Casing & Cementing Project (Drilling, Petroleum Engineering)

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Drilling Engineering

Class 8

Casing

• What is casing?

• Pipe that is API certified for its specific application

• Why is casing set?

• Zonal Isolation when cemented in place

• Casing point selection

• Regulations

• Area Geology

• Formation Pressures

• As the operator, who decides on casing points?

Casing

• API casing is available in standard sizes from 4-1/2” to 20” OD

• Usually steel but can be aluminum, fiberglass, stainless steel, plastic, titanium etc.

• One piece of casing pipe is referred to as a “joint” of casing

• Casing length is dependent on the “range” of pipe • Range-1: 18-22ft

• Range-2: 27-30ft

• Range-3: 38-45ft

• Casing Threads are defined by the coupling type • API Threads

• LTC: Long thread coupling

• STC: Short thread coupling

• BTC: Buttress thread coupling

• Semi & Premium Threads • See VAM Presentation

Casing

• Casing Components

• Casing

• Size, Weight, Grade, Threads

• 9-5/8" 53.5# P-110 LTC Rg 3

• See Casing Data Chart

• What is Drift Diameter?

• Pup Joints

• Float Collars

• Float Shoe

• Guide Shoe

• Centralizers

• Baskets

• Scratchers/Scrapers 4

Casing

• Running Casing

• Bales/Elevators

• Power Tongs

• Torque Turn

• Calculate weight and Hookload HL

• Calculate collapse, how often should you fill the pipe?

• Is the pipe taking the proper amount of fluid to fill? CSGcap • Is the proper amount of fluid coming back to the pits as the

casing is run in the hole? CSGcap & CSGdisp • Once casing is landed, circulated mud. Calculate B/U

Casing • Centralization

• Vertical Wells

• Never truly vertical, usually spiral

• Typically use bow spring type centralizers

• There are state regulations on centralizer placement

• The shoe is very important to be centralized

• Horizontal Wells

• Balance between too many and not enough centralizers

• Many types: rigid, floating, bow spring, bladed, spiral bladed, etc.

• Centralizer design software can model the well as drilled and suggest centralizer placement

• High dogleg areas need more frequent centralizers to obtain sufficient standoff

Casing

• Stand-off

• Pipe Stand-off is a major contributor to hole cleaning, mud removal, and cement quality.

• % 𝑆𝑡𝑎𝑛𝑑𝑜𝑓𝑓 = ൗ𝑊𝑛 𝑅2−𝑅1 ∗ 100%

Casing

• Stand-off

• The Stand-off formula results a percentage, where 0% represents the pipe in contact with the wellbore wall. 100% represents the pipe is perfectly centered in the well.

• When the pipe is not centered, the wider portions will promote flow due to less resistance. There can be pockets of cuttings or mud in the tighter areas causing contamination to cement.

• Modeling software can analyze the As Drilled deviation surveys and generate a casing centralization plan with the casing’s properties.

• 100% standoff is desirable but not realistic

• Industry minimum standard is 67% over the entire well

Casing

• Casing Centralizers

• Casing Baskets

• For lost circ zones

• Scratchers

• For mud cake removal

• Float/Guide Shoe

• Float Shoe will guide and has a one way valve

• Guide Shoe will guide the casing string down the well

Running Casing

• Manual Tongs were commonly used, but few are used today.

• Power Tongs are used to make up (torque) casing joints

Running Casing

• Casing Running/Rotating Tool (CRT)

• Commonly used in ERD wells

• Used to rotate the casing string to achieve further depths in the lateral section

• Allows the rig to pump fluid and circulate the casing

• The combination of rotating and circulating greatly reduces friction

• Static friction is overcome- Kinetic friction is lower

• The fluid gel strengths are broken down due to movement

• Show Tesco video 12

Casing Connections

• API Connections • First developed thread connections • Cheap, easy to machine, designed to seal liquids • LTC, STC, & BTC • Weakest point in the casing string

• Premium Connections • Developed after years of API thread failures • Connections are stronger than pipe body • Designed to seal liquid & gas • Very expensive

• Semi-Premium Connections • Developed most recently bc ‘Premium’ is so expensive • Much stronger and more reliable than API connections • Much cheaper than Premium • Designed for liquids and limited gas

• See Vallourec & VAM Presentation 13

Cement

• Why cement?

• Zonal Isolation

• Isolation for completions frac stages

• Goals

• Protect ground water

• Prevent gas migration

• Stimulate more reservoir

• Protect casing from corrosion

• Increase life of well

• Two Types of Cementing Techniques

• Grouting- Utilizing gravity to pour cement from surface down the annulus

• Displacement- Pumping cement down the inside of casing and using a plug to push cement into the annulus from the bottom of the well to surface

Cement

• What is considered a good cement job?

• Poor isolation is contributed by:

• Channeling

• Micro annulus

• Mud contaminated cement

• In horizontal and deviated wells:

• Mud removal is the most difficult factor to overcome to achieve a good cement bond

Cement

• How to improve the quality of the cement job • Casing movement

• Casing centralization

• Hole and mud conditioning

• Mud properties

• Effective spacers

• Fluid velocity while pumping

• Wiper plugs

• Quality of shoe- single or double floats

• Circulating after casing is landed • Lowers the viscosity, PV, the fluids resistance to flow

• Lower MW if at all possible

• Clean wellbore

• Calculate B/U

Cement

• Casing Movement

• Requires special equipment

• CRT with rotating cement head

• Pipe reciprocation/rotation

• At least one should be practiced if possible

• Energy is needed to break-up the gelled mud

• Mechanical interaction between the pipe and wellbore

• Changes the flow paths

• Monitor Torque and Drag while moving pipe

• Casing Centralization

• Enhances mud removal thus better cement bonds

• Wider annulus promotes flow 17

Cement

• Cement Blend and Requirements

• State regulations specify the type and properties of cement to be used

• Typically require Class A or H cement to be used

• Compressive strength of 500psi before any disturbance of the casing, commonly 8-12hrs: time is crucial in operations

• Compressive strength of 1250psi in 72hrs

• Limited use of Calcium (CaCl or KCl) in blends (Disturb surface water)

• Thickening time of gels

• Little to zero free water

Cement

• All cement blends are lab tested and come with quality reports

• Cement should be tested in the lab to mimic field conditions

• Water temperature- how does this effect cement?

