Petroleum Geology

The Context of Petroleum Geology

What is petroleum geology

• It is the application of geology (the study of rocks) to the exploration for and production of oil and gas.

• Geology itself is strongly based on chemistry, physics and biology, involving the application of essentially abstract concepts to data.

• In the past these data were basically observational and subjective.

• Petroleum geology, in particular still rely on value judgments based on experience and an assessment of validity among the data presented.

• Exploration had advanced over the years as various geological techniques were developed.

A History of Petroleum

Ancient: • Egypt: oil to preserve mummies• China: natural gas for fuel• Babylonia: oil to seal walls and pave streets• America: tar to seal canoes

First Drilling: • America: using cable tool: to 70’ in 1859

First Product: • Kerosene for lamps (Gasoline an unwanted by-product)

Demand: • Industrial Revolution- Internal Combustion Engine (1885)- Global Economic Growth

Natural Oil Spills

Anticlinal Theory

Gas Oil

Water

Petroleum Accumulates in Structural Closure

Drill here!

Exploration and Production : Seismic Surveys

•Seismic surveys are used to locate likely rock structures underground in which oil and gas might be found

• Shock waves are fired into the ground. These bounce off layers of rock and reveal any structural domes that might contain oil

We’ve just established what kind of structures tend to trap oil and gas in the Earth’s crust, but how do we locate potential traps underground? One technique is to use seismic surveys. In this technique, a Vibrator Truck fires shock waves into the ground. The shock waves pass through some rock layers and bounce off others. By recording how long it takes for the shock waves to arrive back at the surface allows geologist to build a picture of the internal structure of the rocks beneath their feet. An example of a seismic survey is shown in the diagram on the right. It reveals a large underground dome in the rocks. As we have seen domes often trap oil and gas so this may be a potential site to drill.

notes: The term seismic is derived from the Greek for “shake” (think earthquakes!)

Industry ‘Technological’ Milestones

1883: Anticlinal theory (where to drill)

1914: Seismograph invented (remote sensing)

2D Seismic LineGulf of Mexico (offshore)

Industry ‘Technological’ Milestones1883: Anticlinal theory (where to drill)

1914: Seismograph invented (remote sensing)

1920s: Introduction of rotary drilling (well control, environment)

Large Land Drilling RigRotary Drilling Rig Schematic

Industry ‘Technological’ Milestones

1883: Anticlinal theory (where to drill)

1914: Seismograph invented (remote sensing)

1920s: Introduction of rotary drilling (well control, environment) Start of waterflooding (improved recovery)

1924: First electrical well logging (formation evaluation)

Industry ‘Technological’ Milestones

1883: Anticlinal theory (where to drill)

1914: Seismograph invented (remote sensing)

1920s: Introduction of rotary drilling (well control, environment) Start of waterflooding (improved recovery)

1924: First electrical well logging (formation evaluation)

1930s: Offshore drilling (access to prospective areas)

Jack-Up Drilling Rig (Texas Federal Waters ~150’ water depth)

Industry ‘Technological’ Milestones

1883: Anticlinal theory (where to drill)

1914: Seismograph invented (remote sensing)

1920s: Introduction of rotary drilling (well control, environment) Start of waterflooding (improved recovery)

1924: First electrical well logging (formation evaluation)

1930s: Offshore drilling (access to prospective areas)

1960s: Digital computers (data manipulation)

1970s: Directional drilling

1980s: 3D seismic (enhanced imaging)

http://www.google.com.my/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=alka-Nh7piAP-M&tbnid=Cgjf1s3xqOaxyM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.wou.edu%2Flas%2Fphysci%2FEnergy%2Foil.html&ei=uVY3UZiqJMqYiAfUm4GIDA&bvm=bv.43287494,d.bmk&psig=AFQjCNEsqUJAEjYUybC3cA_PyuJBEzQyZg&ust=1362667512256268

Relief Well Control

Petroleum System

A Petroleum System is defined as a natural system that encompasses a pod of active source rock and all related oil and gas and which includes all of the geologic elements and processes that are essential if a hydrocarbon accumulation is to exist.

(Leslie B. Magoon and Wallace G. Dow, AAPG Memoir 60)

DEFINITION

MR@Aug2008

• Source Rock - A rock with abundant hydrocarbon-prone organic matter

• Reservoir Rock - A rock in which oil and gas accumulates:- Porosity - space between rock grains in which oil

accumulates - Permeability - passage-ways between pores through which oil and gas moves

• Seal Rock - A rock through which oil and gas cannot move effectively (such as mudstone and claystone)

• Migration Route - Avenues in rock through which oil and gas moves from source rock to trap

• Trap - The structural and stratigraphic configuration that focuses oil and gas into an accumulation

Source: AAPG

PETROLEUM SYSTEM ELEMENTS - DEFINITION

MJH@Mac2007

The elements

Source rock layer

Source rock layer

Reservoir layer

Seal layer

Overburden

Overburden

Top of oil window

Top of gas window

Generation Expulsion Accumulation

GOC

OWC

Migration Preservation

The processes

Reservoir Heterogeneity in Sandstone

Heterogeneity MayResult From:

Depositional Features

Diagenetic Features

(Whole Core Photograph, MisoaSandstone, Venezuela)

Heterogeneity

Segments Reservoirs

Increases Tortuosity of Fluid Flow

Reservoir Heterogeneity in Sandstone

Heterogeneity Also MayResult From:

Faults

Fractures

Faults and Fractures maybe Open (Conduits) or Closed (Barriers) to Fluid Flow

(Whole Core Photograph, MisoaSandstone, Venezuela)

Questions?