Publications

Fractures can act as a major control on porosity distribution in carbonate reservoirs. Fractures in limestone can be found in a wide range of scales, from millimeters to tens of meter long. In general, two different types of open fractures can be found, extensional fractures and stylolites. Both types can be equally important in controlling porosity and permeability distribution. One of the major problems in reservoir simulation of carbonate rocks is to determine the relationship between fracture distribution and facies.Detailed outcrop study of the Oligo-Miocene Rajamandala Formation has been carried out to characterize fracture type, distribution and density. The field observations were made using the one dimensional scan-line method and the data was analyzed utilizing standard statistical methods.The results of the study show that there are fracture characteristics that are strongly dependent on carbonate facies. For example, stylolites are more common in the boundstone facies than the wackestones and packstones. Fracture density is also higher in the boundstone facies. Analysis shows that fracture size is distributed according to a power-law distribution with the fractal dimension, c=1.5 - 2.5. This indicates that small scale fractures form an important part of the overall porosity. However, fracture density is also clearly controlled locally by the presence of faults and folds. In these areas, fracture density can be significantly higher in the vicinity of the fault and along the strike (hingeline) of the anticline. Secondary processes such as dissolution along stylolite surfaces due to the groundwater interaction have also played a major role in enlarging fracture apertures.