Exhibit 99.1

    Gastar Exploration Announces Completion of LOR #4 Well in the
                          Knowles Formation

    HOUSTON--(BUSINESS WIRE)--Sept. 17, 2007--Gastar Exploration Ltd.
(AMEX:GST) (TSX:YGA) announced today completion results for the Lone
Oak Ranch (LOR) #4 horizontal Knowles Limestone well. The LOR #4 well
was completed and is producing at a gross sales rate of approximately
8 MMCFD with 2,500 psi flowing tubing pressure. Gastar has a 50%
working interest and an approximate 37.5% net revenue interest in the
well.

    J. Russell Porter, Gastar's President and CEO, stated, "The LOR #4
is our first horizontal Knowles well, following a vertical Knowles
well completion, the John Parker #3, earlier this year on our East
Texas acreage. We believe that Gastar is the first operator to
establish commercial Knowles production in East Texas. Now that we
have had this initial success with a horizontal well, we plan to
continue to develop the potential of this formation. The opportunity
to develop the Knowles formation is an excellent addition to our deep
Bossier play, due to its shallower depth, lower drilling costs and
apparent attractive production rates."

    Gastar is currently drilling a deep Bossier well, the Wildman
Trust #3 well, at an approximate depth of 8,200 feet. The Wildman
Trust #3 well is located as an offset to Gastar's recently successful
Donelson #3 Bossier well. Gastar has a 67% working interest in the
well with Chesapeake Energy Corporation (NYSE:CHK) owning the
remaining 33% working interest.

    About Gastar Exploration

    Gastar Exploration Ltd. is an exploration and production company
focused on finding and developing natural gas assets in North America
and Australia. The Company pursues a strategy combining select higher
risk, deep natural gas exploration prospects with lower risk coal bed
methane (CBM) development. The Company owns and operates exploration
and development acreage in the deep Bossier gas play of East Texas.
Gastar's CBM activities are conducted within the Powder River Basin of
Wyoming and on approximately 3 million gross acres controlled by
Gastar and its joint development partners in Australia's Gunnedah
Basin, PEL 238, located in New South Wales, and the Gippsland Basin,
EL 4416, located in Victoria. For more information, visit our web site
at www.gastar.com.

    Safe Harbor Statement and Disclaimer:

    This Press Release includes "forward-looking statements" within
the meaning of Section 27A of the Securities Act of 1933 and Section
21E of the Securities Act of 1934. A statement identified by the words
"expects", "projects", "plans", and certain of the other foregoing
statements may be deemed forward-looking statements. Although Gastar
believes that the expectations reflected in such forward-looking
statements are reasonable, these statements involve risks and
uncertainties that may cause actual future activities and results to
be materially different from those suggested or described in this
press release. These include risks inherent in the drilling of natural
gas and oil wells, including risks of fire, explosion, blowout, pipe
failure, casing collapse, unusual or unexpected formation pressures,
environmental hazards, and other operating and production risks
inherent in natural gas and oil drilling and production activities,
which may temporarily or permanently reduce production or cause
initial production or test results to not be indicative of future well
performance or delay the timing of sales or completion of drilling
operations; risks with respect to oil and natural gas prices, a
material decline in which could cause the Company to delay or suspend
planned drilling operations or reduce production levels; and risks
relating to the availability of capital to fund drilling operations
that can be adversely affected by adverse drilling results, production
declines and declines in natural gas and oil prices and other risk
factors described in the Company's Annual Report on Form 10-K, as
filed on March 27, 2007 with the United States Securities and Exchange
Commission at www.sec.gov and on the System for Electronic Document
Analysis and Retrieval (SEDAR) at www.sedar.com.

    The American Stock Exchange and Toronto Stock Exchange have not
reviewed and do not accept responsibility for the adequacy or accuracy
of this release.

    CONTACT: Gastar Exploration Ltd.
             J. Russell Porter, Chief Executive Officer, 713-739-1800
             rporter@gastar.com
             or
             DRG&E
             Lisa Elliott, 713-529-6600 (Investor Relations Counsel)
             lelliott@drg-e.com
             Anne Pearson, 713-529-6600 (Investor Relations Counsel)
             apearson@drg-e.com