Meter-scale lithofacies cycle and controls on variations in oil saturation, Wolfcamp A, Delaware and Midland Basins
Meter-scale lithofacies cycle and controls on variations in oil saturation, Wolfcamp A, Delaware and Midland Basins
复制标题
Wolfcamp A、特拉华和米德兰盆地米级岩相旋回及其对含油饱和度变化的控制
DOI：
10.1306/01152120065
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发表时间：
2021-09
期刊：
影响因子：
3.5
通讯作者：
Deyong Shao
中科院分区：
文献类型：
--
作者：
Tongwei Zhang;Qilong Fu;Xun Sun;Paul C. Hackley;Lucy Tingwei Ko;Deyong Shao
Typical meter-scale lithofacies cycles observed in cores from the Wolfcamp A unit comprise basal carbonate facies overlain by calcareous or siliceous mudrocks. These cycles are the fundamental macroscopic units of deposition in the basinal mudrocks from the subsurface Delaware and Midland Basins. TOC values changes abruptly over meter-scale vertical intervals associated with these lithology variations. Siliceous mudstones are the most TOC-rich facies (TOC > 3 wt.%) whereas fine-grained, thin carbonate beds are the TOC-leanest (TOC < 1 wt.%). Do the thin carbonate-rich beds serve as reservoir for storage of migrated oil or act as a seal? Three 10-foot (3.3 m) intervals of meter-scale lithofacies cycles in the Wolfcamp A unit were selected for sampling and analyzed using X-ray diffraction (XRD) analysis, TOC and HAWK analysis, crushed-rock gas analysis and organic petrography. Oil saturation index, which is the normalized free oil per gram TOC (S1*100/TOC from rock pyrolysis), is used as an indicator of free oil enrichment or depletion. The thin carbonate beds contain the lowest TOC content, but have a similar oil saturation index values compared to TOC-rich siliceous mudstone and calcareous mudstone. Both TOC-lean fine-grained carbonate and TOC-rich siliceous mudstone lithofacies have high oil saturation in these meter-scale cycles. These observations indicate that migrated oil is present, leading to high oil saturation in the fine-grained thin carbonate beds, which have void-filling migrated solid bitumen by petrographic observation. Gas released from rock crushing displays lower gas dryness values (C1/C1-5) but higher oil indicator values (C4+5/C1-5) in TOC-lean thin carbonate beds compared to the TOC-rich mudstones. Abnormal low gas dryness values but high oil indicator values in TOC-lean thin carbonate beds likely indicates a cumulative oil and gas charging effect through source rock maturation. Oil and gas generated at different stages of thermal maturation were partially expelled from OM-rich siliceous/calcareous mudstones, and charged into adjacent OM-lean thin carbonate beds. Multiple-stages charging of migrated oil into overlain thin carbonate beds has resulted in a mixture of heavy crude, normal oil and light oil that is generated at different thermal maturity levels. Short-distance vertical oil migration from TOC-rich siliceous/calcareous mudstones into carbonate rich beds is a key factor in variations of oil saturation in the Wolfcamp A unit. Statement of the background Wolfcamp mudrocks in the Permian Basin have, in the past few years, become one of the primary targets for mudrock oil production. However, the oil production from the Wolfcamp A and B units is much
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影响因子：
4.2
作者：
Shao Deyong;Zhang Tongwei;Ko Lucy T.;Luo Huan;Zhang Dongdong
通讯作者：
Zhang Dongdong
影响因子：
3.5
作者：
Pommer, Maxwell;Milliken, Kitty
通讯作者：
Milliken, Kitty
影响因子：
3.5
作者：
Loucks, Robert G.;Ruppel, Stephen C.
通讯作者：
Ruppel, Stephen C.
影响因子：
4.2
作者：
P. Hackley;Tongwei Zhang;Aaron M. Jubb;B. Valentine;F. T. Dulong;J. Hatcherian
通讯作者：
P. Hackley;Tongwei Zhang;Aaron M. Jubb;B. Valentine;F. T. Dulong;J. Hatcherian
DOI：
--
发表时间：
2012
期刊：
--
影响因子：
--
作者：
Yao Tian;W. B. Ayers;W. McCain
通讯作者：
Yao Tian;W. B. Ayers;W. McCain