Tapered Rod String Analysis

Static loads, stress and stretch for a sucker rod string made of up to four rod sizes. Each taper is one row, top taper first; unused rows are left blank. For each taper it returns the rod area, the weight in air and in the well fluid, the load and stress at the top of the taper and the taper's stretch. For the string it returns the static peak and minimum polished rod loads, the highest rod stress and the total stretch.

Tapered Rod String Analysis Excel workbook
TaperedRodString.xlsx
Tapered Rod String Analysis: Guide sheetTapered Rod String Analysis: Rod String sheet

The fluid load acts over the net lift, the depth from surface to the fluid level in the annulus: the pump depth (the length of the rod string) less the fluid level above the pump. The fluid gradient is 0.433 psi/ft × SG, so specific gravity is the only fluid input. The top of each taper carries the fluid load plus the buoyant weight of that taper and every taper below it. Stretch counts the fluid load, the taper's own weight and the weight of the tapers below, with rod weights taken in air as PO.RP.Rod.Stretch.RodWeight does, so a string of one rod size gives the single-size answer. No API RP 11L dynamic factors and no fatigue check.

Inputs

Named cells you can edit — every result recalculates from them.

Name Description Default Unit
TRS_Dp Plunger diameter 1.5 in
TRS_Hsub Fluid level above pump (submergence) 500 ft
TRS_SG Fluid specific gravity 0.85 —
TRS_Diameters Rod diameter of each taper, top first (four rows) 0.875, 0.75, blank, blank in
TRS_Lengths Length of each taper, top first (four rows) 2000, 3000, blank, blank ft

Calculated from them: TRS_Depth (pump depth, the rod string length), TRS_NetLift (net lift), TRS_G (fluid gradient) and TRS_Fo (fluid load on the plunger).

2 sheets, shown with the values the file opens with

A
1 Tapered Rod String Analysis
2
3 What this workbook does
4 Calculates static loads, stress and stretch for a sucker rod string made of up to four rod sizes (a tapered string). Each taper is one row of the Rod String sheet, top taper first. For each taper it returns the rod area, the weight in air and in the well fluid, the load and the stress at the top of the taper, and the taper's stretch. For the whole string it returns the static peak and minimum polished rod loads, the highest rod stress and the total stretch.
5
6 Method
7 Fluid load on the plunger = plunger area × net lift × fluid gradient. The net lift is the depth from surface to the fluid level in the annulus: the pump depth (the length of the rod string) less the fluid level above the pump. The fluid standing over the pump pushes up on the plunger from below, so only the column above that level loads it. The fluid gradient is 0.433 psi/ft × specific gravity.
8 The top of each taper carries the fluid load plus the buoyant weight of that taper and of every taper below it. The top taper carries the whole string, so the load at its top is the static peak polished rod load, and the minimum polished rod load is the buoyant weight of the string. Stress is the load at the top of a taper divided by its rod area, which is where each rod size carries its highest load.
9 A taper stretches under the fluid load, its own weight and the weight of the tapers hanging below it: (fluid load + weight below) × L / (A × E) + own weight × L / (2 × A × E), with E = 30,000,000 psi. Rod weights are taken in air, as PO.RP.Rod.Stretch.RodWeight does for a single-size string, so a string of one rod size gives the single-size result however it is split into rows.
10
11 How to use it
12 1. Rod String — edit the blue cells on a yellow background: plunger diameter, fluid level above the pump and specific gravity, then each taper's rod diameter and length, top taper first. The pump depth is the total length of the tapers. Leave unused taper rows blank.
13 2. The Rod String sheet prints on one page (File › Print).
14
15 Limits
16 • Static loads only: no API RP 11L dynamic factors (rod acceleration and vibration) and no friction. In a running well the peak polished rod load is higher and the minimum lower than shown.
17 • No fatigue check (modified Goodman diagram) and no taper design from API tables: enter the taper lengths you want to check.
18
19 Requirements
20 The workbook calls Petroleum Office functions (PO.RP.*). It opens with the example results already calculated; recalculating after an edit needs the Petroleum Office add-in.
Opens inNeeds the Petroleum Office add-in: its PO functions show #NAME? without it once Excel recalculates.
Functions used PO.RP.Load.FluidLoadPO.RP.Load.MPRL.SimplePO.RP.Load.PPRL.SimplePO.RP.Rod.AreaPO.RP.Rod.MaxStressPO.RP.Rod.Stretch.FluidLoadPO.RP.Rod.Stretch.RodWeightPO.RP.Rod.WairPO.RP.Rod.Wbuoy
FileTaperedRodString.xlsx, 10 KB
CategoryProduction
For agents and tools Structure (.json) · Descriptor (.md)
Tags:
rod-pumpsucker-rodrod-stringtaperedstressstretchpolished-rod-loadartificial-lift

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