The Geologist is a key player in oil & gas exploration

The Geologist’s role in oil and gas exploration cannot be overemphasized though it is oftentimes overlooked when weighing the merits of a specific drilling program. To demonstrate this importance, let’s examine some of the functions performed by a geologist in a well planned program. Since most drilling taking place today onshore in the USA is done by independents, we will focus on this group of producers.

Drilling for oil and/or gas is a complex enterprise as we have seen. This process begins well before the start of drilling, many times years before. An experienced Geologist first meets with the decision makers of the oil company to identify potential targets. This includes the state in which the Operator is active. Next the Operator and the Geologist discuss zones of interest meaning the geological zones beneath the earth that are of interest. Considerations here include the depth of the zones as well as the history of each zone measured by actual production of oil or gas from each zone.

The geological parameters about each zone of interest should be well understood by the geologist. These parameters include the reservoir volume, rock type, and type of accumulation.

Reservoir volume is measured as: * Reservoir thickness * Lateral area (acres) * Porosity (average, maximum, minimum, and type) * Typical water saturations * Formation volume factors of oil and gas * Gas compressibility * Temperature (depth dependent) * Initial pressure

The Geologist is a key player in oil & gas exploration

Rock or reservoir type is defined as: * Lithology * Depth to top * Permeability (average, maximum, minimum, and type) * Tight formation indicator * Drive mechanism (what source of force exerts pressure) * Residual oil saturation * Well spacing and number of developed spacing units *General and specific trap type

Type of accumulation means: * API gravity of fluids * Crude oil viscosity and pour point * Crude oil sulfur content (including H2S) * Gas-oil ratio * Gas gravity and heating value * Composition of reservoir gas * Resistivity of formation water

The experienced Geologist knows each of the above parameters about each zone of interest. He/she is therefore able to make sound recommendations as to areas that should be considered by the Operator. Even with all that information, there is still more information that must be acquired before drilling begins to maximize the probablility of discovering and producing a commercially viable well.

The Geologist typically has or accumulates histories of all wells drilled and all wells that produced in the area. Using that database, the Geologist refines their estimates to further improve te odds of success. Even with all this information, there is still more needed by the Operator before making a decision. This is where technology like seismic and other advanced tools enter the picture. These tools provide the last bit of technical information needed by the Operator. These tools are discussed in the next major section of our site. You can go there now by clicking on the Technology link in the menu.