Method for multilayered system differentiation plugging

Abstract

The invention discloses a method for multilayered system differentiation plugging. The method comprises the following steps that a potential-free layer with the high permeability is found out and determined from multilayered system oil layers of a full well section; the potential-free layer with the high permeability is shielded and plugged by squeezing in low-density cement paste in a high-displacement mode; then, squeezing in high-density cement paste in a low-displacement mode is adopted for simultaneous plugging of the full well section. In order to solve the problem that the plugging effect is affected by different starting pressures of plugging layers when multilayered system potential-free oil layers need to be plugged at the same time, the stratum extrusion pressure is increased by shielding the potential-free layer with the high permeability by pumping in low-density cement paste in a large-displacement mode at first, the high-density cement paste is applied for simultaneous plugging of the full well section, the plugging strength is improved, and the plugging effect is ensured.

Description

technical field [0001] The invention relates to the cement plugging technology of the oil layer, in particular to a method for multi-layer differentiated plugging. Background technique [0002] In the process of oilfield development, most of the oil wells are exploited in multiple layers at the same time. Due to the impact of high water cut in the later stage, according to the requirements of oilfield development to control water and stabilize oil, it is necessary to change layers for production. In order to simplify the wellbore structure, the method of cement plugging is generally used for the layer series that has lost production potential. At present, the same density cement slurry is used to plug the non-potential layer to prevent affecting the normal production of the oil well after the layer is modified. [0003] Because the non-potential layer to be plugged is a multi-layer oil layer, affected by comprehensive factors such as oil layer permeability and formation pres...

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Problems solved by technology

[0003] Because the non-potential layer to be plugged is a multi-layer oil layer, affected by comprehensive factors such as oil layer permeability and formation pressure, it is easy to cause a large amount of slurry in the low start-up pressure oil layer during the plugging process, and a large amount of slurry in the oil layer when the plugging pressure is raised. In the middle, due to the impact of water loss under high pressure, the high-pressure layer has not yet started or the amount of slurry is small, and the low-pressure layer loses water too quickly and "cement lumps" appear, resulting in the pressure being stable during the plugging process, and the pressure test after drilling. Qualified conditions, resulting in multiple blockages