Publications

Suban Field was technically discovered in 1972 by Suban-1 which penetrated Lower Talang Akar Formation (LTAF). The well test showed low gas rate, hence lead to decision to abandon the field. In 1998, Suban-2 was drilled following success story of Dayung and Sumpal fracture basement exploration. The well penetrated LTAF and Pre-Tertiary basement (PRT) and the well test showed good rate. The successful result was followed up with 3D seismic acquisition and then continued with appraisal drilling until 2003. The exploration and appraisal wells showed that complex reservoir lithology and fracture system is the main contributor to the gas flow. This reservoir characteristic and gas volume make Suban Field as a proven giant gas fractured reservoir in Indonesia. Complete set of logging data consist of gamma ray (GR), resistivity, neutron, density, photoelectric factor (PeF), sonic, image log, drilling log, and gas log were acquired from the early stage of field life. In addition, cores acquired from 8 wells representing most of the main reservoirs. Pressure Build Up (PBU) and Production Logging Tool (PLT) were run in the initial stage and in regular surveillance to characterize the dynamic behavior of the wells. In terms of lithology, core data showed high heterogeneity of the basement and sedimentary rocks that were deposited non-conformally above the basement. The basement consists of metasediment rock as a host rock, Andesite, Granodiorite, and Gabbro. Meanwhile, the sedimentary packages consist of terrestrial clastic sediment, fluvial to marine sediment, multi ages carbonate builds up, and clastic carbonate. The porosity and permeability of the sediment intact rock from core data showed low porosity and permeability. Therefore, non-matrix permeability has an important role in governing the production rate of the field. The non-matrix permeability is dominated by fractures due to multi-phase tectonic deformation. Small fractures can be observed from the cores, but the large-scale fractures cannot be obtained from core samples due to its limitation. To handle this limitation, electric logs data can be used in defining fracture occurrence vertically. In general, a streak of low density, high neutron, high PEF, and high sonic reading indicate fracture occurrence, while resistivity log can be used to indicate fracture at PRT basement reservoir. A qualitative indication can be obtained from drilling log especially losses, high Rate of Penetration (ROP), changes in Stand-Pipe Pressure (SPP), and total gas. High resolution fracture definition can be obtained from image logs, which unfortunately is limited in this field. Fracture occurrence cannot be observed directly from seismic due to resolution limitation. However, most of the seismic scale faults are correlated to some degree of good fracture occurrence. Integration of all available data is the tool to define fracture in a static domain. In dynamic domain, the productive fractures can be defined from PLT data at the well level. In addition, PBU data can help to estimate lateral fracture extension.