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                                                                   EXHIBIT 10.30

                           Subordinated Loan Agreement

                          Dated as of November 30, 1998

                                     Between

                         The Houston Exploration Company

                                       and

                   MarketSpan Corporation d/b/a KeySpan Energy



Borrower:                       The Houston Exploration Company ("Houston     
                                Exploration"), a publicly-traded Delaware     
                                corporation.                                  

Guarantors:                     All Significant Subsidiaries of the Borrower   
                                which may execute a Guaranty Agreement. (There 
                                are currently no Significant Subsidiaries.)    

Lender:                         MarketSpan Corporation d/b/a KeySpan Energy 
                                (the "Lender").

Type of Facility:               Subordinated Loan which will be a six month 
                                Revolving Credit Facility.

Total Commitment Amount:        $150,000,000

Purpose:                        Proceeds of the Facility will be utilized to  
                                temporarily finance hydrocarbon acquisitions. 

Maturity Date:                  All outstanding principal, unpaid accrued 
                                interest and fees will be repaid at maturity,
                                January 1, 2000. Any principal amount that
                                remains outstanding subsequent to the Maturity
                                Date will be converted into equity (the number
                                of shares to be issued to the Lender will be
                                determined based upon the average of the closing
                                prices of Houston Exploration's common stock,
                                rounded to three decimal places, as reported
                                under "NYSE Composite Transactions Reports" in
                                the Wall Street Journal during 20 consecutive
                                trading days ending three days prior to January
                                1, 2000. Because the market value represents an
                                average of Houston Exploration's common stock
                                over twenty consecutive trading days, ending
                                three days prior to maturity, the market price
                                may be higher or lower than the price of the
                                common stock on the conversion date). The total
                                amount converted to equity shall not exceed the
                                Total Commitment Amount. Any unpaid accrued
                                interest or fees that remain outstanding
                                subsequent to the Maturity Date will be paid in
                                cash.                      
                                
Security:                       Unsecured.  The Borrower provides a negative 
                                pledge on unencumbered assets.

Availability:                   The borrowings may be repaid and reborrowed in
                                minimum amounts of $5 million (or increments of
                                $1 million in excess thereof) under the
                                Facility. Subject to the provisions of Section 3
                                of the Subordination Agreement (see Schedule
                                II).

Optional Commitment
Reductions:                     The Revolving Credit commitment may be
                                permanently reduced upon 3 days notice from the
                                Borrower in minimum amounts of $5 million (and
                                integral amounts of $5 million) subject to
                                Prepayments below, provided that any amounts
                                outstanding which would exceed the total
                                commitment 



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                                as reduced, must be prepaid together with
                                interest thereon and any relevant costs. Subject
                                to the provisions of Section 3 of the
                                Subordination Agreement (see Schedule II).

Optional Prepayments:           Borrowings may be prepaid, along with associated
                                interest, subject to one business day notice to
                                the Lender. Subject to the provisions of Section
                                3 of the Subordination Agreement (see Schedule 
                                II).                                           

Mandatory Prepayments:          Upon any default of payment of interest or fees,
                                property sales, or casualty losses, the Borrower
                                shall make a Mandatory Repayment in the amount
                                of such excess amount. Subject to the provisions
                                of Section 3 of the Subordination Agreement 
                                (see Schedule II).

Interest Rates:                 See Schedule 1.

Fees:                           See Schedule 1.

Interest Periods:               The one month LIBOR rate will be set on
                                the date of each drawndown, as quoted in that
                                day's Wall Street Journal (which reflects the
                                previous business day's market rates). The rate
                                will be effective until the rate is reset on the
                                first business day of each month.

Notification Schedule:          The Borrower must provide notice prior to the 
                                proposed date of borrowing, in accordance with 
                                the following schedule:

                                Amounts greater than $10 million - 5 business
                                days Amounts equal to, or less than, $10 million
                                - 3 business days

Default Interest Rate:          Default interest will be 2% in excess of the    
                                LIBOR Rate, plus margins referred to in Schedule
                                1, subject to applicable law. Interest shall    
                                accrue at the post-default rates stated above on
                                amounts which remain unpaid after they become   
                                due and payable.                                

Conditions to Lending:          This Agreement shall be come effective on the   
                                date hereof, if this Agreement shall have been  
                                executed by the Borrower and the Lender, and the
                                Lender shall have received on or before the     
                                effective date:                                 

                                a)      A Promissory Note payable to the order
                                        of the Lender;

                                b)      A counterpart of this Agreement duly
                                        executed by the Borrower and the Lender,
                                        which shall constitute the valid and
                                        legal binding obligation of the
                                        Borrower, legally enforceable in
                                        accordance with its terms. Accompanied
                                        by legal opinions of the Borrower's
                                        counsel, certificates of the Borrower
                                        and other supporting documents as the
                                        Lender may reasonably request.

