<PAGE>


                               AMENDMENT No. 1 TO
                                    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 September 30, 1999

                                       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

                - September 30, 1999 and December 31, 1998                                      3

            Statements of Operations

                - Three month and nine month periods ended September 30, 1999 and 1998          4

            Statements of Cash Flows

                - Nine month periods ended September 30, 1999 and 1998                          5

            Notes to Financial Statements                                                       6

      ITEM 2.    Management's Discussion and Analysis of Financial
                     Condition and Results of Operations                                       10

PART II.    OTHER INFORMATION                                                                  12


SIGNATURES                                                                                     13
</TABLE>




<PAGE>


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



<TABLE>
<CAPTION>
                                                                                September 30,          December 31,
                                                                                    1999                  1998
                                                                               ---------------       ---------------
                                                                                (Unaudited)
<S>                                                                          <C>                   <C>
ASSETS:

Current Assets:
     Cash and cash equivalents                                               $          1,717      $          1,671
     Nonoperating interests income receivable                                          30,562                17,617
     Nonoperating receivable due to property disposition                                   --                24,303
     Other                                                                                 --                 2,992
                                                                               ---------------       ---------------
          Total Current Assets                                                         32,279                46,583
                                                                               ---------------       ---------------

Nonoperating interests in oil and gas
     properties, using full cost accounting                                         4,141,411             4,131,910
Less-Accumulated amortization                                                      (3,550,149)           (3,477,234)
                                                                               ---------------       ---------------
                                                                                      591,262               654,676
                                                                               ===============       ===============
                                                                             $        623,541      $        701,259
                                                                               ===============       ===============


LIABILITIES AND PARTNERS' CAPITAL:

Current Liabilities:
     Accounts Payable                                                        $          4,084      $         42,800
                                                                               ---------------       ---------------


Interest Holders' Capital (3,664,333 Interest Holders'
                          SDIs; $1.00 per SDI)                                        581,990               626,555

General Partners' Capital                                                              37,467                31,904
                                                                               ---------------       ---------------
          Total Partners' Capital                                                     619,457               658,459
                                                                               ===============       ===============
                                                                             $        623,541      $        701,259
                                                                               ===============       ===============
</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                       Nine Months Ended
                                                        September 30,                           September 30,
                                              ----------------------------------       ---------------------------------
                                                   1999               1998                 1999               1998
                                              ---------------    ---------------       --------------     --------------
<S>                                         <C>                <C>                   <C>                <C>
REVENUES:
     Income from nonoperating interests     $         50,535   $         25,863      $       134,532    $       137,706
     Interest income                                     262                287                  740                816
                                              ---------------    ---------------       --------------     --------------
                                                      50,797             26,150              135,272            138,522
                                              ---------------    ---------------       --------------     --------------


COSTS AND EXPENSES:
     Amortization                                     19,919            301,860               72,915            373,597
     General and administrative                       12,702             11,393               45,721             43,432
                                              ---------------    ---------------       --------------     --------------
                                                      32,621            313,253              118,636            417,029
                                              ===============    ===============       ==============     ==============
NET INCOME (LOSS)                           $         18,176   $       (287,103)     $        16,636    $      (278,507)
                                              ===============    ===============       ==============     ==============



Limited Partners' net income (loss)
     per SDI                                $             --   $          (0.08)     $            --    $         (0.08)
                                              ===============    ===============       ==============     ==============
</TABLE>


                 See accompanying notes to financial statements.

                                        4


<PAGE>


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


<TABLE>
<CAPTION>
                                                                                            Nine Months Ended
                                                                                              September 30,
                                                                                   -------------------------------------
                                                                                        1999                  1998
                                                                                   ---------------       ---------------
<S>                                                                              <C>                   <C>
CASH FLOWS FROM OPERATING ACTIVITIES:
     Income (loss)                                                               $         16,636      $       (278,507)
     Adjustments to reconcile income (loss) to
          net cash provided by operations:
          Amortization                                                                     72,915               373,597
          Change in assets and liabilities:
               (Increase) decrease in nonoperating interests income receivable            (12,945)               61,159

               (Increase) decrease in other current assets                                  2,992                    --
               Increase (decrease) in accounts payable                                    (38,716)                2,249
                                                                                   ---------------       ---------------
          Net cash provided by (used in) operating activities                              40,882               158,498
                                                                                   ---------------       ---------------

CASH FLOWS FROM INVESTING ACTIVITIES:
     Additions to nonoperating interests in oil and gas properties                         (9,582)              (19,307)
     Proceeds from sales of nonoperating interests in oil and gas properties               24,384                67,920
                                                                                   ---------------       ---------------
          Net cash provided by (used in) investing activities                              14,802                48,613
                                                                                   ---------------       ---------------

CASH FLOWS FROM FINANCING ACTIVITIES:
     Cash Distributions to partners                                                       (55,638)             (207,061)
                                                                                   ---------------       ---------------
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS                                           46                    50
                                                                                   ---------------       ---------------
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD                                            1,671                 1,585
                                                                                   ===============       ===============
CASH AND CASH EQUIVALENTS AT END OF PERIOD                                       $          1,717      $          1,635
                                                                                   ===============       ===============
</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,  1998  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.

