<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><Version>2.2.0.25</Version><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><ReportLongName>0204 - Disclosure - Acquisitions and business combinations</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelColumn>false</LabelColumn><CurrencyCode>USD</CurrencyCode><FootnoteIndexer /><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><MCU><KeyName>1/1/2010 - 12/31/2010
USD ($)

USD ($) / shares

</KeyName><CurrencySymbol>$</CurrencySymbol><contextRef><ContextID>Jan-01-2010_Dec-31-2010</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0001358071</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2010-01-01T00:00:00</PeriodStartDate><PeriodEndDate>2010-12-31T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS><UnitProperty><UnitID>USD</UnitID><UnitType>Standard</UnitType><StandardMeasure><MeasureSchema>http://www.xbrl.org/2003/iso4217</MeasureSchema><MeasureValue>USD</MeasureValue><MeasureNamespace>iso4217</MeasureNamespace></StandardMeasure><Scale>0</Scale></UnitProperty><UnitProperty><UnitID>USDEPS</UnitID><UnitType>Divide</UnitType><NumeratorMeasure><MeasureSchema>http://www.xbrl.org/2003/iso4217</MeasureSchema><MeasureValue>USD</MeasureValue><MeasureNamespace>iso4217</MeasureNamespace></NumeratorMeasure><DenominatorMeasure><MeasureSchema>http://www.xbrl.org/2003/instance</MeasureSchema><MeasureValue>shares</MeasureValue><MeasureNamespace>xbrli</MeasureNamespace></DenominatorMeasure><Scale>0</Scale></UnitProperty><UnitProperty><UnitID>Shares</UnitID><UnitType>Standard</UnitType><StandardMeasure><MeasureSchema>http://www.xbrl.org/2003/instance</MeasureSchema><MeasureValue>shares</MeasureValue><MeasureNamespace>xbrli</MeasureNamespace></StandardMeasure><Scale>0</Scale></UnitProperty></UPS><CurrencyCode>USD</CurrencyCode><OriginalCurrencyCode>USD</OriginalCurrencyCode></MCU><CurrencySymbol>$</CurrencySymbol><Labels><Label Id="1" Label="12 Months Ended" /><Label Id="2" Label="Dec. 31, 2010" /></Labels></Column></Columns><Rows><Row><Id>2</Id><IsAbstractGroupTitle>true</IsAbstractGroupTitle><Level>0</Level><ElementName>cxo_AcquisitionsAndBusinessCombinationsAbstract</ElementName><ElementPrefix>cxo</ElementPrefix><IsBaseElement>false</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><ShortDefinition>Acquisitions and business combinations.</ShortDefinition><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsSubReportEnd>false</IsSubReportEnd><IsCalendarTitle>false</IsCalendarTitle><IsTuple>false</IsTuple><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><PreferredLabelRole /><FootnoteIndexer /><Cells><Cell><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><NonNumericTextHeader /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios></Cell></Cells><OriginalInstanceReportColumns /><Unit>Other</Unit><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><ElementDefenition>Acquisitions and business combinations.</ElementDefenition><IsTotalLabel>false</IsTotalLabel><IsEPS>false</IsEPS><Label>Acquisitions and business combinations [Abstract]</Label></Row><Row><Id>3</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><Level>0</Level><ElementName>us-gaap_BusinessCombinationDisclosureTextBlock</ElementName><ElementPrefix>us-gaap</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><ShortDefinition>No definition available.</ShortDefinition><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsSubReportEnd>false</IsSubReportEnd><IsCalendarTitle>false</IsCalendarTitle><IsTuple>false</IsTuple><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><PreferredLabelRole>verboselabel</PreferredLabelRole><FootnoteIndexer /><Cells><Cell><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;!--DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" --&gt;
   &lt;!-- Begin Block Tagged Note 4 - us-gaap:BusinessCombinationDisclosureTextBlock--&gt;
   &lt;div style="font-family: 'Times New Roman',Times,serif"&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&lt;b&gt;Note D. &lt;/b&gt;&lt;b&gt;&lt;i&gt;Acquisitions and business combinations&lt;/i&gt;&lt;/b&gt;
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;b&gt;&lt;i&gt;Marbob and Settlement Acquisitions. &lt;/i&gt;&lt;/b&gt;In July&amp;#160;2010, the Company entered into an asset purchase
   agreement to acquire certain of the oil and natural gas leases, interests, properties and related
   assets owned by Marbob Energy Corporation and its affiliates (collectively, &amp;#8220;Marbob&amp;#8221;) for aggregate
   consideration of (i)&amp;#160;cash in the amount of $1.45&amp;#160;billion, (ii)&amp;#160;the issuance to Marbob of $150
   million 8.0% unsecured senior note due 2018 and (iii)&amp;#160;the issuance to Marbob of approximately 1.1
   million shares of the Company&amp;#8217;s common stock, subject to purchase price adjustments, which included
   downward purchase price adjustments based on the exercise of third parties of contractual
   preferential purchase rights in properties to be acquired from Marbob (&amp;#8220;Marbob Acquisition&amp;#8221;).
