[en] The acquisition of seismic reflection involves generating and recording seismic wave field on/near the surface of the earth. Success of producing high quality seismic data depend on choice of seismic sources. There are commonly seismic sources for land seismic surveys such as explosive sources, vibrators and Accelerated Weight Drop (AWD). In some cases, the use of explosive sources often faces many problems, especially related to the costs, permission and environmental issues. The use of vibrators is also similar, facing problems such as the availability of access roads, permits and the environment impact. The use of AWD seems to be a solution as an alternative seismic sources when explosive or vibroseis cannot be used for some reasons. In this research, we have designed and built a mechanical seismic source named AWD250V1.0. This hand-made AWD prototype was developed for shallow seismic surveys. To evaluate the performance of this tool and to improve the design of the prototype, a field tests have been carried out. The test was conducted in Ciparay village, Bandung Regency, West Java. The survey area is mostly paddy field with the near surface covered by clay and highly seismic attenuation. The purposes is simply whether AWD can work properly or not while maintaining data quality and safety standards. In addition, the test is intended to find out how deep penetration of seismic waves using this source. Seismic recorders used were 96 channels with interval between receivers was 10 meters. Findings showed that the deepest reflection can be seen around 450 millisecond or approximately 400 meters. To sum up, the device is work well and is able to produce good quality of seismic sources. The prototype can also meet design criteria that are repeatability, portability, economical and environmetal friendly. (paper)

[en] Ultrasonic tomography is one of many non-destructive methods to image a rock by measuring wave velocities (P or S-wave). Some applications of ultrasonic tomography include research for seismic anisotropy, rock physics, shale gas etc. The objective of this study is to assess the ability of the robotic instrument to measure rock samples using ultrasonic tomography method. As we know that a conventional method are still employed to measure wave velocities in ultrasonic tomography. The conventional method measures a rock manually that it is often difficult and sometime takes quite long time. One of alternatives to cope with the problem is to design a robotic instrument. The robotic instrument is made of microcontroller and stepper motor. The microcontroller and stepper motor control the position of ultrasonic transducers while measuring the rock sample. The robotic instrument is not only able to measure but also have feedback controls. As a result, measured data can be more accurate and precise than those of the conventional method. Several rock samples are used for testing measurements using a MSIRT (Modified Simultaneous Iterative Reconstruction Technique) method. Results show that using the robotic instrument can enhance quality of data and reduce error up to 50%. (paper)

[en] Ultrasonic travel-time tomography using laboratory model were performed in this preliminary study. The measurement was calibrated using a known velocity laboratory model representing an iron with P-wave velocity (V_p) 5920 ms⁻¹. Source and receiver transducers were equally spaced around the model. In the first measurement, the source position was at point 1, and receivers at points 2 to 16. In the second measurement, the source position was at point 2, and receivers at points 3 to 1. The measurements were repeated, and a total of 240 ray path were recorded. Then, the travel-time data inverted and reconstructed to get tomogram using a MSIRT (Modified Simultaneous Iterative Reconstruction Technique) algorithm. Each pixel tomogram represents a point velocity at ray path intersections. It is important to have at least one intersection for each pixel, so each pixel represents an average velocity. The use of robotic instrument provides precise and efficient results in data measurements despite errors between 1% and 3% at the time of motor rotation. The ultrasonic tomography using robotics equipment proves to be helpful in obtaining accurate measurement. (paper)

[en] Along with the rapid development in technology, geophysical methods emerge as one of the research alternatives. Some research requires non-destructive test to determine characteristics of an object without causing any damage, such as core rock samples. Ultrasound tomography is non-destructive methods that reconstructing cross-sectional image of the internal structure of an object by analysing the propagation of ultrasound wave. The conventional method to measure core samples that usually use for determining the position of transducer and receiver sensors is by dragging manually. This manual measurement have weaknesses in terms of efficiency and accuracy. In this research, we design prototype of the Robot RTDs-U100 to improve the quality and efficiency measurements of core samples. The magnetic sensor used to control the rotation of transducer and receiver sensors. With this robotic rotation, the position of sensors is more precise and it takes less time. Our findings of core laboratory measurements show that Robot RTDs-U100 improved measurement error from 0,32% with manual measurement to 0,12% after using Robot RTDs-U100. (paper)

