ABSTRACT In 1994, Atlantic Richfield Company (ARCO) discovered natural gas in Paleocene through Jurassic formations below a Miocene oil field called Wiriagar in the Bintuni basin of eastern Indonesia. The exploratory drilling of the pre-Miocene stratigraphy was justified largely by geochemistry, which showed that the oil in the field was Jurassic despite flowing from a Miocene limestone reservoir. Analysis of pressures in the discovery well indicated that the height of the gas column exceeded 2000 ft (610 m), making the gas accumulation potentially large enough to justify construction of a Liquefied Natural Gas (LNG) plant. From 1994 to 1998, ARCO farmed into adjacent acreage containing the majority of the discovery’s hydrocarbons. improved commercial terms through negotiations with the Indonesian government, appraised the initial well, identified and discovered 2 nearby gas fields, and worked with an engineering firm to certify 24 tcf of natural gas as reserves (14.4 certified as proved; the rest as probable and possible). These reserves are the basis for what the Indonesian government designated in 1997 as the Tangguh LNG Project. Tangguh is the third largest discovery in the history of ARCO, exceeded only by the Prudhoe Bay and Kuparuk River Fields found in the 1960s on the North Slope of Alaska. Tangguh is also the first major pre-Tertiary hydrocarbon discovery in the history of oil and gas exploration in Indonesia.

Abstract Developing a philosophy of exploration is an important step toward becoming a more effective explorationist, both individually and on a team. This chapter discusses various aspects of exploration philosophy with the intent of helping individuals develop their own philosophies.

Results from theoretical models, laboratory experiments, and full-waveform sonic log data converge toward a common interpretational model for Vp/Vs ratios in sedimentary rocks. Moreover, we show that Vp/Vs ratios obtained from sonic logs may be significantly different than those obtained from seismic reflection velocity analysis due to dispersion.