GAS RECOVERY FROM HORIZONTAL WELL
2. 5 0.5 0 Effective permeability (k) = 0.3 µDarcy 0 2 4 6 30
Avg. production for 77
Cumulative production, bcf
8 10 12 14 16 18 20
Source: Reference 1
Study’s theoretical solution
Scaled total production, bcf
0 1 2 3 4 5 678910
*Some deterioration in quality of match seen around Year 8 as interfracture-interference effects begin to appear.
Source: Reference 1
Barnett, have relatively insignificant
effects on production.
We normalized production from all
15,144 wells to the median EUR and
then plotted cumulative production vs.
log-time distribution, along with the
study’s theoretical solution (Fig. 8).
In addition, we conducted an independent econometric-data analysis of about 16,000 wells. 4 Results of
this panel analysis confirmed field-wide well decline rates consistent with
those predicted by the study’s decline
Across Barnett field, many wells
have erratic production with unexplained production increases during
their lifetime. Some of these increases
likely result from secondary refracturing, commencement of artificial lift,
compression additions, or other operational stimuli. Refracturing (refrac)
occurs when an additional fracture
treatment is performed on existing
perforations or additional perforation
intervals are added. Some analysts
speculate that refracturing could be
a significant additional source of reserves.
Our study mathematically identified and quantified stepwise changes
in the month-to-month EUR calculation for the well, using both Chow test
and a statistical forecast measurement
error from the predicted trend where
significant deviations were noted for
visual inspection. This step was performed to distinguish between slope
changes, perhaps due to neighbor interference, and intercept shifts, such
as might result when a refrac occurs.
The process resulted in identification
of wells for visual inspection of the
Because our study did not confirm
each potential case of refracturing with
a given operator, this result should be
considered preliminary. Given that caveat, the total impact from the identified potential refractures was less than
2% of field production, and in most
cases per-well economics do not justify the cost.