[en] The development of a user-friendly Common Reflection Surface (CRS) Stack software that has been built by implementing Graphical User Interface (GUI) is described in this paper. The original CRS-Stack software developed by WIT Consortium is compiled in the unix/linux environment, which is not a user-friendly software, so that a user must write the commands and parameters manually in a script file. Due to this limitation, the CRS-Stack become a non popular method, although applying this method is actually a promising way in order to obtain better seismic sections, which have better reflector continuity and S/N ratio. After obtaining successful results that have been tested by using several seismic data belong to oil companies in Indonesia, it comes to an idea to develop a user-friendly software in our own laboratory. Graphical User Interface (GUI) is a type of user interface that allows people to interact with computer programs in a better way. Rather than typing commands and module parameters, GUI allows the users to use computer programs in much simple and easy. Thus, GUI can transform the text-based interface into graphical icons and visual indicators. The use of complicated seismic unix shell script can be avoided. The Java Swing GUI library is used to develop this CRS-Stack GUI. Every shell script that represents each seismic process is invoked from Java environment. Besides developing interactive GUI to perform CRS-Stack processing, this CRS-Stack GUI is design to help geophysicists to manage a project with complex seismic processing procedures. The CRS-Stack GUI software is composed by input directory, operators, and output directory, which are defined as a seismic data processing workflow. The CRS-Stack processing workflow involves four steps; i.e. automatic CMP stack, initial CRS-Stack, optimized CRS-Stack, and CRS-Stack Supergather. Those operations are visualized in an informative flowchart with self explanatory system to guide the user inputting the parameter values for each operation. The knowledge of CRS-Stack processing procedure is still preserved in the software, which is easy and efficient to be learned. The software will still be developed in the future. Any new innovative seismic processing workflow will also be added into this GUI software. (paper)

[en] Rock properties analysis (porosity, permeability, elastic modulus, and wave velocity) of the rock is important to note as one of the methods to determine the characteristics of the reservoir rock. Rock properties can calculated in conventional (laboratory), indirect (inversion of seismic waves), and digital computation (Digital Rock Physics). This paper will introduce and discuss the digital calculation/simulation and empirical equation to predict the value of the rock properties from reservoir sandstone. The data used is the samples of the data sandstone core (reservoir) subsurface in an oil field. The research method is to combine the data from a thin layer, a digital image of rocks in three-dimensional (μ-CT-Scan), and empirical approaches of the equations of permeability on rocks and Lattice Boltzmann equation. Digital image of a scanned using μ-CT-Scan used to determine value rock properties and pore structure at the microscale and visualize the shape of the pores of rock samples in 3D. The method combined with rock physics can be powerful tools for determining rock properties from small rock fragments. (paper)

[en] The pore geometry of carbonate reservoir consists of such heterogeneous, complex, variation types of pore structure and high chemical material reactivity. Rock physics modeling is applied in this study as it is an accurate, precise and practical method for the case of carbonate reservoirs. It is examined to determine the effect of carbonate reservoir geometry on the seismic wave velocity in carbonate field using fast DEM (Differential Effective Medium) model. We integrate measured logs and petrophysics data from gas-saturated carbonate reservoir. The results show that majority of pore geometry in the research area are interparticle pores and micro-cracks pores. The pore geometry interprets the effects of seismic wave velocity of carbonate reservoir in the study area, stiff pores or the increasing of α values will make the seismic wave velocity to increase rapidly and crack pores or the decreasing of α values will make the seismic wave velocity slower. Generally, we have worked in the common geological condition of carbonate reservoir rocks. In terms of aspect ratio value, our reservoirs controlled by overburden geological process. This indicated that fracturing is closely related to overburden and differential compaction, thus increasing the connection between separate vugs and enhancing permeability dramatically. (paper)

[en] We conducted delay time tomography to determine 3-D seismic velocity structures (Vp, Vs, and Vp/Vs ratio) using micro-seismic events in the geothermal field. The P-and S-wave arrival times of these micro-seismic events have been used as input for the tomographic inversion. Our preliminary seismic velocity results show that the subsurface condition of geothermal field can be fairly delineated the characteristic of reservoir. We then extended our understanding of the subsurface physical properties through determining of attenuation structures (Qp, Qs, and Qs/Qp ratio) using micro-seismic waveform. We combined seismic velocities and attenuation structures to get much better interpretation of the reservoir characteristic. Our preliminary attanuation structures results show reservoir characterization can be more clearly by using the 3-D attenuation model of Qp, Qs, and Qs/Qp ratio combined with 3-D seismic velocity model of Vp, Vs, and Vp/Vs ratio