an alternative to cacl 2 Alkaline completion fluid and preparation method thereof

Abstract

The invention discloses pollution-free low-damage alkaline completion fluid capable of replacing CaCl2, and a preparation method of the pollution-free low-damage alkaline completion fluid. The alkaline completion fluid comprises the following components in percentage by mass: 30 to 70 percent of potassium carbonate, 1 to 3 percent of hydrophobic modified sodium alginate, 1 to 2 percent of an inhibitor, 1 to 2 percent of a filtrate reducer, 0 to 1 percent of a defoaming agent and the balance of water. The novel alkaline completion fluid capable of replacing CaCl2 saline completion fluid with the density being 1.40 g / cm<3> is prepared by taking hydrophobic modified sodium alginate as a completion fluid tackifier and functional component with environmental friendliness and high compatibility for the first time. The alkaline completion fluid is prepared by adding potassium carbonate, the hydrophobic modified sodium alginate, the inhibitor, the filtrate reducer and the defoaming agent into water sectionally and stirring uniformly. The preparation method is simple and safe, and has extremely good industrial prospect.

Description

technical field [0001] The invention relates to the technical field of brine completion fluid, in particular to a CaCl substitute 2 Alkaline completion fluid and preparation method thereof. Background technique [0002] Completion fluid is the working fluid used in the well completion process. Its main functions include balancing formation pressure, carrying suspended solid particles, and improving reservoir protection capabilities. The use of inferior completion fluids can reduce well productivity by more than 30%, while causing damage to the formation. [0003] CaCl 2 Brine completion fluid is a well-killing fluid system often used in the well completion process at present. Its advantage is that it is cheap and the liquid density can reach 1.40g / cm3 after being completely dissolved. 3 around; however CaCl 2 There are also many disadvantages in brine completion fluid: 1) During construction in winter, due to the low outdoor temperature (below 10°C), due to its physical ...

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Problems solved by technology

Using inferior completion fluids can reduce well productivity by more than 30% while causing damage to the formation

[0003] CaCl 2 Brine completion fluid is a well-killing fluid system often used in the well completion process at present. Its advantage is that it is cheap and the liquid density can reach 1.40g / cm3 after being completely dissolved. 3 around; however CaCl 2 There are also many disadvantages in brine completion fluid: 1) During construction in winter, due to the low outdoor temperature (below 10°C), due to its physical and chemical properties, CaCl 2 The dissolution rate is slow, the solid phase content increases, and the density of the brine solution is difficult to meet the requirements, and sometimes it can only reach 1.25g / cm 3 left and right; 2) due to poor solubility, insoluble particles of inorganic salts invade and cause formation pore blockage; 3) due to CaCl 2 For divalent metal salt, Ca 2+ Salt is prone to scaling, which is not environmentally friendly and will damage the reservoir; 4) The lack of performance of the completion fluid system itself will loosen the cemented particles and dissolve them, dissolve or recrystallize minerals, and cause particle migration and mineral precipitation, resulting in rock formation damage to the reservoir

After the reservoir is damaged, first, it is easy to reduce the production capacity of the oil reservoir, and in severe cases, it will completely lose the oil production capacity, resulting in huge economic losses in the oil field; second, it is very difficult to restore to the original level, and of course the cost is also very expensive

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