Question

Question-4.125 points A drillstring made up of steel drill pipe, drilil collar and a drill bit is hanging from the hook (offbottom) in a well, as shown in the diagram below (a) Determine the tensile stress at A (at the top cross-section of drill pipe), C (at bottom cross-section 20 points of drill pipe), and B (at bottom cross-section of drill collar). [2x10 section A? Explain. [5 points] Data: Weight of the bit-500 N (b) If the yield strength (ay) for steel is 250 MPa, will the tensile stress cause plastic deformation at Unit weight of drill collar-700 N/m Length of drill collar -215 m Drill collar Outer Diameter = 80 mm Drill collar Inner Diameter 75 mm Unit weight of drill pipe- 300 N/m Length of drill pipe 2835 m Drill pipe Outer Diameter, D-115 mm Drill pipe Inner Diameter, d- 95 mm Drill pipe Drill collar

Answer 1

Tension Foste eight of drill pipe p unit ueigt x Lergth of pipe : 3oox2 335 ニ850500 N weig 사 こ 700x215 150 500 ~ A302.6 MPa (1151-95リ 4577 Mpa Tensile stress ato "6 = o, o 238 MPa

if stress induled is gy®a㎞tta n yield strength then the makerial sill depon pla htaly 303. 오Go defotnshon de formaton zone