Komputasi dan Analisis Kecepatan Rambat Gelombang Seismik di Perairan Tarakan Bagian Timur Provinsi Kalimantan Utara
Manik, Henry M.
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Tarakan is one of the largest oil and gas producing regions in the new province. The existence of layers of rock containing reservoir which can trap hydrocarbons and coal makes Tarakan research areas of interest to be explored further by seismic methods. Seismic survey is a method currently used to determine the structure of the seabed, the depth of the ocean, oil and gas as well as sediment. Reflection seismic exploration is divided into two shallow seismic and seismic normally used to search for oil and gas. In the recording of seismic data in the sea, there is a lot of interference which appear as multiple, self-noise emanating from the tool used, wind, waves, and rain. One of the consequences caused by noise when recording in the field is the multiple that could interfere in the interpretation of seismic signals, it is necessary for the processing or signal processing to reduce the multiple effects. One that can be done is to increase the signal to noise ratio (SNR) through the analysis of the true velocity and in accordance with the subsurface geological conditions which is close to real situation, so that the returning signal is actually a representation of the subsurface geology without signals originating from multiple and noise. The purpose of this study is to measure the sound velocity obtained from seismic surveys and analyze the results. The study lasted for eight months which was started with the acquisition of seismic survey data that have been carried out in September - October 2012 in the sea east of Tarakan, Northern Kalimantan. This area is located at coordinates 3 ° 19 'N - 3 ° 20' N and 118 ° 34 'E - 119 ° 38 'E. Data was processed at the Ocean Acoustic Data Computation Laboratory, Department of Marine Science and Technology, Faculty of Fisheries and Marine Science, Bogor Agricultural University and at the Marine Geological Institute Bandung. Seismic data processing used Landmark ProMAX software. Data in the format SEG-D, then the data was processed so it produced data in the format SEG-Y which free noise and multiple. The raw data survey SEG-D was the main data input in this study which was then done geometric correction, trace muting, low cut filter, True Amplitude Recovery (TAR), deconvolution. Common Deep Point (CDP) is a term in seismic data taking for source-receiver configuration where there is a fixed point below the earth's surface. This CDP was then analyzed velocity root mean square (rms). The first velocity analysis was done by picking every 250 CDP and showed that the results was not good enough, it was known by the visible presence of multiple processes that must have been done to eliminate them using radon demultiple. The second velocity analysis done every 125 CDP and cross-sectional display showed that the results was better than before. The next process used the Normal Move Out (NMO) which was used to eliminate the effects of distance and Stacking. Furthermore, the velocity results that have been obtained could be seen in the table menu on promax software which was then velocity exported to a format that was able to be read in Microsoft Excel for making the velocity curves at each CDP TRKN 6 data. TRKN 6 seismic data showed the deltaic layer, small hills at seabed, sediment and a fault in the cross section display. Views seismic tend to be flat in the beginning and then small hilly seabed up toward the sea. The layer of sediment at the bottom of the waters of TRKN 6 seismic data is predicted to have the type of sediment or material content types clayey silt, sand silt clay, sand silt, silty sand, and very fine sand. The values of sound velocity on TRKN 6 seismic data are divided into 5 (five) color section that shows the rated velocity started from 1506 m / s to 2570 m / s. The color blue has velocity range from 1506 m / s - 1650 m / s, the color cyan has velocity range from 1651 m / s - 1850 m / s, the color green has velocity range from 1851 m / s - 2250 m / s, color yellow has velocity range from 2251 m / s - 2370 m / s and the red color has velocity range from 2371 m / s - 2570 m / s. The variation of velocity values can be influenced by many factors such as fracture, temperature, pressure, depth, lithology variations and fluid content variations and gas with porous rock, rock age, as well as the density of the sediment. The deeper from the subbottom, the greater the value of seismic waves velocity and will disappear to certain limit due to seismic signal suffers from energy loss of attenuation.
- MT - Fisheries