
	June 30, 2025
	(In thousands)
Beginning balance	$	196,202
Additions to capitalized exploratory well costs pending the determination of proved reserves	11,315
Reclassification due to determination of proved reserves	—
Capitalized exploratory well costs charged to expense	—
Ending balance	$	207,517

The following table provides an aging of capitalized exploratory well costs based on the date drilling was completed and the number of projects for which exploratory well costs have been capitalized for more than one year since the completion of drilling:


	June 30, 2025		December 31, 2024
	(In thousands, except project counts)
Exploratory well costs capitalized for a period of one year or less	$	—	$	—
Exploratory well costs capitalized for a period of one to five years	69,746		63,552
Exploratory well costs capitalized for a period of six to ten years	137,771		132,650
Ending balance	$	207,517	$	196,202
Number of projects that have exploratory well costs that have been capitalized for a period greater than one year	2		2

As of June 30, 2025, the projects with exploratory well costs capitalized for more than one year since the completion of drilling are related to the Yakaar and Teranga discoveries in the Cayar Offshore Profond block offshore Senegal and the Tiberius discovery in Keathley Canyon Block 964 in the Outer Wilcox play in the Gulf of America.

Yakaar and Teranga Discoveries — In May 2016, we drilled the Teranga-1 exploration well in the Cayar Offshore Profond block offshore Senegal, which encountered hydrocarbon pay. In June 2017, we drilled the Yakaar-1 exploration well in the Cayar Offshore Profond block offshore Senegal, which encountered hydrocarbon pay. In November 2017, an integrated Yakaar-Teranga appraisal plan was submitted to the government of Senegal. In September 2019, we drilled the Yakaar-2 appraisal well which encountered hydrocarbon pay. The Yakaar-2 well was drilled approximately nine kilometers from the Yakaar-1 exploration well. In March 2024, the current phase of the Cayar Block exploration license was extended an additional two years to July 2026. The Yakaar and Teranga discoveries are being analyzed as a joint development. During 2025, we are working with the partnership to finalize the concept design.

Tiberius Discovery — In July 2023, we spud the Tiberius infrastructure-led exploration prospect located in Block 964 of Keathley Canyon in the Gulf of America, which encountered hydrocarbon pay. Initial fluid and core analysis supports the production potential of the well, with characteristics analogous with similar nearby discoveries in the Wilcox trend. In March 2024, we completed the acquisition of an additional 16.7% participating interest in the Keathley Canyon Blocks 920 and 964, offshore Gulf of America. As a result of the transaction, Kosmos’ participating interest in the Tiberius discovery area increased from 33.3% to 50.0%. The Tiberius project is being analyzed as a phased development with discussions currently ongoing with our partner to finalize the development plan. Following additional evaluation, a final investment decision for the development of the project is expected to be made.