Chow Weng Sum

By Maman Hermana, Deva Prasad Ghosh and Chow Weng Sum

Information about mechanical rock properties is essential when tight reservoir is to be stimulated using hydrofracturing technique. The brittle area has to be considered as a priority region for determining the location of hydrofracturing initiation. Seismic data are commonly used to estimate the geomechanical properties such as brittleness average from elastic properties: Poisson’s ratio and Young’s modulus. This paper discusses the process of brittleness estimation based on elastic properties, which can be derived by inverting the pre-stack seismic data that can produce acoustic impedance, shear impedance, and density simultaneously. Novel methods, scaled inverse quality factor of P-wave (SQp) and scaled inverse quality factor of S-wave (SQs) attributes, have been used for identification of brittleness, fracture density, and hydrocarbon bearing in the fractured basement reservoir. The effectiveness of the proposed method has been tested in the field, which is consistent with fracture density log from formation micro-imager (FMI) log and hydrocarbon column data. The result showed that there is a significant correlation between brittleness, estimated from elastic properties, and fracture density logs. New attributes, the SQp attribute is potentially to be used as a fracture density indicator, while SQs attribute indicates the existence of hydrocarbon, which is confirmed with neutron porosity-density logs.

Part of the book: Exploitation of Unconventional Oil and Gas Resources

By Haylay Tsegab and Chow Weng Sum

The Peninsular Malaysia is divided into Western, Central, and Eastern tectonostratigraphic belts based on major geological and geophysical phenomena. The Kinta Limestone is a Paleozoic succession located within the Western Belt. Due to structural and tectonothermal complexity, the sedimentological and paleontological works in these carbonates have proven to be problematic unless combined with geochemical approach. Thus, the current study has integrated stratigraphical, sedimentological, and geochemical studies to assess the lithofacies variations and to interpret the depositional environments. An intensive fieldwork has been carried out in order to assess the extent of metamorphism and to locate the less altered sections for further studies. Three boreholes have been drilled on N-S transect of the Kinta Valley recovering a 360 m core. The core description, the mineralogical analysis, and the geochemical analyses including major and trace elements and organic carbon contents have allowed for a significant advancement of the knowledge existing on this basin. The obtained results have indicated that the Kinta Limestone is chiefly composed of carbonate mudstones, siltstones, shales, and minor cherty units. It preserves the main sedimentary features from metamorphism, especially in the northern part of the Kinta Valley. The detrital siliciclastic debris is minimum in the limestones. The overall dominance of fine-grained textures, the lacking of detrital siliciclastic deposits, presence of bedded cherts, and high organic carbon content outlined by geochemistry and the occurrence of uncommon benthic fauna have suggested the deposition in a slope environment with low energy and low oxygen content. The lithological changes from carbonate to siliciclastic deposits have outlined the occurrence of sea level fluctuations in the Paleozoic. The various analyses combined with chemostratigraphy, an independent of type locality and stratotype, enable to interpret the depositional environment of the Kinta Limestone. Thus, it can be useful to correlate to other formations in or similar types of basins in the southeast Asia.

Part of the book: New Insights into the Stratigraphic Setting of Paleozoic to Miocene Deposits

By Maman Hermana, Maya Genisa, Luluan A. Lubis and Chow Weng Sum

Ground-penetrating radar or georadar is a popular method in engineering and archeology for investigation of objects in shallow subsurface at high resolution. Georadars produce electromagnetic waves which propagate into the subsurface, and its interaction with the dielectric contrast is reflected and recorded in the radargram. It is an environmentally safe and nondestructive method and can be used for monitoring of active faults in the landslide-prone regions. This chapter explains the concept of georadar and its implementation on the detection of the active fault—Lembang fault—located in Bandung, Indonesia. Bandung is a highly populated city with many living around the active fault which poses a high risk of landslides. The Lembang fault was created by tectonic forces during the Pleistocene and has been constantly reactivated by recent volcanic events. It is the largest active fault in West Java, Indonesia, which is located in the midst of a densely populated urban area. A georadar survey using 25 MHz and 50 Hz frequency antenna was conducted to detect the fault in the urban setting. Unix-based seismic software was used to process the electromagnetic signals. The results showed that the georadar method was successful in identifying the active fault with clear imaging of the subsurface structures and basement of the region.

Part of the book: Earth Crust