Solid-free, pollution-free, low-injury, high-density well completion fluid and preparation method thereof

Abstract

The invention discloses a solid-phase-free pollution-free low-damage high-density well completion fluid and a preparation method thereof. The well completion fluid is prepared from, by mass, 1-5% of potassium hydroxide, 5-10% of potassium dihydrogen phosphate, 15-40% of potassium monohydrogen phosphate, 1-5% of potassium formate, 10-30% of potassium pyrophosphate, 5-12% of cesium formate, 0.2-0.8 % of the viscosity, 1-2% of filtrate-loss reducer and the balance water, the density of the well completion fluid is 1.7-1.9 g / cm<3>, the water solubility of the well completion fluid is good even in low temperature, room temperature and high temperature states, an applicable temperature range is wide, and no solid phase existing in the well completion fluid is really achieved. In addition, the well completion fluid has the advantages that chemical precipitates and dirt are not produced in an underground formation, reservoir pollution is small, damage is small and the formation is not blocked. Furthermore, the preparation method of the well completion fluid is simple, and instant assembly in a field is completely satisfied.

Description

technical field [0001] The invention relates to the technical field of environment-friendly completion fluid, in particular to a solid-phase, pollution-free, low-damage, high-density completion fluid and a preparation method thereof. Background technique [0002] In the well completion process, some salt liquids are usually used as well killing fluid (liquid used to control formation pressure) and workover fluid (liquid for maintaining production wells), which are all working fluids in the well completion process. Adjust the density of the saline solution base fluid according to the desired fluid density. [0003] Typically, chloride or sodium formate is used for lower liquid densities, bromide or potassium formate, etc. for higher liquid densities. For example, if the required density of the formation is only 1.20g / cm 3 Below, use potassium chloride or sodium chloride; if the required density of formation is 1.30g / cm 3 Sodium formate is used; if the formation requires a ...

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Problems solved by technology

[0004] At present, the low-density intervals are all monovalent metal salts, so the damage and pollution to the reservoir are relatively small, so the existing problems are relatively small; while there are many problems in the high-density intervals, such as when calcium salts are used to prepare completion fluids, on-site dispensing Difficult to liquid, especially in winter, a lot of solid particles precipitate out, it is difficult to meet the construction requirements of ready-to-use, and the liquid density is difficult to meet the requirements due to the low solubility; in addition, divalent calcium salts, zinc salts in It is easy to scale and precipitate in the downhole formation, causing reservoir blockage and polluting the reservoir; although sodium bromide can reach a density of 1.50g / cm 3 About, but the price is expensive; although the saturated solution of potassium formate can be increased to close to 1.60g / cm 3 Density, which is achieved by adding more than 3 tons of potassium formate to 1 ton of water, the large amount will lead to high prices

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