An Integrated Governance Technology Based on Magnetic Steering System for Cementing Plug in Open-Hole Section of Underground Gas Storage: Theoretical Analysis and Field Test

Abstract

Abstract The paper describes a comprehensive control technology based on a magnetic steering system for plugging the cementing plug in open holes without clear beacons in underground gas storage (UGS). Utilizing depleted oil and gas reservoirs for natural gas storage is an important approach towards achieving carbon neutrality. Plugging old wellbores that affect sealing performance is prioritized according to relevant standards. The challenge with open holes with cement plugs is that there are no clear beacons in the wellbore, and the extent of compaction is unknown. Accurate positioning of the cement plug is crucial and the current technical methods, such as electromagnetic and acoustic waves, have limitations. Magnetic steering technology, which is mature and widely used in drilling complex structure wells, requires beacons like pipes and metal pipe strings. On the other hand, acoustic positioning technology is still experimental and suffers from large distance and azimuth errors due to the attenuation characteristics of acoustic waves in heterogeneous formations. These existing technologies are unable to directly position open holes with cement plugs. The paper proposes a comprehensive control technology based on the magnetic steering system. It starts by measuring the positional relationship between the drilling wellbore and a magnetic reference wellbore using the magnetic steering system. The skew data is then used with the ISCWSA model to determine the location of the plugged wellbore and the magnetic reference wellbore. By calculating the relative positional relationship between the drilling wellbore and the plugged wellbore, the cement plug reentry can be achieved within the error ellipse range below the sidetracking point. After reentry, specific work such as crushing, element logging, caliper logging, and full hydrocarbon gas detection is performed to verify if the wellbore is still in the original position and if the caprock is properly squeezed and plugged. The comprehensive treatment technology plan was tested on five wells in the Bohai Bay, successfully addressing the problem of positioning open holes with cementing plugs. The process system expands the field of magnetic guidance technology and demonstrates significant industrial application value. It provides a means of plugging complex old wells.