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75 Cards in this Set
- Front
- Back
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What are the objectives of primary cementing?
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Zonal Isolation
Support the Casing Protect the Casing |
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Name 7 characteristics of an ideal wellbore.
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-Properly conditioned hole and mud
-Gauge diameter -Centered Casing -Accurate BHST/BHCT -Thin, impermeable mud filter cake -No Losses/No Flow -Min annular gap: 3/4, ideal 1.5 |
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What is the mud removal process?
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- Clean the hole
- Condition the mud - Displace the drilling fluid from the annulus |
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How do you prepare the well?
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- Drill with good mud properties
- Have an in-gauge hole - Maintain wellbore stability - Clean cuttings from hole |
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Characterisitics of hole cleaning
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- Controlled/optimized mud properties
- Wiper trips - >95% total hole volume in circulation - Caliper log |
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Characteristics of mud conditioning
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- Lower Ty and Pv
- Solids content <6% - Determine MPG to find Qmin for all-around flow - Break gel strength |
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Characteristics of displacing mud from the annulus
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-Optimize slurry placement
-Centralize Casing (STO>75%) -Casing Movement |
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Name 3 goals of circulating/conditioning mud
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-Circulate a minimum of 1 hole volume
- Lower rheologies as much as possible - Lower solids content - Satisfy MPG requirement |
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What is the purpose of fluid calipers?
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To determine circulation efficiency or amount of fluid which is moving in the wellbore
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Criteria for effective mud removal?
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Centralize Casing
Move Casing Scratchers Wiper Plugs Washes/Spacers Flow Regime Selection |
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Name 3 characteristics of the density heirachy
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Chemical Washes arent considered
Slurry has priority Density of displacing fluid is greater than that of the fluid being displaced |
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Rules of Effective Laminar Flow
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Density Heirachy
Friction Pressure Heirachy MPG Differential Velocity |
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Name 3 characteristics of Minimum Pressure Gradient
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To have flow, Ty(mud) < WSS
Applies only to fluids with YP All fluids flow in the well |
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Name 3 characteristics of the Friction Pressure Heirachy
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Nature takes easiest route
Displacing fluid needs to be stronger Given to be a 20% friction pressure difference between displace and displaced fluid |
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Name 3 characteristics of Differential Velocity
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Fluid has a preference to flow on the west side
Needs to be an upper limit (Qmax) Function of standoff/density differential |
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T/F Effective Laminar Rules apply to the fluids in the casing
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False
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What CWs are for WBMs?
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CW7, CW100
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What CW's are for OBMs?
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CW8, CW101
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What CW's are for intermediate casings?
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CW7, CW8
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What CW's are for production casings?
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CW100, CW101
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Name 3 required properties of spacers
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Compatible with all other fluids
Stability Controllable Density/Rheology Good Fluid Loss Control Environmentally Safe |
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What's the D code for Mudpush II?
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D970 and D971
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Name 4 major problems resulting from fluid incompatibility
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Poor interfaces
High rheological properties Changes in Cement Slurry Properties Reduction of hydraulic bond |
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How do you do a compatibility tests and what values of R indicate compatibility?
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Take rheologies of different concentrations of mud and spacer at ambient and BHCT.
R at 100RPM: <0 Compatible 0<R<40 Compatible (check FP) |
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Herschel Bulkley better predicts under what conditions?
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At low shear rates and when extrapolating at very high shear rates
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Name 4 characteristics of reciprocating the casing
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1-5 min per cycle
Need scratchers to be effective Casing may become stuck during movement Excessive swab/surge pressures may be created |
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Name 4 characteristics of rotating the casing
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Cannot be the only method of mud removal
Scratchers help efficiency Need special rotary cement head/power swivels Torque must be closely monitored |
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Which API standard applies to lab operations?
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Spec 10
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Name 6 lab tests completed on cement
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Thickening time, Fluid Loss, Free Water, Compressive Strength, Free Water, Rheology
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Name 4 Slurry Properties
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Free Water/ Sedimentation
Density Pumpability Fluid Loss Rheology |
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Name 4 properties of set cement
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Bonding, Sulphate Resistance, Strength Retrogression, Permeability
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What volume of sample is mixed for slurry testing in the lab?
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600mL
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How long and at what speeds are normal slurries prepared
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15s @4000RPM
35s @1200RPM |
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How long and at what speeds are CREETES prepared. Why is it a different procedure?
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5 min @ 4000RPM
As to not crush the little spheres (D124) |
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How many mL of slurry are needed for a free water test. How long does it take?
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250mL
2hrs |
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How is the fluid loss determined if the slurry is dehydrated in less than 30 min?
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F = 2 X Filtrate at time X sqrt(30/t)
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What speeds are tested during rheologies?
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300, 200, 100, 60, 30, 6, 3
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What calculation is used to determine Pv and Ty
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Pv = (Reading@300 - Reading@100) X 1.5.
Ty = Reading@300 - Pv |
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What is the reading at 3 and 6 RPM used for. Why not test at 600RPM as well?
