- 83 -  Borrowing costs relating to drilling of development wells that have been capitalized as part of oil and gas properties  during the year ended 31 December 2014 was $3.4 million (2013: $1.3 million). The interest capitalization rate for  both years ended 31 December 2014 and 2013 was 100%.  2014 2013 Year ended 31 December  US$’000 US$’000 Costs carried forward in respect of areas of interest in:  Development and production assets, at cost:  Producing assets  652,035  297,469  Wells-in-progress  56,043  55,636  Development and production assets, at cost:  708,078  353,105  Accumulated depletion  (117,613)  (40,635)  Provision for impairment  (71,452)  (240)  Total Development and Production Expenditure  519,013  312,230  a) Movements in carrying amounts:  Development expenditure  Balance at the beginning of the period  312,230  79,729  Amounts capitalised during the period  350,196  219,121  Amounts transferred from exploration phase  59,209  31,999  Fair value of assets acquired  -  54,258  Allocation of working interest assets acquired  2,244  -  Reclassifications to assets held for sale  -  (10,489)  Impairment expense  (71,212)  -  Depletion expense  (85,357)  (36,294)  Development and production assets, net of accumulated  amortization, sold during the period  (48,297)  (26,094)  Balance at end of period  519,013  312,230  NOTES TO THE CONSOLIDATED FINANCIAL STATEMENTS  NOTE 16 – DEVELOPMENT AND PRODUCTION ASSETS