Session 5: CASING DRILLING® Hydraulics

ENGINEERING TOPICS FOR REVIEW HYDRAULIC ISSUES System comparison Annular flow & ECD Hydraulic lift Hole cleaning Underreamer activation Mud selection MECHANICAL ISSUES Torque and Drag Casing protection Buckling Fatigue Wear Vibration Wireline Operations DIRECTIONAL DRILLING Motor selection Directional performance

CHANGING PARADIGMS: CONVENTIONAL PRACTICE TO CASING DRILLING® Our industry has a long history of developing “best practices” for conventional drilling. Natural tendency is to transfer conventional “best practices” to CASING DRILLING®. Often conventional “best practices” need to be adjusted for unique conditions of CASING DRILLING®. The following sessions are aimed at helping sort through these issues.

Tesco CDE Software is Main Engineering Calculation Tool

Functions of the Hydraulic System Transport drilled cuttings out of hole. Control near wellbore fluid. Support wellbore wall. Lubricate bit and drillstring. Power downhole motor (if used). While avoiding: Erosion of borehole wall. Fracturing the formation. Damage to production zone.

Comparison of Casing to Drillpipe & Collars EXAMPLE Hole Size = 8.75” Bit depth = 8,000 ft 9-5/8” set at 500 ft Flow rate = 450 gpm Bit Jets = 14, 14, 14, 14 11.8 PPG MUD PV = 14 Yp = 11 8,000 ft of 7” 23# Casing COMPARED TO 540 ft 6.25 x 2.812 drill collars 7460 ft of 4” Drill Pipe DP & Collars

Annular Velocity for Casing is High, but Constant DP & Collars Re = 2584 Re = 3947 All sections in turbulent flow Re = 3268

Inverted Pressure Profile (450 GPM) 1438 psi 2181 psi 7” Casing DP & Collars ECD = 13.5 ppg ECD = 12.0 ppg DPbit=487 psi

Re-designed Hydraulics for CASING DRILLING® (DECREASE FLOW TO 300 GPM, MUD WT TO 10.8 PPG & BIT JETS TO 11-11-11-11) 1042 psi 2181 psi 300 GPM 450 GPM Re = 1919 ECD = 11.9 ppg 7” Casing

PUMP HORSEPOWER HHP = P * Q / 1714 Conventional CASING DRILLING® HHP = Hydraulic horsepower P = pump pressure ,psi Q = flow rate, gpm Conventional Flow Rate = 450 gpm Delta P = 2,181 psi HHP = 572 hp CASING DRILLING® Flow Rate = 300 gpm Delta P = 1,042 psi HHP = 182 hp Diesel => 145,000 BTU/gal Assume 40% efficiency Diesel cost => $4.00/gal Savings: 390 hp $1300/day 40% fuel savings observed on TESCO CASING DRILLING® rigs.

Minimum ECD ECD Friction Flow Rate Increased flow rate reduces cuttings load in annulus. Increased flow rate increases friction in annulus. Optimum ECD Friction Cuttings load Flow Rate

Drilling with 6 1/8” DC and 4” DP Lower Flow Rate is Optimal Drilling with 7” Casing Drilling with 6 1/8” DC and 4” DP Depth = 3,200 ft Mud Wt = 8.9 Conventional operating range Casing Drilling operating range

Cuttings Transport ¥ 50 25 12.5 16.7 10 Lower limit set by Sand in water Typical muds and cuttings Annular velocity, ft/min Typical Casing Drilling range From Applied Drilling Engineering pp175

Is High Annular Velocity Detrimental? Borehole erosion may be associated with turbulent flow. Turbulence typically begins at a Reynolds Number of 2100 – 2500. Re = 928 * r * Vel * de / m r = mud density, ppg Vel = fluid velocity, ft/sec m = fluid viscosity, cp de = equivalent hydraulic diameter Dhole2 - ODpipe2 Best Estimate: de = Dhole2 + ODpipe2 – Ln(Dhole / Odpipe) Approximation: de = 0.816 * (Dhole - Odpipe)

