<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 June 30, 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

                - June 30, 1998 and December 31, 1997                                3

            Statements of Operations

                - Three month and six month periods ended June 30, 1998 and 1997     4

            Statements of Cash Flows

                - Six month periods ended June 30, 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                                                       11


SIGNATURES                                                                          12
</TABLE>



<PAGE>

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



<TABLE>
<CAPTION>
                                                                                          June 30,           December 31,
                                                                                            1998                 1997
                                                                                       ---------------     ----------------
                                                                                        (Unaudited)
         <S>                                                                           <C>                  <C>           
         ASSETS:

         Current Assets:
              Cash and cash equivalents                                                $        1,613       $        1,585
              Nonoperating interests income receivable                                         58,443               78,390
                                                                                       ---------------     ----------------
                  Total Current Assets                                                         60,056               79,975
                                                                                       ---------------     ----------------
         Nonoperating interests in oil and gas
              properties, using full cost accounting                                        4,151,242            4,204,224
         Less-Accumulated amortization                                                     (2,976,915)          (2,905,178)
                                                                                       ---------------     ----------------
                                                                                            1,174,327            1,299,046
                                                                                       ---------------     ----------------
                                                                                       $    1,234,383       $    1,379,021
                                                                                       ===============     ================


         LIABILITIES AND PARTNERS' CAPITAL:

         Current Liabilities:
              Accounts Payable                                                         $        5,267       $        5,747
                                                                                       ---------------     ----------------

         Interest Holders' Capital (3,664,333 Interest Holders' SDIs;
                                   $1.00 per SDI)                                           1,191,948            1,322,883
         General Partners' Capital                                                             37,168               50,391
                                                                                       ---------------     ----------------
                  Total Partners' Capital                                                   1,229,116            1,373,274
                                                                                       ---------------     ----------------
                                                                                       $    1,234,383       $    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                  Six Months Ended
                                                          June 30,                           June 30,
                                              ---------------------------------  ---------------------------------
                                                   1998              1997             1998              1997
                                              ---------------   ---------------  ---------------   ---------------
<S>                                           <C>               <C>              <C>               <C>            
REVENUES:
   Income from nonoperating interests         $        42,417   $        75,576  $       111,842   $       229,800
   Interest income                                        289               225              529               397
                                              ---------------   ---------------  ---------------   ---------------
                                                       42,706            75,801          112,371           230,197
                                              ---------------   ---------------  ---------------   ---------------

COSTS AND EXPENSES:
   Amortization                                        34,566            42,043           71,737           104,944
   General and administrative                          16,658            18,553           32,038            41,003
                                              ---------------   ---------------  ---------------   ---------------
                                                       51,224            60,596          103,775           145,947
                                              ---------------   ---------------  ---------------   ---------------
NET INCOME (LOSS)                             $        (8,518)  $        15,205  $         8,596   $        84,250
                                              ===============   ===============  ===============   ===============



Limited Partners' net income (loss)
   per unit                                   $            --   $            --  $            --   $           .02
                                              ===============   ===============  ===============   ===============
</TABLE>


                 See accompanying notes to financial statements.

