<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-04-29</periodOfReport>

    <issuer>
        <issuerCik>0000072207</issuerCik>
        <issuerName>NOBLE ENERGY INC</issuerName>
        <issuerTradingSymbol>NBL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001575410</rptOwnerCik>
            <rptOwnerName>Elliott J. Keith</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1001 NOBLE ENERGY WAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77070</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>Sr. VP Eastern Mediterranean</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Noble Energy, Inc. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-04-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>121</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>36.11</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>68714</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Reflects shares relinquished to Noble Energy, Inc. by the reporting person out of, and to cover estimated tax withholding for, restricted shares granted on April 29, 2013, and vesting on April 29, 2016. The stock price reflected in Table I Column 4 was determined based on &quot;fair market value,&quot; defined in the 1992 Plan for this transaction as the closing trading price of Noble Energy, Inc. common stock on the NYSE on April 29, 2016.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Aaron G. Carlson, Attorney-in-Fact</signatureName>
        <signatureDate>2016-05-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
