# Characterization of methane microseepage from natural gas reservoirs in mild climate: A case study of Xinchang gas field

## TL;DR

This study examines methane microseepage from natural gas reservoirs in a mild climate, using the Xinchang gas field as a case study to understand methane release patterns and their impact on climate.

## Contribution

The study provides new insights into methane microseepage behavior in mild climates and identifies three methane release patterns.

## Key findings

- Surface methane flux in Xinchang gas field is weak and exhibits three release patterns: continuous, episodic, and flat.
- Spiked anomalies of acid-hydrolyzed hydrocarbons and altered carbonates suggest methane migration from reservoirs to surface.
- Hydrocarbon composition and carbon isotope profiles confirm the thermogenic origin of methane.

## Abstract

Methane microseepage from oil and gas fields significantly contributes to atmospheric methane level, making it a critical factor in global climate change. Therefore, accurate monitoring of surface flux and investigating migration mechanism are pivotal to evaluating and mitigating the impact of methane microseepage. In this study, methane microseepage from natural gas reservoirs in a mild climate was investigated, using Xinchang gas field as a case study. Soil samples were collected to analyze geochemical anomalies of acid-hydrolyzed hydrocarbons (AHH) and altered carbonates (AC). Surface methane flux from natural gas reservoirs were monitored, using a greenhouse gas analyzer and static gas collection chambers. Methane release patterns and migration mechanism were then discussed. Headspace and soil gas samples were collected to determine the hydrocarbon composition and carbon isotope profile. The results indicate that surface methane flux in Xinchang gas field is weak, exhibiting three release patterns: continuous, episodic, and flat. Spiked anomalies of AHH and AC co-exist in the test area, suggesting methane migration from reservoirs to surface. Hydrocarbon composition and carbon isotope profile in headspace and soil gas samples confirm thermogenic origin of methane. These findings offer new insights into the behavior of methane microseepage from natural gas reservoirs in mild climate. It is also suggested that close monitoring and stringent regulation of methane microseepage, as well as continuous investigation on factors affecting this phenomenon, are essential to the management of geological methane emissions. The conclusions of this work align with previous studies and are applicable to managing methane microseepage from oil and gas reservoirs in a wider scope.