Seismic is one of the most important tools available to the petroleum geologist. It is a method used to determine the depth and orientation of rock formations without actually having to drill a well.
Eksplorasi seismik adalah istilah yang dipakai di dalam bidang geofisika untuk menerangkan aktivitas pencarian sumber daya alam dan mineral yang ada di bawah permukaan bumi dengan menggunakan gelombang seismik. Hasil rekaman yang diperoleh dari survei ini disebut dengan seismogram yang kemudian diproses menjadi penampang seismik.
Eksplorasi seismik atau eksplorasi dengan menggunakan metode seismik banyak dipakai oleh perusahaan-perusahaan minyak untuk melakukan pemetaan struktur di bawah permukaan bumi untuk bisa melihat kemungkinan adanya jebakan-jebakan hidrokarbon berdasarkan interpretasi dari penampang seismiknya.
Di dalam eksplorasi seismik dikenal 2 macam metode, yaitu:
Seismic On Land
Although the working mechanics of the process are extremely complicated, the concept is simple.
The Seismic Process
A source of energy is applied at the surface of the ground. This energy may be applied by a thumper truck, which uses a large, heavy iron plate to strike the ground. Sometimes, the source will be dynamite, placed in a shallow hole and exploded. Sound waves from the source travel down into the ground and are reflected back by the rock layers back up to the surface. A system of listening microphones, or geophones, pick up the reflected sound waves. The simple picture shown here shows only one receiver.
In practice, many such receivers are used at once. The more receivers used, the better the quality of the received data. The geophones, being spaced out at regular intervals, record the returning sound waves.
Seismic In The Ocean
In a similar way, seismic data can be acquired for the sea floor and the rock layers beneath the sea.
Marine Seismic
To do this, a ship at sea tows a sound source behind it. The source provides very strong waves of sound energy. This energy is often supplied by blasts of compressed air from air guns towed behind the ship. The sound waves penetrate the sea floor.
They are then bounced off the rock layers, and are picked up by hydrophones (listening devices located on the streamer) towed behind the ship. The produced undersea data is processed the same way as land seismic.