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    <periodOfReport>2014-11-19</periodOfReport>

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    <issuer>
        <issuerCik>0001502012</issuerCik>
        <issuerName>QR Energy, LP</issuerName>
        <issuerTradingSymbol>QRE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001507034</rptOwnerCik>
            <rptOwnerName>Campbell John H Jr</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1401 MCKINNEY</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 2400</rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77010</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President &amp; COO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

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                    <value>See Footnote</value>
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                    <value>See Footnote</value>
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                    <value>59843</value>
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        <derivativeTransaction>
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                    <value>20795</value>
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                    <value>0</value>
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                    <value>D</value>
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    <footnotes>
        <footnote id="F1">Pursuant to the Agreement and Plan of Merger dated as of July 23, 2014 (the &quot;Merger Agreement&quot;), by and among QR Energy, LP (the &quot;Partnership&quot;), QRE GP, LLC, Breitburn Energy Partners LP (&quot;Breitburn&quot;), Breitburn GP LLC, and Boom Merger Sub, LLC (&quot;Merger Sub&quot;), Merger Sub merged with and into the Partnership (the &quot;Merger&quot;), with the Partnership surviving the Merger and continuing as a wholly-owned subsidiary of Breitburn. Pursuant to the Merger Agreement, any performance units granted under the QRE GP, LLC Long-Term Incentive Plan vested immediately prior to the November 19, 2014 closing of the Merger, and were settled in a number of common units determined based on the actual attainment of the applicable performance goal(s) as of two business days prior to the closing. Each resulting common unit was converted at the closing into the right to  receive 0.9856 Breitburn common units, or in the case of fractional Breitburn units, cash (without interest and rounded up to the nearest whole c</footnote>
        <footnote id="F2">Pursuant to the Agreement and Plan of Merger dated as of July 23, 2014 (the &quot;Merger Agreement&quot;), by and among QR Energy, LP (the &quot;Partnership&quot;), QRE GP, LLC, Breitburn Energy Partners LP (&quot;Breitburn&quot;), Breitburn GP LLC, and Boom Merger Sub, LLC (&quot;Merger Sub&quot;), Merger Sub merged with and into the Partnership (the &quot;Merger&quot;), with the Partnership surviving the Merger and continuing as a wholly-owned subsidiary of Breitburn. Pursuant to the Merger Agreement, any common units of the Partnership that were granted under the QRE GP, LLC Long-Term Incentive Plan and subject to time-based vesting or forfeiture conditions vested upon the November 19, 2014 closing of the Merger and the restrictions with respect thereto lapsed, and each resulting common unit was converted at the closing into the right to  receive 0.9856 Breitburn common units, or in the case of fractional Breitburn units, cash (without interest and rounded up to the nearest whole cent) in an amount equal to the product of (i) such</footnote>
        <footnote id="F3">Pursuant to the previously disclosed Contribution Agreement, dated March 2, 2014, by and among QR Energy, LP (the &quot;Partnership&quot;), QRE GP, LLC (the &quot;General Partner&quot;), QR Holdings (QRE), LLC (&quot;QRH&quot;) and QR Energy Holdings, LLC (&quot;QREH&quot;),  the General Partner distributed 3,826,393 Class B units to QRH and 2,307,165 Class B units to QREH. Pursuant to the Agreement and Plan of Merger dated as of July 23, 2014 (the &quot;Merger Agreement&quot;), by and among the Partnership, General Partner, Breitburn Energy Partners LP (&quot;Breitburn&quot;), Breitburn GP LLC, and Boom Merger Sub, LLC (&quot;Merger Sub&quot;), Merger Sub merged with and into the Partnership (the &quot;Merger&quot;), with the Partnership surviving the Merger and continuing as a wholly-owned subsidiary of Breitburn. Upon the November 19, 2014 closing of the Merger, each Class B unit of the Partnership was converted into the right to receive 0.9856 Breitburn common units, or in the case of fractional Breitburn units, cash (without interest and rounded up to the nea</footnote>
        <footnote id="F4">Pursuant to the previously disclosed Contribution Agreement, dated March 2, 2014, by and among QR Energy, LP (the &quot;Partnership&quot;), QRE GP, LLC (the &quot;General Partner&quot;), QR Holdings (QRE), LLC (&quot;QRH&quot;) and QR Energy Holdings, LLC (&quot;QREH&quot;),  the General Partner distributed 3,826,393 Class B units to QRH and 2,307,165 Class B units to QREH. Reporting person owns an economic interest in QREH</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Gregory S. Roden on behalf of John H. Campbell Jr.</signatureName>
        <signatureDate>2014-11-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
