%

14.1%

3.9%

4.8%

4.8%

100.0%

56.8%

22.2%

9.7%

2.7%

4.1%

100.0%

11,799

10,551

1,772

472

830

1,441

26,866

Current Daily Gas (Mcf/d)

26,116

4,274

1,905

1,371

1,500

2,096

Cum. Gas Jan '11 - May /18 (MMcf)

12,935

4,728

807

467

866

1,674

GOR (cf/bbl)

1,226

1,211

1,382

# Wells

% of Total Wells

157

Current Daily Oil (bbl/d)

21,301

Current Crude Oil/Well (bbl/d)

21,301

Percent of Cum. Oil

43.9%

% of Daily Oil/d

Cum. Oil Jan '11 - May '18 (Mbbl)

Percent of Daily Gas

Percent of Cum. Gas

156

8,310
53

39.3%

70.1%

11.5%

60.2%

22.0%
514

61

3,626
48

6.6%
5.1%
3.8%
525

17

21

995

1,719

59

103

1.8%
3.7%
2.2%

1,379

4.6%

3.1%
4.0%
4.0%

21

1,541
73

433

37,492

5.4%

100.0%

5.6%

100.0%

7.8%

100.0%

37,262
21,477
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OCTOBER PBIOS 2018 155
PBIOS - October 2018

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