New Environmentally Friendly Acid System for Iron Sulfide Scale Removal

Hany Gamal,Khaled Abdelgawad,Salaheldin Elkatatny

doi:10.3390/su11236727

Hany Gamal, Khaled Abdelgawad + Show 1 more

Open Access

https://doi.org/10.3390/su11236727

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Journal: Sustainability	Publication Date: Nov 27, 2019
Citations: 13	License type: CC BY 4.0

Affiliation: King Fahd University of Petroleum and Minerals

Abstract

Iron sulfide scale is a common problem in the oil and gas industry. The precipitation of the iron sulfide scale on the well completion tools or inside surface flow lines restricts the flow of the produced fluids and might affect the integrity of the pipelines or the surface and subsurface tools. Failure of the downhole completions tools will not only reduce the production rates but it might require workover and remedial operations that will add extra cost. The main objective of this paper is to evaluate a new environmentally friendly acid system (NEFAS) for iron sulfide scale removal using an actual field sample. The scale sample collected from a natural gas well is dominated by pyrrhotite (55%) in addition to calcite (21%), pyrite (8%), and torilite (6%) with minor traces of hibbingite, siderite, geothite, akaganeite, and mackinawite. High-temperature solubility tests were performed by soaking 2 g of the scale field sample with 20 cm3 of the NEFAS under static condition at 125 °C for different time periods (2, 6, 12, 18, and 24 h). The solubility results were compared with commercial solutions for iron sulfide scale removal such as hydrochloric acid (15 wt.%), glutamic acid diacetic acid (GLDA, 20 wt.%), and high density converters (HDC-3) under the same conditions. The corrosion test was performed at 125 °C for the developed solution after mixing with 2 wt.% corrosion inhibitor (CI) and 2 wt.% corrosion intensifier (CIN). The results were compared with HCl (15 wt.%) under the same conditions. NEFAS consists of 75 wt.% biodegradable acid at pH of 0.04. NEFAS achieved 83 g/L solubility of iron sulfide scale after 6 h at 125 °C under static conditions. The solubility efficiency was very close to 15 wt.% HCl after 24 h where the solubility was 82 and 83 g/L for NEFAS and HCl, respectability. HDC-3 and GLDA (20 wt.%) achieved a lower scale solubility; 18 g/L and 65 g/L respectively, after 24 h. NEFAS achieved a corrosion rate of 0.211 kg/m2 after adding the CI and and CIN compared to 0.808 kg/m2 for HCl. The new environmentally friendly biodegradable acid system provides efficient performance for the scale removal without harming the environment and causing any side effects to the operation.

Highlights

Iron sulfide scale is one of the major problems of flow assurance in the oil and gas industry
Iron sulfide scale usually causes many operational problems in the oil and gas industry as it accumulates in perforations, downhole tubing equipment, surface flow lines, and even inside the pore space of the reservoir rock itself [1,2,3]
The formation of iron sulfide scale can affect the performance of downhole tools such as artificial lift equipment

Summary

Introduction

Iron sulfide scale is one of the major problems of flow assurance in the oil and gas industry. Iron sulfide scale usually causes many operational problems in the oil and gas industry as it accumulates in perforations, downhole tubing equipment, surface flow lines, and even inside the pore space of the reservoir rock itself [1,2,3]. The formation of iron sulfide scale can affect the performance of downhole tools such as artificial lift equipment. Iron sulfide scale usually interferes with the safe operation of pipeline valving systems and rapidly erodes surface chokes because of the high erosion rate when it flows with the produced gas stream [4,5,6].

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Conclusion