In the construction industry, well cement is an essential material that is specifically used for cementing wells. It is necessary to establish a tight seal between the surrounding geological formation and the well casing. This seal is essential to keeping the well’s structural integrity and preventing fluid migration between different rock layers.
Well cement, which is widely used in gas and oil wells, must endure high pressures and temperatures. It guarantees the stability of the wellbore and the efficient and safe extraction of hydrocarbons. It is essential for both onshore and offshore drilling operations due to its special qualities.
Portland cement, pozzolans, and other performance-enhancing additives are commonly combined to create well cement. These additives have the ability to change the setting time, strengthen, and enhance resistance to challenging circumstances. It is essential to comprehend the technical properties of well cement in order to choose the appropriate kind for a given set of well conditions.
This article will examine the various varieties of well cement, including their composition and technical attributes. We’ll also go over how they’re used in different well construction situations, giving you an understanding of why well cement is such an important part of the well construction industry.
- Composition and features
- Main technical characteristics
- Classification of cement slurry mixtures
- Marking and its decoding
- Additives to improve tamponal solutions
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Composition and features
The composition of well cement is nearly identical to that of Portland cement. On the other hand, clinker content requirements have increased. The percentage of clinker in cementing can be 100%. An admixture of up to 3.5% ground gypsum is required.
The material can be enhanced with different mineral elements, which together will not account for more than 12% of its mass, to improve its properties. Limestone should make up no more than 10% and slags, up to 20%.
Tampon cement’s requirements, material standards, and intended use are outlined in GOST 1581. The percentage share of refractory impurities and other components determines the type of substances. The manufacturer’s formula for the final cement may differ.
- the smallest grinding;
- accelerated process of hardening;
- increased mechanical strength and stiffness;
- When diluting water, the consistency differs from that in other types of cement.
The building rates, standards, and regulations have more stringent requirements. With tiny technological holes, the cement solution should move at a speed of 1.5 m/s. In locations where such composition sand is used, reinforcement, formwork, and crushed stone are not added due to the exceptionally high pressure. As such, the only ingredient is the astringent.
High standards are set for such a composition’s use as a building material by its characteristics. It ought to lessen the force applied to the pipeline or other area receiving insulation. A higher solidification rate for the cement slurry is also required, and this is accomplished during manufacturing by adding different additives.
Main technical characteristics
- Mechanical strength after 8 hours reaches 2.1-10.3 MPa depending on temperature. The maximum value is observed at 60 °C.
- Bending rigidity varies in the range of 0.7-3.5 and depends on the manufacturer and brand.
- Residual weight on a sieve with mesh No. 0.08 – no more than 15%.
- Specific surface – no more than 270 m²/kg.
- The moisture separation index should not exceed 10.
- Spreadability under the influence of moisture varies depending on the type. Unplasticized oil well cement can flow at a speed of up to 200 mm. Plasticized — up to 220.
- The composition hardens to a consistency of 30 in 90 minutes or more.
The manufacturer’s note needs to include information on all characteristics as well as the date of production. Portland cement becomes less functional after six months or when exposed to air.
The hardening rate will depend on the temperature indicators in the well and the percentage of alkaline substances in the composition. If the temperature exceeds 60 °C, the hardening time may change.
Classification of cement slurry mixtures
According to GOST, all specifications for this kind of cement are standardized. Cement comes in various varieties based on its properties.
Density indicators are typically used to distinguish between two types:
- Lightweight type — normal mixture.
- Heavyweight, containing impurities that increase the mass.
The following types vary based on the temperature regime:
Nomenclature name | Temperature range, °C |
Low and normal | 15-50 |
Moderate | 51-100 |
Increased | 101-150 |
Composition types based on how resistant a material is to chemicals found in groundwater:
- without increased resistance;
- resistant to sulfates, including special additives.
There are two degrees of sulfate resistance for certain types: increased and moderate.
Based on the condition of the cement paste, the substance is separated into:
- Unplasticized;
- Hydrophobized.
Specialized cement known as "well cement" is mostly used during the construction of gas and oil wells in order to seal the casing and stop leaks. Its special composition ensures the well structure’s integrity by withstanding high temperatures and pressures. Because it offers a robust seal and long-lasting durability in challenging subterranean conditions, this cement is essential to the effectiveness and safety of drilling operations. Professionals in the building and energy sectors must comprehend its characteristics and uses.
Marking and its decoding
There is a nomenclature name for every type of oil well cement that corresponds to its properties.
There are five designations on the oil well marking:
- PTsT — oil well portland cement.
- Type of binder and a note about lightweight or heavy composition.
- The third numerical value corresponds to the strength level of the product. This indicator is determined by the manufacturer.
- The next number determines the temperature level and the state of the cement paste. For example, 150-PL – for work with elevated temperatures. Plasticized dough.
- The last note is the regulatory act that the manufactured product complies with.
Additives to improve tamponal solutions
In order to enhance the solution’s operational attributes,
- Sodium calcium chloride and sodium carbonate accelerate the time of cement settling. When adding to the liquid, a mixture of quick setting is obtained, it can be used for temperature indicators up to 65 ° C. For expansion properties, add up to 30% gypsum-alumina cement.
- If you add gypsum, the hardening time is significantly reduced, as a result, a stone with increased strength is formed 3-4 hours after pumping the solution. To prevent hardening in the drills themselves, inhibitors of the process are added.
- Bentonite increases the initial mobility of the solution, which is especially important when pumping it.
- Compositions with the inclusion of clay additionally improve the viscosity of the material during its extrusion, which allows for subsequent hardening of the solution with an increase in plastic strength.
- Cement-resin composition with the addition of plastic substances, mainly epoxy aliphatic resins, is used if there are aquifers near the well.
- If it is necessary to pump the solution to a depth of more than 100 m, diesel fuel is added. Cement is completely inert to organic hydrocarbons, and the solution becomes much more viscous. Strength is acquired after the hydrocarbons are replaced by water.
Aspect | Details |
What is Well Cement? | A type of cement used in the drilling of oil and gas wells. |
Where is it Used? | Primarily in oil and gas well construction to secure casing and prevent fluid migration. |
Composition | Mainly consists of clinker, gypsum, and additives for improved performance under high temperatures and pressures. |
Technical Characteristics | High sulfate resistance, ability to withstand extreme temperatures and pressures, low permeability. |
Well cement is a specific kind of cement that is mostly used for drilling operations in the oil and gas sector. It is necessary to seal the gap between the well casing and the borehole, stop leaks, and guarantee the well’s stability.
It is perfect for deep well applications because of its special composition, which contains additives that give it a high resistance to extreme temperatures and pressures. Because of these technical features, well-cement is dependable and resilient in challenging circumstances.
All things considered, well cement is essential to the development and upkeep of gas and oil wells. Its resilience to harsh conditions guarantees the effective and safe operation of drilling operations.