Oppotunities on Lacustrine Basin Unconventional Play. Implication for Unconventional Exploration In Indonesia

OPORTUNITIES ON LACUSTRINE BASIN PLAY. IMPLICATION FOR UNCONVENTIONAL RESOURCES EXPLORATION IN INDONESIA

ABSTRACT
Lacustrine basin represent both source rock and reservoir for hydrocarbon. In term of conventional petroleum concept, lacustrine deposit is organic rich, mud-dominated, and therefore act as source rock for hydrocarbon. For unconventional petroleum concept, lacustrine deposits can act as reservoir rock for hydrocarbon. In today's exploration, there has been a growing interest in unconventional resources associated with fine-grained organic facies. This paper aims to introduce some basic concept relating unconventional play in lacustrine basin, implication for shale gas and shale oil potential, and best well design. Lacustrine depositional systems differ from marine systems because they area more subjected to a fast changing lake level, a change in balance between evaporation and precipitation (Barry Katz and Fang Lin, 2014). Such changes limit area of sedimentation to a permanent lake level. Thus, areal extend of lacustrine source is limited but the thickness is greater than marine source rocks and lacustrine basin is lack of conventional reservoir. The unconventional play is focused on this. In shale, hydrocarbon remain trapped in micro-porosity and fracture porosity of shale. Because these fluids charge, areas of over-pressured shale and anomalous seismic velocity are potential unconventional plays. Factor affecting viabilities of unconventional play considered to be important is brittleness of shale formation, mineralogy, maturity of source rocks, and nature of reservoir. Geological assessment units include total organic carbon (TOC) values greater than 2 weight percent, Type I or Type II kerogen is dominant, overpressured, thickness is tens of meters, and occur at depths necessary to retain enough reservoir pressure. Thermal maturity values (Ro) between 0.55 to 1.1 percent Ro characterize potential shale-oil reservoirs whereas Ro values greater than about 1.1 percent characterize potential shale-gas reservoirs (USGS, 2014). Stages of development include identification of resources, resource evaluation, pilot production evaluation and testing, commercial development, and project completion. For Paleogene and older shale formation it is recommended to use multi hydraulic fracture because the brittleness. Lacustrine basin petroleum systems in Indonesia account for majority of Indonesia producing source rocks. Understanding of lacustrine sedimentation is important for a better exploration.