NOTES TO THE CONSOLIDATED FINANCIAL STATEMENTS  NOTE 23 – RESTORATION PROVISION  NOTE 24 – DEFERRED TAX ASSETS AND LIABILITIES The restoration provision represents the best estimate of the present value of restoration costs relating to the  Company’s oil and natural gas interests, which are expected to be incurred up to 2043. Assumptions, based on the  current economic environment, have been made which management believes are a reasonable basis upon which to  estimate the future liability. The estimate of future removal costs requires management to make significant  judgments regarding removal date or well lives, the extent of restoration activities required, discount and inflation  rates. These estimates are reviewed regularly to take into account any material changes to the assumptions. However, actual restoration costs will reflect market conditions at the relevant time. Furthermore, the timing of  restoration is likely to depend on when the fields cease to produce at economically viable rates. This in turn will  depend on future oil and natural gas prices, which are inherently uncertain.  Deferred tax assets and liabilities are attributable to the following: 2014 2013 Year ended 31 December  US$’000 US$’000 Balance at the beginning of the period  5,074  1,228  New provisions  3,677  1,601  Changes in estimates  1,541  2,021  Disposals  (2,314)  (146)  New provisions assumed from acquisition  822  397  Reclassified to assets held for sale  -  (109)  Unwinding of discount  66  82  Balance at end of period  8,866  5,074  2014 2013 Year ended 31 December  US$’000 US$’000 Net deferred tax assets:  Share issuance costs 2,172  1,069  Net operating loss carried forward  1,826  473  Unrecognized foreign currency gain (loss)  -  761  Total net deferred tax assets  3,998  2,303  Deferred tax liabilities:  Development and production expenditure  (106,343)  (114,042)  Derivatives  (3,351)  -  Offset by deferred tax assets with legally enforceable right of set-off:  Net operating loss carried forward  5,943  10,373  Other  1,083  958  Total net deferred tax liabilities  (102,668)  (102,711)  - 88 - 