Lab 2: Seismic Data QC

The objective of this lab session is to ensure that data is accurate to obtain an accurate seismic image of subsurface structures. There are a few quality control (QC) steps which includes:
  1.   De-multiplexing
  2.   Reformatting
  3.   Setup of field geometry
  4.   Trace editing
  5.  Gain application
  6.   Application of field statics
     This lab will focus on step 4 and 5 which are the trace editing and gain application.
     
     1.       View shot number 11-14 
          
          
Figure 1: Wiggle shot for shot 11-14 before muting

      2.       Display original data before muting of shot number 1-18


Figure 2: Wiggle shot for shot 1-18 before muting

3.       Display original data after muting (shot number 1-18)

This is done to mute all the noises or anything other than desired signal or in other words, replace by a zero trace particularly in trace 31 of shot gather number 16. 

Figure 3: Shot gather number 16 before muting 


Figure 4: Shot gather number 16 after muting 

(As you can see, the noise in Figure 3 (red circle) is removed after we apply muting as seen in Figure 4)

Figure 5: Wiggle shot for shot 1-18 after muting 


4.       Gain application

a. Display shot number 8

Figure 6: Shot gather number 8 before gain


b. Display envelope trace number 33

Figure 7: Displaying envelope trace before gain 


c. Apply gain to shot number 8

Figure 8: Shot number 8 after gain is applied 

Figure 9: After gain is applied at T=0



Figure 10: Display the average amplitude envelope in dB at T=0 (after gain)

d. Time correction =1 


Figure 11: After gain is applied at T=1


Figure 12: Display the average amplitude envelope in dB at T=0 (after gain)


5.       RMS amplitude AGC

This method requires segmenting each trace into fixed time gates

Figure 13: Shot number 8 after applying RMS amplitude AGC 


Figure 14: Display the average amplitude envelope in dB after RMS amplitude AGC (shot number 8)


6. Instantaneous AGC 







Comments

Post a Comment

Popular posts from this blog

Lab 5: Sorting, Velocity Analysis, Stacking

Image
After performing various seismic data processing steps such as data quality control, frequency filtering and deconvolution on the east Texas real seismic data, the objective of today's lab session is to display the true image of the subsurface which required compressing the seismic data to infer a first approximation for such image. This includes :  1. Sorting the shot gathered data into common mid-point gathers (CMP) 2. Picking appropiate stacking velocities and applying accordingly normal move-out corrections (NMO).  3. Stacking all the CMPs such as average each CMP to form stacked CMP and then concatenate all stacked CMP traces together.  1. Common Midpoint Sorting  Figure 1: CMP Sorting  Seismic data acquisition with multifold coverage is done in shot-receiver ( s, g ) coordinates.  Figure 1  depicts the geometry of a CMP gather and raypaths associated with a flat reflector. Note that CDP gather is equivalent to a CMP gather only when reflectors are hor
Read more

Lab 6: Static Corrections

Image
Seismic reflection data in different traces are not always lying on a hyperbole for a horizontal reflector. Reflected data have certain displacement due to the different length of ray paths. Static displacements can be caused by topographic conditions (difference in elevation), weathered/unconsolidated layer; slow velocity, different borehole/gun and cable depth, tidal wave as well as water layer effect.  Figure 1: Topographic and weathered layer effect of seismic survey Thus, static corrections are applied to seismic data in order to compensate for various effects on the data such as those related to near surface, variations in elevations, weathering, and reference to a datum. By applying static corrections, we aim to determine the reflection time assuming the existence of a flat surface plane with no weathering layer.  These corrections include: 1. Elevation static correction, which accounts for variable elevations of the sources and receivers. 2. Residual static co
Read more

INTRODUCTION

Image
I am Nur Khalisa Binti Abdul Hamid (20381). Welcome to my blog Mr. Halim! Hope you like it! For our lab assignment, as a student who is taking Geophysics as a major, we are expected to go through every lab module and understand the concept of processing the seismic data from the very beginning until the migration process. The software that we use is called the MATLAB which lately, has been an increasingly popular tool in earth sciences. It has been used for finite element modeling, processing of seismic data, analyzing satellite imagery, and for the generation of digital elevation models from satellite data. The objective of this lab is to explore the functions of MATLAB, familiarize with seismic coding language, as well as to u nderstand how to use basic MATLAB functions and plotting commands on data vector which relates to the subject we are taking ; Seismic Data Processing.  Common procedures to streamline seismic data processing include: 1. Working wi
Read more