In 2020, in West Texas we participated in the drilling of seven wells: one for 8.6% interest which was brought into production in July of 2020, and six wells with an average 47.5% interest that were drilled but not completed at
year-end
and therefore classified as Proved Undeveloped in the
year-end
reserve report. The Company invested approximately $8.0 million in these seven wells in 2020. Also in 2020, proved producing reserves were added in West Texas through the addition of 11 horizontal wells completed in Midland County, Texas, in which we receive 0.56% to 1% over-riding royalty interest.
In 2021, in West Texas, we participated with Apache in the drilling of three additional horizontals on the Kashmir Tract in Upton County, Texas and completed these three wells in September of 2021 along with six other wells drilled in 2020 on the same lease that were drilled but uncompleted at
year-end
2020. The Company has an average of 47.8% interest in these nine wells and invested approximately $30 million in these horizontal wells.
In our Oklahoma, Scoop-Stack play, in 2019, we participated in the drilling and completion of six wells on our WM Wallace tract for 7.67% interest, and nine wells, included on our Slash, Osborn, and Leon tracts, with an average 1.34% interest. In addition, three wells drilled in Oklahoma in 2018, were completed in 2019 converting 24 Mboe of reserves to proved developed. Also in Oklahoma, six wells designated as
Shut-in
on December 31, 2018, were brought into production in 2019: five located on our Ruthie tract, and one on our Braum tract.
In 2019, in our Gulf Coast region, we added production through the recompletion of three vertical wells in Polk County, Texas: one operated by the Company in which we have 72.5% interest, and two operated by Unit Petroleum in which the Company owns 2.81% working interest and 3.77% net revenue interest. In 2020, the Company successfully recompleted one additional operated well in the Segno field with a 72.5% interest.
At December 31, 2020, in total, the Company had 3,221 Mboe of proved undeveloped reserves attributable to 13 wells operated by others, 10 of which were drilled but not completed by
year-end
2020, and three that were not drilled until 2021. The three new horizontals along with the six uncompleted wells at
year-end
were brought online in late September and early October of 2021. These successful new wells are on our Kashmir tract in Upton County, Texas operated by Apache Corporation. These nine PUD wells at
year-end
2020 accounted for 3,127 Mboe of the total undeveloped reserves where the Company has an average 47.5% interest and invested approximately $30 million dollars in these wells. The four other PUD wells, drilled but not completed at
year-end
2020, are located in Grady County, Oklahoma and accounted for 95 Mboe of the total undeveloped reserves.
At December 31, 2021, the Company had 159 Mboe of proved developed
shut-in
reserves attributable to three horizontal wells drilled and completed in Canadian County, Oklahoma in December of 2021, but not yet online. Three of the four wells were successfully completed and online in January, 2022, while one well had completion issues and has been temporarily abandoned. In regard to the four drilled but uncompleted PUD wells in Grady County, Oklahoma, noted in the paragraph above, reserves previously attributed to these wells were not included in the 2021
year-end
reserve report as the operator has no near-term plans for their completion.
In the first quarter of 2022, in our West Texas horizontal drilling program, the Company participated with 10.3% interest in the drilling of four horizontal wells with SEM Operating Company and has received proposals for an additional 23 horizontal wells to begin this year. In total the Company is likely to invest approximately $76 million in these 27 wells. In Oklahoma, thus far in 2022, the Company is participating for 9.38% interest with Ovintiv
Mid-Continent
in the drilling of four wells in Canadian County, Oklahoma. These four wells and the four SEM wells are anticipated to be online in July of this year. Additional drilling and future development plans will be established based on an expectation of available cash flows from operations and availability of funds under our revolving credit facility.
We employ technologies to establish proved reserves that have been demonstrated to provide consistent results capable of repetition. The technologies and economic data being used in the estimation of our proved reserves include, but are not limited to, electrical logs, radioactivity logs, geologic maps, production data, and well test data. The estimated reserves of wells with sufficient production history are estimated using appropriate decline curves. Estimated reserves of producing wells with limited production history and for undeveloped locations are estimated using performance data from analogous wells in the area. These wells are considered analogous based on production performance from the same formation and with similar completion techniques.