Reservoir simulation and geological modeling for development planning of the Natuna gas field

Abstract

Abstract A three-dimensional, two-phase (gas and water) reservoir simulation model of the Natuna gas field was constructed, based on a complex geological model. This simulation model was used for evaluation of the gas reservoir including both field gas production performance and field development planning strategy. The Natuna gas field which was discovered in 1973 is located in Indonesian waters about 225 kilometers northeast of Natuna Island in the Natuna Sea. The gas reservoir is an isolated, dome-shaped carbonate build-up structure approximately 25 kilometers long and 15 kilometers wide. A total of five exploration and appraisal wells have been drilled in the field; three of the wells penetrated the gas-water contact. The volume of gas in the reservoir is estimated to be 222 trillion standard cubic feet (6.29 trillion std m3). The composition of the gas is 71% carbon dioxide, 28% methane plus heavier hydrocarbons, and 1% others. The basis for the geological model, used in the reservoir simulation model of the Natuna field, was a detailed sequence stratigraphic study of the gas field that incorporated seismic, well log and core data. The simulation model was used to analyze field performance for a proposed Natuna field development plan based on producing 2,400 million scf/d (68 million std m3/d) of methane. The model investigated the impact of horizontal and vertical permeability on well completion strategies, as well as the number and location of producing platforms and wells. The reservoir simulation and geological model results confirm that the Natuna field is capable of supplying large volumes of gas for long periods of time. The reservoir is estimated to be able to sustain a 2,400 million scf/d (68 million std m3/d) methane production rate for about 30 years with the ability of continuing to supply gas at lower rates after the initial gas contracts expire.