                                c)      A certificate of the Secretary or an
                                        Assistant Secretary of the Borrower
                                        certifying copies (i) of the resolutions
                                        of the Board of Directors of the
                                        Borrower approving such Agreement, (ii)
                                        of all documents evidencing other
                                        necessary corporate action and
                                        approvals, and (iii) that all lenders
                                        and other parties in privity with the
                                        Borrower whose consents are, or with
                                        reasonable certainty may be,
                                        prerequisite to the consummation of the
                                        Facility or of the transactions
                                        contemplated hereunder, shall have
                                        consented to the same.


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                                d)      A certificate of an officer of the
                                        Borrower certifying the names and true
                                        signatures of the officers of the
                                        Borrower authorized to sign this
                                        Agreement and the other documents and
                                        instruments to be delivered hereunder
                                        and thereunder.this Agreement and each
                                        this Agreement and the other documents
                                        and instruments to be delivered
                                        hereunder and thereunder.

                                e)      All fees and costs required under the
                                        Agreement to be paid by the Closing Date
                                        shall have been paid in full. Subject to
                                        the provisions of Section 3 of the
                                        Subordination Agreement (see Schedule
                                        II).

                                f)      Since September 30, 1998, there shall
                                        not have occurred any material adverse
                                        change in the financial condition,
                                        business, properties or results of
                                        operations of the Borrower.

                                g)      After consummation of this financing and
                                        after giving effect to the transactions
                                        contemplated hereunder, such
                                        consummation and transactions will not
                                        violate any other material agreement or
                                        contractual obligation of the Borrower
                                        or its subsidiaries.

                                h)      Written certification of the completion
                                        of the Chevron acquisition for total
                                        consideration of no more than $86
                                        million.

Representations and
Warranties:                     The Borrower hereby represents and warrants to 
                                the Lender, on and as of the date hereof, and  
                                after giving effect to this Agreement          

                                a)      Corporate authority;

                                b)      Execution, delivery and performance of
                                        Loan Documents do not violate existing
                                        law or existing agreements or require
                                        consents;

                                c)      No material litigation;

                                d)      No material adverse change in the
                                        financial condition or results of
                                        operations;

                                e)      Accuracy of financial statements;

                                f)      Material compliance with ERISA;

                                g)      No material environmental issues;

                                h)      Legality, validity, binding effect and
                                        enforceability of this Agreement;

                                i)      Solvency

                                j)      Compliance with laws;

                                k)      Not an investment company or a "holding
                                        company" within the meaning of the
                                        Public Utility Holding Company Act of
                                        1935, as amended; and

                                l)      Title to properties.



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Financial Covenants:            So long as any Note shall remain unpaid or the  
                                Lender shall have any commitment hereunder, the 
                                Borrower will not, without the written consent  
                                of the Lender:                                  

                                a)      permit the total debt to capitalization
                                        ratio to exceed 60%. Total Debt shall be
                                        defined as (a) all borrowed money, (b)
                                        trade debt which is past due, c)
                                        liabilities under any bond, note,
                                        security, letter of credit (other than
                                        L/C's issued hereunder for trade credit
                                        but including L/C's issued hereunder as
                                        performance guarantees) or acceptance
                                        financing, (d) guarantees, (e) capital
                                        lease obligations and (f) all Hedging
                                        Agreement obligations once such
                                        obligations become "debt"; and

                                b)      permit the interest Coverage Ratio
                                        (EBITDA / Interest Expense) to be
                                        greater than or equal to 2.5x.

Covenants:                      Customary for transactions of this nature,   
                                including but not limited to, the following: 

                                a)      Reporting requirement;

                                b)      Negative pledge of unencumbered assets;

                                c)      Limitation on additional indebtedness;

                                d)      Limitation on liens except permitted
                                        liens;

                                e)      Restriction on mergers, consolidations
                                        and sale of oil and gas properties in
                                        excess of $500,000;

                                f)      Use of proceeds;

                                g)      Maintenance of insurance;

                                h)      Maintenance of books and records;

                                i)      Visitation rights;

                                j)      Material compliance with all laws and
                                        payment of taxes;

                                k)      Maintenance of title;

                                l)      Limitations on Dividends;

                                m)      Transactions with affiliates on an arms
                                        length basis;

                                n)      Limitations on creation of Subsidiaries;
                                        and

                                o)      Hedging limited to 70% of projected
                                        production and may not exceed beyond 2
                                        years.


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Events of Default:              The events of default that follow are     
                                subordinate to the Subordination Agreement
                                (Schedule II):                            

                                a)      Failure to pay principal when due; and
                                        interest and fees within three business
                                        days of when due;

                                b)      Representations and Warranties
                                        materially incorrect;

                                c)      Failure to comply with covenants (with
                                        notice and cure periods as applicable);
 
                                d)      Cross-default to payment defaults on
                                        principal aggregating $500,000 or to
                                        default or event if the effect is to
                                        accelerate principal aggregating
                                        $1,000,000;

                                e)      Bankruptcy / insolvency;

                                f)      Unsatisfied judgment or order in excess
                                        of $1,000,000;

                                g)      ERISA; and

                                h)      Direct or indirect Brooklyn Union Gas
                                        corp. ownership of the Borrower of at
                                        least 60%.