                                        4


<PAGE>


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

<TABLE>
<CAPTION>
                                                                                           Six Months Ended
                                                                                               June 30,
                                                                               ----------------------------------------
                                                                                     1998                    1997
                                                                               ---------------          ---------------
<S>                                                                             <C>                     <C>            
CASH FLOWS FROM OPERATING ACTIVITIES:
    Income (loss)                                                               $        8,596          $        84,250
    Adjustments to reconcile income (loss) to
      net cash provided by operations:
      Amortization                                                                      71,737                  104,944
      Change in assets and liabilities:
        (Increase) decrease in nonoperating interests income receivable                 19,947                    2,726
        Increase (decrease) in accounts payable                                           (480)                     (98)
                                                                               ---------------          ---------------
      Net cash provided by (used in) operating activities                               99,800                  191,822
                                                                               ---------------          ---------------
CASH FLOWS FROM INVESTING ACTIVITIES:
    Additions to nonoperating interests in oil and gas properties                      (14,933)                  (4,527)
    Proceeds from sales of nonoperating interests in oil and gas properties             67,915                       --
                                                                               ---------------          ---------------
      Net cash provided by (used in) investing activities                               52,982                   (4,527)
                                                                               ---------------          ---------------
CASH FLOWS FROM FINANCING ACTIVITIES:
    Cash distributions to partners                                                    (152,754)                (187,270)
                                                                               ---------------          ---------------
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS                                        28                       25
                                                                               ---------------          ---------------
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD                                         1,585                    1,505
                                                                               ---------------          ---------------
CASH AND CASH EQUIVALENTS AT END OF PERIOD                                      $        1,613          $         1,530
                                                                               ===============          ===============
</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
         statement.

                  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.

(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.

                                       7

<PAGE>

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


(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 $99,800 and $191,822 for the six months
ended June 30, 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 these  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.  Cash  provided by proceeds  from  property  sales
totaled  $67,915 for the six months ended June 30,  1998.  The  Partnership  has
expended  all  of  the   partners'  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 $152,754 and $187,270 for the six months
ended June 30, 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

      The  following  analysis  explains  changes in the  revenues  and  expense
categories  for the quarter ended June 30, 1998 (current  quarter) when compared
to the quarter  ended June 30,  1997  (corresponding  quarter),  and for the six
months ended June 30, 1998  (current  period),  when  compared to the six months
ended June 30, 1997 (corresponding period).

Three Months Ended June 30, 1998 and 1997

      Income  from  nonoperating  interests  decreased  44 percent in the second
quarter of 1998 when  compared  to the same  quarter in 1997.  Oil and gas sales
declined  $40,750 or 31 percent in the second  quarter of 1998 when  compared to
the  corresponding  quarter in 1997,  primarily  due to  decreased  oil  prices.
Current quarter oil prices declined 36 percent or $5.82/BBL. The decrease in oil
prices had a significant impact on partnership performance. Also, gas production
decreased  11  percent  and  oil   production   declined  20  percent,   further
contributing to decreased  revenues.  Declines in revenues were partially offset
by an increase in gas prices of 50 percent or $.75/MCF  when  compared to second
quarter 1997 prices.

                                       9

<PAGE>


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


      Associated  amortization  expense  decreased  18 percent or $7,477 in 1998
compared to second  quarter  1997,  also  related to the  decline in  production
volumes.

Six Months Ended June 30, 1998 and 1997

      Income from nonoperating  interests  decreased 51 percent in the first six
months  of 1998 when  compared  to the same  period  in 1997.  Oil and gas sales
declined $156,150 or 45 percent in the first six months of 1998 when compared to
the  corresponding  period  in  1997,  primarily  due to  decreased  gas and oil
production.  Gas production  decreased 38 percent and oil production declined 17
percent.  The  decrease  in  production  volumes  had a  significant  impact  on
partnership  performance.  The partnership's  sale of several properties in 1997
had an impact on 1998 partnership  production volumes.  Also, current period oil
and gas  prices  declined  36 percent or  $6.35/BBL  and 7 percent or  $.14/MCF,
respectively, further contributing to decreased revenues.

      Associated  amortization  expense  decreased 32 percent or $33,207 in 1998
compared  to the first six  months  of 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.


                                       10

<PAGE>


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




ITEM 5.    OTHER INFORMATION


                                     -NONE-





                                       11

<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:     August 4, 1998    By:        /s/ John R. Alden
          --------------               ---------------------------------
                                       John R. Alden
                                       Senior Vice President, Secretary
                                       and Principal Financial Officer

Date:     August 4, 1998    By:        /s/ Alton D. Heckaman, Jr.
          --------------               ---------------------------------
                                       Alton D. Heckaman, Jr.
                                       Vice President, Controller
                                       and Principal Accounting Officer


                                       12