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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0001140361-09-004416.txt : 20090217
<SEC-HEADER>0001140361-09-004416.hdr.sgml : 20090216
<ACCEPTANCE-DATETIME>20090217185648
ACCESSION NUMBER:		0001140361-09-004416
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20090213
FILED AS OF DATE:		20090217
DATE AS OF CHANGE:		20090217

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Stallings Alex G
		CENTRAL INDEX KEY:			0001406205

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-33503
		FILM NUMBER:		09616620

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		(918) 524-8100

	MAIL ADDRESS:	
		STREET 1:		6120 SOUTH YALE AVENUE, SUITE 700
		CITY:			TULSA
		STATE:			OK
		ZIP:			74136

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SemGroup Energy Partners, L.P.
		CENTRAL INDEX KEY:			0001392091
		STANDARD INDUSTRIAL CLASSIFICATION:	PIPE LINES (NO NATURAL GAS) [4610]
		IRS NUMBER:				208536826
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		TWO WARREN PLACE
		STREET 2:		6120 SOUTH YALE AVENUE, SUITE 700
		CITY:			TULSA
		STATE:			OK
		ZIP:			74136
		BUSINESS PHONE:		(918) 524-8100

	MAIL ADDRESS:	
		STREET 1:		TWO WARREN PLACE
		STREET 2:		6120 SOUTH YALE AVENUE, SUITE 700
		CITY:			TULSA
		STATE:			OK
		ZIP:			74136
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-02-13</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001392091</issuerCik>
        <issuerName>SemGroup Energy Partners, L.P.</issuerName>
        <issuerTradingSymbol>SGLP</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001406205</rptOwnerCik>
            <rptOwnerName>Stallings Alex G</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>6120 SOUTH YALE AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 500</rptOwnerStreet2>
            <rptOwnerCity>TULSA</rptOwnerCity>
            <rptOwnerState>OK</rptOwnerState>
            <rptOwnerZipCode>74136</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <officerTitle></officerTitle>
            <otherText>CAO &amp; Sec. of GP of Issuer</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common units representing limited partner interests</value>
            </securityTitle>
            <transactionDate>
                <value>2009-02-13</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>23963</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.51</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>91037</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">As disclosed in a Current Report on Form 8-K filed on July 21, 2008, the phantom units owned by Mr. Stallings vested on a change of control of the general partner, SemGroup Energy Partners G.P., L.L.C. (the &quot;General Partner&quot;), of SemGroup Energy Partners, L.P. (the &quot;Partnership&quot;).  75,000 phantom units were reported as owned in prior Form 4 filings.  The vested phantom units have since been issued to Mr. Stallings and 23,963 common units were withheld on February 13, 2009 to fulfill tax obligations as permitted by the Long-Term Incentive Plan of the General Partner.</footnote>
    </footnotes>

    <remarks>Mr. Stallings is the CAO and Secretary of SemGroup Energy Partners G.P., L.L.C., the general partner of SemGroup Energy Partners, L.P.</remarks>

    <ownerSignature>
        <signatureName>/s/ Alex G. Stallings</signatureName>
        <signatureDate>2009-02-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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