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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 FOY8z0dNrGbzYQIk2v2tLUXMnyGMmYu7pfMsTZPX5GZKor06CEhy/PoHKRXl/Nhe
 fcDB3f4CIvnKuqKZ1tZdrw==

<SEC-DOCUMENT>0001181834-09-000005.txt : 20090902
<SEC-HEADER>0001181834-09-000005.hdr.sgml : 20090902
<ACCEPTANCE-DATETIME>20090902115000
ACCESSION NUMBER:		0001181834-09-000005
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20090831
FILED AS OF DATE:		20090902
DATE AS OF CHANGE:		20090902

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			YOUNGBLOOD GARY C
		CENTRAL INDEX KEY:			0001181834

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-07810
		FILM NUMBER:		091050193

	MAIL ADDRESS:	
		STREET 1:		605 RICHARD ARRINGTON JR BLVD N
		CITY:			BIRMINGHAM
		STATE:			AL
		ZIP:			35203-2707

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ENERGEN CORP
		CENTRAL INDEX KEY:			0000277595
		STANDARD INDUSTRIAL CLASSIFICATION:	NATURAL GAS DISTRIBUTION [4924]
		IRS NUMBER:				630757759
		STATE OF INCORPORATION:			AL
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		605 RICHARD ARRINGTON JR BLVD N
		CITY:			BIRMINGHAM
		STATE:			AL
		ZIP:			35203-2707
		BUSINESS PHONE:		2053262997

	MAIL ADDRESS:	
		STREET 1:		605 RICHARD ARRINGTON JR BLVD N
		CITY:			BIRMINGHAM
		STATE:			AL
		ZIP:			35203

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ALAGASCO INC
		DATE OF NAME CHANGE:	19851002
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-08-31</periodOfReport>

    <issuer>
        <issuerCik>0000277595</issuerCik>
        <issuerName>ENERGEN CORP</issuerName>
        <issuerTradingSymbol>EGN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001181834</rptOwnerCik>
            <rptOwnerName>YOUNGBLOOD GARY C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>605 RICHARD ARRINGTON JR. BLVD. NORTH</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BIRMINGHAM</rptOwnerCity>
            <rptOwnerState>AL</rptOwnerState>
            <rptOwnerZipCode>35203-2707</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>and Retired Officer</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>55418</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock (deferred)</value>
            </securityTitle>
            <transactionDate>
                <value>2009-08-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>69</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>41.99</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>23085</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Energen Corporation Deferred Compensation Plan; number of securities is estimated based on recordkeepers' unit accounting.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>J. D. Woodruff, Attorney in Fact</signatureName>
        <signatureDate>2009-09-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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