An examination of the fluid inclusions of the well RP3-1 at the Halahatang Sag in Tarim Basin, northwest China: Implications for hydrocarbon charging time and fluid evolution

The well RP3–1 lies in the Tarim Basin, which is located in the southern Xinjiang Uygur Autonomous Region in northwest China. This region is one of the world's largest frontier basins. Drilling data that we collected on the well RP3–1 reveal a 2398–7066m thick sedimentary sequence, containing O...

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Published in:Journal of petroleum science & engineering 2016-10, Vol.146, p.326-339
Main Authors: Ni, Zhi-Yong, Wang, Tie-Guan, Li, Mei-Jun, Fang, Rong-Hui, Li, Qi-Ming, Tao, Xiao-Wan, Cao, Wei
Format: Article
Language:English
Subjects:
Bars
Basins
Buried history
Crude oil
Fluid inclusions
Fluids
Hydrocarbon charging age
Inclusions
Isochors intersection
Microscopy
Salinity
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Summary:The well RP3–1 lies in the Tarim Basin, which is located in the southern Xinjiang Uygur Autonomous Region in northwest China. This region is one of the world's largest frontier basins. Drilling data that we collected on the well RP3–1 reveal a 2398–7066m thick sedimentary sequence, containing Ordovician to Tertiary strata. The Yijianfang (O2yj) formation of the Middle Ordovician sequence is one of the most important reservoir stratums. The O2yj formation consists mainly of bioclast and intraclast limestones. Two different fluid types are identified by the associations they have with veinlets, which are colors caused by petroleum inclusions under UV light. Early-stage petroleum fluids are characterized by a blue-white color under UV-epifluorescence microscopy, and early-stage aqueous fluid inclusions are mainly homogenized between 54 and 102°C, with salinities ranging from 12.0 to 16.7wt% NaCl equiv. Late-stage petroleum fluids are characterized by a yellow color under UV-epifluorescence microscopy, and late-stage, aqueous-fluid inclusions are mainly homogenized between 85 and 135°C, with salinities ranging from 2.0 to 8.0wt% NaCl equiv. In order to obtain accurate measurements of both the trapped temperature (Ttrap) and pressure (Ptrap) of these fluids, we use 10 pairs of petroleum inclusions and coeval aqueous fluid inclusions to measure the intersection of a number of isochors. The Ttrap of early-stage fluids we surveyed were between 82 and 97°C, with the Ptrap ranging from 97 to 259 bars. In contrast, the Ttrap of late-stage fluids were between 141 and 170°C, with Ptrap values ranging from 430 to 608 bars. When combined with the regional buried history, the early-stage fluids charged from 422Ma to 412Ma BP, and the late-stage fluids charged from 20Ma to 6Ma BP. •The fluid inclusion research is one of the effective methods to determinate petroleum charging stages and age.•Confocal laser scanning microscopy is used to obtain the accurate vapor/liquid ratio of petroleum inclusions.•The intersection of isochores for coexisting petroleum and aqueous is used to obtain trapping temperature and pressure.•The burial history of RP3-1 well is reconstructed based on numerical modeling.•Ordovician oil reservoir in RP3-1 well has undergone two oil charging events.
ISSN:0920-4105
1873-4715
DOI:10.1016/j.petrol.2016.04.038