University of Indonesia Student Chapter of AAPG has successfully held a short course entitled “Seismic Interpretation” presented by three guest speakers from PT. Pertamina Hulu Energy. The course held on Saturday afternoon and started at 1.00 p.m. attended by AAPG student members.
Mohammad Freddy as first speaker explained about basic of seismic method. Physical contrasts or anomalies are the main objects we are looking e.g. density and velocity. Anomalies either in density or velocity are the main target of geophysical method to show us the differences between target zone and the surroundings. Body waves in seismic method are discussed mainly. Body wave penetrates through the interior of the earth which has higher frequency than surface wave. Any contrasts appeared are the result of the difference in velocity which influenced by density. Density contrast leads to impedance contrast. Where impedance is the result of multiplication between density and velocity. These impedance contrasts could give us information about reflector’s description. Geophysical measurement obtained data plus noise, where data is what we need from the measurement and noise should be removed.
The result from seismic interpretation is a subsurface model to be analyzed based on geological and geophysical understanding. There were several method in seismic interpretation:
a. Horizon and fault interpretation
b. Depth structure map
c. Isopach map
From these three methods, we could analyze these five petroleum systems:
1. Source rock
Generation of hydrocarbon depends on three main factors:
• The presence of organic matter rich enough to yield hydrocarbons
• Sufficient time to bring the source rock to maturity
2. Reservoir rock
A subsurface body of rock having sufficient porosity and permeability to store and transmit fluids such as water, oil, and gas.
An impermeable rock acts as a barrier to further migration of hydrocarbon liquids.
The movement of hydrocarbons from their source into reservoir rocks.
A structural configuration geometry suitable for fluid deposition of hydrocarbons and sealed by a relatively impermeable formation through which hydrocarbons will not migrate.
Arieffian and Robby Insan Kamil as the second and third speakers described the purpose of seismic interpretation and the steps of interpreting seismic model. Seismic model came as a result of seismic data processing began with data acquisition. The first step in seismic acquisition is to record seismic waves by detonating dynamite as source of vibration and the waves received by geophone then data is stored in main unit. The next step is data processing to produce seismic model. By looking at the seismic model and checking on the geological data obtained, there are some structure which could be interpreted such as fault, fold, anticline/syncline, the direction of tectonic force, depositional environment, and the history of sedimentation. By using the integration of well data, those interpretation would be verified and give more accurate result.
After the three guest speakers finish the presentations. The audience were divided into groups of three students. Then 2 piece of A3 paper showing seismic model were distributed. Those group were obligated to make seismic interpretation based on those seismic model. Geological structures and features should be the consideration of the interpretation. There were an award given to the best group for the three best group members. The course ended at 4.30 p.m. after audience photo session with the guest speakers.