Well-killing workover method used with water plugging

Abstract

The invention discloses a well-killing workover method used with water plugging. The well-killing workover method sequentially comprises the following steps of (1) calculating the use level of required well-killing fluid according to volume of a shaft; (2) determining the density of the well-killing fluid according to formation pressure; (3) determining polymer gel formula which is not easy to degrade in an operation period at formation temperature according to the formation temperature, or determining a gel particle type matched with the size of a pore throat according to characteristics of porosity-permeability of a reservoir; (4) preparing polymer gel or gel particle liquor; and (5) pumping the well-killing fluid into the shaft to perform underground construction operation. By the well-killing workover method, thinking limitation that temporary plugging or lost circulation prevention is often used to recover capacity in existing well-killing workover is overcome, the polymer gel or gel particles with a selective water plugging function serves as the well-killing fluid, two yield increasing technologies comprising oil well water plugging and reservoir temporary plugging protection are combined, a synergistic effect of the two yield increasing technologies is achieved, the capacity after workover of an oil well is improved to a maximum extent, and the well-killing workover method has a wide application prospect in the field of workover of intermediate-high water cut oilfields.

Description

technical field [0001] The invention relates to a well killing and workover method combined with water shutoff, and belongs to the field of oil and gas well kill and workover engineering. Background technique [0002] Most of my country's onshore oilfields have entered the middle and late stages of development. Production wells are generally in a situation of high water cut. The phenomenon of oil well production with disease is common, and workover operations are also frequent. It is worth paying attention to whether oil wells can restore their original production capacity after workover. Especially for low-permeability and low-yield oil wells, the congenital underdevelopment and the pollution caused by improper workover operations in the later stage may even cause the oil well to be scrapped. In order to reduce the damage caused by solid-phase plugging in the workover process, the current development trend of well killing fluids is solid-free. For a long time in the past, s...

AI Technical Summary

Problems solved by technology

This type of completion fluid does not contain bentonite and other solid phases, and the density can be adjusted by adding different types and amounts of soluble inorganic salts, but there are the following problems: On the one hand, the clean brine has a large amount of filtration, especially for low-permeability reservoirs. The leakage of killing fluid in the formation will cause serious water phase trap damage. On the other hand, the density of brine is greatly affected by climate and temperature, and improper control will cause safety accidents. Therefore, its application is greatly limited

The common problem of many solid-free well killing fluids currently developed is that the concentration of the main agent is high, and most of them need to use various and complicated chemical additives, such as fluid loss reducers, stabilizers, viscosifiers, etc. operating costs, but also increases the complexity of on-site configuration, therefore, the problem is obvious

At present, people have not fundamentally recognized the "potential benefits" that this "leakage" or "filtration" can produce, that is, can it trigger the selective water shutoff effect to reduce the water cut of the oil well? Even if the killing fluid leaks into the high-permeability layer, it is expected to further increase production if it can play a selective water shutoff effect

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