Pore pressure and

fracture pressureGRAPHS AND TABLES

M.V.V.S ANUPRAKASH, PETROLEUM TECHNOLOGY

Normal Formation pressure gradients

• The list of values of the normal

formation pressure gradients for

several areas of active drilling in USA

Normal Subsurface fluid pressure

distribution in shallow deltaic sediments

One dimensional compaction

model of sediments

Bulk density curve from density log data

Average porosity from porosity log data

Vertical over burden stress resulting from geostatic

stress and bulk density

On

rearranging

the

equation

By substituting in

the equation

From porosity vs Depth graph

by fitting the trend line

In offshore areas integration of

the equation by separating into

0 to Dw (sea water)

Dw to D (subsurface formation)

Ds= D-Dw

Examples for calculation using the

previous formulas

Abnormal pore pressure cases

Abnormal pore pressure cases

Abnormal pore pressure cases

Abnormal pore pressure cases

Possible mechanism of formation pressure

seal above abnormal pore pressure zone

Situations of upward fluid migration resulting

abnormal shallow fluid pressures.

Predicting formation pressures

Relationship between Porosity, Interval transit time, Matrix

transit time, formation pressure gradient

Seismic record of transit time

data and calculation of porosity

Typical behavior of formation pressure, well pressure,

and formation fracture resistance in abnormally

pressured well.

Prediction of

Formation Fracture

Prediction model for fracture

pressure

Hubbert and Willis equation

Mathews and Kelly’s correlation

Pennebaker correlation

Eaton’s correlation

Christman correlation

MacPheron and Berry Correlation

Hubbert and Willis equation

Mathews and Kelly’s correlation

Pennebaker

correlation(similar to Mathews and Kelly)

1. Fa from the Graph 1

2. Overburden gradient from

graph2

Fa from the

Above Graph

Overburden gradient from

above graph

Eaton’s correlation

Christman correlation

MacPheron and Berry Correlation

Leak off test