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Seismic survey

What kind of survey is that and in what way it is going to be implemented?

Energy companies all over the world have been using the seismic survey technology for the exploration of natural resources deposited deep under the ground for decades. This survey facilitates the geologists to identify more precisely the prospects possibly containing oil. In case oil or gas is discovered, the seismic survey allows establishing the locations for the drilling of exploration wells.

Seismic survey is quite simple: 4-5 m depth and 75 mm diameter holes are drilled as per established regular grid lines on the land plot subject to the survey. A small amount of explosives that make no impact on the environment are placed into the holes. Detonation of the explosives causes a small scale vibration. The generated sound waves reflect from different types of rocks laying deep underground and are recorded by special recorders, geophones, on the surface. The geophones are as if sensitive electronic ears, which record the echo travelling from the underground. 

Drilling of a 4-5 m depth hole can be compared to the drilling of a pit for the erection of a power supply pole. Thousand kilometers of seismic survey lines were carried out in Lithuania during 1960-1980 using far more heavy mechanisms and drilling deeper holes.

Meantime, the works are carried out using small portable equipment: GPS units for the delineation of seismic lines, light drilling machine and portable drilling unit, autonomous seismographs for the registration of seismic signals.

The modern seismic works make no harm to the environment, and no damage to the agricultural land and the nature.

Is heavy machinery used in seismic survey?

The advanced technologies allow avoiding the use of heavy vehicles and other big size machinery in seismic survey. The heavy vehicles, vibrocisers, used to be employed in seismic operations previously, and that disturbed the people in the villages, where the works were carried out.

Currently, the seismic survey does not use source vibrators that required heavy machinery and, thus, damaged the environment. The modern facilities are mobile and the works can be done only with a few specialists in the field.

Heavy trucks are also not needed. The seismic survey is carried out using truck with total weight of 4 tons or even less. The degree of impact, which the truck has on the soil while crossing the field, depends on the land surface (arable land, meadow, crop field, etc.) and weather conditions (wet, dry, frost).

How long does exploration last?

Seismic survey is a long term process and, depending on the size of the area subject to the survey, may last from half a year to a few years. However, it does not mean that the field works will be in progress all that period of time. The specialists work with the equipment in the field not every day, for sure.

What is next?

The obtained data is interpreted, and it provides information about the layers of the rocks located underground at that place and whether they are perspective in terms of natural resources. Highly qualified experienced geologists, geophysicists and reservoir engineers analyze the obtained seismic data and decide where to drill the test wells.

It is necessary to point out that the seismic survey helps minimizing the number of wells to be drilled, thus, the impact on the local environment. Analysis of the underground reflections allows identifying geological faults, what is very important in well drilling, as the obtained data helps to avoid them. 

When and for what purpose will the seismic survey be carried out in Rietavas license block?

Seismic survey in Rietavas license area will be carried out within the period and on the conditions envisaged in the License Agreement for Rietavas block between UAB “LL investicijos" and Lithuanian Government (No. (11-0)-1), signed on September 5, 2007. It is important to point out that the seismic survey is one of UAB “LL Investicijos" obligations to the Lithuanian Government. In other words, the seismic survey shall be carried out at the order of the Government rather than at the request of the company, but at the account of the company.