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;On October&amp;#160;7, 2010, the Company closed the Marbob Acquisition. At closing, the Company paid
   approximately $1.1&amp;#160;billion in cash plus the unsecured senior note and common stock described above
   for a total purchase price of approximately $1.4&amp;#160;billion. The total purchase price as originally
   announced was reduced due to third party contractual preferential purchase rights in the Marbob
   properties. Certain of the third parties contractual preferential purchase rights became subject to
   litigation, as discussed below.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;The Company funded the cash consideration in the Marbob Acquisition with (a)&amp;#160;borrowings under
   its credit facility and (b)&amp;#160;net proceeds of $292.7&amp;#160;million from a private placement of
   approximately 6.6&amp;#160;million shares of the Company&amp;#8217;s common stock at a price of $45.30 per share that
   closed on October&amp;#160;7, 2010.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;Certain of the Marbob interests in properties contained contractual preferential purchase
   rights by third parties if Marbob were to sell them. Marbob informed the Company of its receipt of
   a notice from BP America Production Company (&amp;#8220;BP&amp;#8221;) electing to exercise its contractual
   preferential purchase rights in certain of Marbob&amp;#8217;s properties as a result of the Marbob
   Acquisition.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;On July&amp;#160;20, 2010, BP announced it was selling all its assets in the Permian Basin to a
   subsidiary of Apache Corporation (&amp;#8220;Apache&amp;#8221;). Marbob and BP owned common interests in certain
   properties subject to contractual preferential purchase rights. BP and Apache contested Marbob&amp;#8217;s
   ability to exercise its contractual preferential purchase rights in this situation. As a result,
   Marbob and the Company filed suit against BP and Apache seeking declaratory judgment and injunctive
   relief to protect Marbob&amp;#8217;s contractual right to have the option to purchase these interests in
   these common properties.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;On October&amp;#160;15, 2010, the Company and Marbob resolved the litigation with BP and Apache related
   to the disputed contractual preferential purchase rights. As a result of the settlement, the
   Company acquired a non-operated interest in substantially all of the oil and natural gas assets
   subject to the litigation for approximately $286&amp;#160;million in cash (the &amp;#8220;Settlement Acquisition&amp;#8221;).
   The Company funded the Settlement Acquisition with borrowings under our credit facility.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;The results of operations of the Marbob and Settlement Acquisitions are included in the
   Company&amp;#8217;s results of operations since their respective closing dates in October&amp;#160;2010.
   &lt;/div&gt;
   &lt;!-- Folio --&gt;
   &lt;!-- /Folio --&gt;
   &lt;/div&gt;
   &lt;!-- PAGEBREAK --&gt;
   &lt;div style="font-family: 'Times New Roman',Times,serif"&gt;
   &lt;div align="center" style="font-size: 15pt; margin-top: 0pt"&gt;
   &lt;b&gt;
   &lt;/b&gt;
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;The following tables represent the allocation of the total purchase price of the Marbob and
   Settlement Acquisitions to the acquired assets and liabilities assumed. The allocation represents
   the fair values assigned to each of the assets acquired and liabilities assumed:
   &lt;/div&gt;
   &lt;div align="center"&gt;
   &lt;table style="font-size: 10pt; text-align: left" cellspacing="0" border="0" cellpadding="0" width="98%"&gt;
   &lt;!-- Begin Table Head --&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td width="76%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="2%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="8%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="2%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="8%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td colspan="9" align="left" style="border-top: 2px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="line-height: 6pt"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 10pt" valign="bottom"&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="center" colspan="2"&gt;&lt;b&gt;Marbob&lt;/b&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="center" colspan="2"&gt;&lt;b&gt;Settlement&lt;/b&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 10pt" valign="bottom"&gt;
       &lt;td nowrap="nowrap" align="left"&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&lt;b&gt;(in thousands)&lt;/b&gt;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="center" colspan="2"&gt;&lt;b&gt;Acquisition&lt;/b&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="center" colspan="2"&gt;&lt;b&gt;Acquisition&lt;/b&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;!-- End Table Head --&gt;
   &lt;!-- Begin Table Body --&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td colspan="9" align="left" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&lt;b&gt;Fair value of net assets:&lt;/b&gt;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:37px; text-indent:-15px"&gt;Proved oil and natural gas properties
