New Ways of Handling and Running C.R.A. Tubulars Prevent Corrosion in H2S and CO2 Environments

Abstract

Abstract In a corrosive downhole environment, the service life of a completion can be severely reduced if no precautions against corrosion are taken. Pipe made of corrosion resistant alloys (C.R.A.) is used to minimize corrosion. An analysis of various corrosion mechanisms shows that the surface integrity is an important factor for corrosion prevention [3]. Conventional spider and elevator inserts as well as conventional hydraulic power tong dies made of steel cause die marks that support corrosion. A gripping system named Micro-Grip distributes the required load equally onto a large number of small peaks, minimizing the indentation of each single peak [1-3]. This system is available for power tongs as well as accessories such as safety clamps. In corrosive downhole environments, such as those that contain relevant quantities of CO2 and/or H2S at elevated temperature, C.R.A. materials with a high chromium content are often selected for the tubular and related accessories. In these environments using C.R.A., companies developed a "zero marking" policy especially for the makeup of the connections. In connection with higher torque values, this required a new gripping technology. A so-called Diamond-Grip gripping system was developed, together with a hydraulic gripping system for the power tong that delivers the required radial forces. The paper describes this new gripping technology and a series of tests that were performed within pre-qualification processes for C.R.A. handling and running tenders in Qatar as well as in the Gulf of Mexico. The tests showed that there is no negative impact of Diamond-Grip and Micro-Grip in regards to corrosion under the severe influence of H2S and CO2.