Abstract
The Minami Kuwayama oil field is located 2 km to the northwest of Gosen city, Niigata prefecture. The reservoir depth is at 3,000-3,500m, formed out of tuffaceous sands. Soon after the field discovery in 2003, early commercial production was started. In this field, it is thought that asphaltenes have been deposited in the reservoir since the early production period, while asphaltane deposition trouble arises generally in surface facilities or wellbore tubing. Costly chemical treatments, such as solvent injection into the reservoir, have been applied several times. However, it is found that effects of the treatment do not last long, i.e. any permanent solutions are necessary to develop this field efficiently.
In the first step for the solution, laboratory experiments and reservoir simulations were carried out. In the laboratory experiments, it was found that asphaltenes were precipitated in the reservoir condition and its size was large enough to plug the pore space. Reservoir simulations suggested that the decline of production was due to the asphaltene deposition by taking into account the asphaltene precipitation and deposition process.
