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The Corrected d-exponent, also known as dc-exponent or cd-exponent, is a parameter used in mud logging and formation pore pressure analysis in the petroleum industry. It is an extrapolation of certain drilling parameters to estimate a pressure gradient for pore pressure evaluation while drilling, particularly in over-pressured zones.
The pressure value that is attempted to compute, is such that when plugged into momentum equations a divergence-free velocity field results. The mass imbalance is often also used for control of the outer loop. The name of this class of methods stems from the fact that the correction of the velocity field is computed through the pressure-field.
Using the figures above, we can calculate the maximum pressure at various depths in an offshore oil well. Saltwater is 0.444 psi/ft (2.5% higher than fresh water but this not general and depends on salt concentration in water) Pore pressure in the rock could be as high as 1.0 psi/ft of depth (19.25 lb/gal)
Fracture pressure can be expressed as a gradient (psi/ft), a fluid density equivalent (ppg), or by calculated total pressure at the formation (psi). Fracture gradients normally increase with depth due to increasing overburden pressure .
In fluid mechanics, the pressure-gradient force is the force that results when there is a difference in pressure across a surface. In general, a pressure is a force per unit area across a surface. A difference in pressure across a surface then implies a difference in force, which can result in an acceleration according to Newton's second law of ...
The horizontal pressure gradient is a two-dimensional vector resulting from the projection of the pressure gradient onto a local horizontal plane. Near the Earth's surface, this horizontal pressure gradient force is directed from higher toward lower pressure. Its particular orientation at any one time and place depends strongly on the weather ...
The second equation expresses that, in the case the streamline is curved, there should exist a pressure gradient normal to the streamline because the centripetal acceleration of the fluid parcel is only generated by the normal pressure gradient. The third equation expresses that pressure is constant along the binormal axis.
Under formation pressure, there are 3 levels: normally pressured formation, abnormal formation pressure, or subnormal formation pressure. Normally pressured formation As the fluids above the formation are usually some form of water, this pressure can be defined as the pressure exerted by a column of water from the formation's depth to sea level.