Cenozoic Carbonates and Petroleum Systems of South Sulawesi, 2003
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© IPA, 2006 - Cenozoic Carbonates and Petroleum Systems of South Sulawesi, 2003 The Cenozoic carbonates and petroleum systems of South Sulawesi IPA Field Excursion October, 2003 Moyra wilsonl and Alit ~scaria' 1. Department of Geological Sciences, Durham University, South Road, Durham, UK, DH13LE 2.Pertamina Exploration Division, Kwarnas Pramuka Building, 1 lth floor J1. Medan Merdeka Timur no.6., Jakarta 101 10, Indonesia Formerly of SE Asia Research Group, University of London, Geology Department, Royal Holloway, Egham, Surrey, TW20 OEX, United Kingdom ITINERARY Day 1: Flight to Ujung Pandang, Sulawesi Introduction to the geology and petroleum systems of South Sulawesi Eocene to middle Miocene shallow water platform carbonates of the Tonasa Formation: Depositional environment, reservoir quality, karstification, caves & waterfalls Eocene clastics of the Malawa Formation: Reservoir and source rocks Structure of South Sulawesi: the Walanae Depression and fault system Drive to, and overnight in Watampone (Bone) - traditional Bugis welcome Day 2: Shallow water buildups of the Tacipi Formation: depositional environment & reservoir quality Volcaniclastic sealing lithologies to the Tacipi Formation Active gas seeps from carbonate buildups of the Tacipi Formation Modem lacustrine environments of Lake Tempe (source rocks of the future) Traditional Bugis meal and overnight in Sengkang Day 3: Structure and petroleum system of western central Sulawesi Distal and proximal synorogenic clastics of the Pliocene Walanae Formation Thrusting and folding in the Latimojong Mountains Depositional environments and active oil seeps from the Eocene-Oligocene Toraja Formation Kete Kesu: a traditional Toraja village and the Oligo-Miocene carbonates of the Makale Formation Day 4: Return to Makassar and Jakarta CONTENTS Itinerary Contents Acknowledgements . Fieldtrip practicalities . Introduction . Carbonates and hydrocarbons . Introduction to South Sulawesi carbonates Tectonic Setting Petroleum Systems of South Sulawesi The Fieldtrip . Day 1: Geology of South Sulawesi Day 2: Tacipi knoll reefs and reservoirs. Day 3: Toraja Petroleum system . References . Many people and organisations were involved in making this fieldtrip and guidebook possible. Moyra and Alit's PhD studies on the carbonates of South Sulawesi were undertaken at the University of London and were funded by BP and both are gratefully acknowledged. The Geological Research and Development Centre in Bandung and the Ujung Pandang office of Kanwil provided significant logistical support. Pertamina and the University of Durham are thanked for allowing us time off work to lead the fieldtrip. The 'petroleum systems' part of the trip was originally run for the IPA with Dana Coffield and Nusatriyo Gurito, both formerly of ARCO, and their substantial input is acknowledged. Atlantic Richfield Indonesia, Inc. (New Ventures), Southeast Asia Research Group (University of London), ARCO Alaska Inc., and the Indonesian Petroleum Association (PA) all provided logistical and financial support. Energy Equity Corporation is thanked for allowing us access to their gas processing plant, and for allowing us to use their seismic section. Richard Garrard provided material for this guidebook and, more importantly, is responsible for the development of many of the concepts presented here. FIELDTRIPPRACTICALITIES Hammer, handlens, pen, sunhat, sunscreen, stout boots and plenty of water are all essential. Compass clinometer, camera, notebook, sample bags and a small pair of field- glasses would be optional, but useful extras. There is no particularly strenuous fieldwork on this trip although short walks and small scrambles are required. In one locality it is necessary to cross a narrow river, which depending on the amount of rain prior to fieldwork, a short wade may be required. South Sulawesi has an equatorial monsoonal climate. Temperatures are uniformly high, ranging from about 24°C to 34°C with an average of about 32°C and a humidity reaching 70% to 90%. It is therefore essential to be adequately protected against the sun with both sunhat and sunscreen. The high temperatures and often strong winds in South Sulawesi, can result in considerable water loss from the body and it is advisable to drink regularly throughout the day to prevent dehydration. We will carry a supply of soft drinks in the vans. The N-S trending Western Divide Range forms an effective barrier to rainfall as it is oriented perpendicular to the prevailing wind directions. Regions on either side of this range have wet seasons at opposing times of the year, depending on the prevailing wind direction. Areas west of the Western Divide Range receive most of their rainfall between the