• Formation temperature

• Quality of water used; take samples from location

• How do Chlorides effect cement? (brine, saltwater)

• Pumps times should be calculated based on volumes and pump truck output

• We want the cement to thicken quickly to minimize waiting time, but we need it to remain “pump-able” until the job is complete plus a safety factor (70 bc time)

• Two stage cement jobs (lead & tail) can help reduce ECD and lower costs

• See example Lab Test Results & Cement Additives on ecampus

Cement Procedures

1. Once the casing is landed, the driller will begin circulating the well with mud while monitoring TQ/Drag. Pump highest flow rate possible through the shoe, with at least several B/U.

a) The mud engineer will monitor mud properties. Attempt to lower PV and MW if at all possible. Why?

b) Derrickman will monitor the shakers for cuttings/debris return and notify driller of anything abnormal.

c) Floor hands/Motorman will rig down the power tongs and clean the rig floor.

2. While circulating, the cement crew will stage their trucks and equipment, plumb into water tanks and cement silos, then begin to batch mix the spacer.

Cement Procedures

3. Next step is to hold a cement job safety meeting a) Communicate the plan/procedure to everyone on location b) Define each persons roles/responsibilities c) Talk through pump schedule going over calculations with cement supervisor

4. Stop circulating, rig up cement head equipment, and plumb well into cement pump truck

5. Cement crew will fill lines with water and pressure test equipment 6. Begin pumping following a pump schedule

c) Spacer with Chemical Wash d) Lead Cement Slurry e) Tail Cement Slurry (if two stage) f) Drop wiper plug and displace with water g) Slow down the pump rate as plug approaches shoe h) Land the plug with landing pressure i) “Bump” the plug with ~500psi over landing pressure j) Check that the floats hold: release pressure and measure water returns. Should

get no more than a few bbls back k) Bleed pressure to zero and wait on cement, WOC 21

Cement

• Spacer- A liquid (typically water & Barite), weighted heavier & more viscous then the circulating mud, that pushes the mud out of the well ahead of the cement. In OBM systems it will help water wet the casing & formation and enhance the cement bond. Recommended to have 10min contact time or 1,000ft of coverage.

• Wash- A low dense liquid chemical pumped to break up mud cake off the wellbore and treat the formation for a better cement bond. 22

Cement Calculations

• Converting cement slurry volume to sacks of cement

• Cement blends will have a slurry yield (given)

#𝑠𝑘𝑠𝐶𝑀𝑇 = 𝑉𝐶𝑀𝑇(𝑏𝑏𝑙𝑠) ∗ 5.6146(

𝑓𝑡3

𝑏𝑏𝑙 )

𝑆𝑙𝑢𝑟𝑟𝑦 𝑌𝑖𝑒𝑙𝑑 ( 𝑓𝑡3

𝑠𝑎𝑐𝑘 )

• Cylindrical Volume

𝑉 𝑏𝑏𝑙𝑠 = 𝑑2 𝑖𝑛

1029.4 ∗ 𝐿(𝑓𝑡)

Cement Calculations

• Annular Cylindrical Volume

𝑉 𝑏𝑏𝑙𝑠 = 𝑑𝑜2 𝑖𝑛 − 𝑑𝑖2(𝑖𝑛)

1029.4 ∗ 𝐿(𝑓𝑡)

• Lifting force on the casing

𝐹𝐿 = 𝑊𝑐𝑠𝑔 ∗ 𝐷 ∗ 𝐵𝐹 − (𝑃𝐿 ∗ 𝐴)

Where, 𝐹𝐿 is the net lifting force in lbs: denote downward as positive

𝑊𝑐𝑠𝑔 is the air weight of casing in lbs/ft, D is the casing set depth in

ft, BF is buoyancy factor, 𝑃𝐿 is the pressure required to land the wiper plug at the shoe in psi, A is the cross sectional area of the shoe in inches. 24

Cement Calculations • Example: A. Calculate how many sacks of cement is required for

the single stage cement job below. Assume perfect hole (no excess), and cement to surface

20” 94ppf J-55 STC Rg2 casing is previously set at 800’

12-1/4” hole TD= 3500’

9-5/8”, 36#/ft, J-55 Casing run to 3450’

Yield: 1.2 cu.ft/sk; 8.5gal H2O per sack for 14ppg slurry

Cement Calculations

• Example cont’d

B. How many sacks of cement are needed if we pumped 30% excess in the open hole section?

C. How many bbls of water is needed to mix the slurry (with 30% excess OH) and to displace the wiper plug to the shoe?

D. What will be the pressure needed to land the wiper plug, ignoring friction?

E. How much pressure is needed to hold the cement in place if the float shoe happened to fail?

F. Given the floats hold, what is the lifting force on the casing?

Cement Plugs

• Plugs can be “spotted” for several reasons

• Abandon a well

• Artificial KOP

• Lost tools downhole

• Directional driller is off plan and can’t achieve doglegs to recover

• Pilot well was vertically logged deep beyond producing zone

• Class H cement is designed for plugs

• High compressive strength

• Plugs can be set in air or fluid filled hole