Higher Transition Velocity for Narrow Annuli Turbulent 8.75 “ hole, 10 ppg mud, Pv = 10, YP = 5

Is high annular velocity a concern? Observations: Annular velocity is often higher for CASING DRILLING® than around drill pipe for conventional drilling. It is not unusual for the flow regime to be turbulent for CASING DRILLING® applications. No detrimental effect of turbulent flow has been observed while drilling with casing (even at 475 ft/min with water). Some publications indicate borehole wall damage once thought to be from turbulent flow is actually caused by drillstring vibration. Designing flow rate based on ECD and hole cleaning will take care of concerns about hole erosion.

Eccentric Casing in Borehole Results in Reduced ECD 30% reduction

Annular DP times end area DP from cuttings times end area Hydraulic Lift Flow in annulus lifts casing to reduce WOB Also occurs with drill pipe, but is much less Is a good monitor of hole cleaning Better indicator in vertical wells. Annular Pressure Drag Force End Force Fluid Flow Hydraulic Lift = Fluid Drag + Annular DP times end area DP from cuttings times end area

Hydraulic Lift Calculations Drag Force + End Force HL = p/4 * [Dh*Dc*Dpa + + 0.052*Dc2* (re - rm ) ] Cuttings Force HL = Hydraulic lift, lb Dh = borehole diameter, in Dc = casing OD, in Dpa = annular pressure loss, psi rm = clean mud density, ppg re = effective mud density including cuttings, ppg

VAQUILLAS A1 198 Pump-Off Observed at 2074 ft 32,000 lb Pump-Off Fill Pipe Note: Blocks were stationary Time, seconds

Hydraulic Lift Helps Monitor Condition of Hole Balling on casing Pack off on borehole wall Balled Shale from shaker after working casing.

Procedure to Monitor Hydraulic Lift Record hookload with bit off bottom, pumps off, and casing rotating slowly. Engage mud pump(s) and bring flow rate up to drilling speed and record hookload. Difference in hookload between having pumps on and off is hydraulic lift. Zero WOB Begin drilling In fast drilling formations, if ROP decreases while drilling joint down, pick up an re-zero WOB to zero out cuttings loading effect.

Back-Reaming May Help Clean the Hole 30000 Trip Pump-Off 25000 Trip Predicted 20000 Backreamed each connection 15000 Hydraulic Lift, lb. 10000 5000 1200 2200 3200 4200 5200 6200 Measured Depth, ft ANB Cattle Co

Typical Lobo Hydraulic Lift (without Back Reaming) * Predicted before drilling, constant 320 gpm Walter Despain

Hydraulic Lift Warns of Lost Circulation Vaquillas A1 198

Annular Pressure May Change as Joint is Drilled Time, minutes BMT 179 Example 1585 ft

Annular Pressure Changes While Drilling WOB Zero Harder formation Soft formation BMT 179 high speed data Time, minutes Example 2518 ft

Hydraulic Lift Affects Proper Bit Start After Connection Start rotary (breaks gels). Bring up mud pump. After pressure stabilizes, zero WOB. Set bit on bottom. Adjust RPM & WOB. Must be done each time flow rate is changed.

What Happens if flow Rate is Changed with Bit on Bottom? One-time change in WOB due to casing length change. Permanent change in hydraulic lift. Must pick up off bottom to change flow rate and re-zero WOB.

Thin Mud is Better than Reduced Flow Rate Mud A – 9.25 ppg, 18 cp, 12lb/100 ft2 Mud B – 8.9 ppg, 12 cp, 5lb/100 ft2 5,000 10,000 15,000 20,000 1000 3000 5000 Measured depth, ft Hydraulic Lift, lb Mud A - 300 gpm Mud A - 250 gpm Mud B - 300 gpm

CASING DRILLING® Mud Selection Conventional mud design uses chemistry and commercial mud products to develop fluid loss control. Rheology designed for cuttings carrying capacity at low velocities. Drilled solids and “Plastering Effect” with CASING DRILLING® provides superior fluid loss control. Operator often wants to provide “Cadillac” mud on initial use of CASING DRILLING®. Thin muds with slightly lower density are much superior for CASING DRILLING®.

