TITLE:
New Pore Pressure Evaluation Techniques for LAGIA-8 Well, Sinai, Egypt as a Case Study
AUTHORS:
Ahmed Zakaria Noah
KEYWORDS:
Pore Pressure, Resistivity and Sonic Methods, Seismic Velocities, Formation Damage
JOURNAL NAME:
International Journal of Geosciences,
Vol.7 No.1,
January
28,
2016
ABSTRACT: Drilling into a
geopressured zone will generally cause a change in a number of basic formation/
drilling relationships. This change is usually seen as a reversal of a gradual
depth related trend in a lithologically uniform formation. Of all the
geophysical methods, the reflection seismic method is essentially the only
technique used to predict pore pressures. The seismic method detects changes of
interval velocity with depth from velocity analysis of the seismic data. These
changes are in turn related to lithology, pore fluid type, rock fracturing and
pressure changes within a stratigraphic column. When the factors affecting the
velocity are understood for a given area, a successful pressure prediction can
be made. For clastic environments such as the Tertiary section of the Gulf of
Mexico or the Niger delta, the interval velocity of the rocks increases with
depth because of compaction. In these areas, deviations from normal compaction
trends are related to abnormally high pore pressures. The adapted methods
provide a much easier way to handle normal compaction trend lines. In addition
to well log methods, pressure detection can be obtained via drilling parameters
by applying Eaton’s DXC methods. Seismic velocities have long been used to
estimate pore pressure, indeed both these quantities are influenced by
variations in rock properties such as porosity, density, effective stress and
so on, and high pore pressure zones are often associated with low seismic
velocities. Pressure prediction from seismic data is based on fundamentals of
rock physics and seismic attribute analysis. This paper hence tries to assess
the use of seismic waves as a viable means to calculate pore pressure,
especially in areas where no prior drilling history can be found. Then we
applied these methods on LAGIA-8 well, Sinai, Egypt as a case study. Pore
pressure prediction from Seismic is a very essential tool to predict pore
pressure before drilling operation. This could prevent the well problem as well
blowout and to prevent formation damage, especially in areas where no prior
drilling history can be found.