Bài giảng Well drilling engineering - Chapter 7: More casing design - Đỗ Quang Khánh

1 Well Drilling Engineering  More Casing Design Dr. DO QUANG KHANH 2 Casing Design - cont’d Casing Threads Using the Halliburton Cementing Tables Yield Strength of Casing (in tension) Burst Strength Effect of Axial Tension on Collapse Strength Effect of Pipe Bending Effect of Hydrogen Sulfide Selection of Casing Settling Depths 3 Read:  Applied Drilling Engineering, Ch.7 HW # 4 Rounded Threads * 8 per inch ~ Square Threads * Longer * Stronger Integral Joint * Smaller ID, OD * Costs more * Strong 5 6 7 Tensile force balance on pipe body Example 7.1: Compute the body-yield strength for 20-in ., K-55 casing with a nominal wall thickness of 0.635 in . and a nominal weight per foot of 133 lbf/ft . 8 Pipe Body Yield Strength where 9 Pipe Body Yield Strength Example What is yield strength of body of 7” , 26 #/ft , P-110 casing? 10 Internal Yield Pressure for Pipe (Burst) where F P = DLP F T = 2tLY P DLP = 2tLY P F P F T 11 Example For 7” , 26 #/ft P-110 pipe 12 Ellipse of Plasticity 13 TENSION COLLAPSE 14 15 D L = (R + r) Dq - R Dq Dq R + r R Length of arc, L = R Dq rad (7.14a) L 16 Figure 7.14 - Incremental stress caused by bending of casing in a directional well The area of steel, A s , can be expressed conveniently as the weight per foot of pipe divided by the density of steel. For common field units, Eq. 7.14a becomes 17 Example F ab = 64 * 5 * 7 * 35 = 74,400 lbf F ab = 74,400 lbf 18 R c = 22 ( R c = 22 corresponds to a yield strength of about 90,000 psi ) 19 20 21 22 23 Production casing design load for burst. 24 Production casing design load for collapse. 25 Tensile Strength of Casing What is the maximum length of N-80 casing that can hang in an air-filled wellbore without exceeding the minimum yield strength of the pipe? 26 Tensile Strength of Casing What is the maximum length of N-80 casing that can hang in an air-filled wellbore without exceeding the minimum yield strength of the pipe? F W F MAX = 80,000 A s = A s L MAX 490/144 L MAX = 80,000 * 144/490 L MAX = 23,510 ft { With a 1.8 design factor, L MAX = 13,060 ft }