A suspended cement plug suitable for coiled tubing operations and its application method

Abstract

The invention relates to a suspended cement plug applicable to continuous oil pipe injection and an application method of the suspended cement plug. The suspended cement plug comprises the following three formulae: a reservoir cement formula, an intermediate layer isolating liquid formula and a surface layer cement plug formula, wherein the reservoir cement formula is prepared by adding 1%-2% of a dispersant, 1%-2% of a fluid loss agent, 5%-10% of micro-silicon and 0.1%-0.5% of a retarder into G-level high sulfate resistant oil well cement, and the water cement ratio is 0.45; the intermediate layer isolating liquid formula is prepared by starting to apply 0.5% polyacrylamide water solution to a position which is 500m lower than the contact surface between clean water and a surface layer cement plug, and the 0.5% polyacrylamide water solution needs to be prepared before 4h; the surface layer cement plug formula is prepared by adding 1% of a dispersant, 1% of a fluid loss agent and 0-0.2% of a retarder into the G-level high sulfate resistant oil well cement, and the water cement ratio is 0.45. According to the suspended cement plug, expensive cement slurry is replaced with intermediate layer isolating liquid, so that the production cost is greatly lowered when the sealing quality is guaranteed, and furthermore, the cement slurry at the reservoir and the surface layer is good in performance and rheological property and strong in anti-pollution capacity and can still maintain good overall performance when 20% of cement slurry is polluted. The suspended cement plug is applicable to the sealing of abandoned wells.

Description

technical field [0001] The invention relates to the technical field of petroleum cementing, in particular to a suspended cement plug suitable for continuous tubing operations in the cementing process of abandoned oil and gas wells and an application method thereof. Background technique [0002] With the continuous development of oil and gas resources, many well plants at home and abroad have entered the middle and late stages of development, and a large number of unused or scrapped wells will appear. These scrapped wells still have some oil and gas left, and many wells still have residual oil and gas at the bottom. There is H 2 S and other highly toxic substances, most of the supporting equipment and pipelines of the well plant have been damaged, and some have not been supervised for a long time, which poses a high safety risk and needs to be blocked to prevent the overflow of residual oil gas and toxic substances. A large amount of clay minerals are often accumulated at th...

AI Technical Summary

Problems solved by technology

At present, cement plugs for coiled tubing operations at home and abroad are usually closed for the entire well section, which is expensive and has low anti-pollution ability of cement slurry. The wellbore needs to be washed with a large amount of spacer fluid in the early stage. The low-cost suspended cement plug formula with strong anti-pollution ability is still available. No report

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