<Page>
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
FORM 8-K
CURRENT REPORT
PURSUANT TO SECTION 13 OR 15(d) OF
THE SECURITIES EXCHANGE ACT OF 1934
DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED) August 14, 2001 (August 10,
2001)
MARKWEST HYDROCARBON, INC.
(EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)
DELAWARE 1-11566 84-1352233
(State or other jurisdiction of (Commission File Number) (I.R.S. Employer
incorporation or organization) Identification Number)
155 INVERNESS DRIVE WEST, SUITE 200, ENGLEWOOD, CO 80112-5000
(ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)
REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE: 303-290-8700
<Page>
ITEM 5. OTHER EVENTS
On August 13, 2001, MarkWest Hydrocarbon, Inc. issued the following press
release:
MARKWEST ACQUIRES CANADIAN NATURAL GAS PRODUCTION
COMPANIES FOR $51 MILLION (U.S.)--MORE THAN DOUBLING RESERVES
DENVER--August 13, 2001--MarkWest Hydrocarbon, Inc. (AMEX: MWP), today
announced the acquisition of two privately owned independent exploration and
production companies--Leland Energy Canada Ltd. and Watford Energy Ltd., both
headquartered in Calgary, Alberta, Canada--for $51 million (U.S.). The same
management directs both companies and will remain in place and continue to
operate as before the transaction.
The two entities will add 15,000 Mcf (thousand cubic feet) per day and 190
barrels of oil per day to MarkWest's current net production of 6,100 Mcf per
day. The reserve report on the Canadian entities by Gilbert Laustsen Jung
Associates indicates net acquired proved reserves of 26.4 billion cubic feet
equivalent (Bcfe), which will increase MarkWest's total net proved reserves to
more than 63 Bcfe. The current present value discounted at 10 percent (PV10) of
the acquired companies' proved reserves is $47 million, while MarkWest's PV10
prior to this transaction was $36 million.
Importantly, the acquisition adds more than 300 drillable locations, mostly
defined by three-dimensional (3D) seismic. The Canadian companies' net land base
is more than 106,000 acres, with 80 percent being highly exploitable. The
acreage is located in central and southern Alberta and has excellent year-round
access. The existing wells are approximately 3,500 feet deep, with relatively
high initial production and a reserve life of five to seven years. 3D seismic,
scheduled for late 2001, is anticipated to provide many additional drillable
locations. The capital expenditure budget is expected to exceed $40 million over
the next 24 months.
The transaction has been financed using bank debt through an expanded $130
million line with MarkWest's lead banker, Bank of America N.A. The acquisition
is expected to be accretive to both earnings and EBITDA in 2002 and beyond. John
Fox, CEO, commented, "Unused capacity under our increased borrowing arrangement
will be approximately $25 million to $30 million. Absent further acquisitions,
we expect cash flow to fully fund ongoing capital expenditures."
Leland and Watford employ 19 people as permanent staff and consultants and
operate most wells with a high operating interest. The management group has been
working together for more than a decade and has been highly successful both at
Chevron Canada and independently, operating Leland and Watford. As with most of
MarkWest's exploration projects, there is an attractive gathering and processing
opportunity associated with this multiyear development project.
Fox added, "This is a major new core area for MarkWest in a prolific
gas-producing basin. Not only will it more than triple our equity gas
production, but the future development potential over the next four to five
years is outstanding. We are very impressed with our Canadian management team
and are very pleased they will remain with the company. Finally, this not only
provides a fee-based midstream opportunity, but it also further reduces the more
<Page>
volatile Appalachian liquids margin business to less than 25 percent of our cash
operating income."
Banc of America Securities LLC served as advisor to MarkWest on the
transaction.
