OIL WELL CEMENT

 

Lafarge API Class G (HSR) cements is used in the production and exploration of oil and gas onshore and in deep water offshore wells to depths of up to 10,000feets (3,048 meters).

 

A typical well can be thousands of meters deep, less than a meter wide, and is constructed by using a metal casing surrounded by a special cement slurry mix that fills the annulus between the outer face of the tubing and the wall formation of the hole.

 

Lafarge well cements provide a base ingredient in the slurry mix that is pumped into the interior metal section of the well and forced back toward the surface from the base of the borehole filling the annulus. Well cement slurries are designed for a multitude of purposes from the establishment of the well's safety and structural integrity during drilling to the isolation of the zone of interest and the production of oil and gas upon completion. Given the complexity of the application and its extreme conditions of temperature and pressure, oil well cement must be carefully designed to meet demanding requirements such as predictable thickening time (set time), high sulfate resistance, high durability, fluid loss control, consistency, lowviscosity, low free fluid, and strength. Unlike surface construction, oil well completion is much less tolerant to errors. For instance, premature thickeningcan have disastrous consequencesdue to loss of circulation inthewell,whereas toolongthickeningtimescan cause financial losses duetoexcessive Wait-On-Cement(WOC)betweendrilling periods.

Quality

The types of cement are categorized according to the American Petroleum Institute (API) Specification10A standards, which has identified 8 classes of cement according to the depth of the well, the temperature and pressure. Cement is also classified in grades: Ordinary (O), Moderate Sulfate Resistant (MSR), and High Sulfate Resistant (HSR). Sulfate resistance is based upon the C3A (Tricalcium Aluminate) content, which has a bearing on the durability of the cement under sulfateattacks. When oil well cement is produced, the clinker is analyzed microscopically to ensure that the crystals and clinker mineralogy have the required characteristics. Oil well cement must also be designed and tested to perform with specific admixtures that are added to the slurry mix in order to achieve the desired thickening timeand rheology. The four most commonly used well cement types are Class A,Class C, Class G, and Class H.

 

Class A cements are being used inmilder, less demanding well conditions, while Classes G and H are specified for deeper, hotter and higher pressure well conditions. (HSR) cement meeting and ex-ceeding API specifications, and leads the industry in quality, and consistentperformance.

API Class G (HSR) cement

Benefits

  • Thickening Times controllable with additives to enable placement to 550º F (287º C).
  • Excellent Retarder Response for higher economic benefit in mix design.
  • Low Free Fluids for cement integrity and durability.
  • High Sulfate Resistance for high durability under harsh conditions.
  • Non-Setting for uniformity in the column.
  • Consistent Quality for slurry design portability.

Performance

Technical features

Chemical Composition

API Standard requirement

Average Values Class G-HSR

Loss on ignition

≤ 3.0 %

< 2 %

Insoluble residue

≤ 0.75 %

< 0,6 %

MgO

≤ 6.0 %

< 2 %

SO3

≤ 3.0 %

< 3 %

Alkali content (expressed as Na2O equivalent)

≤ 0.75 %

< 0,7 %

C3S

48 - 65 %

> 59 %

C3A

≤ 3.0 %

< 2 %

C4AF + 2C3A

≤ 24 %

< 18 %

Physical Properties

 

 

Free fluid content

≤ 5.9 %

< 4,5 %

Compressive Strength

 

 

Compressive Strength 8h, 38°C

≥ 2.1 MPa

> 4,5 Mpa

Compressive Strength 8h, 60°C

≥ 10.3 Mpa

> 14 Mpa

Thickening time

90 - 120 min

> 100

Maximum consistency (15-30 min)

≤ 30 Bc

< 18 Bc

Packaging

API Class G (HSR) cement can be supplied in, big bags (Jumbo Bag) 1.5 ton.

We now offer bags with a single lifting loop as an integral part of the carrier bag. Single lifting loop makes handling faster and safer.