      Oil and Gas Revenues -

                  Oil and gas revenues are reported using the entitlement method
        in which the Partnership  recognizes its interest in oil and natural gas
        production as revenue.

                                       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 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  Operating   Partnership  will  convey  to  the
        Partnership  nonoperating  interests 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.

(7)  Year 2000 -

                  The  Year  2000  issue  results  from  computer  programs  and
        embedded computer chips with date fields that cannot distinguish between
        the years 1900 and 2000. The Managing  General  Partner has  implemented
        the steps necessary to make its operations and the related operations of
        the  Partnership  capable  of  addressing  the Year  2000.  These  steps
        included  upgrading,  testing and  certifying  its computer  systems and
        field   operation   services   and   obtaining   Year  2000   compliance
        certification  from  all  important  business  suppliers.  The  Managing
        General Partner formed a task force during 1998 to address the Year 2000
        issue and prepare its business  systems for the Year 2000.  The Managing
        General Partner has either replaced or updated mission  critical systems
        and has  substantially  completed  testing  and will  continue  remedial
        actions as needed.

                  The Managing  General  Partner's  business  systems are almost
        entirely  comprised of  off-the-shelf  software.  Most of the  necessary
        changes  in  computer  instructional  code were made by  upgrading  this
        software.  In  addition,  the  Managing  General  Partner  has  received
        certification  as to Year 2000  compliance  from  vendors or third party
        consultants.

                  The  Managing  General  Partner  does not  believe  that costs
        incurred  to address  the Year 2000 issue with  respect to its  business
        systems  will have a  material  effect on the  Partnership's  results of
        operations,  or its  liquidity and  financial  condition.  The estimated
        total cost to the Managing  General  Partner to address Year 2000 issues
        is  projected to be less than  $150,000,  most of which was spent during
        the testing phase. The  Partnership's  share of this cost is expected to
        be insignificant.



                                       8


<PAGE>


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

                  The  failure  to correct a material  Year 2000  problem  could
        result  in an  interruption,  or  failure  of  certain  normal  business
        activities or  operations.  Based on  activities  to date,  the Managing
        General  Partner  believes  that it has resolved any Year 2000  problems
        concerning   its   financial   and   administrative   systems.   It   is
        undeterminable  how all the  aspects  of the Year 2000 will  impact  the
        Partnership.  The most  reasonably  likely  worst  case  scenario  would
        involve a prolonged disruption of external power sources upon which core
        equipment   relies,   resulting  in  a   substantial   decrease  in  the
        Partnership's  oil and  gas  production  activities.  In  addition,  the
        pipeline  operators  to whom the  Managing  General  Partner  sells  the
        Partnership's  natural gas, as well as other  customers  and  suppliers,
        could be prone to Year  2000  problems  that  could not be  assessed  or
        detected by the Managing General  Partner.  The Managing General Partner
        has  contacted its major  purchasers,  customers,  suppliers,  financial
        institutions  and others  with whom it conducts  business  to  determine
        whether  they will be able to resolve  in a timely  manner any Year 2000
        problems directly  affecting the Managing General Partner or Partnership
        and to inform them of the Managing General Partner's internal assessment
        of its Year 2000  review.  There  can be no  assurance  that such  third
        parties will not fail to appropriately address their Year 2000 issues or
        will not  themselves  suffer a Year 2000  disruption  that  could have a
        material  adverse  effect  on the  Partnership's  activities,  financial
        condition  or  operating  results.  Based upon these  responses  and any
        problems  that  arise,  contingency  plans or back-up  systems  would be
        determined and addressed.


                                       9


<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  partner  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 partners or 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. 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 distributions to
partners  or  Interest  Holders  are  determined  quarterly,  based upon the net
profits interest payment received from the companion operating partnership, less
general  and  administrative  expenses.  The net  profits  interest  payment  is
determined  based upon net proceeds  from sale of oil and gas  production  after
payment of lease operating  expense,  taxes and development  costs. In addition,
future  partnership  cash  requirements  are taken  into  account  to  determine
necessary cash reserves.


      Net cash provided by operating activities totaled $40,882 and $158,498 for
the nine months ended September 30, 1999 and 1998, respectively. The decrease in
cash  provided by operating  activities  in 1999 is related to changes in assets
and  liabilities.  Cash  provided  by  proceeds  from the  sale of  nonoperating
interests in  properties  totaled  $24,384 and $67,920 for the nine months ended
September 30, 1999 and 1998,  respectively.  Cash distributions  totaled $55,638
and  $207,061  for  the  nine  months  ended   September   30,  1999  and  1998,
respectively.  In 1999, cash distributions were effected by production  declines
from the Partnership's  depleting  property interests and low oil and gas prices
received during the first part of this year.