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;1,014,734&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;185,337&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:37px; text-indent:-15px"&gt;Unproved oil and natural gas properties
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;334,866&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;101,582&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:37px; text-indent:-15px"&gt;Other long-term assets
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;20,771&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;-&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:65px; text-indent:-15px"&gt;Total assets acquired
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;1,370,371&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;286,919&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="line-height: 6pt"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:37px; text-indent:-15px"&gt;Asset retirement obligations and other liabilities assumed
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="left"&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;(7,851&lt;/td&gt;
       &lt;td nowrap="nowrap"&gt;)&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="left"&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;(689&lt;/td&gt;
       &lt;td nowrap="nowrap"&gt;)&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:75px; text-indent:-15px"&gt;Total purchase price
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;1,362,520&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;286,230&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 3px double #000000"&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 3px double #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="line-height: 6pt"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&lt;b&gt;Fair value of consideration paid for net assets:&lt;/b&gt;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:37px; text-indent:-15px"&gt;Cash consideration
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;1,127,747&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;286,230&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:37px; text-indent:-15px"&gt;Marbob $150&amp;#160;million senior unsecured 8% note, due 2018
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="left"&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;159,000&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap"&gt;&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;(a)&lt;/sup&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;-&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:37px; text-indent:-15px"&gt;Common stock, $0.001 par value; 1,103,752 shares issued
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="left"&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;75,773&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap"&gt;&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;(b)&lt;/sup&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;-&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:75px; text-indent:-15px"&gt;Total purchase price
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;1,362,520&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;286,230&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 3px double #000000"&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 3px double #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="line-height: 6pt"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td colspan="9" align="left" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;!-- End Table Body --&gt;
   &lt;/table&gt;
   &lt;/div&gt;
   &lt;div align="left"&gt;
   &lt;div style="font-size: 3pt; margin-top: 6pt; width: 18%; border-top: 0px solid #000000"&gt;&amp;#160;
   &lt;/div&gt;
   &lt;/div&gt;
   &lt;table width="100%" border="0" cellpadding="0" cellspacing="0" style="font-size: 9pt; text-align: left"&gt;
   &lt;tr&gt;
       &lt;td width="3%"&gt;&lt;/td&gt;
       &lt;td width="1%"&gt;&lt;/td&gt;
       &lt;td width="96%"&gt;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="top"&gt;
       &lt;td nowrap="nowrap" align="right"&gt;&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;(a)&lt;/sup&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;
   &lt;div style="text-align: justify"&gt;The fair value of the $150&amp;#160;million 8.0% senior unsecured note due 2018 issued to Marbob, was calculated by reference
   to the
   traded market yield of Concho&amp;#8217;s 8.625% senior unsecured notes due 2017, at September&amp;#160;30, 2010.
   &lt;/div&gt;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 10pt"&gt;
   &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="top"&gt;
       &lt;td nowrap="nowrap" align="right"&gt;&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;(b)&lt;/sup&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;
   &lt;div style="text-align: justify"&gt;The fair value of the Concho common stock issued to Marbob was valued at the average of the high and low price on the
   closing date (October&amp;#160;7, 2010), of $68.65 per share.
