Publications

The Kerendan Field Complex of onshore Central Kalimantan, Indonesia, is a mid-sized gas field currently in its early stage of development, producing from the Oligocene Berai carbonate reservoir. The Berai carbonate is a complex interval with matrix porosity of various origins, and where natural fractures are also interpreted to occur. Natural fractures in carbonate reservoirs introduce high levels of uncertainty to properly understand the heterogeneity of the porosity and permeability at field scale. This may result in an inappropriate plan of field development. Detailed characterization of the origin, distribution and properties of the natural fractures, separately from the matrix itself, is critical to determine the potential contribution of those fractures on controlling fluid flow. In this exercise, borehole image logs can provide irreplaceable inputs. A conceptual model of the distribution of natural fractures occurring within the Berai carbonate reservoir of the Kerendan Field Complex was developed on the basis of several vintages of borehole image logs. As the image logs originate from different tools, with variable quality and resolution, a systematic hand-picking of fractures on all available logs was undertaken, and fractures were classified in one common and standardized scheme on the basis of their electrical response and continuity. The consolidated structural interpretation, paired and calibrated with core descriptions, and seismic interpretation, allowed dips and orientations of the natural fractures to be highlighted and the various fractures sets forming the fracture network to be derived. The natural fracture network of the Berai carbonate in the Kerendan Field Complex is interpreted to comprise sets of diffuse fractures and fault-related fractures. Though several sets of diffuse fractures are identified, their orientations and densities do not provide the conditions for field-scale permeability anisotropy and their impact on fluid flow is expected to be limited. Organized in well-defined corridors around faults, larger fault-related fractures present much higher density values and have probably the capability to ensure lateral reservoir communication, at least locally in the vicinity of faults. Where opened and connected, these fault-related fractures may impact on reservoir and drilling performance.