Demand for commodities such as gasoline, diesel, and petrochemical products increases each year, and it is imperative for oil companies to supply that demand at a profit. Although drilling oil wells cost millions of dollars (depending on the size and scope of the project), often spending a lot of time and effort on a “dry-hole.” Oil companies make up for this cost and risk by diversifying their fields and doing their due diligence on the front-end of every play.
Discovering and developing profitable fields: Those with enough reserves to support the project and subsurface geologies that won’t cost extra time and money with difficult drilling operations. Historically, companies had to test drill anywhere where they assume oil might be. As time passed and more technological developments surfaced, however, geologists have become a crucial aid to oil companies eliminating the need to waste their efforts on unproven and undesirable fields.
Today, methods such as seismic interpretation have become one of the most common ways to determine oil deposits for drilling. The American Association of Petroleum Geologists (AAPG) defines seismic interpretation as the science and art of inferring what lies underground at any given area based on the seismic data provided. In using this method, geologists must use their understanding of the collected data to infer the most likely interpretation out of the different possibilities.
While seismic interpretation is not a guarantee that each drill will be successful, it has become a tool for oil companies to get higher profits. With more informed decisions, they make fewer but surer drilling expeditions, allowing them to save billions on drilling and labor costs.
Drilling for oil: A Background
Oil is formed from the decayed remains of flora and fauna from millions of years ago. With the lack of oxygen underground, microorganisms, along with the pressure and heat of sediments, convert these remains into crude oil and natural gas.
The extraction of oil dates back to as far as 347 AD, though the methods of finding it during that time were unrefined and rudimentary.
By the time oil mining became a lucrative industry, geologists were already responsible for finding oil deposits. To do so, they had to find the right conditions for an oil deposit based on the rocks and other sediments surrounding the area. According to a HowStuffWorks article, authored by biologist and Doctor of Physiology Craig Freudenrich and contributing writer Jonathan Strickland, the carbon compounds formed from flora and fauna remains flow until they accumulate in thicker, more porous rocks called reservoir rocks. During shifts in the earth, the reservoir rocks get trapped between layers of impermeable rocks called cap rocks.
Before seismic interpretation, geologists had to study aspects of the ground such as the features of the surface, the rocks, soil types, and samples from shallow drilling. Some used the earth’s gravitational field, sensitive magnetometers, and other equipment. Among all these possibilities, seismology and seismic interpretation became the most common and reliable method for determining oil deposits.
Seismic Interpretation: Uses and Commercial Benefits
In seismic interpretation, geologists create shockwaves to monitor underground movement and interpret the waves reflected back to the surface. Using explosives, compressed-air guns (for offshore mining), thumper trucks (for land mining) and other seismic sources, geologists mimic the effects of an earthquake to send shockwaves underground. Certain rock layers can reflect the waves back to the surface, the speed of which would be determined by the type or density of the rock layers. Once the shockwaves return to the surface, geologists record them and read the results for possible oil content.
Seismic interpretation falls into three categories: structural, stratigraphic, and lithologic seismic interpretation. In structural seismic interpretation, the data collected is used to create a three-dimensional subterranean map which is used as a visual representation of the area to identify the most optimal drilling location.
A stratigraphic seismic interpretation helps geologists develop chronostratigraphic frameworks to determine the age of a rock layer based on the data. The boundaries between rock layers help determine the pattern formed by the shockwaves.
A lithologic seismic interpretation, unlike the other types, focuses on the different porosity, fracture intensity, and general lithology collected from the data. It can provide valuable indicators of hydrocarbon, a component of oil, which helps find oil deposits within a given region.
All three are used to determine an accurate model for finding hydrocarbon reservoirs, which provides commercial benefits. According to SPRI, oil drilling expeditions that are backed by scientific evidence and facts can reduce the risks in exploration and development for oil companies looking for more potential oil deposits. In the past, drilling for oil was a gamble for many oil and gas businesses.
Many companies today such as Gulf Oil, Texaco, and Exxon got their start due to deposits such as Spindletop. However, finding a non-renewable resource is becoming increasingly less. Oil companies, with the help of seismic interpretation from reliable geological services, can look at oil drilling as more of a smart business decision and less as a gamble.
Performing seismic interpretation is not a fail-proof solution. The oil industry is a highly regulated business, and data alone cannot guarantee results. It is possible for drilling expeditions to uncover dry deposits due to poorly constructed data, and for reservoirs to be underused due to wrong estimates.
Companies, therefore, should be careful when handling seismic interpretations. They could lose millions in a failed oil expedition, after all. Geologists must understand, as well, the gravity of their findings which influence decisions. The best way to go for oil drilling operations is to work with experienced geologists who have the latest equipment to determine the most accurate results – all while asking relevant questions throughout their study.
Despite the limitations of seismic interpretation, one cannot deny that it has had an extremely useful contribution to finding oil deposits. It allows a more efficient and accurate way of spotting oil deposits compared to other methods in the past. This is important, given the rapidly increasing need for crude oil and other products made from it.
By working with skilled geologists who can make accurate interpretations, oil companies can benefit from reduced risk of losses, better supply, and higher profits. They must turn to geologists or other expert professionals with innovative petrophysical analysis methods for improved results and better ROI.