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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.
grad(P) = pressure gradient = 8.33 / 19.25 = 0.43273 psi/ft. and the hydrostatic bottom hole pressure (BHP) is then BHP = TVD * grad(P) = 21,000 * 0.43273 = 9,087 psi. However, the formation fluid pressure (pore pressure) is usually much greater than a column of fresh water, and can be as much as 19 lb/U.S. gal (e.g., in Iran). For an onshore ...
Subnormal pore pressure is defined as any formation pressure that is less than the corresponding fluid hydrostatic pressure at a given depth. [6] Subnormally pressured formations have pressure gradients lower than fresh water or less than 0.433 psi/ft (0.0979 bar/m).
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 ...
Subnormal formation pressure. Subnormal formation pressure is a formation pressure that is less than the normal pressure for the given depth. It is common in formations that had undergone production of original hydrocarbon or formation fluid in them. [12] [13] [14] [15]
The pressure gradient and the gravity term are identical for the flux and the rate equations, and will, therefore, be discussed only once. The task here is to have a gravity term that is consistent with the applied units ("H-units") for the pressure gradient. We must, therefore, place our conversion factor together with the gravity parameters.
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 ...