Seismic Exploration.

    My part in Team E research is to research and find the best way to explore for oil and other resources using seismic surveys. In this quest I came to realize that there are many ways to tackle this issue. First let me say that any case of seismic survey is intrusive. This is not a magnetic survey which can be done from a certain distance without actually coming into any kind of contact with the environment you are trying to explore. This kind of survey requires a certain contact that may or may not result in a severe impact on its subject. So first of all, let’s explore the concept of seismic exploration.

Overview

    The seismic exploration phase is a very important to the exploration activities, because this is the most precise way to approximate where the oil might be, thus enabling to cut down on wrong location drilling. Basically, the more precise the method, the less you have to drill. Seismic exploration varies in precision due to different derivatives of the data. It is possible to construct 2D, 3D and now 4D maps using seismology. The later method is the most precise and it uses repetition of the 3D method. Of course, the more dimensions you have, the more equipment you need and so the cost will rise.

There are many resources available online and offline in order to research seismic exploration method. I will try to introduce the method shortly.

As explained by the Utah BLM Stone Cabin, in the web link http://www.ut.blm.gov/stonecabin/Q&As.htm

“Seismic survey methodologies are tools for analysis of geologic formations and features in the subsurface. The process consists of using a source of energy that is directed into the subsurface and then recorded back at the surface (with geophones) as the energy waves travel through the subsurface and reflect back to the surface. Various types of rock reflect the energy waves differently, and these differences are measured. Data helps show the tops and bottoms of formations, thickness, and structural configurations. It cannot identify pools of oil and gas, but rather, conditions favorable for the possible accumulation of oil and gas.”

In simpler terms, in order to map the inner layers of the ground or sea bottom, seismic technology uses sound waves generated at or near the surface that travel downward, later on reflecting at different angles and times from different layers and rocks in the ground. While actually those sound waves change direction, they are being picked up by geophones located at the surface or slightly beneath it. These geophones are connected to a computer which is able to analyze the data and built an actual map of the underneath area.

The Whales and Dolphin Conservation Society (WDCS) published a number of articles regarding the using of offshore seismic survey techniques and their effect on the mammal life.

In the following link to an article, http://www.wdcs.org/dan/publishing.nsf/allweb/6B7D8FD1BAB453F4802568FF004B9189, WDCS are addressing the issue that mammals change their migrational patterns especially to avoid as much as possible the “noise source”, being the airgun used in offshore exploration.

Different techniques of seismic exploration

Explosives

Seismic geophones are able to collect their data from many sources of sound. One of those sources is explosives. By drilling small holes into the ground, approx. 12 meters deep, and packing them with 10 pounds of capped explosives (directed towards the center of earth), followed by detonation of those explosives, the geophones will be able to get sufficient data to map the are underneath the receivers.

“Thumper” trucks, Vibroseis

 30,000 pounds trucks generate vibrations underneath the ground by elevating themselves above the ground on a short pole, thus concentrating their entire weight on this small platter and “shaking” for several second per location, thus sending vibrations to the ground. The rest of the process is very similar to the explosive process because all that is left is the data gathering phase.

This is an image of such truck operating in Utah region.

Airgun

Airgun is an excellent example of an offshore method. This exploration technique is used with assistance from a ship that actually carries all the equipment necessary to both send signal and to analyze. Such ship will carry an airgun and many receivers at greater distance that actually read the sound data as it is reflected from different rock formations and layers in the ocean bottom. Thus, just as the land surveys, the data being processed by a computer which is later on able to generate a detailed map of several layers underneath the sea bottom.

Data Processing

The data is being received by geophones, which are relatively small devices placed on the ground. Those devices are synchronized with computer and placed on the ground using GPS equipment. This way the computer that analyzes the data has all the variables, the time of the vibrations, the relative distances at which the reflections are measured, and the strength (wavelength) of the vibrations. Different rocks and layers give different reflections of vibration, different changes in frequencies in the wavelength of the vibration. Using this data, gathered from the sensors, the main computer unit is able to constructed a detailed map, thus enabling it’s user to analyze the map for possible oil location.

My recommendation

 After considering all the information I gathered during my research period, I recommend the usage of explosive technique as our primary seismic exploration technique. The use of such technique will minimize both the intrusion factor of the teams to the ANWR environment and the total damage done to the environment itself. Furthermore, I recommend the use of the Ice Code Drills, especially the 2” drill which is 20kg and can be carried and operated by one person. More information can be found at http://www.icedrill.ch/

A team of 2 people will set of in snowmobiles to drill 12 meter holes. Later, 50 pound charges will be place inside those holes. The drilling time is around 2-4 hours per hole. After placing the charges in the holes, they should place the geophones on the ground to cover the desired area. This area is then should be evacuated, as the charges can be set off from a distance as low as 100 feet away.

Anton Katz
Team E