A temperature-sensitive low fluid loss underground cross-linking plugging agent for sealing cracks and its application

Abstract

A temperature-sensitive low fluid loss underground cross-linking plugging agent for sealing cracks and its application method. The plugging agent includes the following components in weight percentage: starch, acrylamide, cross-linking agent, initiator, and reinforcing agent , the balance is water; when in use, add starch to water and fully stir to disperse it evenly, configure it into a starch slurry, then add acrylamide, cross-linking agent, initiator and reinforcing agent and mix evenly to form a reaction solution, and the reaction solution Inject into formations with a temperature of 65-90°C and shut down the well for several days to seal the fractures. The invention overcomes the problem that the current monomer gel plugging agent system is easy to leak into the matrix and damage the formation during the injection process. The invention has gelatinization under reservoir conditions and the gelatinization time is short, and the viscosity quickly increases to 200-900mPa ·s, while ensuring injectability, it also reduces the fluid loss of the plugging agent system in the matrix.

Description

technical field [0001] The invention relates to the technical field of oil and gas field development, in particular to an underground cross-linking plugging agent with temperature sensitivity and low fluid loss for sealing fractures. Background technique [0002] Horizontal well production in reef limestone reservoirs has technical advantages such as increasing the oil drainage area of ​​the reservoir and improving the production degree of thin oil and gas layers, and has a wide range of applications. Reef limestone reservoirs are generally composed of matrix and micro-fracture systems. Among them, the matrix permeability is generally 150mD-450mD, and the fractures are mostly high-angle fractures, resulting in serious heterogeneity of the reservoir and more complicated water flooding mechanism. For bottom-water fractured reef limestone reservoirs, the problem of water production is usually more serious. Therefore, solving the problem of rapid rise in water cut, reducing the ...

AI Technical Summary

Problems solved by technology

[0003] The existing plugging agents suitable for fractured reservoirs can be divided into above-ground cross-linking plugging agents and underground cross-linking plugging agents according to their cross-linking forms during injection. Among them, one of the disadvantages of above-ground cross-linking plugging agents is pumping performance. At the same time, according to Wang Baohui and others in the article "The Effect of Mechanical Shearing on the Viscosity of Polymer Solution", the viscosity of water-soluble polymer blocking agent will have a large loss after shearing, such as Liu Rui The secondary cross-linked gel proposed in the patent CN108300441B can solve the problem of gel-type plugging agents to seal cracks to a certain extent, but the secondary cross-linked gel still faces shear degradation during the injection process, and before gelation Viscosity loss is a serious problem, and in the case of low viscosity, the polymer plugging agent is easily absorbed by the reservoir matrix, resulting in the fluid loss of the plugging agent in the matrix, and finally reducing the permeability of the matrix and the recovery factor.

For the underground cross-linking plugging agent, it has good pumping performance, but the conventional underground cross-linking agent has the problem that: due to the low initial viscosity of the underground cross-linking plugging agent, it is very easy to flow into the reservoir after being injected into the formation. Matrix penetration causes the filtration loss of the plugging agent. At the same time, due to the different absorption efficiencies of the reservoir matrix to the different components in the underground cross-linking plugging agent, the content and ratio of each component in the plugging agent when cross-linking reaction is different from the The optimal ratio is different, resulting in poor gel effect or even no gelation

Therefore, based on the aforementioned problems, the performance of the current underground cross-linking plugging agent in the application of crack plugging needs to be further improved

Images