# Tensile Overpressure: How to Trap a Liquid-Filled Fracture?

• Nick
In summary, the conversation discusses the concept of liquid-filled fractures and how they can be propagated or trapped. The driving pressure of liquid is determined by the minimum compressional stress and the fluid pressure inside the fracture. The possibility of trapping a fluid-filled fracture is also mentioned, with the example of magma with a lower density than surrounding rock. In diagram 4, the fluid density is intermediate between crust and mantle, causing it to stop opening a fracture and halt at the Moho.
Nick
Hello,

I'm working on how liquid-filled fractures can propagates or be trapped.

I understand that the driving pressure of liquid : Pd = Pm - sigma3
sigma 3 = minimum compressional stress
Pm = (rho_fluid*g*z) + Po = fluid pressure inside the fracture
rho_fluid*g*z = weight of the fluid column
Po = overpressure

But I don't understand how can you trap a fluid-filled fracture in the case of example 4 in the attached document. Since I will need negative overpressure.. and there is no void inside the earth..

thank you

#### Attachments

• Overpressure.pdf
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Consider the fluid as a magma derived from gravitational separation of the local melt. That fluid has a density that is less than the surrounding rock. Where there is a significant vertical connection for the fluid there is a differential pressure between the fluid and the rock that forces the fluid to move upwards creating a fracture that may close behind. Fluid can only rise while the fluid is less dense than the surrounding rock. When it reaches a density transition such as the Moho where there is a step change in rock density, the density differential is removed and so stops the upward migration.

In diagram 4 the fluid density is intermediate between crust and mantle. The bubble of fluid therefore stops opening a fracture and halts at the Moho.

## What is tensile overpressure?

Tensile overpressure refers to the pressure applied to a material or substance that is greater than its tensile strength, causing it to expand or rupture.

## How does tensile overpressure affect liquid-filled fractures?

Tensile overpressure can cause liquid-filled fractures to widen, creating pathways for the liquid to escape. This can lead to contamination of surrounding areas or loss of valuable resources.

## What is the purpose of trapping a liquid-filled fracture?

The purpose of trapping a liquid-filled fracture is to prevent the escape of the liquid and contain it within the fracture. This helps to protect the environment and conserve resources.

## What techniques can be used to trap a liquid-filled fracture?

There are several techniques that can be used to trap a liquid-filled fracture, including hydraulic fracturing, injection of sealing materials, and installation of permeable barriers.

## What are the potential risks of trapping a liquid-filled fracture?

Some potential risks of trapping a liquid-filled fracture include increased pressure and stress on the surrounding rock, potential for induced seismicity, and difficulty in monitoring and controlling the fracture. It is important to carefully consider and manage these risks in order to effectively trap the fracture.

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