A New Mechanical Tool and Method to Accessing Casing-Casing-Annulus to Remove Compromised Cement and Injecting a New Sealant

Abstract

Abstract This work presents experimental studies on a new tool concept to address casing-casing-annulus (CCA) pressure leak challenges in the drilling industry. The new method uses an intervention-type tool that allows for exiting the casing, cleaning cement behind, and injecting any required sealant to block fluid migration on the annular side. Addressing such CCA challenges is essential for increasing the production time and maintaining wellbore pressure integrity. A combination of 3D modeling and experimental studies is used to evaluate the feasibility of the new concept for addressing CCA fluid migration challenges. This study focuses on the development and evaluation of a tool that allows accessing and sufficiently cleaning cement in multiple CCAs. We have successfully tested a scaled tool. This tool can punch a small hole in a casing at a unique angle and clean cement behind it by drilling spirals on the annular side. The new method for accessing the annular side of the casing and cleaning cement behind it has been developed and successfully tested using scaled model rigs. Studies have involved an early proof of the concept in plastic and steel. We have also simulated cement with fluid communication channels behind the casing with a successful attempt of removing it. The experimental test results are being used to further develop a robust, downhole field-deployable tool and method that captures the essential features required to access and operate in CCA areas. The current study suggests that a significant section of cement can be removed by the proposed method: One small-diameter hole is drilled in the casing, and then a cement removing assembly is run in a spiral motion on the annular side of this casing. A suitable sealant can be injected in the created void in cement to stop potential fluid migration. This experimental study suggests that the CCA can be accessed and resealed with a minimum time and equipment if required. This CCA milling-injection system (patent pending) utilizes a novel, easily-deployable tool. This tool enables milling access into the annular side of designated casings, and enables cleaning the cement behind it. The new system only mills one hole in the casing limiting its damage and providing the ability to clean a significant section of the cement at the desired depth. This helps address potential CCA leaks, saves time and cost.