Autoclave design for high pressure-high temperature corrosion studies

Abstract

Purpose – The purpose of this paper is to develop an autoclave that can be used to assess corrosion behaviour of suitable material in high-pressure–high-temperature (HPHT) environments. Many new discoveries of oil and gas field are in HPHT environments. The development of such fields requires appropriate selection of materials that are able to withstand not just the service loads but also corrosive production fluids in the HPHT environment. Design/methodology/approach – The exposure of material samples to elevated pressure and temperature is usually done using an autoclave. The suitability of an existing autoclave for HPHT corrosion studies is provided together with suggestions on necessary design modifications. An alternative design of the autoclave is proposed based on functionality requirements and life cycle cost assessment. Findings – It is concluded that the existing autoclave was unsuitable for HPHT corrosion tests, and modifications were very expensive to implement and/or not foolproof. A new autoclave was designed, manufactured, tested and successfully used to study the effect of aqueous solution on the corrosion of a pipe subject to a combination of axial tension, internal pressure and elevated temperature. Research limitations/implications – The maximum design pressure of 15 MPa is more than sufficient for high-pressure corrosion studies in aqueous solution where partial pressure of the dissolved gas is one of the main controlling parameters. However, the design pressure is only suitable for corrosion studies in a seawater environment of up to 1,500 m water depth. Originality/value – A new design of autoclave together with all the necessary piping, assembly and control system is proposed for HPHT corrosion studies. The autoclave can be used as standalone or integrated with a mechanical testing machine and thus enables corrosion studies under a wide range of loading.