Table of Contents
What is pore pressure fracture gradient?
Special Problems of Deep-Sea Oil and Gas Engineering The relationship of formation fracture pressure gradient and depth. The pore pressure gradient is the maximum pressure gradient of oil and gas fluid in the formation pore.
What is pore pressure and normal pore pressure gradient?
1. n. [Geology] The change in pore pressure per unit of depth, typically in units of psi/ft or kPa/m. Pressure increases predictably with depth in areas of normal pressure.
How do you calculate pore pressure gradient?
The basic steps in performing a conventional 1D pore pressure analysis are:
- Calculate total vertical stress (σv) from rock density.
- Estimate vertical effective stress (σe)from log measurements (DT or RES) or seismic (velocity).
- Pore pressure is then PP = σv – σe.
How do you find the gradient of a fracture?
Fracture gradient is obtained by dividing the true vertical depth into the fracture pressure. The fracture gradient is the upper bound of the mud weight; therefore, the fracture gradient is an important parameter for mud weight design in both stages of drilling planning and operations.
What is pore pressure?
Pore pressure is the pressure of the fluid in the pore space of the rock, and as mentioned above, when it exceeds the hydrostatic pressure, overpressure situation occurs.
What is formation fracture pressure?
When a formation fractures, cracks are created within the rock matrix, and fluid in the wellbore will be lost into the fractures. The pressure required to create a fracture is termed “fracture pressure.”
What determines the amount of pressure a formation will support before fracturing?
The factor used to determine formation fracturing pressure as a function of well depth in units of psi/ft. For example, a fracture gradient of 0.7 psi/ft [15.8 kPa/m] in a well with a true vertical depth of 8000 ft [2440 m] would predict a fracturing pressure of 5600 psi [38.6 MPa].
How does the pore fluid pressure influence the formation of fracture?
Increased pore pressure decreases effective stress, leading to fracture failure. Decreasing pore pressure increases effective stress, which can produce crushing.
What is the effect of pore pressure in strength of soils?
A founding principle of slope stability is that a rise in pore-water pressure reduces the shear strength of the soil (Skempton, 1960).