Geology of the Red River

Red River Units -- Continental Resources
from various sources, including CLR 10-Ks

South Dakota Buffalo Red River Units. Three contiguous Buffalo Red River units (Buffalo, West Buffalo and South Buffalo) are located in Harding County, South Dakota, approximately 21 miles south of the MPHU. When we purchased the units in 1995, there were 73 vertical producing wellbores and 38 injection wellbores under HPAI producing approximately 1,906 net Bbls of oil per day. We operate and own an average working interest of 95% in the 32,900 acres comprising the three units. From 2005 to 2008, we re-entered 42 existing vertical wells and drilled horizontal laterals to increase production and sweep efficiency from the three units. Production for the month of December 2007 was 1,945 net Bbls of oil per day compared to an average of 1,162 net Bbls of oil per day for the first half of 2005. We currently plan to drill 5 horizontal extensions of existing wellbores and 25 new horizontal wellbores in the Buffalo Red River units over the next two years. We believe these operations will increase production and sweep efficiency. In 2008, we plan to invest $23 million for drilling in the Buffalo Red River units.

Montana

The Cedar Hills West unit (CHWU), in Fallon County, Montana, is contiguous to the northern portion of CHNU. As of December 31, 2007, this 7,800-acre unit contained ten horizontal producing wells and five horizontal injection wells. We operate and own a 100% working interest in the CHWU. 

North Dakota

Cedar Hills North Unit


Medicine Pole Hills Unit


Data points from a presentation provided by a reader.

• Red River formation; Ordovician period; in southwestern North Dakota
• over 700 feet thick in the center of the basin, in Dunn County
• Comment: I haven't really considered Dunn County southwestern North Dakota, but I guess one could characterize it as such
• like other formations, an "upper" and a "lower" part
• the upper unit is divided into "A," "B," "C," and "D" zones --increasingly "restrictive"
• "restrictive" --> anoxic --> excellent for preservation of organic matter --> hydrocarbons
• "A" zone: laminated dolomite
• "B" and "C" zones: non-porous; overlying porous dolomite; anhydrite beds prevent loss of hydrocarbons
• "D" zone: source rock for the Red River; beds of black kerogen rich dolomite, up to 20 cm thick, up to 59% total organic carbon (TOC) [The Bakken is up to 11% TOC]
• this kerogen-rich dolomite is found throughout the Williston Basin; considered the source rock for the Red River formation
• hydrocarbons have been produced from all four layers, but particularly from "B," "C," and "D" layers

Continuing:

• the "B" porosity zone is particularly important: it is laterally pervasive over much of the Williston Basin; production from "B" zone in Bull Run, Williams Creek, and Cash oil fields
• upper "B" zone might be the preferred to the lower "B" zone: lower porosity, but higher permeability, higher degree of oil saturation
• in the mid-1990s, horizontal drilling tested the Red River in Bowman County; decline rates were 30% to 45% but many of the better wells had annual decline rates of 5%; natural fracks helped

Source rock:

• earlier it was stated that the "D" zone likely to be a source to the Red River
• in addition, the Winnipeg shale, vertically below the Red River, may also be a source rock for the Red River
• at depths of 9,000, the Red River is thermally mature