Variability of Oil and Gas Well Productivities for Continuous (Unconventional) Petroleum Accumulations

By Ronald R. Charpentier and Troy A. Cook

2013

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Variability Comes from Several Factors

Spatial Changes in EUR

Changes in EUR with Time

Changes in EUR with Horizontal Well Design

Figure 27. Changes with respect to time in EUR distributions for Barnett Shale vertical wells. Each box-whisker plot is based on a 

group of approximately 200 wells.

Figure 28. Changes with respect to time in average EUR for Barnett Shale horizontal wells, in average EUR per 1000 feet of lateral 

length, and in average lateral length. Note the trend of relatively stable productivity per 1000 feet of lateral length over more than 9000 

horizontal wells in at least 13 different counties. Values for each line have been smoothed by a 50-well moving average.

Figure 20. This plot of EUR distributions by county for Barnett Shale vertical 

wells shows the variability in well productivity from county to county. Compare with the comparable graph for horizontal wells (figure 21).

Figure 21. This plot of EUR distributions by county for Barnett Shale horizontal wells shows the variability in well productivity from county to county. 

Compare with the comparable graph for vertical wells (figure 20).

Figure 22. This plot of EUR distributions by operator for Barnett Shale vertical wells shows the variability in well productivity from operator to operator. 

Compare with the comparable graph for horizontal wells (figure 23).

Figure 23. This plot of EUR distributions by operator for Barnett Shale horizontal wells shows the variability in well productivity from operator to operator. Compare with the comparable graph for vertical wells (figure 22).

Figure 24. This plot of EUR distributions by operator for Barnett Shale vertical wells for a single county shows the variability in well productivity from 

operator to operator. Compare with the comparable graph for horizontal 

wells (figure 25).

Figure 25. This plot of EUR distributions by operator for Barnett Shale horizontal wells for a single county shows the variability in well productivity 

from operator to operator. Compare with the comparable graph for vertical 

wells (figure 24).

Figure 26. This plot of EUR distributions by operator for Barnett Shale horizontal wells 

for two counties shows that the variability in well productivity in this case is greater 

from county to county than from operator to operator. Operators are represented more 

than once in this figure if they produced wells in both counties, however a majority of 

the operators are the same in the two counties. Solid blue lines are EUR distributions 

for the first county; dashed red lines are EUR distributions for the second county.

Figure 29. Plot showing increases in EURs for horizontal wells with increase in approximate lateral length. 

Approximate lateral length is defined as 80 percent of the horizontal difference between the surface location 

and the bottom-hole location.

Figure 30. Plot showing decreases in EUR per 1000 feet of approximate lateral length for horizontal wells 

with increase in approximate lateral length. Although EUR increases with longer lateral length (figure 29), 

it does so with a diminishing rate of return.

Figure 31. Plot showing increases in maximum monthly production for horizontal wells with increase in approximate lateral length. Maximum monthly production is normally the first full month of production.

Figure 32. Plot showing decreases in maximum monthly production per 1000 feet of approximate lateral 

length for horizontal wells with increase in approximate lateral length. Although maximum monthly production increases with longer lateral length (figure 31), it does so with a diminishing rate of return.

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Conclusions

Examination of oil and gas well productivities in continuous AUs shows a complex 

interaction of factors such as geologic variability and differences in well design. 

Analysis of the data can lead to better estimation of productivity for undrilled sites.

References Cited

Charpentier, R.R., and Cook, Troy, 2010, Improved USGS methodology for assessing 

continuous petroleum resources using analogs: U.S. Geological Survey Open-File 

Report 2010–1309, 27 p. Available at http://pubs.usgs.gov/of/2010/1309/.

Cook, Troy, and Charpentier, R.R., 2010, Assembling probabilistic performance 

parameters of shale-gas wells: U.S. Geological Survey Open-File Report 2010- 

1138, 17 p. Available at http://pubs.usgs.gov/of/2010/1138/.

U.S. Geological Survey Oil and Gas Assessment Team, 2012, Variability of distribu

tions of well-scale estimated ultimate recovery for continuous (unconventional) oil 

and gas resources in the United States: U.S. Geological Survey Open-File Report 

2012–1118, 18 p. Available at http://pubs.usgs.gov/of/2012/1118/.

Open-File Report 2013–1001

Sheet 3 of 3 

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Suggested citation:

Charpentier, R.R., and Cook, T.A., 2013, Variability of oil and gas well productivities

for continuous (unconventional) petroleum accumulations: U.S. Geological Survey 

Open-File Report 2013–1001, 3 sheets