GENERALIZATION OF THE API RP14E GUIDELINE FOR EROSIVE SERVICES

The commonly used practice for controlling sand erosion in gas and oil producing wells is to limit production velocities following the provi sions of American Petroleum Inst. (API) RP14E. This guideline contains a procedure to calculate a threshold velocity, the flow velocity belo w which an allowable amount of erosion occurs. While providing the adv antage of computational ease, the approach has some disadvantages. One is that, while many factors influence the erosion rate, API RP14E inc ludes only one factor, the density of the medium. Thus, such factors a s flow geometry, type of metal, sand size, and Reynolds number are not accounted for. Another disadvantage is that API RP14E does not specif y the tolerable amount of erosion, in terms of loss of wall thickness. A method is presented to overcome these disadvantages by (1) accounti ng for many of the physical variables in the flow and erosion processe s and (2) including a way to predict the maximum penetration rate for sand erosion. The capabilities of the method are evaluated by comparin g pre dieted penetration rates with experimental data found in the lit erature. In this paper, the method is applied to calculate threshold v elocities. The computational procedure allows an allowable amount of e rosion to be specified in mils per year for elbows, tees, and direct-i mpingement geometries. Threshold flow-stream velocities are calculated for carrier fluids of crude oil, water, and methane at elevated press ure. Resulting threshold velocities are presented for a range of sand sizes, pipe diameters, sand production rates, and methane pressures. R esults show that threshold velocities for single-phase gas flows are m uch lower than those for single-phase liquid flows.