Chapter 1 : Oil Well Cement & Cement Additives - Classification & Properties Flashcards

Question

What are the Fluid loss Considerations?

Answer 1

- Salt - affect most FL additives - When used at Low temperature - will delay the setting of cement slurry because of the retarding action of many FL additives -Need dispersant to be effective - help to increase effectiveness & temperature range - Introduce gas or foam to slurry - results in a 3 phase system that will have a lower fluid loss rate

Answer 2

Used to modify the rheology of the cement by reducing the viscosity of a cement slurry. Usage of dispersant: 1. reduces the pumping rate necessary to get turbulent flow for specific well condition 2. reduces the pressure exerted (ECD) on weak formations 3. reduces surface pressure & HHP requirement 4. improves ability to mix higher densities by reducing water-to-cement-ratio 5. improves ability to mix LWC slurries which has high solid contents as lightweight spheres.

Answer 3

A formaldehyde condensate of lignosulfonic acid Example: PNS - Polynaphthalene sulfonate

Answer 4

When adding dispersant, slurry may show sedimentation and free water separation. Stabilizers are used in Heavy Weight slurries to suspend the weighting material We want STABLE FLOCCULATED SLURRY

Answer 5

Extenders are materials and systems that allow the cement slurry to be mixed at a lower density without excessive free water development. -to reduce density -use light weight material

Answer 6

1. Reduce slurry density - reduces the Hydrostatic pressure during cementing, prevent loss of circulation 2. Increase Slurry Yield -extenders help to reduce the amount of cement required to produce a given volume of set product. This results in a greater economy.

Answer 7

1. Water extenders 2. Low density aggregates 3. Gaseous extenders

Answer 8

1. Lightweight particles 2. Chemical extenders 3. Pozzola 4. Fume silica 5. Hollow microspheres & ceramic spheres 6. Nitogen

Answer 9

-Lightweight-particle extenders reduce the slurry density because they are lighter than the cement particles. Such extenders include expanded perlite, powdered coal, gilsonite, and either glass or ceramic microspheres. - Most extenders in this category are INERT with respect to the cement. 1) Attapulgite -yield of attapulgite is independent of salinity -highly dependent on shear -does not impart fluid loss control to the slurry 2) Expanded perlite -crushed volcanic glass that expands when heated to the point of incipient fusion. -rarely used today 3) Gilsonite -SG 1.05 -a natural asphaltite mineral -as a black angular solid, usually supplied as a ground material -The water requirement for gilsonite is low giving low-density cement systems with relatively high compressive strength within BHST 300°F [149°C]. 4) Powdered coal - SG 1.3 - It is coarsely ground (50% of particles between 6 and 12 mesh) and is often used to prevent lost circulation.

Answer 10

- densities significantly less than the density of water - HGM - manufactured HCS - obtained by separating very lightweight portions of fly ash through floatation -Both materials have a pressure limit above which the sphere will collapse.

Answer 11

Difficulty of simultaneously achieve adequate: -FL control - acceptable slurry rheology - no solids settling

Answer 12

To increase the density of the slurry not chemically

Answer 13

Barite Hematite & ilmenite Manganese tetraoxide (Micromax)

Answer 14

- Barite requires large amounts of water to wet the surface, and therefore has limited use in cement slurries - Barite can be used in combination with other weighting agents to help limit free water development and settling - Slurries with densities up to 19.0 lbm/gal can be prepared with barite

Answer 15

- heavy iron ores that have large particles Hematite: -at high concentration, need dispersant to prevent excessive slurry viscosity Ilmenite: -has little effect on cement hydration

Answer 16

Used to combat cement lost into very permeable, cavernous or fractured formations 2 ways to prevent the loss of cement by: - preventing fracture inducement by reducing Hydrostatic Pressure -by forming a low permeability bridge across the permeable opening . Common LCM can be classified as fibrous, granular and flakes.

Answer 17

Silica Antifoam & defomers

Answer 18

To prevent strength retrogression. Silica is added to cement which reacts to form stable crystalline forms at higher termperature

Answer 19

-At temperatures exceeding 230°F (110°C), the crystalline structure of cement changes. -The resulting structure will be higher in permeability and have lower strength.

Answer 20

-Function: to reduce the air entrainment of cement slurries Antifoam -works by changing the surface tension of the water and preventing foams from forming -As such, it is added to the mix water, or dry blended into the cement prior to mixing -2 classes of antifoam agents are commonly used: polyglycol ethers and silicones. They will prevent the formation of a foam, but once a foam is generated in a system, will do little to disperse existing foam Defoamers - eliminating existing foams. As noted, these are not readily available and not normally used.