Publications

Naturally fractured reservoirs are considered problematic particularly when it comes to understanding their behaviour, including the various length scales, distribution, and different intensities, presenting challenges in the modelling and flow simulation due to the limited data coverage and resolution from well and seismic data. Pre-Tertiary sediments of North Sumatra Basin still remain unexplored hydrocarbon potential and provide a prominent outcrop information to be utilized as an analogue to evaluate natural fractures characteristics and attributes. By incorporating traditional fieldwork with digital data acquisition, a 3D model was built based on orientation, geometry, as well as density parameters, resulting in a comprehensive fracture model that can be used to constrain subsurface interpretation. The Pre-Tertiary Alas Formation in the Pintu Angin area is comprised predominantly of meta-limestone sediment, deposited during late syn-rift to early post-rift stage of deformation. A total of 1006 m x 462 m coverage area was investigated, using a combination of photogrammetry and field data measurement. The fractures were recognized as veins, open fractures (extension), and shear fractures with length ranging from tens to hundreds of meters, generating a total of 99 major fracture planes interpreted as a basis for structural framework and classification model. Four major structural lineaments trends were identified of orientation NW-SE, NNW-SSE, N-S, and NE-SW. In addition, the structural model suggested that our study area was formed as part of a dextral strike-slip fault, with fracture intensity showing 7 – 10 fractures per grid (5 x 5 m) adjacent to the faults and the development of the fractures were thought to have been strongly influenced by the distance of the fault and surface deformation both laterally and vertically, constrained by data distribution. This approach reveals that fracture characterization using outcrop analogue can be used to represent the distribution in the subsurface, hence can assist fluid flow simulation for the reservoir model. The utilization of Digital Outcrop Model (DOM) demonstrates that this method has the advantage of predicting the subsurface fractures trend by correlating the fracture intensity with vertical and horizontal distance from the fault.