<PAGE>

                                    FORM 10-Q



                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549


            [ X ] QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF
                       THE SECURITIES EXCHANGE ACT OF 1934

                  For the quarterly period ended March 31, 1998

                                       OR

            [ ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF
                       THE SECURITIES EXCHANGE ACT OF 1934

       For the transition period from ________________ to _______________

                         Commission File number 0-20154


                   SWIFT ENERGY PENSION PARTNERS 1991-C, LTD.
             (Exact name of registrant as specified in its charter)

<TABLE>
<S>                                            <C>
                  Texas                                    76-0350269
(State or other jurisdiction of organization)  (I.R.S. Employer Identification No.)
</TABLE>


                        16825 Northchase Drive, Suite 400
                              Houston, Texas 77060
                    (Address of principal executive offices)
                                   (Zip Code)

                                  (281)874-2700
              (Registrant's telephone number, including area code)

                                      None
              (Former name, former address and former fiscal year,
                          if changed since last report)


Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the  preceding 12 months (or for such  shorter  period that the  Registrant  was
required  to file  such  reports),  and  (2) has  been  subject  to such  filing
requirements for the past 90 days.

Yes  X      No
   ----       ----




<PAGE>

                   SWIFT ENERGY PENSION PARTNERS 1991-C, LTD.

                                      INDEX



<TABLE>
<CAPTION>
PART I.    FINANCIAL INFORMATION                                       PAGE
      <S>                                                                <C>
      ITEM 1.    Financial Statements

            Balance Sheets

                - March 31, 1998 and December 31, 1997                   3

            Statements of Operations

                - Three month periods ended March 31, 1998 and 1997      4

            Statements of Cash Flows

                - Three month periods ended March 31, 1998 and 1997      5

            Notes to Financial Statements                                6

      ITEM 2.    Management's Discussion and Analysis of Financial
                     Condition and Results of Operations                 9

PART II.    OTHER INFORMATION                                           10


SIGNATURES                                                              11
</TABLE>



<PAGE>

                   SWIFT ENERGY PENSION PARTNERS 1991-C, LTD.
                                 BALANCE SHEETS



<TABLE>
<CAPTION>
                                                                                          March 31,           December 31,
                                                                                            1998                 1997
                                                                                       --------------       --------------
                                                                                         (Unaudited)
         <S>                                                                           <C>                  <C>           
         ASSETS:

         Current Assets:
              Cash and cash equivalents                                                $        1,592       $        1,585
              Nonoperating interests income receivable                                         76,913               78,390
                                                                                       ---------------     ----------------
                   Total Current Assets                                                        78,505               79,975
                                                                                       ---------------     ----------------
         Nonoperating interests in oil and gas
              properties, using full cost accounting                                        4,177,060            4,204,224
         Less-Accumulated amortization                                                     (2,942,349)          (2,905,178)
                                                                                       ---------------     ----------------
                                                                                            1,234,711            1,299,046
                                                                                       ---------------     ----------------
                                                                                       $    1,313,216       $    1,379,021
                                                                                       ===============     ================


         LIABILITIES AND PARTNERS' CAPITAL:

         Current Liabilities:
              Accounts Payable                                                         $        4,723       $        5,747
                                                                                       ---------------     ----------------

         Interest Holders' Capital (3,664,333 Interest Holders's SDIs;
                                    $1.00 per SDI)                                          1,263,526            1,322,883
         General Partners' Capital                                                             44,967               50,391
                                                                                       ---------------     ----------------
                   Total Partners' Capital                                                  1,308,493            1,373,274
                                                                                       ---------------     ----------------
                                                                                       $    1,313,216       $    1,379,021
                                                                                       ===============     ================
</TABLE>


                 See accompanying notes to financial statements.

