Sacramento basin

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The Sacramento Basin is primarily a natural gas region that was created during the late-Mesozoic and early-Cenozoic time period. The Basin is Surrounded by Sierra Nevada Mountains, the Klamath mountains, and Coast ranges. Covering 12,000 square miles of California's central valley producing an estimated 9 Trillion Cubic feet of natural gas. This basin includes many reservoirs with the main ones being the Cretaceous Starkey, Winters, Forbes, Kione, and the Eocene Domengine sands. The Sacramento basin occupies the northern half of the Great Valley of California. It is a long, narrow asymmetric basin, with a steep west flank and a broad, shallow east flank. Sediments range in age from Jurassic to Holocene, with essentially dry gas production coming from sediments of Late Cretaceous, Paleocene, and Eocene age. The basin can be divided into four areas: the northern San Joaquin, Delta, Suisun, and northern Sacramento areas. In the northern San Joaquin area, production has come from anticlinal closures, mostly along the up-thrown sides of two major faults. Future production probably also will be located on anticlinal highs. In the Delta area, production has come from anticlines, fault traps, some stratigraphic traps, and traps against two major gorges. Future production will probably be found in fault and gorge traps. Production in the Suisun area has been located on anticlines. Future production may come from presently unknown anticlines and from new pools found on known anticlinal trends. In the northern Sacramento area, production has come mostly from stratigraphic traps in sandstone of the Forbes Formation, with additional production from anticlinal trends and from domes overlying buried volcanic plugs. Future production will probably be from Forbes stratigraphic traps. Over half the gas in the Sacramento basin probably has been discovered. Future exploration will be concentrated in the Delta and northern Sacramento areas. It is possible, but doubtful, that future major production may come from formations deeper than those presently productive, and from parts of the basin presently considered non prospective. California Resources Corporation (CRC) operates 53 fields in the Sacramento Basin primarily consisting of dry gas production. CRC currently holds approximately 517,000 net mineral acres in the basin, approximately 38 percent of which we hold in fee. We believe our significant acreage position in the Sacramento Basin gives us the option for future development and rapid production growth in an attractive natural gas price environment. The Sacramento Basin is a deep, thick sequence of sedimentary deposits within an elongated northwest-trending basin located in northern California covering approximately 12,000 square miles and forming the northern part of California’s Central Valley. It contains a thick sequence of sedimentary deposits that range in age from lower Cretaceous to Neogene sediments in an area that is approximately 200 miles long and 45 miles wide. Producing reservoirs range from upper Cretaceous-age to Pliocene-age. The main reservoirs are the Cretaceous Starkey, Winters, Forbes, Kione, and the Eocene Domengine sands. Exploration in the basin started in 1918 and was focused on seeps and topographic highs. In the 1970's, the use of multi-fold 2D seismic surveys led to large discoveries in the basin. The acquisition of 3-D seismic surveys in the mid-1990's helped define trapping mechanisms and reservoir geometries. The Sacramento Basin has been extensively explored for petroleum resources, and more than 10 trillion cubic feet of natural gas have been produced.[1] [2]

Outline of the Sacramento Basin located in northern California


Conventional Plays

There are two main conventional plays located in the Sacramento Basin. The Northern Forbes-Kione and the winters through domingene play. Understanding these two conventional plays by looking at the reservoirs, Source rock, exploration status and resource potential gives an in depth assessment of the basin and its potential in producing natural gas and oil.

The Northern Forbes-Kione Play

The Forbes-kione play measures 7108 square miles of the north Sacramento basin. The trapping mechanisms are primarily a combination but do have stratigraphic and structural traps within this play. The primary rock located in this play is the late cretaceous sandstone with its thickness ranging from 11 to 490 feet. According to the U.S. geological Survey the mature source rock for this formation is not certain but is believed to come from the delta depocenter in the Forbes Formation.  Over time the gas migrated north through the Forbes formation where it was eventually trapped in the stratigraphic traps which were then deformed into structural traps. Of the traps discovered the range of depth is from 980 to 6260 feet sealed by shale. Most of the current wells in this play run north to south in the middle of the basin. The most likely place to find new oil will be to expand these drilling sites.[3]


The Southern Forbes-Kione Play

The southern Forbes-Kione Play covers 4712 square miles of the south Sacramento Basin. This play is part of the down dip extension of the Forbes formation. As with the Northern Forbes-Kione play the primary source rock type is late cretaceous sandstone as well as being sealed by shale and siltstone facies.The primary source rock is unknown but most likely gas-prone shales found in the Forbes or Dobbins Formation. As the gas was being formed in the late Cretaceous to the Miocene time periods the gas was migrating to the Northern Forbes-Kione Play. The exploration and resource potential of the play is rather difficult due to the depths that the traps are located. This play can be found underneath the Winters to Domingene Play which means companies would have to extend their wells past the current field.[3]

