Changes

==Oil and gas zones==

==Oil and gas zones==

[[file:evaluating-source-rocks_fig6-7.png|300px|thumb|{{figure number|1}}Approximate boundaries for kerogen types I, II, and III. Copyright: Tissot and Weite, 1984; courtesy Springer-Verlag.]]

[[file:evaluating-source-rocks_fig6-7.png|300px|thumb|{{figure number|1}}Approximate boundaries for kerogen types I, II, and III. Copyright: Tissot and Welte;<ref>Tissot, B. P., and D.H. Welte, 1984, Petroleum Formation and Occurrence, 2 ed.: New York, Springer-Verlag, 699 p.</ref> courtesy Springer-Verlag.]]

Oil and gas zone boundaries can be established using vitrinite reflectance data. The boundaries are approximate and vary according to kerogen type. [[:file:evaluating-source-rocks_fig6-7.png|Figure 1]] shows the approximate boundaries for kerogen types I, II, and III. Time-temperature relationships and mixing of various sources of organic matter may alter these boundaries.

Oil and gas zone boundaries can be established using vitrinite reflectance data. The boundaries are approximate and vary according to kerogen type. [[:file:evaluating-source-rocks_fig6-7.png|Figure 1]] shows the approximate boundaries for kerogen types I, II, and III. Time-temperature relationships and mixing of various sources of organic matter may alter these boundaries.

[[file:evaluating-source-rocks_fig6-8.png|300px|thumb|{{figure number|2}}See text for explanation.]]

 

[[file:evaluating-source-rocks_fig6-8.png|300px|thumb|{{figure number|2}}Sample where the mean value reported is 1.27% R_o, based on 14 measurements. The interpretation of the mean value would place this sample past the oil generation zone. The true reflectance of the indigenous vitrinite in this sample is 0.7% R_o, providing an extremely different interpretation and placing the sample in the early stage of liquid hydrocarbon generation.]]

Abimodal distribution or a large spread in the range of measured values produces a mean R_o value that does not accurately represent the maturity of the rock sample. Variations or errors in vitrinite reflectance measurements may be caused by the following:

Abimodal distribution or a large spread in the range of measured values produces a mean R_o value that does not accurately represent the maturity of the rock sample. Variations or errors in vitrinite reflectance measurements may be caused by the following:

==Recognizing good data==

==Recognizing good data==

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file:evaluating-source-rocks_fig6-9.png|{{figure number|3}}See text for explanation.

file:evaluating-source-rocks_fig6-9.png|{{figure number|3}}Histogram with a single mode in the distribution curve tightly clustered about a mean value.

file:evaluating-source-rocks_fig6-10.png|{{figure number|4}}See text for explanation.

file:evaluating-source-rocks_fig6-10.png|{{figure number|4}}Example of a poor profile due to a lack of data.

file:evaluating-source-rocks_fig6-11.png|{{figure number|5}}See text for explanation.

file:evaluating-source-rocks_fig6-11.png|{{figure number|5}}Histogram representing poor-quality vitrinite reflectance data due to contamination by caving.

file:evaluating-source-rocks_fig6-12.png|{{figure number|6}}See text for explanation.

file:evaluating-source-rocks_fig6-12.png|{{figure number|6}}Bimodal distribution.

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