Governing Law:                  State of New York

Indemnification:                Borrower will indemnify the Lender and its     
                                officers, directors, shareholders, employees,  
                                agents and attorneys (the "Indemnitees") against
                                all costs, expenses (including fees and        
                                disbursements of counsel) and liabilities     
                                arising out of or relating to the Facilities and
                                the transactions contemplated thereby, including
                                consequences of their own negligence, provided 
                                that none of the indemnitees will be indemnified
                                for the consequences of its gross negligence or
                                willful misconduct.                         


                                MARKETSPAN CORPORATION D/B/A KEYSPAN ENERGY


                                BY:    /s/ Robert R Wieczorek
                                       ----------------------------------------
                                       Robert R. Wieczorek
                                       Vice President, Secretary and Treasurer
                                       One Metrotech Center
                                       Brooklyn, New York



                                THE HOUSTON EXPLORATION COMPANY


                                BY:    /s/ Thomas W. Powers
                                       ----------------------------------------
                                       Thomas W. Powers
                                       Senior Vice President
                                       1100 Louisiana, Suite 2000
                                       Houston, Texas  77002




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                                                                      Schedule I

                           Subordinated Loan Agreement

                          Dated as of November 30, 1998

                                     Between

                         The Houston Exploration Company

                                       and

                   MarketSpan Corporation d/b/a KeySpan Energy


Total Commitment Amount:        $150,000,000
                                

                                                                               
Interest Rate and Fees:                   Interest Rate & Fee Margins
                       --------------------------------------------------------
                       LIBOR                      140 bps
                       --------------------------------------------------------
                       Commitment Fee  12.5 bps on unused portion of the Total 
                                              Commitment Amount
                       --------------------------------------------------------
                       Upfront Fee               $50,000
                       --------------------------------------------------------

Initial Interest Period:        November 30, 1998 through January 4, 1999.

Interest                        Periods: The one month LIBOR rate will be set on
                                the date of each drawndown, as quoted in that
                                day's Wall Street Journal (which reflects the
                                previous business day's market rates). The rate
                                will be effective until the rate is reset on the
                                first business day of each month.

Interest Payment Dates:         In arrears, on the first business day following
                                the end of each calendar month.

Payments and 
Computations:                   The Borrower shall make each payment hereunder
                                to the Lender, on the day when due, in lawful
                                money of the United States of America in same
                                day funds, by wire transfer to the Lender's
                                account (provide wire instructions) not later
                                than 12:00 noon (New York City time).

                                Computations of the LIBOR rate, commissions, and
                                fees shall be made by the Lender on the basis of
                                a year of 360 days for the actual number of days
                                (including the first day but excluding the last
                                day) elapsed.

                                Whenever any payment to be made hereunder shall
                                be stated to be due, or whenever the last day of
                                any Interest Period would otherwise occur, on a
                                day which is not a Business Day, such payment
                                shall be made, and the last day of such Interest
                                Period shall occur, on the next succeeding
                                Business, and such extension of time shall in
                                such case be included in the computation of
                                interest, commission or fee, as the case may be.


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Maturity Date:                  All outstanding principal, unpaid accrued
     
                                interest and fees will be repaid at maturity,
                                January 1, 2000. Any principal amount that
                                remains outstanding subsequent to the Maturity
                                Date will be converted into equity (the number
                                of shares to be issued to the Lender will be
                                determined based upon the average of the closing
                                prices of Houston Exploration's common stock,
                                rounded to three decimal places, as reported
                                under "NYSE Composite Transactions Reports" in
                                the Wall Street Journal during 20 consecutive
                                trading days ending three days prior to January
                                1, 2000. Because the market value represents an
                                average of Houston Exploration's common stock
                                over twenty consecutive trading days, ending
                                three days prior to maturity, the market price
                                may be higher or lower than the price of the
                                common stock on the conversion date). The total
                                amount converted to equity shall not exceed the
                                Total Commitment Amount. Any unpaid accrued
                                interest or fees that remain outstanding
                                subsequent to the Maturity Date will be paid in
                                cash.                    
                                


MARKETSPAN CORPORATION D/B/A KEYSPAN ENERGY


BY:      /s/ Robert R. Wieczorek
         ---------------------------------------
         Robert R. Wieczorek
         Vice President, Secretary and Treasurer
         One MetroTech Center
         Brooklyn, New York


THE HOUSTON EXPLORATION COMPANY
BY:      /s/ Thomas W. Powers
         ---------------------------------------
         Thomas W. Powers
         Senior Vice President
         1100 Louisiana, Suite 2000
         Houston, Texas  77002



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