New method for forming manual well wall in oil and gas well by water-absorbing resin

Abstract

The invention relates to a new method for forming manual well walls in an oil and gas wells by water-absorbing resin. In the method, the water-absorbing resin is mixed with freshwater or saline to form a well completion fluid or a workover fluid; the water-absorbing resin is starch-type water-absorbing resin or cellulose-type water-absorbing resin or synthetic water-absorbing resin and comprises the following components by weight percentage: 1 to 2% of water-absorbing resin, 0.2 to 0.5% of water-absorbing initiator, 0.2 to 0.5% of colloid protective agent, and the remaining quantity of water or monovalent saline. The density of the water-absorbing resin well-completion fluid or the workover fluid can be adjusted by adding monovalent salt NaCl or KCl; the solution apparent viscosity can be controlled by adjusting the concentration of the water-absorbing resin; and the dosage of the well completion fluid or the workover fluid can be designed according to the volume of a shaft. In the method, the physical and the chemical changes can occur under the high temperature to form a manual well wall, namely a gelatine temporary plugging layer; therefore, the bearing capability of the high-and low-pressure stratum can be effectively improved; the leakage of the well completion fluid or the workover fluid can be prevented at the producing layer, the operation safety and the capacity of the oil and gas well can be ensured, the construction technology is simple, and the cost is relatively low.

Description

technical field [0001] The invention relates to an artificial well formed in oil and gas wells by using water-absorbing resin in order to protect reservoirs, reduce production costs, and shorten construction period in well completion and workover operations of oil and gas wells in under-injection or depleted development oil and gas reservoirs. New way to wall. Background technique [0002] Many oil and gas fields in my country have entered the middle and late stages of development. Due to under-injection or depletion development, the formation pressure gradient of the main production layers has been much lower than the original formation pressure gradient, and may even be lower than the water column pressure. In this case, if oil and gas wells are to be completed and worked over, during the operation, a large number of completion fluids and workover fluids will inevitably be lost and solid relative to the productive layer will be blocked, making the oil and gas well after op...

AI Technical Summary

Problems solved by technology

The existing problems are: (1) the stability period is short, and the foam killing fluid is stable for 24 to 48 hours. Once it fails, it will cause an excessive positive pressure difference and a large amount of fluid loss; (2) the process is relatively complicated, requiring The use of special liquid dispensing devices and various additives, such as foamers, nitrogen-generating equipment, etc., is costly; (3) The environmental pollution is large, and the discharge of the foam system after the operation will cause a large area of ​​foam pollution on the ground

Its disadvantages are: (1) Special pickling operation is required to resume production after the operation, which increases the operating procedures and prolongs the operating time; (2) The solid phase in the completion fluid will enter the production layer, and the smaller particles will Under the action of pressure difference, it enters the production layer with good porosity and permeability, forming blockage in the production layer and affecting productivity; (3) The polymer of the completion fluid will damage the production layer. On the other hand, the polymer will be adsorbed on the surface of rock particles, reducing the area of ​​the flow channel and reducing the permeability of the oil phase

[0018] Aiming at the protection of oil and gas layers during the completion and workover of normal pressure and low pressure oil wells, some oil and gas fields adopt snubbing operations. The existing problems are: (1) Snubbing operations are highly risky. Due to the risk of blowout, high pressure Oil and gas wells, especially those containing hydrogen sulfide, are not suitable for snubbing operations

When performing snubbing operations in low-pressure oil and gas wells, attention should also be paid to preventing blowout; (2) Snubbing operations need to rent or import special wellhead equipment and blowout prevention equipment, which is expensive

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