The most important function of oil & gas well primary cementing is to isolate the various zones within the wellbore. In others words, the cement must prevent fluids or gases in one particular zone from mingling with those of another. A properly designed and placed cement slurry accomplishes this by creating the necessary seal between the casing and the formation. The cement must prevent migration or fluid channeling throughout the cement.
Today's well cement systems must perform in a variety of down hole conditions, from 0°C - over 350°C, and at bottom hole pressures in excess of 30,000 psi.
Eneroil provides a complete line of cement additives, which modify the characteristics and performance of the cement slurry. This means that a slurry can be designed to function over the wide range of conditions that occur in the wellbore.
Accelerators are materials that cause cement to hydrate and develop strength earlier and faster. They are commonly used to provide improved strength at low temperatures and to counteract the retarding effects of other additives. Accelerators shorten the thickening time.
Antifoam agents prevent or reduce the foaming tendencies of the cement when it is mixed. This is necessary because the properties of cement slurries and the set cement depends on the water/cement ratio. Most flied mixtures determine the ratio by measuring the density of the slurry, so entrained air causes the slurry to be mixed at improper ratios. Some materials can be used as antifoam agents, but not as defoamers. Other materials act as either defoamers or foam preventers.
In some cases gelation is caused by the chemical makeup of the cement. Many times this gelation can be controlled by dispersants but special materials may be required.
Deep CHEM liquid cementing additives were created for short transition time and early compressive strength development. Such properties are necessary for isolation and early casing release to ensure successful cementation in the unconsolidated, low temperature environment of the surface and conductor casings in deepwater wells. They are also useful in other low-temperature situations.
Dispersants act to reduce the viscosity of cement by breaking up aggregates of the fine cement particles. This reduction in viscosity allows mixing at lower water/cement ratios for higher density, improved fluid-loss control and pumping at reduced pressures.
Expanding additives react chemically after hydration (setting) to produce an increase in the bulk volume of the cement. This reaction provides benefits in zonal isolation and protection of the casing. When used across soft formations, flexible systems may be required to prevent microannulus formation.
Extenders allow the production of a greater volume of slurry from the powdered cement. This feature can result in reduced cost and where the extenders are lightweight (or they allow additional water to be used), lower density. The advantage of reduced cost is obvious. Reduced density is important where weak formations are to be cemented. Such weak formations could part and allow loss of the slurry during the cementing operation. A variety of extenders are available to provide for different requirements of lower density, lower cost and other performance parameters.
Fluid-loss control additives minimizes the loss of water from the slurry into permeable formations. This helps to maintain the properties of the cement slurry during placement and until the cement sets.
Gas migration control additives are used to reduce the risk of gas invading the cement and migrating into the wellbore.
Materials used to prevent or halt losses of slurry from the wellbore are called LCM. In addition to LCM added to the cement, special lost circulation control products are available for combining lost circulation during operations other than cementing.
Retarders are used to lengthen the time that a cement slurry can be pumped or remains fluid so that other operations (such as pulling pipe after spotting a cement plug) can be performed. They are required at elevated temperatures or when large volumes of slurry require a long time to pump at lower temperatures.
Surfactants are used in chemical washes and spacers with OBM and to create stable foam when adding a gas to make foamed cement.
Occasionally, segregation can occur in a cement slurry. This segregation may be in the form of water separation (known as free fluid) or in solid particle sedimentation. In either case, a material to suspend the solids is used to maintain slurry integrity.
Thixotropic additives produce an intentional gelation of the cement to aid in the placement of the cement.
UniSLUURY additives have unique and synergistic properties. These additives have been purpose built to perform their function and have properties that distinguish them from other fluid-loss or set-control (retarder) additives.
Weighting agents are used to increase density of the cement when needed for well control.
Spacers are generally thickened, weighted fluids used to aid in mud removal and to separate the mud from the cement to prevent any compatibility problems.
Chemical washes are generally thin fluids with surfactants to aid in mud removal and to separate the mud from the cement to prevent any compatibility problems.
Cement Additives, Fluid-Loss Control Additives, Gas Migration Control Additives, Lost Circulation Control Materials, Antisettling Agents, Thixotropic Cement Additives, Cementing Equipment, Cementing Services, Cement Additives, Gas Migration Control.