Ground Detection Tool Development for Buried Legacy Wells and Its Application in the Ordos Basin

Abstract

Legacy oil and gas wells can cause safety risks for shallow underground utilization such as coal mining and gas storage, including cased wells and uncased wells. Since the 1900s, oil and gas development of many oilfields in the world has been oriented by single resource, and the lack of systematic planning for the collaborative development of deep and shallow superimposed resources has led to a large number of abandoned oil wells buried in the subsequent shallow development zones, resulting in complex geological safety and environmental risks (Jin et al. 2018; Ma et al. 2022; Yang 2023; Li 2024). In many old oilfield with gas storage, oil wells are connected with the gas storage and affect the airtightness (Wei et al. 2023). In the field of coal mine development, a large number of oil wells are abandoned due to production decline, and deep fluid can migrate to shallow coal seams through old wells, causing major safety hazards for coal mining. In addition, according to the data of proceedings of the National Academy of Sciences, abandoned oil and gas wells will release a large amount of methane, hydrogen sulfide and other substances into the air, and also bring underground toxins to the ground, polluting groundwater and the surrounding environment. According to estimates by the U.S. Environmental Protection Agency, abandoned oil and gas wells in the United States leaked about 263000 tons of methane in 2019, equivalent to the carbon emissions of more than five coal-fired power plants. It can be seen that abandoned oil wells have become a major hidden danger source restricting the safe and efficient mining of coal mines and a source of pollution (Zhai. 2025). The important premise of treating abandoned oil wells is to detect the wellhead position. Due to the burial of wellheads and the lack of accurate history data, this is difficult to accurately detect, and positioning technology for different depths and types of abandoned oil wells is facing great difficulties (Saint-Vincent et al. 2020). The United States first used ground magnetic positioning to improve the positioning accuracy. Magnetic ranging has been used to accurately locate and successfully plug abandoned oil and gas wellheads (Dorey and Rassadkin. 2021). Buried old wells were found in the Marcellus area in western Pennsylvania by using magnetic positioning on helicopters (Veloski et al. 2024). Through multi-channel surface wave analysis and surface wave backscattering analysis, buried mines were found in Kansas area of the United States (Ivanov et al. 2021).