Plugging method of fluid gel for plugging off gas layers by using formation temperature to generate plugging valve

Abstract

The invention discloses a blocking method adopting fluid gel for producing a blocking valve by a formation temperature to block a gas reservoir. The blocking method comprises the following steps that a), a gel crosslinked system and a gel initiator are uniformly mixed until the mixed solution has no fish eye-shaped structure so that a fluid solution is obtained; b), the fluid solution is fed into a shaft by a pump and forms gel after gelation waiting; c), after ground operation, a gel breaker aqueous solution is added into the gel in the shaft, wherein the gel breaker aqueous solution comprises 2-5wt% of a gel breaker and the total weight of the gel breaker is 0.1-2% of that of the gel crosslinked system; and d), after the fed gel breaker aqueous solution contacts with the gel, the gel breaker makes the gel lose blocking performances and the broken gel is fed back to the ground. The blocking method has simple processes. The fluid gel for blocking has a low cost and very high pressure resistance.

Description

technical field [0001] The invention relates to a method for preparing a fluid used to form a gel isolation valve to seal an oil and gas layer by using formation temperature. The prepared fluid gel is especially suitable for an oil and gas reservoir as a casing valve to form an isolation area between the reservoir and the ground , It is convenient for low-pressure operations such as wellhead disassembly and assembly. Background technique [0002] In the process of wellhead construction in medium and low pressure reservoirs, in order to prevent formation fluids (oil, gas, water) from gushing out of the wellhead and cause danger, mechanical packers are often lowered and installed in the wellbore at a certain depth, between the wellbore and the surface. Form a blockage between them, which is convenient for wellhead construction operations. [0003] At present, the price of mechanical casing valves used is relatively high, and the equipment is mainly imported. The domestic rese...

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Problems solved by technology

[0006] 1. In the existing patent literature, there is no disclosure of the method of using the above-mentioned gel for plugging;

[0007] 2. The existing gel formula is relatively complicated, the gel cost is high, and the pressure resistance and sealing are not enough;

[0008] 3. The existing gel formula has poor water retention performance after being gelled, and lacks better water retention monomers in the gel;

[0009] 4. The cross-linking agent only uses potassium persulfate or ammonium persulfate, which belongs to the water-soluble inorganic peroxygen gel initiator. This type of initiator is greatly affected by temperature, that is, the reaction must be initiated at a certain temperature and the reaction is easy to occur. Inhomogeneous gel, local dehydration

[0010] 5. In the existing patent literature, the method of mechanically breaking the gel with the drill bit is used to unblock the gel, but for the gel with viscoelasticity, mechanical breaking is difficult to achieve