months of November to April. East of the Western Divide Range the wet season occurs between April to November. The driest area is along the south coast of South Sulawesi, which experiences a prolonged dry season between April and November. It is unlikely to rain during fieldwork in the western part of Southern Sulawesi, however, short showers can be expected in the eastern part of South Sulawesi. The Cenozoic carbonates and petroleum systems of South Sulawesi fieldtrip will visit the southwestern arm of Sulawesi in central Indonesia (Figs. 1.1 and 1.2). The island has been famous through history for its pivotal role in regional economics, culture and science. The island formed the staging area for the great Buginese seafarers that dominated trade in the region for centuries. The various peoples who inhabit the island have retained their unique cultures, the most famous perhaps are the mountain people of Tana Toraja in South Sulawesi. It is also Sulawesi where Asian and Australian fauna and flora interact to produce plants and animals unique to this island, and provided Alfred Wallace in the 1800's with the evidence to develop the modern theory of evolution independently of Darwin. South Sulawesi is a frontier petroleum exploration province with proven hydrocarbon source rocks, reservoir rocks, generating kitchen areas and, most importantly, hydrocarbon accumulations. Reserves of approximately 600 bcfg have been discovered to date and these are soon to go on production for local power generation. The proven presence of all the elements required for a petroleum system analogous to the prolific systems of western Indonesia, and the presence of multiple documented kitchen areas, provides the impetus for continuing exploration in this relatively unexplored region of Indonesia (Fig. 1.3). CARBONATESAND HYDROCARBONS Almost half the world's oil production comes from carbonate reservoirs and a similar percentage of Indonesia's hydrocarbon production is from carbonate reservoirs (Park et al., 1995). Hydrocarbon bearing and potentially hydrocarbon bearing carbonates occur in most marine basins, excellently placed with respect to source and seal lithologies, and very definitely form worthwhile exploration targets. Figure 1.4 shows the distribution of Tertiary carbonates in SE Asia which have or may have hydrocarbon potential. However, carbonate reservoirs are notoriously fickle and unpredictable (Park et al., 1995). It is only through a knowledge of processes of carbonate sedimentation, carbonate depositional environments, the development and 'growth' of carbonate platforms, and subsequent diagenesis of carbonates that a better understanding of the inheterogeneity of carbonate reservoirs can be achieved. In this course you will have the opportunity to study a range of extremely well-exposed, shallow- and deeper-water Tertiary and modem carbonates, which were deposited in a wide variety environments. The effects different processes had on the deposition and accumulation of these carbonates, resultant facies distribution and the nature of their faunal composition will be assessed. The carbonates studied form extremely useful analogues for other SE Asian carbonates, which often form hydrocarbon rcservoirs in the subsurface UJUNQ Xo urn. Figure 1.2) Localities to be visited in South Sulawesi a JNQCIPEMAMNA ALF RUORS (Thomlon M 81.. 1991) A OIL IMPREGNATION Figure 1.3) Distribution of Petroleum systems in South Sulawesi Study area of South Sulawesi Location of Miocene carbonates which act as hydrocarbon reservoirs or have hydrocarbon potential Location of Eocene to Miocene carbonates which act as hydrocarbon reservoirs or have hydrocarbon potential krn Philippine Sea Figure 1.4) Map of Southeast Asia showing Tertiary carbonates with reservoir potential and location of the research area in South Sulawesi. INTRODUCTIONTO SOUTHSULAWESI CARBONATES South Sulawesi (Fig. 1.5), located on the eastern margin of Eurasia, has an almost complete stratigraphic sequence spanning the late Cretaceous to the present day (Sukamto 1975; Hamilton 1979; van Leeuwen 1981). Carbonates were deposited throughout much of the Tertiary (Fig. 1.5) and outcrops of limestone cover large areas of South Sulawesi. The Eocene to middle Miocene Tonasa Limestone Formation outcrops over much of western South Sulawesi, whilst the middle Miocene to earliest Pliocene Tacipi Formation outcrops in the eastern part of South Sulawesi (Fig. 1.6). In addition to well-exposed Tertiary carbonates, a range of modem shallow-water carbonate depositional environments can be studied on the Spermonde Shelf, offshore Ujung Pandang or offshore Manado, in North Sulawesi. In essence, South Sulawesi provides a remarkable open air workshop in which to study Tertiary and modem carbonate sediments, depositional environments and large-scale depositional