The Winters to Domingene Play

This play covers 4712 square miles of the southern Sacramento basin. This Play can be found directly above the Sacramento formation. The primary source rock comes from the Late Cretaceous to Oligocene with the Eocene age rocks in the Domingene formation being the most prominent. With almost all of the sands being deposited in a marine environment. The primary seals are shales and siltstones found in the Sacramento formation and shales that were formed in the Eocene time period. The source rock for the gas found in this play most likely comes from the winters shale. While this gas was being formed it traveled east through the midland fault and settled in combination traps. The well depth of the reservoir ranges between 2200 to 9700 feet. The reservoir thickness ranges from 13 to 350 feet and porosity ranging from 18 to 34 percent. [3]

Stratigraphic map of the the Sacramento Basin.

Production

California Resources Corporation® (CRC) holds approximately 500,000 net acres in the Sacramento Basin. In 2015, CRC produced 44 million cubic feet of natural gas – or 7,000 barrels of oil equivalent per day – in the Sacramento Basin, which could supply all the homes in the City of Sacramento for nearly two years. [4]

Crude Oil

California Resources Corporation's (CRC) oil production is connected to California markets via our oil gathering pipelines which are used almost entirely for our production. We generally do not transport, refine or process the oil we produce and we sell almost all of our oil into the California refining markets. We believe these markets are among the most favorable in the U.S. because California imports a significant percentage of its oil requirements from outside the state, mostly from foreign locations.

Natural gas liquids

CRC’s production from oil and gas reservoirs typically includes oil, produced water, natural gas (methane), and natural gas liquids (NGLs) that include ethane, propane, butane and natural gasoline. CRC processes NGLs through our processing plants, which facilitate access to third-party delivery points near the Elk Hills Field.

Natural gas

CRC is the largest natural gas producer in California, which imports approximately 90 percent of the natural gas consumed in the state. We sell our natural gas production in the state and use intrastate transportation contracts to facilitate delivery of our natural gas to customers.

Electricity

Elk Hills Power, LLC, a joint venture of CRC and a portfolio company of Ares Management, L.P., generates electricity from natural gas in the Elk Hills Field. With a capacity of 550 megawatts (MW), the plant’s electricity powers the Elk Hills Field and supplies excess power to a local utility and California’s electrical grid sufficient to supply more than 300,000 homes. CRC operates a 45 MW cogeneration facility that provides steam and electricity as needed to the Elk Hills Field, and THUMS Long Beach Company operates a 45 MW power generating facility that provides electricity to the Wilmington Field in Long Beach.


History

Exploration in this province started in 1918, and by the end of 1990, almost 2,600 new field wildcats had been drilled. The most active period of exploration occurred between 1960 and 1980. About 2,300 wells were drilled to depths that ranged from 3,000 to 10,000 ft, with several wells approaching 20,000 ft. The Sacramento Valley is principally a dry gas province, the basin has been traced back to late Mesozoic- early Cenozoic. There is an active tectonic history with giveaways shown in the complex stratigraphic relationships, a widespread of faulting and deformation, as well as the presence of igneous intrusions. If you look at the chemical and isotope data you will find four principal sources of gas in the basin. The western delta area has gases that were generated from mature source rocks within the oil and condensate window. Gases in the northern and southeastern basin are mixtures of indigenous gas, dry thermogenic gas migrated from post-mature source rocks in the basin deep, and nitrogen-rich gases thought to originate in meta-sedimentary rocks deep beneath the basement.[5][4]

References[6][5]

  1. Scheirer, Allegra, et al. Assessment of Undiscovered Natural Gas Resources of the Sacramento Basin Province of California, 2006. U.S Geological Survey, 2006, pubs.usgs.gov/fs/2007/3014/. PDF: https://pubs.usgs.gov/fs/2007/3014/fs2007-3014.pdf
  2. P. D. Jenden, I. R. Kaplan; Origin of Natural Gas in Sacramento Basin, California. AAPG Bulletin ; 73 (4): 431–453. doi: https://doi.org/10.1306/44B49FC9-170A-11D7-8645000102C1865D
  3. 3.0 3.1 3.2 https://certmapper.cr.usgs.gov/data/noga95/prov9/text/prov9.pdf
  4. 4.0 4.1 https://www.crc.com/images/documents/publications/2016_Sacramento_Basin_Snapshot_Brochure.pdf
  5. 5.0 5.1 Sterling, Robert. “Online Journal for E&P Geoscientists.” Datapages, Inc., 2018, www.searchanddiscovery.com/pdfz/documents/2018/11091sterling/ndx_sterling.pdf.html.
  6. Sullivan, Raymond & Sullivan, Morgan. (2012). Sequence Stratigraphy and Incised Valley Architecture of the Domengine Formation, Black Diamond Mines Regional Preserve and the Southern Sacramento Basin, California, U.S.A. Journal of Sedimentary Research.