<SEC-DOCUMENT>0001084991-19-000045.txt : 20190701
<SEC-HEADER>0001084991-19-000045.hdr.sgml : 20190701
<ACCEPTANCE-DATETIME>20190701174246
ACCESSION NUMBER:		0001084991-19-000045
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20190628
FILED AS OF DATE:		20190701
DATE AS OF CHANGE:		20190701

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Taylor Stephen Charles
		CENTRAL INDEX KEY:			0001316004

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-31398
		FILM NUMBER:		19934447

	MAIL ADDRESS:	
		STREET 1:		2911 SOUTH COUNTY ROAD 1260
		CITY:			MIDLAND
		STATE:			TX
		ZIP:			79706

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NATURAL GAS SERVICES GROUP INC
		CENTRAL INDEX KEY:			0001084991
		STANDARD INDUSTRIAL CLASSIFICATION:	OIL, GAS FIELD SERVICES, NBC [1389]
		IRS NUMBER:				752811855
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		508 WEST WALL STREET
		STREET 2:		SUITE 550
		CITY:			MIDLAND
		STATE:			TX
		ZIP:			79701
		BUSINESS PHONE:		432-262-2700

	MAIL ADDRESS:	
		STREET 1:		508 WEST WALL STREET
		STREET 2:		SUITE 550
		CITY:			MIDLAND
		STATE:			TX
		ZIP:			79701
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2019-06-28</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001084991</issuerCik>
        <issuerName>NATURAL GAS SERVICES GROUP INC</issuerName>
        <issuerTradingSymbol>ngs</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001316004</rptOwnerCik>
            <rptOwnerName>Taylor Stephen Charles</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>404 VETERANS AIRPARK LANE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 300</rptOwnerStreet2>
            <rptOwnerCity>MIDLAND</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>79705</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Executive Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2019-06-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>98755</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>17.29</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>413388</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>51596</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Rabbi Trust</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>17.29</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2019-06-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>32919</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>32919</value>
                    <footnoteId id="F4"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>72692</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeHolding>
            <securityTitle>
                <value>Employee Stock Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>19.9</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2011-01-18</value>
            </exerciseDate>
            <expirationDate>
                <value>2020-01-17</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>30000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>30000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The acquisition reflects an award of Restricted Stock pursuant to the Company's 2019 Equity Incentive Plan.  The award vests in one-third annual increments beginning on the first anniversary of the grant date, subject to accelerated vesting under certain circumstances.</footnote>
        <footnote id="F2">The amount of securities beneficially owned has been adjusted to add 557 shares of Company common stock in order to correct an inadvertent error in the number of shares withheld for tax withholding in connection with the Form 4 filed on March 19, 2019.</footnote>
        <footnote id="F3">Not Applicable.  The acquisition reflects an award of Restricted Stock Units (&quot;RSU&quot;) pursuant to the Company's 2019 Equity Incentive Plan.  Each RSU represents the right to receive one share of Company common stock upon vesting.</footnote>
        <footnote id="F4">Not Applicable.  Each RSU represents the right to receive one share of Company common stock upon vesting without payment.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Stephen C. Taylor</signatureName>
        <signatureDate>2019-07-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