###
The Company's management will hold a conference call at 2:00 MDT (4:00 EDT)
on Tuesday, August 14, 2001, to discuss the transaction and the implications for
MarkWest. To participate in the teleconference, please dial the following number
five minutes prior to the scheduled start time:
719-457-2679, CONFIRMATION CODE 589725
This conference call will be broadcast live simultaneously over the
Internet. If you wish to listen via this method, go to our Web site at
HTTP://WWW.MARKWEST.COM. Click on the "Investor Relations" tab, then on the
"Click Here for Details" link on the pop-up menu regarding the conference call,
then on "Live Webcast" under CONFERENCE CALLS.
If listening via the Web, please allow extra time prior to the call to
visit the site and, if necessary, download the streaming media software required
(MEDIAPLAYER). A replay of the broadcast will be available within one hour of
the live call and for the next 90 days. If you have any questions, please
contact Anita Blackman, Investor Relations, at (800) 730-8388.
###
MARKWEST HYDROCARBON, INC., OPERATES THROUGH TWO BUSINESS SEGMENTS:
GATHERING, PROCESSING, AND MARKETING AND EXPLORATION AND PRODUCTION. THE
GATHERING, PROCESSING, AND MARKETING PORTION IS OUR TRADITIONAL "MIDSTREAM"
BUSINESS, WHICH INVOLVES GATHERING NATURAL GAS FROM THE WELLHEAD AND REMOVING
IMPURITIES SUCH AS CO2 AND SULFUR DIOXIDE ALONG WITH THE VALUABLE NATURAL GAS
LIQUIDS. WE ALSO HAVE VERY EXTENSIVE STORAGE, TRANSPORTATION AND MARKETING
FACILITIES. THE EXPLORATION AND PRODUCTION SEGMENT PRODUCES NATURAL GAS IN THE
SAN JUAN BASIN OF COLORADO AND NEW MEXICO, WESTERN AND EASTERN MICHIGAN, AND
WITH THIS TRANSACTION, ALBERTA, CANADA. NOT ONLY IS THIS SECOND SEGMENT GROWING
VERY RAPIDLY, BUT IT ALSO HELPS DRIVE OUR MIDSTREAM BUSINESS AS WE PROVIDE
SERVICES TO OTHER PRODUCERS.
THIS PRESS RELEASE INCLUDES "FORWARD-LOOKING STATEMENTS" WITHIN THE MEANING
OF SECTION 27A OF THE SECURITIES ACT OF 1933, AS AMENDED, AND SECTION 21E OF THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED. ALL STATEMENTS OTHER THAN
STATEMENTS OF HISTORICAL FACTS INCLUDED OR INCORPORATED HEREIN MAY CONSTITUTE
FORWARD-LOOKING STATEMENTS. ALTHOUGH THE COMPANY BELIEVES THAT THE EXPECTATIONS
REFLECTED IN THE FORWARD-LOOKING STATEMENTS ARE REASONABLE, IT CAN GIVE NO
ASSURANCE THAT SUCH EXPECTATIONS WILL PROVE TO BE CORRECT. THE FORWARD-LOOKING
STATEMENTS INVOLVE RISKS AND UNCERTAINTIES THAT AFFECT THE COMPANY'S OPERATIONS,
FINANCIAL PERFORMANCE AND OTHER FACTORS AS DISCUSSED IN THE COMPANY'S FILINGS
WITH THE SECURITIES AND EXCHANGE COMMISSION. AMONG THE FACTORS THAT COULD CAUSE
RESULTS TO DIFFER MATERIALLY ARE THOSE RISKS DISCUSSED IN THE COMPANY'S FORM
10-K FOR THE YEAR ENDED DECEMBER 31, 2000.
<Page>
SIGNATURE
Pursuant to the requirements of the Securities and Exchange Act of 1934, the
Registrant has duly caused this report to be signed on its behalf by the
undersigned, thereunto duly authorized.
MARKWEST HYDROCARBON, INC.
(Registrant)
Date: August 14, 2001 BY: /s/ Gerald A. Tywoniuk
-----------------------------------
Gerald A. Tywoniuk
Chief Financial Officer and
Vice President of Finance
(On Behalf of the Registrant and as
Principal Financial and Accounting
Officer)