What is cement used for in oil wells?

Using cement to fill the void between the casing and the borehole has three basic functions: Supports the casing and protects it from corrosion. Isolates oil-, gas- and water-producing zones of the well. Prevents blowouts by forming a seal.

Which class of cement is used in oil-well?

API Classes G and H are the most widely used. Oilwell cements are also available in either moderate sulfate-resistant (MSR) or high sulfate-resistant (HSR) grades. Sulfate-resistant grades are used to prevent deterioration of set cement downhole caused by sulfate attack by formation waters.

What is the effect of silica in cement?

Silica fume is also a highly reactive pozzolanic material that reacts with calcium hydroxide (CH) from the cement hydration to form calcium silicate hydrates that contributes to dense structure and strength development of concrete.

What is oil rig cement?

Most commonly, cementing is used to permanently shut off water penetration into the well. Part of the completion process of a prospective production well, cementing can be used to seal the annulus after a casing string has been run in a wellbore.

How do you make hydrophobic cement?

Hydrophobic cement is obtained by grinding portland cement clinker with a film-forming substance such as oleic acid in order to reduce the rate of deterioration when the cement is stored under unfavourable conditions. It is also known as Hydrographic cement.

Which type of cement is used for the lining of deep tubewell?

Portland – Pozzolana cement
Portland – Pozzolana cement (PPC) is used in lining of deep tube wells.

What is the difference between Class G and Class H cement?

Class G & H The most common used class is class G, it can be used at temperature up to 200F° without adding modifiers. Class H has coarser grind than class G which gives it better retarding properties for cementing deep wells.

What is Class G cement used for?

Class G Oil Well Cement, as one of basic oil well cements, is one of special hydraulic binding materials. Its main content is clinker of portland cement. It is also named Block Cement or Blockage Cement. Class G Oil Well Cement is especially used in the cementing engineering of oil well or gas well.

Why alumina is used in cement?

Asahi Alumina Cement is an alumina cement product made using a high temperature fusion process that creates quality stability. Alumina cement is an inorganic material that form a dense texture when it reacts with water. It is known for its refractoriness, rapid hardening, resistance to chemical attack .

What is the role of alumina in cement?

Alumina (Al2O3) Alumina imparts quick setting property to the cement. In general, high temperature is required to produce required quality of cement. But alumina when added with cement ingredients it behaves as a flux and reduces the clinkering temperature which finally weakens the cement.

Why are wells cemented?

Cementing helps to protect and seal a wellbore.

What is Class G cement?

Class G cements are sulfate-resistant Portland cements with different setting time requirements and have a common field of use in the oil industry. Compared to other American Petroleum Institute class cements, Class G has a utilization of more than 95% worldwide in oil well applications.

What is cement blending?

The process of uniformly mixing those dry cement additives into the cement at the design concentration is termed “cement blending.” The importance of proper cement blending is evident when one considers that for some cement systems as little as 20 lbm of an additive is blended with 20,000 lbm of cement.

How to test the quality of cement blends?

Cement Blends Quality Control Testing: The first checkpoint for the quality of the blend is the measurement of its SG; this gives a clear indication of the right proportions of the major components in the mixture.

How does additive blending affect the performance of a wellbore?

Nonuniform additive blending (e.g., small variations in additive concentrations) or incorrect additive concentration results in improper slurry performance in the wellbore and may have drastic consequences in the well.