Fault Seal Risk Capacity Calculation Using Surface Data Assessment For Decreasing Hydrocarbons Exploration Uncertainty : Study Case In Semilir Formation


In any hydrocarbon explorations, there are many uncertainities in estimating the petroleum prospects, sealing capacity is
considered as the most common uncertainty occured. Fault coefficient is such a fundamental thing in influencing the sealing of
hydrocarbons accumulation. Despite of fault ability to seal, the thickness ratio of low permeable rock is also considered in
determining the sealing capacity either the fault is sealing or not. This observation takes focus on outcrop data assessment in
analyzing the fault sealing risk located in Piyungan, Gunung Kidul, DIY. Generally, this area has an interbedded sandstonesiltstone and volcanic breccia facies, known as Semilir Formation members. Faults found in the area has a SE-NW trend shown
in the normal fault and thrust fault.
In analyzing the fault sealing capacity with outcrop data, we use algorithm calculation in determining the influence of the shale to
increase sealing capacity. It consists of SGR (Shale Gouge Ratio), SSF (Shale Smear Factor), and CSP (Clay Smear Potential)
(Yielding, 1997).The data required to calculate it are lithology logging, including shale thickness, fault identification, and the
distance of the source bed. The XRD analysis provides the type of clay minerals in sealing ability and the origin of the clay.
Based on the algorithm calculation, it can be concluded that the area has a moderate-poor sealing capacity which means
increasing the risk for hydrocarbons accumulations leaking.
Keywords: Fault seal risk capacity, semilir, hydrocarbons exploration,sueface data