Ideas & Research
Geological Ideas
Every prospect starts with a geological idea. Most generating geologists have knowledge of a specific oil and gas basin or geographic region. Each takes his knowledge of the area's geological structures, faults, producing wells, dry holes, and other data to generate ideas on where to look for drilling opportunities.
Five elements must be present for an oil and gas prospect to be successful and, if any one of them fails, neither oil nor gas will be found when the well is drilled:
Source Rock - When a source rock is subjected to high pressure and temperature deep within the earth over an extended period of time, hydrocarbons form. The main types of sedimentary source rocks are:
- Shales - Layers of clay minerals.
- Sandstones - Particles of sand (mostly quartz grains) pressed together by the weight of sediments deposited above.
- Carbonates - Fossilized skeletons and crystals of calcium carbonate. Limestone is a common carbonate.
- Evaporites (Salts) - Salts left behind as a result of evaporating seawater.
Combinations of these source rocks can also occur. Sandy shales or shaley sands would represent a blend of two rocks.
Whatever the rock type, source rocks that ultimately generate commercial hydrocarbons have two key characteristics:
- Porosity - Hydrocarbons are created in the tiny pore spaces of the rock. If the source rock does not have adequate porosity, hydrocarbons would not have been created.
- Permeability - A measure of the level of connectivity between the source rock's pore spaces. Without adequate permeability, the hydrocarbons created within the pore spaces of the source rock cannot migrate from the source rock to a reservoir.
Migration - Hydrocarbons are expelled from the source rock. Hydrocarbons are less dense than their precursor organic sediment, so they migrate upwards over time to the earth's surface unless they are trapped.
Trap - As the hydrocarbons migrate away from the source rock they must find a structure, or trap that has the right conditions to stop the oil and gas from reaching the surface. There are two types of traps capable of capturing hydrocarbons preventing further migration:
- Structural Traps - De-formed rock layers primarily the result of folding and/or faulting, or both. Anticlines and salt domes are common examples of structural traps.
- Stratigraphic Traps - Formed when other rock beds seal a reservoir bed.
Reservoir - Oil and gas is trapped in the porous spaces of a reservoir rock; usually sandstone or limestone. As is the case with source rock, the reservoir rock must also be permeable so that the hydrocarbons can flow to the surface during production.
Seal Rock - An impermeable rock that prevents the hydrocarbons from escaping to the surface.
Every generating geologist is familiar with these elements and their various attributes within their basin / region. Prospect ideas come from combining regional geology with new knowledge that comes from logged successful wells and dry holes drilled in the region and technical data that the geologist may have.
Preliminary Research
Preliminary prospect research involves an investment of primarily time to make a determination whether or not a prospect is worth pursuing. Developing a prospect for potential sale can involve risking a material amount of capital. Generation companies do not want to invest capital to completely develop a prospect unless they believe further development will reasonably result in drilling and completing a successful well. Preliminary research might include:
- Preliminary lease checks. If the idea is on acreage under lease or held by production, there is no need to proceed further.
- Researching and mapping logged wells (productive and dry holes) in the prospect area.
- Reviewing seismic the generation company may have in its library.
- QC publicly available seismic.
- Compare notes with other geologists with experience in the prospect area.
All of these activities build the case for the geologist to drop the prospect or propose the generation company develop the prospect to drill.