                                        3


<PAGE>

                   SWIFT ENERGY PENSION PARTNERS 1991-C, LTD.
                            STATEMENTS OF OPERATIONS
                                   (Unaudited)



<TABLE>
<CAPTION>
                                                                                           Three Months Ended
                                                                                             March 31,
                                                                                 ---------------------------------
                                                                                       1998               1997
                                                                                 --------------    ---------------
         <S>                                                                     <C>               <C>
         REVENUES:
             Income from nonoperating interests                                  $        69,425   $       154,223
             Interest income                                                                 239               172
                                                                                 ---------------   ---------------
                                                                                          69,664           154,395
                                                                                 ---------------   ---------------
         COSTS AND EXPENSES:
             Amortization                                                                 37,171            62,901
             General and administrative                                                   15,379            22,449
                                                                                 ---------------   ---------------
                                                                                          52,550            85,350
                                                                                 ---------------   ---------------
         NET INCOME (LOSS)                                                       $        17,114   $        69,045
                                                                                 ===============   ===============
</TABLE>


         Limited Partners' net income (loss)
             per unit

         March 31, 1998                       $            --
                                              ===============
         March 31, 1997                       $           .02
                                              ===============


                 See accompanying note to financial statements.

                                        4


<PAGE>
                   SWIFT ENERGY PENSION PARTNERS 1991-C, LTD.
                            STATEMENTS OF CASH FLOWS
                                   (Unaudited)


<TABLE>
<CAPTION>
                                                                                           Three Months Ended
                                                                                                March 31,
                                                                                ---------------------------------------
                                                                                      1998                    1997
                                                                                ----------------        ---------------
<S>                                                                             <C>                     <C>
CASH FLOWS FROM OPERATING ACTIVITIES:
    Income (loss)                                                               $         17,114        $        69,045
    Adjustments to reconcile income (loss) to
      net cash provided by operations:
      Amortization                                                                        37,171                 62,901
      Change in assets and liabilities:
        (Increase) decrease in nonoperating interests income receivable                    1,477                (30,226)
        Increase (decrease) in accounts payable
          and accrued liabilities                                                         (1,024)                   925
                                                                                ----------------        ---------------
                 Net cash provided by (used in) operating activities                      54,738                102,645
                                                                                ----------------        ---------------
CASH FLOWS FROM INVESTING ACTIVITIES:
        Additions to nonoperating interests
           in oil and gas properties                                                     (10,813)                (8,460)
        Proceeds from sale of nonoperating interests
           in oil and gas properties                                                      37,977                     --
                                                                                ----------------        ---------------
                 Net cash provided by (used in) investing activities                      27,164)                (8,460)
                                                                                ----------------        ---------------
CASH FLOWS FROM FINANCING ACTIVITIES:
      Cash distributions to partners                                                     (80,895)               (94,179)
                                                                                ----------------        ---------------
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS                                           7                      6
                                                                                ----------------        ---------------
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD                                           1,585                  1,505
                                                                                ----------------        ---------------
CASH AND CASH EQUIVALENTS AT END OF PERIOD                                      $          1,592        $         1,511
                                                                                ================        ===============
</TABLE>


                 See accompanying notes to financial statements.

                                        5


<PAGE>

                   SWIFT ENERGY PENSION PARTNERS 1991-C, LTD.
                          NOTES TO FINANCIAL STATEMENTS
                                   (UNAUDITED)

(1)  General Information -

                  The financial statements included herein have been prepared by
        the  Partnership  and are  unaudited  except  for the  balance  sheet at
        December  31,  1997  which has been  taken  from the  audited  financial
        statements at that date. The financial  statements reflect  adjustments,
        all of which were of a normal recurring nature, which are in the opinion
        of the  managing  general  partner  necessary  for a fair  presentation.
        Certain  information  and  footnote  disclosures  normally  included  in
        financial  statements  prepared in accordance  with  generally  accepted
        accounting  principles  have  been  omitted  pursuant  to the  rules and
        regulations  of the  Securities  and Exchange  Commission  ("SEC").  The
        Partnership  believes adequate disclosure is provided by the information
        presented.  The financial  statements should be read in conjunction with
        the audited  financial  statements  and the notes included in the latest
        Form 10-K.

