Cementing
Introduction
Oil well cementing is the process of mixing and displacing a slurry down the casing and up the annulus, behind the casing, where is allowed to “set”, thus bonding the casing to the formation. Some additional functions of cementing include:
• Protecting producing formations
• Providing support for the casing
• Protecting the casing from corrosion
• Sealing off troublesome zones
• Protecting the borehole in the event of problems
The main ingredient in most cements is “Portland” cement, a mixture of limestone and clay. This name comes from the solid mixture resembling the rocks quarried on the Isle of Portland, off the coast of England.
All cement is manufactured in essentially the same way. Calcareous and argillaceous materials (containing iron and aluminum oxides) are finely ground and mixed in correct proportions, either in a dry condition (dry processing) or with water (water processing). The mixture is then fed into the upper end of a sloping kiln at a uniform rate. The kiln is heated to temperatures from 2600o to 3000oF. As the mixture falls to the lower end, the mixture melts and chemical reactions occur between the raw materials.
When the mixture cools, it is called “clinker”. The clinker is then ground with a controlled amount of gypsum (1.5 to 3.0% by weight), to form portland cement.
The principle compounds resulting from the burning process are Tricalcium Silicate (C3S), Dicalcium Silicate (C2S), Tricalcium Aluminate(C3A), and Tetracalcium Aluminoferrite(C4AF). contains more information on the properties of these compounds. These materials are in an anhydrous form. When water is added, they convert to their hydrous form, which is then called a “cement slurry”.
The American Petroleum Institute (API) has established a classification system for the various types of cements, which must meet specified chemical and physical requirements. classifications and their applications to depths of 16,000 ft. (4880 m), under various temperature and pressure conditions.
Introduction
Oil well cementing is the process of mixing and displacing a slurry down the casing and up the annulus, behind the casing, where is allowed to “set”, thus bonding the casing to the formation. Some additional functions of cementing include:
• Protecting producing formations
• Providing support for the casing
• Protecting the casing from corrosion
• Sealing off troublesome zones
• Protecting the borehole in the event of problems
The main ingredient in most cements is “Portland” cement, a mixture of limestone and clay. This name comes from the solid mixture resembling the rocks quarried on the Isle of Portland, off the coast of England.
All cement is manufactured in essentially the same way. Calcareous and argillaceous materials (containing iron and aluminum oxides) are finely ground and mixed in correct proportions, either in a dry condition (dry processing) or with water (water processing). The mixture is then fed into the upper end of a sloping kiln at a uniform rate. The kiln is heated to temperatures from 2600o to 3000oF. As the mixture falls to the lower end, the mixture melts and chemical reactions occur between the raw materials.
When the mixture cools, it is called “clinker”. The clinker is then ground with a controlled amount of gypsum (1.5 to 3.0% by weight), to form portland cement.
The principle compounds resulting from the burning process are Tricalcium Silicate (C3S), Dicalcium Silicate (C2S), Tricalcium Aluminate(C3A), and Tetracalcium Aluminoferrite(C4AF). contains more information on the properties of these compounds. These materials are in an anhydrous form. When water is added, they convert to their hydrous form, which is then called a “cement slurry”.
The American Petroleum Institute (API) has established a classification system for the various types of cements, which must meet specified chemical and physical requirements. classifications and their applications to depths of 16,000 ft. (4880 m), under various temperature and pressure conditions.
