FRACTURE ANALYSIS AT CORE AND OUTCROPS OF RAJAMANDALA FORMATION LIMESTONE, CIKAMUNING HILL, PADALARANG, WEST JAVA

• Main Author: Suhada Lanin, Eril
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/77270
• Institution: Institut Teknologi Bandung

Fracture found in a variety of scales, from micro-sized up to hundreds of kilometers. On the whole scale range, the fracture has a significant influence on the proceses in the crust. Fractal geometry is a term suitable to describe an object demonstrate the scaling behavior. Analysis of 2407 fracture distribution has been carried out by measuring extension fracture, shear fracture, and styllolite with scanline method of core data over a total of 261 meter (from 3 wells) and scanline path of the Rajamandala Formation Limestone outcrops along a total of 291.82 meter (from 6 scanline location) in Cikamungin Hill. Effect of limestone type on fracture intensity indicated by the number of fractures data in outcrops is more intensively on the Platform Limestone (242 extension fractures and 536 shear fractures) compared with Turbidite Limestone (62 extension fracture and 318 shear fracture). In addition to fractures, styllolite analysis on core also showed a similar thing, where the number of styllolite on Platform Limestone is more (614 syllolite) compared with Turbidite Limestone (140 styllolite). Effect of fault on fracture intensity seen on the scanline P location, where the fracture intensity is reduced the farther from the fault. The fracture intensity at this location reaches 20 fractures per metres near the fault plane and gradually reduce to 2 fractures per meter at a distance of 12 metres from the fault. Fractal analysis in 1 dimension (1D) from fracture at the outcrops has been conducted on the characteristics of the fracture aperture, spacing, and lenght by classifying the measurements result of the entire scanline path into two type of limestone, namely Platform and Turbidite Limestone, as well as merging data of extension and shear fractures. Visually, the power law exponent can be viewed as the slope of the regression line, where the gentle slope show a wide range of data, whereas a steep slope would indicate a narrow range of data. The range of these data illustrate the fractal dimension of fracture, which is related to the degree of rock deformation and rock properties, where strong deformation and more brittle rocks will show a wide range of fracture data (eg from micro-to kilometer-scale) while the weak deformation and less brittle rock will only show fracture in a narrow range. The results of fractal analysis for all fractures in both types of limestone give a power law exponent (c) for fracture aperture is around 1.2, while for fracture spacing between 1.4 – 1.6, and for the length of fracture of 0.8.