FILTERING
Filtering is an attempt to 'save' the desired frequency of seismif waves and the 'throw' is not required. There are several kind of band pass filtering,low pass (high cut) and high pass (low cut). In seismik data processing,band pass filte is more commonly used because it is usually contaminated with seismic waves of low frequency noise (such as ground roll) and high frequency nois (ambient nois).
WAVE COMPONENT
Wave component at a seismic trace is the amplitude,peak,trough,zero crossing,height and wavelength.
FREQUENCY SEISMIC WAVE
Frequency seismic waves are 'useful' usually located in a joint 10 to 76 HZ with about 30 HZ (Ozdogan Hilmaz). Dominant frequency,ampliude spectrum of characters also used.
FOLD COVERAGE
Ford coverage is the number of reflections on a field of reflection on the rocks. The greater number of signal reflection on field, it is expected that the better the quality of data generated. Ford coverage is important when the stacking of data processing. At the the time of stacking the data is expected to be carried by the signal can be removed. Time to simulate fold coverage based on the position of shot point and trace the theorytical,simulation and actual. There are mang ways to calculate the fold. But there is the formula that can be used as the basic for calculating fold equation,namely:
Ford =NS*NC*b^2
Where :
NS= the number of shot point per unit area
NC= number of active channel
b = dimensional
For example,say you have 80 shot point per square kilometer with 600 actice channel,and the dimensions of the bin of 25meter. Then fold that we get is :
Fold = 80/km^2*600* (25m)^2=30.
This is a quick way to find out if we want to fold coverage are in accordance with the parameter that we use.
FIRST BREAK
First break is the seismic wave was first recorded. This wave is the wave of the fastest to reach the recipient. In the study of seismic reflection,the first break is used for static correction. In the study of seismic tomography, first break is used as infut to image the wave travel time of seismic wave velocity anomalies below the surface.
GEOPHYSICAL METHODS
In general,geophysical method are divided into two categories: active and passive methods.passive method is done by measuring the field emitted by the earth's natural. Actice method is done by making field disturbance and then measuring the response of the earth. Natural terrain in referrea to here as the earthquake wave radition,earth's gravitation field,earth's magnetic field,electric field and electromagnetic earth, and radioactivity of the earth. Artificial fied can be a dynamite explosion,providing and electrical current into the ground, sending radar signals and so forth. Seismic survey is a type of active geophysical metods, because we use the seismic terrain/ man-made sources of vibrotion. Made is seismic vibrotion source can generated by the detonation of dynamite, air gun or vibrotor.
Filtering is an attempt to 'save' the desired frequency of seismif waves and the 'throw' is not required. There are several kind of band pass filtering,low pass (high cut) and high pass (low cut). In seismik data processing,band pass filte is more commonly used because it is usually contaminated with seismic waves of low frequency noise (such as ground roll) and high frequency nois (ambient nois).
WAVE COMPONENT
Wave component at a seismic trace is the amplitude,peak,trough,zero crossing,height and wavelength.
FREQUENCY SEISMIC WAVE
Frequency seismic waves are 'useful' usually located in a joint 10 to 76 HZ with about 30 HZ (Ozdogan Hilmaz). Dominant frequency,ampliude spectrum of characters also used.
FOLD COVERAGE
Ford coverage is the number of reflections on a field of reflection on the rocks. The greater number of signal reflection on field, it is expected that the better the quality of data generated. Ford coverage is important when the stacking of data processing. At the the time of stacking the data is expected to be carried by the signal can be removed. Time to simulate fold coverage based on the position of shot point and trace the theorytical,simulation and actual. There are mang ways to calculate the fold. But there is the formula that can be used as the basic for calculating fold equation,namely:
Ford =NS*NC*b^2
Where :
NS= the number of shot point per unit area
NC= number of active channel
b = dimensional
For example,say you have 80 shot point per square kilometer with 600 actice channel,and the dimensions of the bin of 25meter. Then fold that we get is :
Fold = 80/km^2*600* (25m)^2=30.
This is a quick way to find out if we want to fold coverage are in accordance with the parameter that we use.
FIRST BREAK
First break is the seismic wave was first recorded. This wave is the wave of the fastest to reach the recipient. In the study of seismic reflection,the first break is used for static correction. In the study of seismic tomography, first break is used as infut to image the wave travel time of seismic wave velocity anomalies below the surface.
GEOPHYSICAL METHODS
In general,geophysical method are divided into two categories: active and passive methods.passive method is done by measuring the field emitted by the earth's natural. Actice method is done by making field disturbance and then measuring the response of the earth. Natural terrain in referrea to here as the earthquake wave radition,earth's gravitation field,earth's magnetic field,electric field and electromagnetic earth, and radioactivity of the earth. Artificial fied can be a dynamite explosion,providing and electrical current into the ground, sending radar signals and so forth. Seismic survey is a type of active geophysical metods, because we use the seismic terrain/ man-made sources of vibrotion. Made is seismic vibrotion source can generated by the detonation of dynamite, air gun or vibrotor.
PROCESS SEISMIC DATA
The data has been obtained from the acquisition will be processed,thus in creasing the power vertical and horizontal resolution that can generate the actual subsurface conditions,namely in from of migrated time section which is easy to be interpreted by the interpreter to achieve maximum results at the time of exploitation.
SEISMIC DATA ACQUISITION
In general,seismic data acquisition activity is starting to make the artificial vibration source,such as vibroseis or dynamite,and then detect and record it to a receiver device,such as geophones or hidrophone. Blast vibrotion results will penetrate into the earth's surface where most of the signals will be transmitted and partly reflected back by the reflector. Signal reflected back is being recorded by a recorder on surface. While signals that penetrate the earth's surface will be reflected back by the second reflection of the signal will be received back by the tape recorder and so on until the last tape recorder. The recorder will generate a trace of seismic data.
SPEED AND RESOLUTION
1. VELOCITY AS A DIAGNOSTIC TOOL,
The nature of the sediment like porosily,density,temperature,grain size,gas saturation,frequency and pressure affect the speed. Increased speed is influenced by external pressure,grain size and dencity. The speed will be reduced at the shaft and/or sediment have a large pore pressure.
2. VOLECITY MEASURMENTS
Velocity measurment is based on arrival time changes reflected in change in the distance from vibration source to geophones. The distance is krown as offset,while difference in the time of the offset is colled normal moveout. Velocity as the implication is called stacking velocity.
3. RESOLUTION
Resolution is defined as the smallest distance between the two appears to them. The pattern of reflection with two interfaces will appear in a division with a thickness of 1/4 wavelenght, whereas if the thickness is less than it would seem only one interface. Boundary layer thickness that can provide reflectance is about 1/3 of the wavelenght. Frequency seismic waves is smaller than the frequencies used in the well logs, so the ability of seismic change is much greater, about 100 fold. The smaller the frequency and speed, then the wave will be even greater.
