Bài giảng Well drilling engineering - Chapter 5: Drilling Hydraulics - Hydrostatics (Part 1) - Đỗ Quang Khánh

1 Well Drilling Engineering  Drilling Hydraulics - Hydrostatics Dr. DO QUANG KHANH 2 Drilling Hydraulics - Hydrostatics Hydrostatic Pressure in Liquid Columns Hydrostatic Pressure in Gas Columns Hydrostatic Pressure in Complex Columns Forces on Submerged Body Effective (buoyed) Weight of Submerged Body Axial Tension in Drill String s A = F A / A 3 Read:  Applied Drilling Engineering, Ch.4  (Drilling Hydraulics) HW #4 ADE # 4.3, 4.4, 4.5, 4.6 4 Drilling Hydraulics Applications Calculation of subsurface hydrostatic pressures that may tend to burst or collapse well tubulars or fracture exposed formations Several aspects of blowout prevention Displacement of cement slurries and resulting stresses in the drillstring WHY? 5 Drilling Hydraulics Applications cont’d Bit nozzle size selection for optimum hydraulics Surge or swab pressures due to vertical pipe movement Carrying capacity of drilling fluids 6 Fig. 4-2. The Well Fluid System Well Control p pore < p mud < p frac 7 Forces Acting on a Fluid Element F 1 = F 2 = F 3 = F WV = specific wt. of the fluid 8 Pressures in a fluid column At equilibrium, S F = 0 0 = F 1 + F 2 + F 3 (p = r gh) 9 Incompressible Fluids Integrating, 10 Incompressible Fluids In field units, 1’ x 1’ x 1’ cube 11 Incompressible fluids If p 0 = 0 (usually the case except during well control or cementing procedures) then, p 0 p D 12 Compressible Fluids (1) from (3) (3) (2) But, (4) p = pressure of gas, psia V = gas volume, gal Z = gas deviation factor n = moles of gas R = universal gas constant = 80.3 T = temperature, R r = density, lbm/gal M = gas molecular wt. m = mass of gas 13 Compressible Fluids p = pressure of gas, psia V = gas volume, gal Z = gas deviation factor n = moles of gas R = universal gas constant, = 80.3 psi.gal/lb-mole. o R T = temperature, o R r = density, lbm/gal M = gas molecular wt. m = mass of gas, lbm 14 Compressible Fluids From Eqs. (2) and (4): Integrating, Assumptions? 15 Example Column of Methane ( M = 16 ) Pressure at surface = 1,000 psia Z=1, T=140 F (i) What is pressure at 10,000 ft ? (ii) What is density at surface ? (iii) What is density at 10,000 ft ? (iv) What is p surf if p 10,000 = 8,000 psia? 16 Fig. 4-3. A Complex Liquid Column 17 Fig. 4-4. Viewing the Well as a Manometer P a = ? 18 Buoyancy Force = weight of fluid displaced (Archimedes, 250 BC) Figure 4-9. Hydraulic forces acting on a foreign body 19 Effective (buoyed) Weight Buoyancy Factor Valid for a solid body or an open-ended pipe! 20 Example For steel, immersed in mud, the buoyancy factor is: A drillstring weighs 100,000 lbs in air. Buoyed weight = 100,000 * 0.771 = 77,100 lbs 21 Axial Forces in Drillstring F b = bit weight 22 Simple Example - Empty Wellbore Drillpipe weight = 19.5 lbf/ft 10,000 ft OD = 5.000 in ID = 4.276 in A = 5.265 in 2 W = 19.5 lbf/ft * 10,000 ft = 195,000 lbf AXIAL TENSION, lbf DEPTH, ft 0 lbf 195,000 lbf 23 Example - 15 lb/gal Mud in Wellbore Drillpipe weight = 19.5 lbf/ft 10,000 ft OD = 5.000 in ID = 4.276 in A = 5.265 in 2 W = 195,000 - 41,100 = 153,900 lbf AXIAL TENSION, lbf DEPTH, ft 0 195,000 lbf Pressure at bottom = 0.052 * 15 * 10,000 = 7,800 psi F = P * A = 7,800 * 5.265 = 41,100 lbf 153,900 - 41,100 24 Anywhere in the Drill Collars:   Axial Tension = Wt. - Pressure Force - Bit Wt. 25 Anywhere in the Drill Pipe:   Axial Tension = Wts. - Pressure Forces - Bit Wt. F T 26 Axial Tension in Drill String Example A drill string consists of 10,000 ft of 19.5 #/ft drillpipe and 600 ft of 147 #/ft drill collars suspended off bottom in 15#/gal mud (F b = bit weight = 0). What is the axial tension in the drillstring as a function of depth ? 27 Fig. 4-11. Axial tensions as a function of depth for Example 4.9