Characteristics and Origin of Natural Gases in the Puguang and Maoba Gas Fields, NE Sichuan Basin, China

Abstract

Northeastern Sichuan Basin is one of the most significant areas for natural gas exploration in China, and Puguang and Maoba are the two most important and typical gas fields there. The common characteristics of the natural gases in the Puguang and Maoba gas fields include extremely high dryness, high H 2 S contents, high δ 13C 1 values, with a wide range of δ 13 C 2 values. Based on gas composition and stable carbon isotope values, natural gases in the study area are classified into three genetic groups, derived from type III kerogen, type II kerogen and those with a complex origin. The latter group is most likely the result of mixing between low maturity ethane inherited from earlier oil accumulation and high maturity methane generated from subsequent in-reservoir oil cracking and thermochemical sulfate reduction. In conjunction with regional source rock data, the Upper Permian Longtan Formation is considered to be the main source rock for the gases in the Feixianguan-Changxing reservoirs of the Puguang and Maoba gas fields.

Characteristics and Enrichment Factors of Supergiant Lower Cambrian Longwangmiao Gas Reservoir in Anyue Gas Field: The Oldest and Largest Single Monoblock Gas Reservoir in China

“…Although a total of 138 bituminous veins as thick as 15.3 m had been discovered in the Sinian-Lower Cambrian strata in the Longmenshan area in the Sichuan Basin, showing a good hydrocarbon potential (Wang et al, 2011). Large discovery had not yet been made in the exploration of Sinian-Lower Palaeozoic of the Sichuan Basin over 40 years since a Sinian gas field was discovered in the 1960s (Gao et al, 2012;Hu et al, 2013). Until 190.68 × 10 4 m 3 /d gas was obtained from the Lower Cambrian LF in Well Moxi 8 in 2012, a great breakthrough was made in the exploration of Sinian-Lower Palaeozoic oil and gas in the Sichuan Basin.…”