Title: Petroleum inclusions in and organic geochemical characteristics of source rocks in Leiyang Depression
Abstract: Using fluorescent microscopy at higher magnification,relatively abundant tiny petroleum inclusions were discovered in the Shuinan Member dark mudstones of Lower Cretaceous Leiyang Formation,Leiyang Depression. Most of them were distributed in detrital minerals and authigenic minerals of sandy mudstones. The dark mudstones were considered to be excellent oil and gas source rocks with an enrichment of alginite and amorphous kerogens. Organic geochemical analyses show that they had a TOC of 1.14% to 3.00% ,S1 of 0.16 mg/g to 0.83 mg/g,S2 of 4.45 mg/g to 22.8 mg/g,and IH of 390 mg/g to 671 mg/g,respectively,indicating a good potential of hydrocarbon generation. Biomarker assemblage of extracted organic matter from mudstones demonstrated a predominance of phytane with a Pr/Ph ratio of 0.25 to 0.43,relatively abundant tricyclic terpenoids and pentacyclic terpenoids characterized by high concentration of norhopane and gammacerane,low content of Ts and Tm,the V -type distribution of regular steranes and 4-methylsteranes,and low maturity as revealed by sterane and terpane parameters,suggesting alginite as a main contributor to organic source and an anoxic depositional environment with a salty and stratified water body. Homogenization temperatures of petroleum inclusions in source rocks ranged from 78.5 ℃ to 82 ℃ and its trapped pressures calculated from PVTsim simulation were from 281.2× 105 Pa and 282.5× 105 Pa. Based on tectonic evolution and results of paleotemperature and paleopressure reconstruction,it can be deduced that,before tectonic uplift in the early Himalayan movement,the Shuinan Member mudstones of Lower Cretaceous Leiyang Formation should experience a hydrocarbon generation and expulsion process with a temperature of 82 ℃ and a buried depth of above 2800 m. Comprehensive studies from organic geochemistry of source rocks and petroleum inclusions provide new insights on the assessments of petroleum exploration in this basin.
Publication Year: 2008
Publication Date: 2008-01-01
Language: en
Type: article
Access and Citation
Cited By Count: 1
AI Researcher Chatbot
Get quick answers to your questions about the article from our AI researcher chatbot