(2)  Organization and Terms of Partnership Agreement -

                  Swift Energy Pension  Partners  1991-C,  Ltd., a Texas limited
        partnership  ("the  Partnership"),  was formed on December 30, 1991, for
        the purpose of  purchasing  net  profits  interest,  overriding  royalty
        interests and royalty interests (collectively, "nonoperating interests")
        in producing oil and gas properties within the continental United States
        and Canada. Swift Energy Company ("Swift"), a Texas corporation, and VJM
        Corporation ("VJM"), a California corporation, serve as Managing General
        Partner and Special  General Partner of the  Partnership,  respectively.
        The sole limited partner of the Partnership is Swift Depositary Company,
        which has assigned all of its beneficial  (but not of record) rights and
        interest  as  limited  partner  to  the  investors  in  the  Partnership
        ("Interest  Holders"),   in  the  form  of  Swift  Depositary  Interests
        ("SDIs").

                  The Managing  General  Partner has paid or will pay out of its
        own corporate funds (as a capital  contribution to the  Partnership) all
        selling commissions,  offering expenses,  printing, legal and accounting
        fees and other  formation costs incurred in connection with the offering
        of SDIs and the  formation  of the  Partnership,  for which the Managing
        General  Partner  will  receive  an  interest  in  continuing  costs and
        revenues of the Partnership. The 350 Interest Holders made total capital
        contributions of $3,664,333.

                  Generally,   all  continuing  costs  (including   general  and
        administrative  reimbursements  and direct  expenses)  and  revenues are
        allocated  85  percent  to the  interest  holders  and 15 percent to the
        general  partners.   After   partnership   payout,  as  defined  in  the
        Partnership  Agreement,  continuing costs and revenues will be shared 75
        percent by the interest holders, and 25 percent by the general partners.

(3)  Significant Accounting Policies -

       Use of Estimates --

                  The  preparation  of financial  statements in conformity  with
        generally accepted  accounting  principles  requires  management to make
        estimates and assumptions that affect the reported amounts of assets and
        liabilities  at the date of the  financial  statements  and the reported
        amounts of revenues and expenses  during the  reporting  period.  Actual
        results could differ from estimates. Certain reclassifications have been
        made to prior year amounts to conform to the current year presentation.


                                       6


<PAGE>


                   SWIFT ENERGY PENSION PARTNERS 1991-C, LTD.
                    NOTES TO FINANCIAL STATEMENTS (CONTINUED)
                                   (UNAUDITED)


     Nonoperating Interests in Oil and Gas Properties --

                  The Partnership accounts for its ownership interest in oil and
        gas properties using the proportionate consolidation method, whereby the
        Partnership's  share of assets,  liabilities,  revenues  and expenses is
        included in the appropriate classification in the financial statements.

                  For financial  reporting purposes the Partnership  follows the
        "full-cost"  method of accounting for nonoperating  interests in oil and
        gas property costs. Under this method of accounting,  all costs incurred
        in the acquisition of  nonoperating  interests in oil and gas properties
        are capitalized.  The unamortized cost of nonoperating  interests in oil
        and gas  properties is limited to the "ceiling  limitation"  (calculated
        separately for the Partnership,  limited partners and general partners).
        The  "ceiling  limitation"  is  calculated  on  a  quarterly  basis  and
        represents the estimated future net revenues from nonoperating interests
        in proved  properties  using current  prices  discounted at ten percent.
        Proceeds from the sale or disposition of  nonoperating  interests in oil
        and  gas  properties  are  treated  as a  reduction  of the  cost of the
        nonoperating  interests  with no gains or  losses  recognized  except in
        significant transactions.

                  The Partnership computes the provision for amortization of oil
        and gas properties on the units-of-production method. Under this method,
        the provision is calculated by multiplying the total unamortized cost of
        oil and gas  properties  by an overall rate  determined  by dividing the
        physical  units of oil and gas  produced  during the period by the total
        estimated  units of proved oil and gas reserves at the  beginning of the
        period.

