| Over recent years, underbalanced drilling technology has gained popularity because of its effectiveness in reducing or eliminating the impact of drilling fluid invasion, especially in horizontal wells. The objective of this work is to use the measured bottomhole pressure and total production data during the drilling operation to estimate the reservoir permeability and its variation along the length of the wellbore.;During underbalanced drilling, the total transient production rate depends on reservoir characteristics as well as the bottomhole pressure and well penetration rates. It carries information about reservoir permeability, etc. Analysis of the production data is similar to a complex well test. Part of the complexity arises from the fact that the boundary conditions (i.e. the well trajectory open to flow) change with time during the test. Other sources of complexity are the variable drilling rate and the variable bottomhole pressure.;In this work, analysis is initially preceded using Laplace transformation with the following assumptions: constant bottomhole pressure and fixed wellbore length for the new exposed segment, no pressure drop along the length of the wellbore, 1-dimensional transient flow perpendicular to the wellbore and convergent flow into the horizontal well. (Abstract shortened by UMI.)... |
