Origin and migration model of natural gas in L gas field, eastern slope of Yinggehai Sag, China
Title
Origin and migration model of natural gas in L gas field, eastern slope of Yinggehai Sag, China
Subject
coal-type gas
crustal inorganic CO
eastern slope of Yinggehai Sag
gas-source correlation
L lithologic gas field
migration model
Description
Based on the chemical and stable carbon isotopic composition of natural gas and light hydrocarbons, along with regional geological data, the genetic type, origin and migration of natural gases in the L lithologic gas field, the eastern slope of Yinggehai Sag were investigated. The results show that these gases have a considerable variation in chemical composition, with 33.6%–91.5% hydrocarbon, 0.5%–62.2% CO2, and dryness coefficients ranging from 0.94 to 0.99. The alkane gases are characterized by δ13C1 values of –40.71‰––27.40‰, δ13C2 values of –27.27‰––20.26‰, and the isoparaffin contents accounting for 55%–73% of the total C5–C7 light hydrocarbons. These data indicate that the natural gases belong to the coal-type gas and are mainly derived from the Miocene terrigenous organic-rich source rocks. When the CO2 contents are greater than 10%, the δ13CCO2 values are –9.04‰ to – 0.95‰ and the associated helium has a 3He/4He value of 7.78×10–8, suggesting that the CO2 here is crustal origin and inorganic and mainly sourced from the thermal decomposition of calcareous mudstone and carbonate in deep strata. The gas migrated in three ways, i.e., migration of gas from the Miocene source rock to the reservoirs nearby
vertical migration of highly mature gas from deeper Meishan and Sanya Formations source rock through concealed faults
and lateral migration along permeable sandbodies. The relatively large pressure difference between the “source” and “reservoir” is the key driving force for the vertical and lateral migration of gas. Short-distance migration and effective “source – reservoir” match control the gas distribution.
Publisher
Petroleum Exploration and Development
Date
2019-06-01
Contributor
YANG, Jihai
HUANG, Baojia
Type
journalArticle
Identifier
VTCX2DBC
1876-3804
10.1016/S1876-3804(19)60028-5
Collection
Citation
“Origin and migration model of natural gas in L gas field, eastern slope of Yinggehai Sag, China,” Lamar University Midstream Center Research, accessed May 4, 2024, https://lumc.omeka.net/items/show/2219.