ABSTRACT

Oil and gas companies apply different methods to limit erosion-corrosion of mild steel lines and equipment during the production of hydrocarbons from underground reservoirs. One of the frequently used methods is limiting the flow velocity to a so-called “erosional velocity,” under which it is assumed that no erosion-corrosion would occur. Over the last 40 years, the American Petroleum Institute recommended practice 14E (API RP 14E) equation has been used by many operators to estimate the erosional velocity. The API RP 14E equation has become popular because it is simple to apply and requires little in the way of inputs. However, due to its simplicity the API RP 14E equation has been frequently misused through generalizing the observed empirical c-factors to conditions and applications where it was invalid. Even when constrained to its defined conditions and applications, the API RP 14E has some serious limitations; such as not providing any quantitative guidelines for estimating the erosional velocity in the two commonest scenarios in the field, when solid particles are present in the production fluids and when erosion and corrosion are both involved. Field data showed that the API RP 14E equation is inadequate for estimating the erosional velocity and other operating parameters involved in erosion, corrosion and erosion-corrosion such as material properties, flow geometry, flow regime, sand production rate, and concentration of corrosive species; all need to be accounted for in establishing a correct estimation of the erosional velocity.

INTRODUCTION

Erosion of carbon steel piping and equipment is a major problem during the production of hydrocarbons from underground reservoirs. It becomes even more complicated when electrochemical corrosion is involved. Operators continuously dig deeper in the reservoirs or use proppants and reservoir fracturing techniques in order to maintain production rates. Thus, deeper aquifers are encountered, water cuts are increased, more multiphase streams are produced, and more solids and corrosive species are introduced into the production, transportation and processing systems, which in turn leads to increased erosion-corrosion problems.1-4

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