Exploration&

Production 101

Susan M. Landon

IPAMS

2004

How do we pick the spot for that wildcat well?!?

OBJECTIVES OFPETROLEUM GEOLOGY

• Find and Effectively Produce Oil and Natural Gas

• Improve Predictability

• Reduce Risk

GEOLOGICAL REQUIREMENTS FORHYDROCARBON ACCUMULATIONS

Source Rock Migration Path Reservoir Rock Trap Timing

• Petroleum: a natural yellow-to-blackflammable liquid hydrocarbon found beneath the earth’s surface

• Hydrocarbon:an organic compoundmade up of carbon and hydrogen atoms

What is Petroleum?

What are Hydrocarbons?

Mixtures of hydrogen and carbon atoms with various impurities like sulfur, oxygen, etc.

Hydrocarbon Composition

Carbon + Hydrogen = HydrocarbonAtoms Atoms Molecules

HC + H = H C H

H

Methane gas CH4

simplest

hydrocarbon molecule

Gas Composition

Methane

Ethane

Propane

Butane

CH4

C2H6

C3H8

C4H10

H

C HH

H

C

H H

H

H

C

H

H

H

C

H H

H C

H

HC

H

H

H

C

H H

H C

H

H

C

H

H

C

H

H

The Alphabet Game

LNG = Liquefied Natural Gas

LPG = Liquefied Petroleum Gas

NGL = Natural Gas Liquids

Origin of Hydrocarbons

Generated from organic matter preserved in the sediments

As sediments are subjected to higher temperatures with increasing burial, the organic matter is simplified to molecules of carbon and hydrogen with some impurities

Quality of Source Rock

• Quality of a source rock (how much hydrocarbon can the organic matter generate) is measured by the amount of organic carbon present in the rock – Total Organic Carbon– 1% or more TOC is considered poor– 3 to 5% or greater is considered a good

source rock

Type of Organic Matter

Plant material tends to generate gas

Algal and animal material (amorphous organicmatter) tends to generate oil

Oil can be cracked to gas (just like in a refinery)when it is subjected to high enoughtemperatures

RESERVOIR ROCKPorosity

percent by volume of pore space in the rock – how much fluid or gas will fit between the

grains(%)

Permeability measure of the degree of difficulty the fluid or

gas has in moving through the rock(darcies or millidarcies)

Types of Porosity

Intergranular

Dissolution

Fracture

Clays depositedon grains creating

microporosity

Oil-stained Thin SectionWhite Pine Mine - Wisconsin

Migration of Oil and Gas

Trap

Caprock or Seal

Types of Hydrocarbon Traps

• Structural

• Stratigraphic

• Combination

• Unconventional (basin-centered, coalbed methane, shale gas)

Structural Traps

Oil Seeps

Source Rock

Monroe and Wicander, 1992

Fault TrapAnticlinal Trap

Oil

field

Oil

field

Stratigraphic Traps

Source Rock

Unconformity Trap

Combination Trap

/Seal

/Seal

TIMING…..

Traps must be in place before oil and gas begin to migrate.

Basin-Centered (Continuous)Trap

An “unconventional trap”

- regional

- diffuse boundaries

- low permeability reservoir

- frequently abnormally pressured

- closely associated with source rocks

Types of Data

• LIBRARY!

What has been done before?

• Field work

• Information from Drilling

Field Geology

Drilling

Most of the data usedto find and efficientlyproduce hydrocarbonscomes from wellsthat have been drilled.

What data do we need andhow do we integrate andinterpret the data todetermine where to drill?

Data Collected From Wells

• Drilling time – record of how fast the bit is cutting downward

• Mud Log - measured gas released by drilling

• Cuttings – chips of rock cut by the bit and described by the well site geologist

• Core – special bit cuts a cylinder of rock

• Drill Stem Tests – samples fluid and measures pressure

• Wireline Logs

Wireline Logging

Computer

Logs measure physicalcharacteristics of therocks drilled. A tool islowered down the wellbore and, as it is pulledback to the surface, itmeasures a property likenatural radioactivity.

RIG

Typesof Logs

1 2 Rock/fluid 3 4 5

1. Gamma Ray

2. Caliper (dashed)(diameter of hole)

3. Spontaneous Potential

4. Electrical Resistivity

5. Density

6. Sonic

Log Response to Rock

Beach Sand

Channelsand

Density decreasesPorosity increases

From Hancock, 1992

GR (API)

Neutron Porosity (%)

Bulk Density (gm/cc)

Formation Image Log

Fracture

Bedding

Formation Image Log

Horizontal Well Bore

Bedding Planes

Types of Maps

• Topographic maps - variation in elevation• Geologic maps - distribution of geologic

features• Structure maps - variation in the shape of a

subsurface layer• Isopach maps - equal thickness• Contour map of any distribution of values• Anything else you can think of!

Structure Map

•Show the shape of a subsurface rock layer, usually with reference to sea level

•Show structural features such as folds and faults

Map View ofRiver Meander

Cross Section

Point Bars

Point Bar

Fluvial Deposition

Gra

in s

ize

dec

reas

ing

up

war

ds

Erosion

Coyote CreekField

Berg, 1986

Isopach Map

Channel Sandstone Reservoir

0

100’

Berg, 1986

Cross Section

Structural cross section - shows present daygeometry of the rock layers in the subsurface.

Ranger Formation, Wilmington Field, CA

From Morton-Thompson and Arnold, 1992

Cross Section

Stratigraphic cross section - provides a picture of the history of deposition and structural development. An internal boundary is the datum.

Ranger Formation, Wilmington Field, CA

From Morton-Thompson and Arnold, 1992

Geophysical Methods

• Gravity

• Magnetics

• Seismic

• Other techniques

Technological Advancements:An Opportunity

Seismic Profile

1. Signal emitted by vibrator truck

2. Reflected waves received by geophones

3. Data transmitted to laboratory truck

Synthesis

http://www.elf.fr/odyssee/us/depot/204.htm (Thanks to Jane Woodward)

2D

3D

4D

SeismicLine

1

Shot Points

Reflections

Formations

REEF

3-D Seismic

Courtesy of ExxonMobil

3-D Seismic

A time slice from a 3-Dseismic program in northTexas - like a map.

Can you interpret the environment of deposition?

From the AAPG Explorer

Now we have decided where we would like to drill. How do we obtain

permission to drill for and (hopefully) produce

hydrocarbons?

Leasing – Land OwnershipUnited States

• Private - 2/3 of US is in private ownership• State

– Onshore– Offshore

• Federal– Onshore (BLM, Forest Service, DoD, etc.)

• Most Federal land is located west of the Mississippi

– Offshore (MMS)

Basic Land Questions

• Where is the land located?

• Who owns it?

• Is the owner's title clear?

• What rights are needed?

Where is the land located?

• There are two basic types of land surveys– Metes and bounds (early surveys)– Rectangular survey

• Most of the western U.S. is described with by the rectangular survey

Rectangular Survey System

Typical Section640 acres

ONEMILE

SE/4SE/4 40 ac

W/2

320 acONEMILE

NE/4

160 ac

6

Public Owners• federal government• state governments, counties,

cities or towns• school systems

Private Owners individuals

companies

institutions

Who Owns the Land?