RECORDING

Cabel Link and Geophone

String scan

Proccess Seismic

Recording Channels

String Scan for Check Leakage

Laul (Line Auxiliaary unit)

Unit Crew Recording

Laux (Crossing line Auxiliary Unit),Cable link,Geophone

Geophone

Parameters test

Labo Unit Recording

Recording (data recorder) is responsible for recording with a good productivity while maintaining data quality. Recording job deceription include :
1. Coordinate and ferform the work recording seismic data.
2. Coordinate and oversee the transportation of equipment in the field.
3. Installing,dismantling,transporting and caring for their instruments an accessories in the field.
4. Install geophone on track surveys to achive a stable layer of soil with the help of suppressor geophones with a distance of geophone in the field according to parameter set by partners.
5. On hard surface,such as limestone or gravel,use a super planter for punching holes in the ground so that the geophones mounted steadily.
6. Caring for the whole field equipment,ranging from the geophones,cables.FDU,key controls and other recording equipmen.
7. Install and connect a group of geophones on the track as well as connecting to FDU.
8. Installing LAUL,LAUX,batter,cable and other equipment at the position of recording is required and the work goes well.
9. Opening the drill hole that has been filled with explosives and detonator with wires connecting the firing line blaster.
10. Perform test detonator,detonator work well if the work was continued to the next stage. That meant working with a detonator well is eligible for detonated.
11. Detonated explosive in coordination with the obsever located at labo.
12. Doing re-drill or drill new holes and then fill it with explosives and re-record thesa data if the previous bullet point occurs misfire. Position the new hole is at a maximum radius of 5 metres from the previous hole.
13. Improving the geophones,cables,LAUL,LAUX,and other equipment damaged.
14. Data recording performed on two tapes at once.
15. Remove the geophones from the ground and the connection with FDU,disconnect the link cable and roll it.

UNIT AND RECORDING EQUIPMENT

CREW LANDSCAPE
Landscape crew assigned to stretching FDU link cable and geophones on the track in accordance with the track. Results from the landscape crew is cable link that has been installed and ready rojok geophones. The equipment carried by the crew was hauling wood or bamboo cable and geophones,and HT radio also carried by the foreman.

CREW ROJOK
Crew rojou assignet to plant geophones properly. Quality rojokan very influential on the quality of the recording,because it is not good to plant geophones with any potential to cause noise to be larger or other wise geophones can not detect vibrations with no good. Crew rojok bring rope chaining to measure the distance between the geophones,and pipe rojok to plant geophones. The equipment brought by the team are : super planter,planting hole,strap chaining,radio HT,work programs,P3k,blank toolbox meeting,helmet.gloves,shoes,glasses,nose masks.

CREW LABO
Crew labo,labo duty to prepare the location,such as antenna labo, extending cable transper transper of labo into line,and set up tents labo. Labo crew also was instrumental in the transper of labo the equipment brought by the crew labo is: pole antenna, antenna repeater,radio repeater,rope labrang,connector,antenna cable,alternating control,crowbar to labrang,nails ground,ground wires,battries,jumper power,harnes (safety rope),tool set (wrenches,contact cleaner)

OBSERVER LINE
Observer duty to perform troule shooting on the track. And is responsible for oveseing check leakage in the field, the equipment is carried is: tang potong, tang long nose,obeng,contact cleaner,short kck (resistor),ro Ht,work programs,P3k, blank toolbox meeting,helmet,gloves,shoes,glasses,nose,masks.

Jenis-Jenis Noise

Noise

Noise sering dijumpai pada saat perekaman data seismik. Noise adalah sesuatu diluar yang diinginkan (sinyal). Noise bisa dibedakan dalam noise koheren dan random. Berdasarkan lingkungan terjadinya noise bisa dipisahkan dalam 2 kategori yaitu noise darat dan noise laut.

Noise koheren dalam perekaman di laut yaitu efek buble, multiple, ghost dan difraksi. Sedangkan yang termasuk noise koheren dalam perekaman di darat adalah ground roll. Noise koheren ini dapat dihilangkan dengan melakukan langkah-langkah khusus dalam metode pengambilan dan pemrosesan data. Untuk menghilangkan noise yang berupa efek buble dapat dilakukan dengan cara memasang sangkar pada sumber seismik sehingga setiap gelembung yang dihasilkan akibat ledakan akan segera pecah pada saat keluar dari sangkar. Efek ghost dapat diredam dengan filter deghosting. Sedangkan efek multiple (reverberasi) dapat dihilangkan dengan filter dereverberation. Noise difraksi dapat dihilangkan dengan langkah migrasi. Efek ground roll bisa diatasi menggunakan band pass filter atau bisa juga dengan low cut filter. Apabila noise-noise koheren tersebut masih dominan daripada sinyal seismik maka langkah yang mungkin bisa dilakukan dengan menerapkan filter F-K domain, T-P domain dan filter atau domain lain seperti DNA (Diversity Noise Attenuator) yang diterapkan oleh suatu perusahaan minyak terkemuka di dunia.

Stack no T-P Filter (gambar dari slide Susila ZM).

Stack menggunakan T-P Filter (gambar dari slide Susila ZM).

Yang termasuk dalam noise random dalam perekaman di laut berasal dari aktivitas hewan laut, arus dan gelombang air laut. Sedangkan noise random dalam perekaman di darat bisa berasal dari geophone yang tidak tertanam dengan baik, atau dari aktivitas manusia, hewan dan kendaraan. Noise random kecil pengaruhnya terhadap data karena energi getarannya jauh lebih dibandingkan dengan energi yang berasal dari sumber. Noise random ini bisa dihilangkan dengan cara stacking dimana noise tersebut akan berkurang (hilang) dan editing (scaling) bisa secara manual atau automatic.

Beberapa tujuan menghilangkan noise dalam pengolahan data seismik yaitu : Preserved Amplitudo (Stratigrafi) dan Non Preserved Amplitudo (Struktur). Untuk memperoleh preserved amplitudo sebaiknya dihindari menggunakan AGC (Automatic Gain Control) sedangkan untuk non-preserved amplitudo bisa menggunakan AGC.