before the closing on July 30, 2012. The Company received $8.7 million and $51.5 million for acreage and facility costs for new wells drilled subsequent to the closing in 2012 and 2013, respectively. Formation costs of $1.7 million incurred in connection with this joint venture are reflected as a reduction to the gains on sales of oil and gas properties in the consolidated financial statements. COMSTOCK RESOURCES, INC. AND SUBSIDIARIES NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued) On December 30, 2011, the Company acquired oil and gas properties in North Louisiana from a third party for $27.1 million. This acquisition included proved oil and gas reserves of 13 billion cubic feet of natural gas equivalent and leases covering 3,500 net acres. In connection with acquisitions of producing oil and gas properties, the Company estimates the value of proved properties based on estimated future net cash flows and discounts them using a market-based rate that the Company determined appropriate at the acquisition date for the various proved reserve categories. Due to the unobservable nature of the inputs, the fair values of the proved oil and gas properties are considered Level 3 fair value measurements. (3) Oil and Gas Producing Activities Set forth below is certain information regarding the aggregate capitalized costs of oil and gas properties and costs incurred by the Company for its oil and gas property acquisition, development and exploration activities: Capitalized Costs As of December 31, 2012 2013 (In thousands) Unproved properties ........................................... $ 112,851 $ 134,350 Proved properties: Leasehold costs ............................................ 899,914 971,239 Wells and related equipment and facilities ....................... 2,473,781 2,810,074 Accumulated depreciation depletion and amortization .............. (1,541,969) (1,861,894) $ 1,944,577 $ 2,053,769 Costs Incurred For the Years Ended December 31, 2011 2012 2013 (In thousands) Property Acquisitions: Unproved property acquisitions ....................... $ 103,946 $ 13,742 $ 130,113 Proved property acquisitions .......................... 16,879 — 6,471 Development costs ................................... 496,506 331,254 341,970 Exploration costs ..................................... 83,182 5,522 439 $ 700,513 $ 350,518 $ 478,993 F-19