                  The calculation of the "ceiling  limitation" and the provision
        for  depreciation,  depletion and  amortization is based on estimates of
        proved reserves. There are numerous uncertainties inherent in estimating
        quantities  of proved  reserves  and in  projecting  the future rates of
        production,  timing and plan of development. The accuracy of any reserve
        estimate  is a  function  of  the  quality  of  available  data  and  of
        engineering  and  geological  interpretation  and  judgment.  Results of
        drilling,  testing and production subsequent to the date of the estimate
        may justify revision of such estimate.  Accordingly,  reserve  estimates
        are  often  different  from  the  quantities  of oil  and gas  that  are
        ultimately recovered.

(4)  Related-Party Transactions -

                  The  Partnership  entered  into a Net Profits  and  Overriding
        Royalty  Interest  Agreement  ("NP/OR   Agreement")  with  Swift  Energy
        Operating Partners 1991-C, Ltd. ("Operating Partnership"), an affiliated
        partnership  managed  by Swift  for the  purpose  of  acquiring  working
        interests in producing  oil and gas  properties.  Under the terms of the
        NP/OR  Agreement,  the  Partnership  has been  conveyed  a  nonoperating
        interest in the  aggregate net profits  (i.e.,  oil and gas sales net of
        related  operating  costs)  of  the  properties  acquired  equal  to the
        Partnership's proportionate share of the property acquisition costs.


                                       7


<PAGE>


                   SWIFT ENERGY PENSION PARTNERS 1991-C, LTD.
                    NOTES TO FINANCIAL STATEMENTS (CONTINUED)
                                   (UNAUDITED)


(5)  Vulnerability Due to Certain Concentrations -

                  The  Partnership's  revenues are primarily the result of sales
        of its oil and natural gas production.  Market prices of oil and natural
        gas may fluctuate and adversely affect operating results.

                  In the normal  course of  business,  the  Partnership  extends
        credit,  primarily in the form of monthly oil and gas sales receivables,
        to various  companies  in the oil and gas  industry  which  results in a
        concentration  of credit risk. This  concentration of credit risk may be
        affected by changes in economic or other  conditions and may accordingly
        impact the  Partnership's  overall  credit risk.  However,  the Managing
        General  Partner  believes  that  the  risk is  mitigated  by the  size,
        reputation, and nature of the companies to which the Partnership extends
        credit.  In  addition,   the  Partnership  generally  does  not  require
        collateral or other security to support customer receivables.

(6)  Fair Value of Financial Instruments -

                  The Partnership's  financial  instruments  consist of cash and
        cash equivalents and short-term  receivables and payables.  The carrying
        amounts  approximate  fair value due to the highly  liquid nature of the
        short-term instruments.


                                       8


<PAGE>

                   SWIFT ENERGY PENSION PARTNERS 1991-C, LTD.
                MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL
                       CONDITION AND RESULTS OF OPERATIONS

GENERAL

         The Partnership was formed for the purpose of investing in nonoperating
interests in producing oil and gas  properties  located  within the  continental
United States and Canada.  In order to accomplish  this,  the  Partnership  goes
through two distinct yet  overlapping  phases with respect to its  liquidity and
results of  operations.  When the  Partnership  was  formed,  it  commenced  its
"acquisition"  phase,  with all funds  placed in  short-term  investments  until
required for the acquisition of nonoperating interests.  Therefore, the interest
earned on these pre-acquisition investments becomes the primary cash flow source
for  initial  Interest  Holder   distributions.   As  the  Partnership  acquires
nonoperating  interests  in  producing  properties,  net cash from  ownership of
nonoperating  interests  becomes  available  for  distribution,  along  with the
investment   income.   After  all  partnership   funds  have  been  expended  on
nonoperating  interests in producing  oil and gas  properties,  the  Partnership
enters its  "operations"  phase.  During  this phase,  income from  nonoperating
interests  in oil  and gas  sales  generates  substantially  all  revenues,  and
distributions  to Interest  Holders  reflect those  revenues less all associated
partnership expenses.  The Partnership may also derive proceeds from the sale of
nonoperating interests in acquired oil and gas properties, when the sale of such
interests is economically appropriate or preferable to continued operations.

