Chemistry and Classification of Oil well Cements

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Assignment

Basic Cement Slurry Formulation

Using the data provided, calculate the quantity of cement slurry and post-flush fluid required to cement the intermediate string of casing in the Assignment Well. Include a 25% cement contingency.

Casing String	Hole Diameter D_hole (in)	Hole Depth* (feet)	Casing Shoe Depth* L (feet)	Depth to Float Collar* (feet)	Casing OD (in)	Casing ID (in)
Conductor [c]	30	80	L₄=80	N/A	20	19
Surface [s]	17.5	1510	L₃=1505	1465	13.375	12.615
Intermediate [i]	12.25	4015	4008	3968	9.625	8.835

Summary Table
* All depths measured from Rotary Kelly Busing (RKB)

Cement Slurry and Post-flush Fluid Volumes

The fluid volume required to cement the intermediate string of casing of the Assignment well is 692 ft³ without contingency. Class H cement and water is being used for this job.

Part A:

Calculate the number of cement sacks needed, including a 25% contingency.

Part B:

Calculate the volume of mix water needed.

Solution

Part A Solution:

According to API Cement Slurry Specifications the yield for a Class H cement = $1.05\ \tfrac{ft^3}{sack}$

The cement needed for the intermediate string plus 25% of contingency = $692\ ft^3 \times \dfrac{1.25}{1.05\, \tfrac{ft^3}{sk}} = 824\ sacks$

Part B Solution:

According to API Cement Slurry Specifications the water/cement ratio for a Class H cement = $4.3 \tfrac{gal}{sk}$

The amount of mix water needed = $824\ sks \times 4.3 \tfrac{gal}{sk} = 3544\ gallons\ (85\ barrels)$

Assessment

1. API cements are classified according to what oilwell conditions? (Select all that apply.)

A .Mix water
B .Additives
C .Pressure ✔
D .Depth ✔
E .Temperature ✔

Oilwell cements set and develop compressive strength as a result of ________.

A .pressure
B .aeration
C .dehydration
D .hydration ✔

How is a cement slurry mixture categorized if it contains no additives?

A .Common
B .Neat ✔
C .Portland
D .Ordinary

Water in excess of that required for cement to set is necessary for the formation of __________ that can be pumped.

A .a cement slurry ✔
B .aluminosilicates
C .interlocking crystalline structures

What is the recommended ratio of water to cement for mixing oilwell cement?

A .About 5.0 to 6.3 gallons per 94 lbm sack of dry cement, depending on the API Class ✔
B .About 2.8 to 7.3 gallons per 94 lbm sack of cement, depending on the API Class
C .About 4.0 to 5.3 gallons per 94 lbm sack of dry cement, depending on the API Class

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