Undiscovered Oil and Gas Resources An Evaluation of the Department of the Interior's 1989 Assessment Procedures (1991) / Chapter Skim
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C The Effects of Play Mixing in the Permian Basin
C The Effects of Play Mixing in the Permian Basin
Pages 159-172
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From page 159... ...
This mixing of lithologies and depositional systems appears to violate the common definition of "play." The following discussion compares the discovery histories as they appear when analyzed according to the USGS's grouping of fields into plays with the discovery histories as they appear when fields grouped into plays have more consistent lithologies and depositional systems. The committee did not review the makeup of the clusters in the data base, nor was it charged to do so.
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From page 160... ...
Clusters 361 and 363 represent different depositional systems: cluster 361 represents patch-reef to open-platform carbonate deposition, whereas cluster 363 represents fluvialdeltaic to barrier-strandplain sandstones. For this analysis, the field discovery histories for clusters 361 and 363 were partitioned into thirds using the same dates as those used by the USGS (the last third of fields discovered was also divided into halves to give four dates)
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From page 161... ...
This cluster represents patch-reef to open-platform-carbonate deposition. Note that the histogram has a maximum frequency in class 8 and three fields in class 11.
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From page 162... ...
This cluster represents flovial-deltaic to barrier-strandplain sandstones. Compared to the histogram for cluster 361, this histogram is skewed toward smaller field sizes.
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From page 163... ...
. 6 7 8 9 10 1 1 12 13 14 15 Field Size Class FIGURE C.3 Combined histogram for clusters 361 and 363.
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From page 164... ...
For the combination of clusters 369 and 371, compared with cluster 375, the field-size/discovery- history histogram looks very different through the first and second thirds (labeled as first date, second date, etc.; see Figures C.4 and C.5~. The cumulative plots for the third and fourth dates show the development of a much more filled-out pattern having the expected skew toward smaller field sizes for cluster 375, but the combination of clusters 369 and 371 shows somewhat low field numbers in classes 6 and 7, compared with cluster 375.
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From page 165... ...
These clusters represent primarily carbonate lithologies. The histogram shown somewhat low field numbers in classes 6 and 7, compared with the histogram for cluster 375 (see Figure C.S)
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From page 166... ...
~ o To MIX C 30 25 20 o ._ ~ 15 ash Die 3~ Die id Die 1~ Dana 10 5O I '`' '`' ~ .
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From page 167... ...
The combination of clusters 369 and 371 appears as a base, and cluster 375 appears to shape the frequency peaks.
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From page 168... ...
The series of histograms evaluated here shows that a play's discovery history appears different when the play is composed of clusters with different depositional systems and lithologies than it does when the clusters are more homogeneous. This is not a statistically rigorous analysis but it demonstrates qualitatively that the combination of dissimilar depositional systems within plays could mask additional potential discoveries by suggesting a more complete distribution of discovered fields especially toward field-size classes 6 and 7.
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From page 169... ...
PE~1X C C-11 FE~=E Item, E.C., D.~. About, S.J.
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From page 170... ...
C-12 APPENDIX C 30 25 20 ~5 a, · - 15 o at 10 E]
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From page 171... ...
APPENDIX C 30 25 20 o ._ ~ 1510 5o v-~ Oh Dee 3~ Dam 2nd Dee 1 ~ Dais .~ ~ ,`~' ,`~.
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From page 172... ...
Note the similarity in shape of this combined histogram with the individual histograms for the two clusters (Figures C.7 and C.8~.
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