CASING DRILLING® Pilot Bit Selection Best bit for conventional drilling may not be best bit for drilling with casing. Pilot bit is smaller. Flow rate is less. Nozzle size may be dictated by LCM. Typically use fewer blades on PDC bit to better accommodate flow rate and limited nozzle size. May use less aggressive bit than underreamer. Matrix bit is best to control erosion Flow may be high for bit size. Erosion control on steel bit is less effective. Erosion

Underreamer Activation Pressure Type 5 Underreamer Activation Size Pressure 4-1/2” 220 psi 5-1/2” 110 psi 7” 180 psi 9-5/8” 120 psi 10-3/4” 140 psi 13-3/8” 125 psi P1 Spring Force d1 d2 P2 Internal Jet Required activation pressure depends on piston area, rod area, spring design. Required activation pressure independent of mud properties and flow rate. Delivered activation pressure depends on flow rate, mud weight, bit nozzles, and internal nozzle. d3 P3 Bit Jets Pa

Underreamer pressures cannot be determined accurately by surface flow test due to cavitation at low back pressure.

Hydraulic Balancing Mud Motor MWD Underreamer RSS Bit Annulus

Hydraulics Balancing (The Annulus) Is the flow rate enough to clean the hole? 150 ft/min Is the flow rate low enough that it will not break down the formation? (2 ppg leakoff, 9.2 ppg mud) What is the hydraulic lift? 180 GPM Annulus 400 GPM

Hydraulics Balancing (MWD / RSS) CASING DRILLING™ typically required less flow than a conventional application for the size of directional tools used. What flow kits are available in the Is there a pressure drop requirement for the RSS 180 GPM Annulus 400 GPM 300 GPM 600 GPM MWD / RSS

Hydraulics Balancing (The Mud Motor) What are the options for a low flow motor. 7/8 power sections What is the rev/gal. Does this limit the upper flow range? 180 GPM 400 GPM Annulus 300 GPM MWD / RSS 600 GPM 300 GPM Mud Motor 550 GPM

Hydraulics Balancing (The Underreamer) Does the flow rate provide enough differential pressure to open the Underreamer? This is only an issue at very low flow rates 180 GPM Annulus 400 GPM 300 GPM MWD / RSS 600 GPM 300 GPM Mud Motor 550 GPM 210 GPM Underreamer

Hydraulics Balancing (The Bit) What is the HHP? (>2.0) How small can you run the jets? (what is the LCM program?) What’s the minimum pressure drop for RSS to operate. 180 GPM Annulus 400 GPM 300 GPM MWD / RSS 600 GPM 300 GPM Mud Motor 550 GPM 210 GPM Underreamer 310 GPM (4 x 12) Bit

Operating Flow Range for CASING DRILLING™ Hydraulics Balancing (The Sum of the Parts) 180 GPM Annulus 400 GPM 300 GPM MWD / RSS 600 GPM 300 GPM Mud Motor 550 GPM 210 GPM Underreamer 310 GPM (4 x 12) Bit Minimum 310 GPM Maximum 400 GPM Operating Flow Range for CASING DRILLING™

Hydraulics Summary Higher AV is usually not a problem. Higher ECD is manageable. Fluid loss improved by mechanical plastering. Hydraulic lift provides means of monitoring hole conditions. Thin mud should be used as much as possible. Pipe rotation increases pressure only slightly. Discharge coefficient for bit nozzle should be 1.03. CASING DRILLING® requires less horsepower resulting in fuel savings Circulating pressures can be calculated adequately with conventional flow models.