6. Capitalized Exploratory Well Costs

The following table discloses the net changes in capitalized exploratory well costs pending determination of proved reserves during the nine months ended September 30, 2018 (in millions):

Balance at January 1, 2018	$	304
Additions to capitalized exploratory well costs pending the determination of proved reserves		102
Capitalized exploratory well costs charged to expense		(13	)
Balance at September 30, 2018	$	393

The table above does not include well costs incurred and expensed during 2018 of $119 million associated with the Aspy well, offshore Nova Scotia, Canada, the Pontoenoe-1 well, offshore Suriname, the Sorubim-1 well on the Stabroek Block, offshore Guyana, and the Bunga Teruntum-1 well in the North Malay Basin. Capitalized exploratory well costs capitalized for greater than one year following completion of drilling were $251 million at September 30, 2018 and primarily related to:

Gulf of Mexico: Approximately 45% of the capitalized well costs in excess of one year relates to the appraisal of the northern portion of the Shenzi Field (Hess 28% participating interest) in the Gulf of Mexico, where hydrocarbons were encountered in the fourth quarter of 2015. The operator is planning to acquire 3D seismic in 2019 for use in development planning of the northern portion of the Shenzi Field.

Guyana: Approximately 35% of the capitalized well costs in excess of one year primarily relates to the Liza-4, Payara-1, Payara-2 and Snoek-1 wells on the Stabroek Block, offshore Guyana (Hess 30% participating interest), where hydrocarbons were encountered. The operator plans to integrate the Liza-4 discovery into the second phase of development, which is expected to commence production by mid-2022. The operator plans to integrate the Payara-1 and Payara-2 discoveries into the third phase of development, which is expected to commence production as early as 2023.

JDA: Approximately 15% of the capitalized well costs in excess of one year relates to the JDA in the Gulf of Thailand (Hess 50%), where hydrocarbons were encountered in three successful exploration wells drilled in the western part of Block A-18. The operator is currently conducting subsurface evaluations and pre-development planning to facilitate commercial negotiations with the regulator for an extension of the existing gas sales contract to include development of the western part of the Block.

Malaysia: Approximately 5% of the capitalized well costs in excess of one year relates to the North Malay Basin, offshore Peninsular Malaysia (Hess 50%), where hydrocarbons were encountered in one successful exploration well drilled in the fourth quarter of 2015. We are planning to conduct subsurface evaluations and evaluate whether to integrate this discovery into a future phase of field development.