LIQUIDITY AND CAPITAL RESOURCES

         Oil  and  gas  reserves  are  depleting   assets  and  therefore  often
experience   significant   production  declines  each  year  from  the  date  of
acquisition  through the end of the life of the property.  The primary source of
liquidity to the  Partnership  comes almost  entirely from the income  generated
from the sale of oil and gas produced  from  ownership  interests in oil and gas
properties.  Net cash  provided  by  operating  activities  totaled  $54,738 and
$102,645 for the three months ended March 31, 1998 and 1997, respectively.  This
source of  liquidity  and the related  results of  operations,  and in turn cash
distributions,  will decline in future  periods as the oil and gas produced from
the  properties  also declines while  production and general and  administrative
costs remain relatively stable making it unlikely that the Partnership will hold
the properties  until they are fully depleted,  but will likely liquidate when a
substantial  majority of the reserves have been produced.  The  Partnership  has
expended  all  of  the   partner's  net   commitments   available  for  property
acquisitions and development by acquiring producing oil and gas properties.  The
partnership invests primarily in proved producing properties with nominal levels
of future costs of development for proven but undeveloped reserves.  Significant
purchases  of  additional  reserves  or  extensive  drilling  activity  are  not
anticipated. Cash distributions totaled $81,895 and $94,179 for the three months
ended March 31, 1998 and 1997, respectively.

      The  Partnership  does  not  allow  for  additional  assessments  from the
partners or Interest Holders to fund capital  requirements.  However,  funds are
available  from  partnership  revenues or proceeds from the sale of  partnership
property.  The  Managing  General  Partner  believes  that the  funds  currently
available to the Partnership  will be adequate to meet any  anticipated  capital
requirements.

RESULTS OF OPERATIONS

         Income from  nonoperating  interests  decreased 55 percent in the first
quarter of 1998 when  compared  to the same  quarter in 1997.  Oil and gas sales
declined  $115,400 or 53 percent in the first  quarter of 1998 when  compared to
the  corresponding  quarter  in 1997,  primarily  due to  decreased  gas and oil
prices.  A decline in gas prices of 33 percent or $.82/MCF  and in oil prices of
36 percent or $6.87/BBL had a  significant  impact on  partnership  performance.
Also, current quarter gas and oil production declined 54 percent and 13 percent,
respectively,  when  compared  to first  quarter  1997 gas  production  volumes,
further  contributing to decreased  revenues.  The partnership's sale of several
properties in 1997 had an impact on 1998 partnership production volumes.

         Total  amortization  expense  decreased  41  percent or $25,730 in 1998
compared  to first  quarter  1997,  also  related to the  decline in  production
volumes.

         During 1998,  partnership revenues and costs will be shared between the
Interest Holders and general partners in an 85:15 ratio.


                                       9


<PAGE>

                   SWIFT ENERGY PENSION PARTNERS 1991-C, LTD.
                           PART II - OTHER INFORMATION




ITEM 5.    OTHER INFORMATION


                                     -NONE-



                                       10


<PAGE>

                                   SIGNATURES



Pursuant to the  requirements of Section 13 or 15(d) of the Securities  Exchange
Act of 1934,  the  Registrant  has duly  caused  this report to be signed on its
behalf by the undersigned thereunto duly authorized.


                                         SWIFT ENERGY PENSION
                                         PARTNERS 1991-C, LTD.
                                         (Registrant)

                              By:        SWIFT ENERGY COMPANY
                                         Managing General Partner


Date:     May 5, 1998         By:        /s/ John R. Alden
          -----------                    --------------------------------
                                         John R. Alden
                                         Senior Vice President, Secretary
                                         and Principal Financial Officer

Date:     May 5, 1998         By:        /s/ Alton D. Heckaman, Jr.
          -----------                    --------------------------------
                                         Alton D. Heckaman, Jr.
                                         Vice President, Controller
                                         and Principal Accounting Officer


                                       11