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3- used for gel strength @10sec and 10min
6 - used for HB rheology (along with 3 600 - creates too much shear stress in the slurry |
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Name 4 characteristics of Thickening Time
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Reported in Bc
Upper API limit - 100Bc Performed in a pressurized consistometer that simulates T and P Determines the length of time a slurry remains fluid |
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Two ways to determine compressive strength
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Crush Test
UCA |
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Define Gas Migration
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Invation of formation fluids into the annulus due to a pressure imbalance at the formation face (loss of hydrostatic pressure. i.e Pformation>Phdrostatic)
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Name 4 consequences of Gas Migration and an example of each
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Blow Out - lost rig/personnel
Environmental Damage - freshwater aquifers Poor zonal isolation - lost production Repair Required - casing corrosion |
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Name 3 pathways for Gas and what they result from
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A channel - poor mud removal
Invasion during placement - fluid loss Set cement failure(microannulus) - due to shrinking/expanding of casing |
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What are the phases of setting cement?
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Fully Liquid
Early Gelation Hydration Set Cement |
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What are the two types of fluid loss, and consequences of each. What fluid loss is recommended
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Dynamic - increased rheology
Static - promotes early gelation, loss of overbalance <50mL/30min |
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Name 4 causes of set cement failure and a cause of each
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Cracks/Debonding due to downhole stresses
Tensile cracks/well bore stress changes - due to cement expansion Poor interfacial Bonding (Microannulus) - due to casing movement Debonding at formation interface - due to shrinkage |
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Name the 5 pieces to the gas migration control puzzle
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Slurry Design
Mud Removal Set Cement Mechanical Properties Fluid Density Control Cement Hydration |
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What are some ideal slurry properties during and after placement
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Before: Good rheologies for mud removal, zero free fluid, fluid loss less than 50mL/30min
After:Low fluid loss to avoid early gelation, short transition time from 100-500lb/100ft^2 |
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How do you avoid a pathway for gas in set cement
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FlexSTONE - can withstand cyclical stress variation, no shrinkage b/w casing/formation
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Prevention methods for gas migration
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Optimize slurry
Short transition times Special Techniques GASBLOK |
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Physical solution to gas migration
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Annular pressure, multistage cementing, reduced cement column length, increase mud density
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Cement solutions to gas flow. Name 4.
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Compressible Cements
Thixotropic Cements RAS Cement Surfactant Cement Expansive Cements Microsilica Cements Impermeable Cements |
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Name a concept and disadvantage of compressible slurries
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Concept - attempt to maintain cement pore pressure about formation gas pressure
Disadvantage - safety hazard, stability which may cause gas channeling itself, time dependent |
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Name a concept and disadvantage of thixotropic slurries
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Concept - gel strength strongly binds particles before cement sets and gas cannot break the structure
Disadvantage - limited to low gas pressure zones, poor fluid loss control |
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Name a concept and disadvantage of RAS slurries
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Concept - slurry sets to rapidly gas doesnt have a chance to invade
Disadvantage - difficult to accomplish <250 F |
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Name a concept and disadvantage of surfactant slurries
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Concept - formation of a stable foam in slurry if gas enters in annulus. Subsequent impairment of gas flow/migration
Disadvantage - doesnt work on highly permeable zones |
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Name a concept and disadvantage of expansive slurries
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Concept - volumetric expansion of cement close gas channels and improve interfacial seals
Disadvantage - Expansion occurs after gas migration started, can result in unsoundness |
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Name a concept and disadvantage of microsillica slurries
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Concept - extremely small particles pack between larger cement particles preventing gas from entering
Disadvantage - Not efficient under severe conditions |
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Name a concept and disadvantage of impermeable slurries
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Concept - Reduce permeability during liquid-solid transition time
Disadvantage - latex is sensitive to temp, difficult making product for oil industry |
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How do you optimize a slurry?
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Free water, fluid loss control, gelation control, thickening time, hydration kinetics, slurry density
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What is GasBLOK?
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A complete engineered solution to gas migration. Excellent fluid loss control, impemeable film formed during transition period
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GasBLOK works under what conditions?
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Density: 2-24ppg
Temp: 32-375F Depths greater than 20,000ft |
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Temp/Density range for LT GasBLOK
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32-160F
10.5-16.4ppg |
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Temp/Density range for MT GasBLOK
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150-250F
8-23ppg |
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Temp/Density range for HT GasBLOK
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250-375F
8-23ppg |
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GasBLOK Slurry Design Considerations
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<50mL/30min Fluid Loss
Minimize gel strength Slurry stability Short transition time |
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GasBLOK concentration depends on...
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BHST
SVF (Solid Volume Fraction) |
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Additive used to stabilize D700
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D701 - replaced D135
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Deep Water Cementing Objectives
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Competent Hydraulic Seal
Structural Support Long term Cement Sheath Durability Short WOC |
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Special Deep Water Problems
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Shallow Water Flow
Gas Low Temperature Mud Displacement Risk of Losses |
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Where does shallow water flow occur?
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Unconsolidated sands/clays
Faults Over-pressured, high permeability |
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DeepCRETE application range
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Fresh water to 37% salinity
Density 8-13.5ppg Temperature 40-80F Pressure: Surface to 5000psi (else burst D124 spheres) |
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DeepCRETE advantages. What are D185 and D186
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Low density (maintains returns)
Short WOC D185 - Dispersant D186 - Accelerator |
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Depths greater than (..blank..) are considered deep water.
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1000ft
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