Oilfield Cementing Details Processes

Classification of oil well cement:

At present, the commonly used oil well cement is mainly high-grade Portland cement. Limestone or calcareous tuff, clay or shale and a small amount of iron ore are mixed into raw materials according to a certain ratio, and then calcined at a high temperature of 1450℃ to become a kind of clinker with silicate as the main component, and then add an appropriate amount Gypsum is ground into a certain fineness of powder to make this oil well cement. Because the temperature and pressure in the well increase with the increase of the well depth, a variety of oil well cements must be produced to meet the requirements of different well depth conditions.

Adjustment of cement slurry performance:

A large number of cementing practices have proved that: the existing various oil well cements are still difficult to fully meet the requirements of various downhole conditions. For this reason, certain additives must be added to further adjust the related performance of the cement slurry. Including:

• Adjustment of density
• Adjustment ofthickening time
• Fluid loss agent
• Drag reducer

There are also some commonly used cement slurry additives that can improve various properties of cement slurry. For example, defoamers can reduce interfacial tension and inhibit the generation of bubbles; quartz powder is often used in high-temperature well cementing to improve the corrosion resistance of cement stone; salts can improve the cementing strength of rock salt formation cement.

Cement injection:

Cement injection ground equipment Cement injection ground equipment includes cement ash storage tank, cement truck, cement mixing funnel, compressor unit, cement slurry tank, etc. According to the requirements of the cement injection process, the cement slurry pipeline, water pipeline, and gas pipeline connect these equipments to form a cement injection construction device. Cement trucks are the most critical in ground equipment. The number of cement trucks used depends on the number of ash storage tanks, that is, the amount of cement injected. Every time a cement truck is added, other equipment and pipelines must be added accordingly. Generally every two or three ash storage tanks are equipped with a compressor unit.

1. When injecting cement, the compressor blows the cement in the ash tank into the mixing funnel through the air pipeline, and at the same time, the clean water is pumped into the funnel and mixed with the cement to form cement slurry, which enters the cement slurry tank. The cement truck then sucks in the cement slurry and pumps it to the cement slurry manifold through pipelines. The cement slurry pumped by all cement trucks is collected and sent to the wellhead cement head for cement injection cycle.
2. Cementing process After the casing is lowered to the predetermined well depth according to the design, the cement head is installed, and the drilling fluid is circulated to prepare for cementing. Figure 5-10 shows a typical double rubber plug cementing construction procedure. The uppermost device of the casing string is a cement head, which is equipped with upper and lower rubber plugs. The lower rubber plug and the isolation fluid separate the cement slurry from the drilling fluid to prevent the drilling fluid from contacting the cement slurry to affect its performance. The lower end of the casing string is equipped with guide shoes to facilitate casing running. Floating collar is actually a one-way valve, used to prevent the cement slurry in the annulus from flowing back into the pipe, and to seat the rubber plug. The ground equipment is ready and the cementing can be started.

Cement injection process:

Inject spacer fluid→Open the lower rubber stopper pin and pressure rubber stopper→Inject the mixed cement slurry into the casing through the cement slurry manifold and cement head→After the grout is poured, close the grout passage, open the upper rubber stopper pin and the top passage, and use drilling fluid to push the upper rubber plug into the casing→Pump drilling fluid into the casing→Bump→Close the oil well and wait for solidification→Check cementing quality→Go to the next drill

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Shawn

Regional Sales Manager

Zhejiang Ruico Advanced Materials Co., Ltd. (Stock No.873233)

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