Corrosion Control of Drilling Tools Through Chemical Treatments – Effectiveness and Challenges

Abstract

Abstract With increasing demand for energy, the production of oil and gas must increase. However, increasing production is challenging because the wellbore fluids in many new fields are typically multiphase in nature with harsh chemical compositions and conditions, such as high hydrogen sulfide, carbon dioxide, and occasionally dissolved oxygen, in a high temperature and pressure environment. All this makes corrosion control a major concern, especially in the present challenging economic climate, where the risks and cost associated with corrosion may have significant impact on Health, Safety and the Environment (HSE), capital expenditure (CAPEX) and operation expenditure (OPEX) in oil & gas exploration and production. This paper addresses the chemical treatments of drilling mud for corrosion control. Corrosion mechanisms, such as mud deposit attack (pitting), corrosion due to corrosive gases of formation, stress corrosion cracking, and microbiologically influenced corrosion (MIC) are reviewed to emphasize the failure mechanisms through which the drilling fluid parameters, such as, dissolved oxygen, pH, hydrogen sulfide, carbon dioxide and chloride contents may aggravate the corrosion problem and adversely affect the reliability of the downhole equipment. These corrosion issues are addressed by design and control options such as material upgrade, coatings, cladding, and chemical treatment. However, the focus is on chemical treatments, the mechanism through which they can effectively control corrosion and their limitations. Finally, prevention and mitigation measures are discussed to address the limitations of chemical treatments, such as control measures by the drilling company for mud treatment and the development of sensors for monitoring mud chemistry during drilling operations.