   &lt;/div&gt;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;/table&gt;
   &lt;div align="center"&gt;
   &lt;div style="font-size: 3pt; margin-top: 6pt; width: 98%; border-top: 1px solid #000000"&gt;&amp;#160;
   &lt;/div&gt;
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;b&gt;&lt;i&gt;Wolfberry acquisitions. &lt;/i&gt;&lt;/b&gt;In December&amp;#160;2009, together with the acquisition of related additional
   interests that closed in 2010, the Company closed two acquisitions (the &amp;#8220;Wolfberry Acquisitions&amp;#8221;)
   of interests in producing and non-producing assets in the Wolfberry play in the Permian Basin for
   approximately $270.7&amp;#160;million. The Wolfberry Acquisitions were funded with borrowings under the
   Company&amp;#8217;s credit facility. The Company&amp;#8217;s 2009 results of operations do not include any results from
   the Wolfberry Acquisitions.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;The following table represents the allocation of the total purchase price of the Wolfberry
   Acquisitions to the acquired assets and liabilities assumed. The allocation represents the fair
   values assigned to each of the assets acquired and liabilities assumed:
   &lt;/div&gt;
   &lt;div align="center"&gt;
   &lt;table style="font-size: 10pt; text-align: left" cellspacing="0" border="0" cellpadding="0" width="98%"&gt;
   &lt;!-- Begin Table Head --&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td width="87%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="2%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="9%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td colspan="5" align="left" style="border-top: 2px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="line-height: 6pt"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 10pt" valign="bottom"&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="center" colspan="2"&gt;&lt;b&gt;Wolfberry&lt;/b&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 10pt" valign="bottom"&gt;
       &lt;td nowrap="nowrap" align="left"&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&lt;b&gt;(in thousands)&lt;/b&gt;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="center" colspan="2"&gt;&lt;b&gt;Acquisitions&lt;/b&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;!-- End Table Head --&gt;
   &lt;!-- Begin Table Body --&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td colspan="5" align="left" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&lt;b&gt;Fair value of net assets:&lt;/b&gt;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:37px; text-indent:-15px"&gt;Proved oil and natural gas properties
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;212,987&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:37px; text-indent:-15px"&gt;Unproved oil and natural gas properties
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;58,222&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:55px; text-indent:-15px"&gt;Total assets acquired
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;271,209&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="line-height: 6pt"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:37px; text-indent:-15px"&gt;Asset retirement obligations
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="left"&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="right"&gt;(464&lt;/td&gt;
       &lt;td nowrap="nowrap"&gt;)&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="line-height: 3pt"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:70px; text-indent:-15px"&gt;Net purchase price
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;270,745&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" colspan="3" align="right" style="border-top: 3px double #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="line-height: 6pt"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td colspan="5" align="left" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;!-- End Table Body --&gt;
   &lt;/table&gt;
   &lt;/div&gt;
   &lt;!-- Folio --&gt;
   &lt;!-- /Folio --&gt;
   &lt;/div&gt;
   &lt;!-- PAGEBREAK --&gt;
   &lt;div style="font-family: 'Times New Roman',Times,serif"&gt;
   &lt;div align="center" style="font-size: 15pt; margin-top: 0pt"&gt;
   &lt;b&gt;
   &lt;/b&gt;
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;b&gt;&lt;i&gt;Henry Entities acquisition. &lt;/i&gt;&lt;/b&gt;In July&amp;#160;2008, the Company closed its acquisition of Henry
   Petroleum LP and certain entities affiliated with Henry Petroleum LP (which we refer to as &amp;#8220;Henry&amp;#8221;
   or the &amp;#8220;Henry Entities&amp;#8221;) and additional non-operated interests in oil and natural gas properties
   from persons affiliated with the Henry Entities. In August&amp;#160;2008 and September&amp;#160;2008, the Company
   acquired additional non-operated interests in oil and natural gas assets from persons affiliated
   with the Henry Entities. The assets acquired and liabilities assumed in the Henry Entities
   acquisition and the acquired additional non-operated interests are referred to as the &amp;#8220;Henry
   Properties.&amp;#8221; The Company paid $583.7&amp;#160;million in cash for the Henry Properties acquisition. The
   Company&amp;#8217;s results of operations included those from the Henry Properties since August&amp;#160;1, 2008.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;The cash paid for the Henry Properties acquisition was funded with (i)&amp;#160;borrowings under the
   Company&amp;#8217;s credit facility, and (ii)&amp;#160;net proceeds of $242.4&amp;#160;million from a private placement of
   approximately 8.3&amp;#160;million shares of the Company&amp;#8217;s common stock.
   &lt;/div&gt;
   &lt;div align="justify" style="font-size: 10pt; margin-top: 10pt"&gt;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;b&gt;&lt;i&gt;Pro forma data. &lt;/i&gt;&lt;/b&gt;The following unaudited pro forma combined condensed financial data for the
   years ended December&amp;#160;31, 2010 and 2009 was derived from the historical financial statements of the
   Company giving effect to the Marbob and Settlement Acquisitions as if they had occurred on January
   1, 2009. The pro forma financial data does not include the results of operations for the Wolfberry
   Acquisitions as they are not deemed material. The unaudited pro forma combined condensed financial
   data has been included for comparative purposes only and is not necessarily indicative of the
   results that might have occurred had these acquisitions taken place as of the date indicated and is
   not intended to be a projection of future results.
