Petroleum Geology

Forms of Petroleum

Liquid (crude oil), Solid (coal, tar, bitumen), Gas (natural gas)

API Gravity

Measure of crude oil density in degrees; <12° will not flow

Light Oil

Low density, high API gravity, more expensive

Heavy Oil

High density, low API gravity, less expensive

Sweet Crude

Sour Crude

0.5% sulfur, cheap to buy, expensive to refine

Brent Blend

Worldwide benchmark, light and sweet

West Texas Intermediate (WTI)

USA benchmark, light and low sulfur

Dubai-Oman

Asian benchmark, light and sour

Major Crude Oil Products

Gasoline (47%), Diesel/heating oil (23%), Other (18%), Jet fuel (10%), LPG (4%), Asphalt (3%)

Philippine First Commercial Oil

Nido-1 in NW Palawan (1976)

Malampaya Gas Field

2002

Galoc Oil Field

2008

Petroleum System

Source rock, Reservoir rock, Seal rock, Trap

Source Rock

Function: Generate and mature oil/gas; rich in kerogen; must be sedimentary

Kerogen

Organic material in source rock that generates hydrocarbons

Total Organic Carbon (TOC)

Weight % of organic carbon in dry rock; used to assess source quality

Kerogen Type I

Lacustrine, Alginite (algae), Oil-prone

Kerogen Type II

Marine, Exinite (pollen/spores), Oil & gas prone

Kerogen Type III

Terrestrial, Vitrinite (woody plants/coal), Gas-prone

Kerogen Type IV

Inertinite (oxidized/reworked), No hydrocarbon potential

Maturation Stages

Diagenesis → Catagenesis → Metagenesis

Oil Window

Temperature ~60°C to ~120°C

Gas Window

Temperature ~120°C to ~180°C

Vitrinite Reflectance

Common lab technique to measure thermal maturity

Reservoir Rock

Must be porous and permeable; stores and transmits hydrocarbons

Primary Porosity

Space between grains (pre/syn-depositional)

Secondary Porosity

Created after deposition (dissolution, fracturing, diagenesis)

Permeability

Ability of rock to transmit fluids

Acidization

Enhancing reservoir by injecting HCl to dissolve cement

Hydraulic Fracturing

Injecting pressurized fluid + sand to create fractures

Seal Rock / Cap Rock

Impermeable layer that prevents hydrocarbon escape; best are fine-grained, continuous, ductile

Most Common Seal Rock

Shales

Trap

Configuration that stops hydrocarbon movement; preserves accumulation

Structural Trap

Folds, faults, piercements, anticlines

Stratigraphic Trap

Facies change, pinch-out, reefs, dunes

Combination Trap

Structural + stratigraphic

Anticline Trap

Holds most of the world’s petroleum

Primary Migration

Expulsion from source rock to carrier bed

Secondary Migration

Movement from carrier to reservoir

Tertiary Migration

Movement from one reservoir to another

New Palawan Petroleum System - Source

Guinlo Formation (syn-rift)

New Palawan Petroleum System - Reservoir

Nido Limestone (reefal carbonates)

New Palawan Petroleum System - Seal

Pagasa Formation (deep marine shale)

New Palawan Petroleum System - Trap

Structural + stratigraphic

Upstream Industry Phase

Exploration, Appraisal, Development, Production

Midstream Industry Phase

Processing, Storage, Marketing, Transportation

Downstream Industry Phase

Refining, Retail, Petrochemicals

Pre-concession Phase

Basin analysis, identifying oil province vs frontier

Philippine Department of Energy (DOE)

Supervises petroleum exploration via PECR

Seismic Reflection Survey

Main geophysical method using shock waves; uses Snell’s Law

Drillable Prospect

End goal of exploration

STOOIP

Stock Tank Oil Originally In Place

Reserves

Economically recoverable portion of petroleum

Recovery Factor

Oil: 20-30%; Gas: 70-80%

Primary Recovery

Uses natural reservoir energy

Appraisal Phase

Delineate reserves after discovery; most expensive

Abandonment Phase

When production cost = revenue; plug wells and decommission

Oil Seep

Natural leak of oil/gas from seafloor

Oil Spill

Human-caused release of petroleum into environment