Work

Investigating the mechanisms for the gradual and anomalous pattern of increasing H2S content in the Dalan gas field, Coastal Fars of Southern Iran

Year: 2025

Type: article

Abstract: The Coastal Fars is the most critical natural gas production region in southern Iran. In recent years, an increasing trend in H 2 S content has been distinguished in some fields in this region. The anomalous increasing trends have been observed in the eastern and western parts of the Dalan gas field. A comprehensive study of gas geochemistry, petrography of rock samples, and production data was performed to investigate the H 2 S generation mechanisms and disclose the reasons for the anomalous H 2 S increasing pattern in this field to find the best solution strategy. The geochemical analysis of produced gases and petrography studies revealed that H 2 S was generated due to the thermochemical sulfate reduction (TSR) process in the Dalan field. The sulfate ions in this process were sourced from anhydrite in the Lower Dalan and Nar members. Production data revealed the anomalous pattern of increasing H 2 S content in this field. In response to the pressure drop, the rising gas-water contact (GWC) caused the shortest distance between the aquifer and production interval in the Dalan-3 well from the west of the field. The degassing of the dissolved H 2 S from the water caused increasing H 2 S in this well. The relationship between the H 2 S content, produced water, and salinity confirms this conclusion. In contrast, at the Dalan-6 well from the east of the field, there was no direct correlation between salinity and H 2 S concentration. Despite the rise of the GWC level due to pressure drop, the water zone could not affect the production intervals in the Dalan-6 well. Production logs revealed channeling behind the casing, likely due to poor cement quality, facilitated the connection of the production intervals in the Upper Dalan with the Nar member and caused the H 2 S concentration increase in the Dalan-6 well. This paper revealed the increasing pattern of H 2 S content in a field can be irregular in different wells.

Source: Journal of Petroleum Exploration and Production Technology

DOI: 10.1007/s13202-024-01923-3

Authors: Rahim Bagheri Tirtashi, Ahmad Reza Rabbani, Morteza Asemani, Abasali Nikandish

Institutions: Amirkabir University of Technology, Kharazmi University, Iranian Central Oil Fields Company (Iran)

Language: English

Topic: Hydrocarbon exploration and reservoir analysis

Subfield: Mechanics of Materials

Field: Engineering

Domain: Physical Sciences

SDG: Affordable and clean energy

Open Access status: gold

Estimated APC paid: $2,390