      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.  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  revenue  and  expense
categories  for the quarter  ended  September  30, 1999  (current  quarter) when
compared to the quarter ended September 30, 1998  (corresponding  quarter),  and
for the nine months ended September 30, 1999 (current period),  when compared to
the nine months ended September 30, 1998 (corresponding period).

                                      10

<PAGE>


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


Three Months Ended September 30, 1999 and 1998

      Income  from  nonoperating  interests  increased  95  percent in the third
quarter of 1999 when  compared  to the same  quarter in 1998.  Oil and gas sales
increased  $20,946 or 31 percent in the third  quarter of 1999 when  compared to
the  corresponding  quarter  in 1998,  primarily  due to  increased  oil and gas
prices.  Oil  prices  increased  110  percent  or  $9.97/BBL  to an  average  of
$19.00/BBL  and gas prices  increased  41 percent or  $.78/MCF  to an average of
$2.68/MCF  for the  quarter.  Current  quarter  production  volumes  decreased 6
percent as oil  production  increased 5 percent and gas  production  declined 10
percent when compared to third quarter 1998 production volumes.

      Corresponding  production  costs per equivalent MCF decreased 3 percent in
the  third  quarter  of 1999  compared  to the third  quarter  of 1998 and total
production costs decreased 9 percent.

      Total  amortization  expense for the third  quarter of 1999  decreased  93
percent or $281,941 when  compared to the third  quarter of 1998.  In 1998,  two
components, the normal provision,  calculated on the units of production method,
and the additional provision,  relating to the ceiling limitation, make up total
amortization  expense.  Normal  amortization  expense  decreased  39  percent or
$12,948 in the third quarter of 1999 compared to the third quarter of 1998.

      The  Partnership  recorded an additional  provision in amortization in the
third quarter of 1998 for $268,993,  when the present  value,  discounted at ten
percent, of estimated future net revenues from oil and gas properties, using the
guidelines of the Securities and Exchange Commission,  was below the fair market
value for oil and gas properties resulting in a full cost ceiling impairment.

Nine Months Ended September 30, 1999 and 1998

      Income from nonoperating  interests  decreased 2 percent in the first nine
months  of 1999 when  compared  to the same  period  in 1998.  Oil and gas sales
declined $39,780 or 15 percent in the first nine months of 1999 when compared to
the  corresponding  period  in  1998,  primarily  due to  decreased  oil and gas
production.  Current period  production  volumes decreased 16 percent as oil and
gas production declined 11 percent and 19 percent,  respectively,  when compared
to the same  period in 1998.  Oil prices  increased  4 percent or $.41/BBL to an
average of  $11.30/BBL  and gas prices  increased  15 percent or  $.29/MCF to an
average of $2.24/MCF for the current period. Increased oil and gas prices helped
offset the effect of decreased production.

      Corresponding  production costs per equivalent MCF decreased 17 percent in
the first nine months of 1999 compared to the  corresponding  period in 1998 and
total production costs decreased 30 percent.

      Total amortization  expense for the first nine months of 1999 decreased 80
percent or $300,682 when compared to the first nine months of 1998. In 1998, two
components, the normal provision,  calculated on the units of production method,
and the additional provision,  relating to the ceiling limitation, make up total
amortization  expense.  Normal  amortization  expense  decreased  30  percent or
$31,689 in the first nine  months of 1999  compared  to the first nine months of
1998.

      The  Partnership  recorded an additional  provision in amortization in the
first nine months in 1998 for $268,993,  when the present  value,  discounted at
ten percent, of estimated future net revenues from oil and gas properties, using
the  guidelines of the Securities  and Exchange  Commission,  was below the fair
market  value  for oil and  gas  properties  resulting  in a full  cost  ceiling
impairment.

      During 1999,  partnership  revenues  and costs will be shared  between the
Interest Holders and general partners in an 85:15 ratio.


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<PAGE>


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




ITEM 5.    OTHER INFORMATION


                                     -NONE-





                                       12


<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 Amendment No. 1 to Form 10-Q of
Swift Energy Pension Partners  1991-C,  Ltd. for the third quarter of 1999 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:  January 20, 2000     By:        /s/ John R. Alden
       ----------------                ----------------------------------------
                                       John R. Alden
                                       Senior Vice President, Secretary
                                       and Principal Financial Officer

Date:  January 20, 2000     By:        /s/ Alton D. Heckaman, Jr.
       ----------------                ----------------------------------------
                                       Alton D. Heckaman, Jr.
                                       Vice President, Controller
                                       and Principal Accounting Officer


                                       13