Open AccessPreventing sour gas kicks during workover of natural gas wells from deep carbonate reservoirs with anti‐hydrogen sulfide fuzzy‐ball kill fluid
Author(s) -
Yan Zhenfeng,
Okere Chinedu J.,
Zeng Xinghang,
Yao Zhonghui,
Su Guandong,
Gan Maozong,
Fu Yarong,
Tao Xiujuan,
Zheng Lihui
Publication year - 2022
Publication title -
energy science and engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.638
H-Index - 29
ISSN - 2050-0505
DOI - 10.1002/ese3.1158
Subject(s) - wellhead , hydrogen sulfide , petroleum engineering , workover , brine , natural gas , sour gas , carbonate , chemistry , geology , materials science , sulfur , metallurgy , organic chemistry
Workover of natural gas wells in deep carbonate gas reservoirs (DCRs) is facing multiple challenges such as fluid leakage, high temperature, and hydrogen sulfide (H 2 S) gas kick. Hence, well‐killing fluids with satisfactory plugging ability, high‐temperature tolerance, and anti‐H 2 S ability are necessary. In this study, we developed a multifunctional anti‐hydrogen sulfide fuzzy‐ball kill fluid (AFKF) for preventing sour gas kicks in DCRs. The performance of the AFKF was optimized and analyzed via experiments and verified through a case study application. The results showed that the fuzzy‐ball structures in the AFKFs demonstrated good stability under extreme H 2 S aging. The rate of change of certain critical rheological parameters such as apparent viscosity, dynamic plastic ratio, and density of AFKFs before and after hot rolling were no more than 5%. After plugging the fractures with the AFKFs at temperatures between 110°C and 150°C, the inlet driving pressure of the fractures increased from 20.73°C to 21.07 MPa, and no fluid loss was observed at the core outlet after a secondary displacement of formation water. The permeability recovery rate was greater than 90%. Application of AFKF in well DW‐2 showed that the shut‐in pressure rose to 24.6 MPa with no trace of H 2 S gas at the wellhead after 4 days. The investigation of the H 2 S mitigation mechanisms revealed that the plugging of the seepage channels by AFKFs forms interconnected bonds that improve the mechanical properties of the reservoir. Additionally, AFKFs absorb H 2 S gases by protonation and dissociation reactions which convert the hazardous gas into an aqueous solution of sulfide ions (S 2− ). The proposed AFKF has proven to be effective means of mitigating H 2 S in DCRs, and minimize the negative impacts of environmental polution, health risks, and equipment corrosion.