   &lt;/div&gt;
   &lt;div align="center"&gt;
   &lt;table style="font-size: 10pt; text-align: left" cellspacing="0" border="0" cellpadding="0" width="98%"&gt;
   &lt;!-- Begin Table Head --&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td width="76%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="5%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="5%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="2%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="7%"&gt;&amp;#160;&lt;/td&gt;
       &lt;td width="1%"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td colspan="9" align="left" style="border-top: 2px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="line-height: 6pt"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 10pt" valign="bottom"&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="center" colspan="7" style="border-bottom: 1px solid #000000"&gt;&lt;b&gt;Years Ended December 31,&lt;/b&gt;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 10pt" valign="bottom"&gt;
       &lt;td nowrap="nowrap" align="left" style="border-bottom: 1px solid #000000"&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&lt;b&gt;(in thousands, except per share data)&lt;/b&gt;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td style="border-bottom: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="center" colspan="3" style="border-bottom: 1px solid #000000"&gt;&lt;b&gt;2010&lt;/b&gt;&lt;/td&gt;
       &lt;td style="border-bottom: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="center" colspan="3" style="border-bottom: 1px solid #000000"&gt;&lt;b&gt;2009&lt;/b&gt;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 10pt" valign="bottom"&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="center" colspan="6"&gt;(unaudited)&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;!-- End Table Head --&gt;
   &lt;!-- Begin Table Body --&gt;
   &lt;tr valign="bottom"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;Operating revenues from continuing operations
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;1,178,138&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;732,452&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;Income
   (loss) from continuing operations
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;216,984&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;(893&lt;/td&gt;
       &lt;td nowrap="nowrap"&gt;)&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="line-height: 6pt"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;Income
   (loss) from continuing operations per common share:
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="line-height: 3pt"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:37px; text-indent:-15px"&gt;Basic
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;2.16&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;(0.01&lt;/td&gt;
       &lt;td nowrap="nowrap"&gt;)&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="background: #cceeff"&gt;
       &lt;td&gt;
   &lt;div style="margin-left:37px; text-indent:-15px"&gt;Diluted
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;2.14&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td nowrap="nowrap" align="left"&gt;&amp;#160;&amp;#160;$&lt;/td&gt;
       &lt;td align="right"&gt;(0.01&lt;/td&gt;
       &lt;td nowrap="nowrap"&gt;)&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr valign="bottom" style="line-height: 6pt"&gt;&lt;!-- Blank Space --&gt;
       &lt;td&gt;
   &lt;div style="margin-left:20px; text-indent:-15px"&gt;&amp;#160;
   &lt;/div&gt;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
       &lt;td&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;tr style="font-size: 1px"&gt;
       &lt;td colspan="9" align="left" style="border-top: 1px solid #000000"&gt;&amp;#160;&lt;/td&gt;
   &lt;/tr&gt;
   &lt;!-- End Table Body --&gt;
   &lt;/table&gt;
   &lt;/div&gt;
   &lt;/div&gt;
</NonNumbericText><NonNumericTextHeader>&lt;!--DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" --&gt;
   &lt;!-- Begin Block Tagged Note</NonNumericTextHeader><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios></Cell></Cells><OriginalInstanceReportColumns /><Unit>Other</Unit><ElementDataType>us-types:textBlockItemType</ElementDataType><SimpleDataType>string</SimpleDataType><ElementDefenition>Description of a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. This element may be used as a single block of text to encapsulate the entire disclosure (including data and tables) regarding business combinations, including leverage buyout transactions (as applicable).</ElementDefenition><ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 141
 -Paragraph 51, 52

Reference 2: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Emerging Issues Task Force (EITF)
 -Number 88-16

Reference 3: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 141R
 -Paragraph 67-73

Reference 4: http://www.xbrl.org/2003/role/presentationRef
 -Publisher FASB
 -Name Statement of Financial Accounting Standard (FAS)
 -Number 141R
 -Paragraph F4
 -Subparagraph e
 -Appendix F

</ElementReferences><IsTotalLabel>false</IsTotalLabel><IsEPS>false</IsEPS><Label>Acquisitions and business combinations</Label></Row></Rows><Footnotes /><NumberOfCols>1</NumberOfCols><NumberOfRows>2</NumberOfRows><ReportName>Acquisitions and business combinations</ReportName><MonetaryRoundingLevel>UnKnown</MonetaryRoundingLevel><SharesRoundingLevel>UnKnown</SharesRoundingLevel><PerShareRoundingLevel>UnKnown</PerShareRoundingLevel><ExchangeRateRoundingLevel>UnKnown</ExchangeRateRoundingLevel><HasCustomUnits>false</HasCustomUnits><SharesShouldBeRounded>true</SharesShouldBeRounded></InstanceReport>
