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40 acre spacing is established for all wells in Michigan according to R 324.301 of the Administrative Rules of Part 615 of the Natural Resources and Environmental Protection Act, P.A. 451 1994, as amended . Exceptions to these rules have been ordered by the Supervisor of Wells for some formations. The following are general exceptions affecting large areas of the State. Exceptions for individual drilling units are not listed here.
Supervisor of Wells Order 10-12-87 allows for multiple drain holes for Antrim wells north of Town 20 N. ( most of the northern lower Michigan counties). Supervisor of Wells Order(A) 3-3-95 extended this to 34 more counties (42 total) so that all the counties in the Lower Peninsula are covered except for Monroe County. Supervisor of Wells Order (A) 14-9-94 changed the spacing in the Administrative Rules to allow the creation of Uniform Spacing Plans (USPs) within 22 counties with an average spacing of no less than 80 acres per well in each USP. In March of 1999 Supervisor of Wells Order (A) 20-12-98 amended Supervisor of Wells Order (A) 14-9-94 to allow more than two lateral drain holes per well. In July of 2002 an amendment to Supervisor of Wells Order (A) 10-12-87 was issued to include the Sunbury, Bedford, and Ellsworth shales (but not the Berea sandstone), and a similar amendment to Supervisor of Wells Order (A) 14-9-94 was made to include the Sunbury, Ellsworth, and Bedford shales (but not the Berea sandstone). Order (A) 24-8-05, allows twinning of Antrim wells (two wells near one another) in the lower three tiers of Otsego and Montmorency counties.
Map of Antrim spacing
Special Order 1-73 set 80 acre spacing for the Niagaran formation and deeper in many northern lower Michigan counties and some of the southern counties. This order also includes all counties in the Upper Peninsula. This was amended (Special Order 1-73, amended), to add six townships in Calhoun county (Cause No. 12-6-75), and finally, Special Order (A) 2-81 set 40 acre spacing for Oakland county.
Map of Niagaran spacing
Trenton-Black River Formation Spacing
Twenty-one (21) Counties in Southern Michigan: Barry, Eaton, Ingham, Livingston, Oakland, Macomb, St. Clair, Calhoun, Jackson, Washtenaw, Wayne, Branch, Hillsdale, Lenawee, Monroe, Kalamazoo, St. Joseph, Cass, Berrien, Van Buren, and Allegan are spaced for the development of the Trenton and Black River Formations. Order No. 18-2007, as amended, abrogates and supersedes all previous Trenton-Black River spacing orders except for areas which contain an existing producible well or an active permit to drill and operate for a well that has not been plugged as of the effective date of that order i.e. 12/26/2008.
A standard drilling unit shall consist of 40 acres, more or less, in the form of a square, assembled by combining two 20-acre parcels, each of which shall consist of the north and south, or east and west halves of a quarter-quarter section or of adjacent quarter-quarter sections. The bottom hole location shall be anywhere on the drilling unit not less than 330 feet from the drilling unit boundaries.
Map of Trenton-Black River spacing.
Glenwood and below Spacing
Special Order 1-73 and its amendment stemming from Cause No. 12-6-75, set spacing for the Niagaran formation and deeper (which includes the Glenwood) at 80 acres for the Upper Peninsula and many counties in Lower Michigan. Later, Special Order 1-86 set spacing for the Glenwood and deeper in most of these counties and some others also at 640 acres. A few areas not covered by this order are still under the original 80 acre spacing.
Map of Glenwood spacing