Multistage plug classification plugging method suitable for fissured stratum

Abstract

The invention relates to a multistage plug classification plugging method suitable for a fissured stratum. The multistage plug classification plugging method includes the steps that first, the averageopening of fissures in the periphery of a well is determined to be D, bridging particles with the particle size being slightly smaller than D are used in first-stage plugging, the average particle size of the bridging particles is denoted as D<1>, the average particle size D<2> of plugging particles used in second-stage plugging is larger than D<1> / 4, and smaller than D<1>, and the particle sizeof each of the following stages of the plugging particles is successively determined through the same method until the average particle size D<n> of the last stage of the plugging particles is small enough to form a dense sealing layer; second, plugging grout only containing the bridging particles with the average particle size being D<1> is first injected through slugs to form a bridging particlelayer; third, plugging grout containing the plugging particles with the average particle size being D<2>-D<n-1> is injected in several times through a plurality of slugs to form a particle filling layer; and fourth, plugging grout with the average particle size of the plugging particles being D<n> is finally injected through the slugs to form the dense sealing layer. According to the multistage plug classification plugging method suitable for the fissured stratum, the principle is reliable, the fissures in the periphery of the well are more effectively sealed, the cost is saved, and the broadapplication prospects are achieved.

Description

technical field [0001] The invention relates to a multi-segment staged leak plugging method suitable for fractured formations in drilling plugging operations in the field of oil and gas field exploration and development. Background technique [0002] When severe drilling fluid loss occurs in the drilling process of petroleum engineering, it is often caused by natural fractures in the well or induced fractures caused by bottomhole pressure. In order to eliminate or reduce the loss, it is necessary to seal the fractures around the well according to the actual engineering situation. The usual practice is to add plugging materials of different particle sizes and types to the drilling fluid according to the amount of leakage and the location of the leakage, and then inject it downhole at one time to seal the fractures around the well. The basic principle of the formation of plugging is that larger-sized particles form a bridge in the narrow part of the fracture, which narrows the...

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Problems solved by technology

[0003] (1) Changes in wellbore fluid column pressure will cause dynamic deformation of formation fractures, which will change the position, plugging state, and pressure bearing capacity of the original effective sealing layer, which may cause damage to the sealing layer, resulting in repeated leakage;

[0004] (2) Plugging particles of different particle sizes are mixed in the plugging working fluid. Before a tight seal is formed, some small-sized particles will leak into the formation through the gap between the fracture channel and the large-sized particles, resulting in the loss of plugging particles. waste, which increases costs;

[0005] (3) For fractured reservoirs, fractures are the main flow channels for oil and gas migration, so the production of fractured reservoirs is much higher than that of other reservoirs, and during the drilling plugging process, the lost plugging particles enter the formation through fractures Throats block the channels for oil and gas production, greatly reducing production and causing solid particle intrusion damage

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