Ultralow density plugging agent for low-pressure leaking formations and preparation method thereof

Abstract

The invention relates to an ultralow density plugging agent for low-pressure leaking formations and a preparation method thereof. According to the technical scheme, the ultralow density plugging agent is composed of, by weight, water as a continuous phase, 50-70% of a gel plugging agent, 0.1-0.3% of plugging fiber, 2.5-3.5% of a surfactant, 2-6% of a lightweight rigid plugging additive, 1-2% of polymer and 0.5-2% of water-absorbent expansion resin. the invention has the following beneficial effects: through built-in-test, the lowest density of the prepared plugging agent can reach 1.0g / cm<3>, and density is adjustable; the plugging agent has good temperature resistance which can reach 180 DEG C, and is especially suitable for plugging of deep and ultra-deep wells; bearing capability is greater than or equal to 15 MPa, and the plugging agent has characteristics of large plugging depth and good plugging effect and is applicable to various types of formation leakage such as large-sized cracks and pore-fractures, etc.

Description

technical field [0001] The invention relates to the technical field of oil and gas well engineering, in particular to an ultra-low density plugging agent suitable for low-pressure and leaky formations and a preparation method thereof. Background technique [0002] With the deepening of oil and gas exploration and development, the formations encountered in the drilling process are becoming more and more complex. When drilling pressure-depleted formations, broken or weakly cemented formations, and fracture-developed formations, the problem of well leakage is very prominent, especially in some low-pressure and easy-to-leakage formations. There will also be the problem that the density of the plugging slurry is too high to re-press the formation, requiring repeated plugging. Once a leakage occurs, it will not only delay the drilling time, lose the drilling fluid, damage the oil and gas layers, and interfere with the geological logging work, but also may cause a series of complex...

AI Technical Summary

Problems solved by technology

[0006] 1. The density of the plugging slurry configured by the existing plugging technology is too large, and there is a lack of efficient and high-strength ultra-low density plugging technology specially for low-pressure and easy-to-leakage formations;

[0007] 2. For pressure plugging in large channels and fractured complex loss wells, the plugging agent cannot effectively reside in the loss zone, coupled with the flow and scour of the formation water in the loss zone, it is often diluted and lost, making it difficult to The lost zone forms an effective sealing layer, and the formation has low compressive strength;

[0008] 3. Bridge plugging materials with medium and large particles cannot enter the formation, and are easy to seal on the well wall and can only play a temporary plugging role and cannot bear pressure. However, high-strength plugging slurry such as cement has poor bonding ability with the broken formation, and its strength is not high. Matching, it is easy to produce hard and brittle fracture, and the formation bearing strength is low;

[0009] 4. The plugging slurry has poor high temperature resistance, and the plugging material will soften, deform or carbonize in the deep leakage layer, especially under high temperature and high pressure, thus losing its bridging function, and will soon lose its bridging and supporting function in the leakage channel. Thus losing the plugging effect