Ch. 5 Pore Pressures and Fracture Pressures

Terminology - Formation Pore Pressures

• Pore Pressure• P-Z Diagrams• Pore Pressure Gradient• Overbalance• Underbalance• Normal Pressure Gradient• Abnormal Pressures

Pore Pressure Profiles

Overbalance

Typical Pressures

Normal Pressures

Overpressure

Underpressure

Importance of Pore Pressures

• Underbalance• Borehole Collapse

• Influx

• Overbalance• Low ROP

• Formation Fracture

• Differential Sticking

Origin of Overpressure• Overpressure

• Incomplete Sediment Compaction

• Faulting

• Phase Changes

• Massive Rocksalt Deposition

• Salt Diaperism

• Tectonic Compression

• Repressuring

• Hydrocarbon Generation

Origin of Subnormal Pressures

• Sub normal Pressure• Thermal Expansion

• Formation Foreshortening

• Depletion

• Precipitation

• Potentiometric Surface

• Epeirogenic Movements

Uncompacted Sands

Formation Foreshortening

Piezometric Surface

Acquifers

Pore Pressures

Abnormally Pressured Sands

Transition Zone

• Shale Caprock

• Salt Caprock

Transition Zones

Formation Fracture Pressure

• Mechanism of Breakdown• Leak-off Test/Limit Test

• Procedure

• Maximum Mudweight

• Maximum ECD• MAASP

• Calculating Fracture Pressure

Fracture Pressure

Leak Off Test

Fracture Test

Leak Off Test

Limit Test

Mechanism of Breakdown

Leak Off Test

Regional Faulting

Poissons Ratio

HPHTWells