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Development of a model to calculate mechanical specific energy for air hammer drilling systems

Drilling for hydrocarbons is an expensive operation; consequently operators try to save
costs by reducing the number of days spent during this operation. Drilling efficiently
with the highest attainable rate of penetration is one of the ways drilling time could be
reduced. Real-time monitoring of Mechanical Specific Energy will enable drilling
engineers to detect when the optimum drilling rate for a given set of drilling parameters
is not being achieved.
Numerous works have been done on air hammers and rock Mechanical Specific Energy.
Previous research has shown that Mechanical Specific Energy, which is a ratio that
quantifies the input energy and Rate of Penetration (ROP) of a drilling system, is directly
proportional to the rock compressive strength being drilled. The Mechanical Specific
Energy model utilizes drilling parameters such as ROP, Weight on bit (WOB), RPM,
torque, flow-rate, bottom-hole pressure, and bottom-hole temperature to show how
effectively energy being put into the drill string is being converted to ROP at the bit.
This research effort proposes a new model to calculate the Mechanical Specific Energy
for air hammer drilling systems. A thermodynamic model for the air hammer from
which the piston impact velocity and kinetic energy is obtained is presented. To be able
to estimate the effective energy delivered to the rock by the hammer, the stress wave
propagation model is used and factored into the Mechanical Specific Energy model. The Mechanical Specific Energy values obtained from the application of this model
provide a qualitative indicator of formation pressure changes and a means for drilling
engineers to detect when optimum drilling rate is not being achieved. It can be deduced
from the model that the impact energy of the hammer is greatly affected by the pressure
drop across the hammer and since the hammer accounts for about sixty percent of the
energy required for destroying the rock, the ROP can be varied by varying the pressure
drop across the hammer.
Date15 May 2009
CreatorsOkuchaba, Boma Jeremiah
ContributorsSchubert, Jerome J.
Source SetsTexas A and M University
Detected LanguageEnglish
TypeBook, Thesis, Electronic Thesis, text
Formatelectronic, application/pdf, born digital

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