The following table discloses the net changes in capitalized exploratory well costs pending determination of proved reserves during the three months ended March 31, 2020 (in millions):

Balance at January 1, 2020	$	584
Additions to capitalized exploratory well costs pending the determination of proved reserves		47
Capitalized exploratory well costs charged to expense		(125	)
Balance at March 31, 2020	$	506

In the first quarter of 2020, the Corporation expensed previously capitalized well costs of $125 million, primarily related to the northern portion of the Shenzi Field (Hess 28%) in the Gulf of Mexico due to reprioritization of the Corporation’s forward capital program in response to the significant decline in crude oil prices. The table above does not include well costs incurred and expensed during 2020 of $10 million associated with the Oldfield-1 well in the Gulf of Mexico. Capitalized exploratory well costs capitalized for greater than one year following completion of drilling were $319 million at March 31, 2020 and primarily related to:

Guyana: Approximately 80% of the capitalized well costs in excess of one year relate to twelve successful exploration wells where hydrocarbons were encountered on the Stabroek Block (Hess 30%), offshore Guyana. The operator plans further appraisal drilling for certain fields and is conducting pre-development planning for additional phases of development beyond the two existing sanctioned phases of development.

Joint Development Area (JDA): Approximately 10% of the capitalized well costs in excess of one year relates to the JDA (Hess 50%) in the Gulf of Thailand, where hydrocarbons were encountered in three successful exploration wells drilled in the western part of Block A-18. The operator has submitted a development plan concept to the regulator to facilitate ongoing commercial negotiations for an extension of the existing gas sales contract to include development of the western part of the Block.

Malaysia: Approximately 10% of the capitalized well costs in excess of one year relate to the North Malay Basin (Hess 50%), offshore Peninsular Malaysia, where hydrocarbons were encountered in five successful exploration wells. Subsurface evaluation and pre-development studies for future phases of development are ongoing.