Said ALiev Instructor Bailey BubachPTRE – 493 Shale playsFebruary 1, 2018Williston basin Bakken Formation.The Williston Basin is an elliptical shapeddepression, that include the Bakken shale and underlying Three Forks formation.It is known for its rich deposits of petroleum and potash.
United Statesportion of the Williston basin continuous from North Dakota to South Dakota andparts of Montana and Wyoming with approximately one hundred forty square miles.Oil first was discovered in Williston basin along the Cedar Creek anticline insoutheastern Montana in 1920s. Later, after year of exploring, testing, mapping,and drilling it was discovered as one of the largest oil and gas reserve inUnited states of America. Bakken formation is composed of three mainmembers, which is lower member, middle member and upper member.
Also, there isa nine different lithofacies that contains in Bakken formation. Eight of themin the middle member and the only one is occurred in upper and lower members isfacies Mb, which is organic rich black mudstone. For the lower Bakken memberaccumulation of laminated, fine grained, organic rich mud (Lithofacies Mb)occurred in deep water marine, usually take place when sea level rise.
Themiddle Bakken member, which is composed of eight gray mudstones and sandstoneslithofacies. It has a maximum thickens of ninety-eight feet in west- centralSaskatchewan. The middle member is sub-divided into three parts, sub- unit-Athe basal mudstone, sub-unit-B middle sandstone and mudstone and sub- unit C isupper mudstone. These sub-units are located throughout the inner of theWilliston Basin where each has maximum thickness near center and thin to zeronear the basin margin.
Lastly, is upper member which is black mudstone that isvery similar to the lower member. The lower and upped members contain differentattentiveness such as feldspar, quartz, illite, dolomite, calcite, pyrite andhigh concentration of organic matter. Composition of Mb facies contain black clays,silt, quartz silt grain, and amorphous organic materials. Also, it classifiedas primary structure and secondary structures.
Similarly, for the middle memberthat contain eight lithofacies such as St, Sr, Sf, Sw, MSI, Msh, Msm, and Lo. Allof them has a different structures and compositions. All the information ofthis basin can be obtained from core examination, well logs, seismic andpetrographic analysis. Williston Basin has six major depositionalsequences which goes from oldest to the youngest, the Sauk, Tippecanoe,Kaskaskia, Absaroka, Zuni and Tejas. These sequences occur in the differentgeological time scale. For example, the evolution of Willison basin startedwith the Sauk which is sequence of sedimentary rocks and deadwood formation inthe late Cambrian and early Ordovician age. Then, Tippecanoe sedimentation tookplace in Ordovician and Silurian time zone.
After that, deposition of lower Kaskaskiaoccurred in Devonian and upper Kaskaskia in Mississippian age, which created a marineconnection and disconnection in the different sides of basin. Later, AbsarokaSequence took over which created clastic sedimentary as a main element and mixof evaporites and some carbonates. Finally, Tejas sequence which took place inTertiary, Quaternary and Holocene age. In addition, these major sequences areclassifying as different orders; first, second are most likely result fromeustatic changes in sea level.
As well as third, and fourth order could resultfrom tectonic activities or both eustasy and tectonics. Furthermore, Williston Basin has two differentenergy resources beside the hydrocarbon which is Potash that is produced fromthe Williston Basin which makes Canada the worlds leading producer of thatcommodity. Also, Williston Basin holds large coal deposits, primarily in the FortUnion Formation in the Paleogene age. In conclusion, oil and gas production been expandingvery quickly in the Williston Basin.
The Bakken boom has pushed North Dakotainto the top ranks of oil- producing states with the help of advanced hydraulicfracturing and modern horizontal drilling technologies. Therefore, fracking hasunlocked huge U.S shale reserve, increasing in tremendous amount of oil and gasproduction and creating millions of jobs that promote economic growth.