Plug-removing agent for low-permeability heterogeneous sandstone reservoir and its application method

Abstract

The invention discloses a blocking remover for hypotonic inhomogeneous sandstone reservoir and a using method of the blocking remover. The blocking remover comprises an agent A, an agent B and an agent C, wherein the agent A consists of the following components in percentage by weight: 10%-25% of oxidant, 8%-12% of activator and the balance of water; the agent B consists of 10%-15% of a reducing agent, 0.3%-1.2% of a foaming agent, 0.3%-0.6% of a foam stabilizer, and the balance of water; the agent C consists of 8%-12% of HCL, 6%-10% of organic acid, 2%-5% of NH4HF2, 0.5%-1.5% of a corrosion inhibitor, 0.5%-1.5% of an iron ion stabilizer and the balance of water. The using method comprises the steps of step one, preparing the agent A, the agent B and the agent C; and step two, injecting the agent A into a ground layer by a pipeline, then injecting the agent B into the ground layer, and finally injecting the agent C into the ground layer. The blocking remover disclosed by the invention has beneficial effects that the blocking remover disclosed by the invention can be applied to decompression and augmented injection of a water injecting well and deep unblocking of an oil well; and the blocking remover has better effect while being applied to augmented injection of the water well in a reservoir non-homogeneous oil-field block.

Description

technical field [0001] The invention relates to a plug-removing agent and a using method, in particular to a plug-removing agent and a using method for low-permeability heterogeneous sandstone reservoirs. Background technique [0002] At present, in the process of oil production in oil fields, especially for low-permeability oil fields, with the prolongation of production time, the clogging of the near-wellbore area will continue to increase, and the seepage resistance of formation fluid will increase, resulting in the increase of water injection pressure in water wells and the reduction of water injection volume. In order to remove plugging, acidizing technology is the main measure to increase production and injection to maintain high-efficiency oilfield production. At present, matrix acidizing technology is mostly used for plugging removal. For this kind of situation, sandstone matrix acidizing is generally used. From the acidizing mechanism, it can be divided into These a...

AI Technical Summary

Problems solved by technology

[0003] The first category, soil acid acidification uses hydrofluoric acid in soil acid to dissolve silicate minerals such as clay and feldspar in the formation to improve the permeability of the formation near the wellbore. The technical defect of this type is that the improvement radius is small, Easy to cause secondary damage, short validity period

For example, "Analysis of damage to sandstone reservoirs after acid treatment and treatment measures", Inner Mongolia Petrochemical, No. 12, 2005, analyzed various damages and corresponding treatment measures after acidizing sandstone reservoirs; "Sandstone acidification Application of Technology in the Development of Jin 45 Oilfield", Oil and Gas Well Testing, Vol. 10, No. 3, 2001. Soil acid acidification and plugging removal was carried out in Jin 45 sandstone oilfield. Good results were achieved at the initial stage, but the validity period was short

[0004] The second type, slow acid acidification mainly uses formic acid, acetic acid, boric acid, phosphoric acid and other weak acids to react with fluorine salts in the formation to generate hydrofluoric acid, which dissolves silicate minerals such as clay and feldspar in the formation to improve formation permeability The main advantage of this type of acidification is that the radius of action is larger, and the secondary damage is weaker than that of soil acid. However, when applied to heterogeneous formations, the acid mainly enters high-permeability formations, and has a limited effect on improving low-permeability formations. for the purpose of effectively unblocking

[0005] The third category, foam acid acidification is to add a certain proportion of foaming agent to conventional acid liquid, mix with nitrogen, carbon dioxide gas or natural gas and stir at high speed to form a foam system with acid liquid as the continuous phase and bubbles as the dispersed phase. Acids are suitable for production stimulation of low-pressure oil and gas wells that are difficult to flow back. The disadvantages are that the addition of gas increases the mechanical cost of construction, and the size of the generated foam is uneven. During the construction, it is easy to generate gas plugging and cause the construction pressure to be too high. The liquid state used Gas deals cold damage to formations

[0006] The fourth category, thickened acid acidification is to add a certain amount of acid gelling agent or polymer to the conventional acid system, which can reduce the rate of acid fluid loss and the reaction rate between acid and formation rock, thereby greatly increasing the activity The effective penetration distance of acid, its main disadvantage is that the flowback of thickened acid is difficult, and it is easy to cause secondary damage

[0008] 1. Conventional soil acid acidification has a small improvement radius, is prone to secondary damage, and has a short validity period;

[0009] 2. When the retarded acid is applied to the heterogeneous formation, the acid liquid mainly enters the high-permeability formation, and has limited improvement effect on the low-permeability formation, and cannot achieve the purpose of effective plugging removal;

[0010] 3. The size of the foam generated during the acidification of foam acid is uneven, and the gas blockage is easy to occur during the construction process, causing the construction pressure to be too high, and the liquid gas used will cause cold damage to the formation;

[0011] 4. When acidifying thickened acid, it is difficult to flow back and easily cause secondary damage.

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