Week Four OTS WCS
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- What properties do we generally measure with cement laboratory tests?
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Density
Thickening time
Free water
Fluid loss
Rheology
Sedimentation
Gas migration
Compressive strength - What is the ideal wellbore annular gap? What is the minimum that is acceptable?
- An ideal gap is 1 1/2" and the minimum gap is 3/4"
- Describe mud removal as a three step process.
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1. Hole cleaning
2. Conditioning of the drilling fluid
3. Displace the drilling fluid from the annulus - List steps not under the control of a cementing engineer that should be done before a cementing job to best prepare the well.
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1. Drill with good mud properties (thin filter cake, low flat gel strengths)
2. Drill an in-gauge hole
3. Drill a smooth hole with minimal doglegs
4. Maintain wellbore stability
5. Clean cuttings from hole (wiper trips, mud properties optimized for cuttings transport) - List four things that optimize hole cleaning
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1. Optimized mud properties
2. Wiper trips
3. >95% total hole volume in circulation
4. Caliper log (?) - List three things that optimize mud conditioning before a job.
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1. Break the gel strength by circulating
2. Lower Ty and pv
3. Reduce drill solids to under 6%
4. Determine MPG to find qmin for all-around flow - Name three things to best displace mud from the annulus
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1. Optimize slurry placement in CemCADE
2. Have at least 75% standoff
3. Casing movement - What is the minimum amount you should circulate to clean a wellbore before a cementing job?
- A minimum of one hole volume
- What rheology conditions should the drilling mud meet before a cementing job?
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YP = 8-10 lbs/100 ft2
No barite sag
Lower drill solids
Try for 100% circulation efficiency (via MPG) - What is a fluid caliper? How is it used in conjunction with a regular caliper?
- fill in later
- What is the procedure for a fluid caliper?
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1. Run multi-arm open-hole caliper log and determine hole volume
2. Circulate at cementing rate and determine mud pump efficiency
3. Drop marker or tracer in staged intervals
4. Monitor returns for marker
5. Calculate volume circulated from rate and time
6. Increase rate and recalculate efficiency - Name three flow regimes we use at Schlumberger.
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1. laminar
2. turbulent
3. effective laminar - what is the formula to calculate the Reynold's number?
- Re= (density*V*D)/(viscosity)
- What effect does an eccentric pipe have upon the flow regime in a well?
- Frequently the narrow region will experience laminar flow even if the area is supposed to be turbulent.
- What are the three components of the WELLCLEAN system?
- Wellclean, Wellclean II advisor, mudpush
- What two criteria are considered for turbulent flow when designing for mud removal?
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1. Contact time of at least ten minutes
2. Annular spacer length of at least 750 ft - What are the four criteria of effective laminar flow?
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1. MPG
2. Velocity differential
3. Density hierarchy
4. Frictional pressure hierarchy - What does the MPG consider?
- MPG ensure that all the fluids in a well are flowing; it calculates the minimum energy to overcome Ty and thus determines a Qmin for fluid motion to take place all around the casing. In order for the mud to flow, the yield stress of the mud MUST be less than the WSS.
- What phenomena does the friction pressure hierarchy prevent?
- Fingering
- What does the frictional pressure hierarchy demand? What type of interface does it promote?
- The frictional pressure hierarchy demands that a displacing fluid have 1.2 the frictional pressure of the displaced fluid. It promotes a flat, stable interface.
- What physical principle does differential velocity relate to?
- In an eccentric pipe, fluid flow preferentially on the wide side (the side of least resistence)
- To achieve effective laminar flow, how many of the four criteria must be met?
- 75%. Remember that this only applies to fluid in the annulus.
- What are the two WBM-compatible chemical washes?
- CW-7 & CW-100
- What are the two OBM-compatible chemical washes? Which one is compatible with SOBM?
- CW-8 & CW-8ES. CW-8ES is compatible with SOBM.
- What are the four tests of surfact efficiency?
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1. rheological compatibility test
2. casing water wetting test
3. reverse emulsion test
4. grid test - Describe the grid test.
- Spot a tile with mud. Dip it in CW. See how long it takes to erode.
- What are the required properties of spacers?
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Compatible with all other well fluids
Stability (good suspending capacity)
Controllable density and rheology
Good fluid loss control
Environmentally safe and easy to handle in the field - What are the D codes for MudPush II?
- D970 (freshwater) and D971 (sea water)
- Name the three types of centralizers.
- Rigid bow, rigid solid slip, bow
- When reciprocating, what is the recommended stroke and cycle?
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Stroke: 20-40 feet
Cycle: 1 - 5 minutes per cycle - What is the recommended rate of casing rotation?
- 10-40 RPM
- List 5 things that aid in mud removal.
- Centralization, casing movement, scratchers, plugs, washes and spaces, flow regime
- What API specification determine how we test cements?
- API Spec. 10A & 10B
- How long does Schlumberger run thickening time tests? How long does the API recommend we run TT tests?
- Till 70 Bc while the API runs it to 100 Bc.
- What do we use to test for rheology & gel strengths?
- Fann 35
- How do we test for fluid loss under high pressure conditions?
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Place slurry for 30 min across
1000 psi differential pressure
Permeable formation simulated
by 325 mesh screen backed
by 60 mesh screen - What are the two types of fluid loss tests? How do they differ?
- Low pressure and high pressure. One is done at 100 psi differential and one is done at 100 psi differential.
- What volume of slurry do we use for a free water test? How long do we let it sit?
- 250 ml, 2 hours
- What is the rotational speed of the vane rheometer?
- 0.1 rpm
- How do you do a sedimentation test?
- Let slurry set up in a tube. Slice the tube into discs. Measure the density of each slice.