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===Miocene Monterey Shale, Santa Maria Basin, California: Fractured Shale-oil Production===

===Miocene Monterey Shale, Santa Maria Basin, California: Fractured Shale-oil Production===

The first example of producible shale oil is taken from the Miocene Monterey Shale, Santa Maria Basin, California (see Appendix immediately following this chapter, location 49 on North American resource map). The Monterey Shale has been the source of substantial amounts of oil in various conventional reservoirs in this basin, but also produces from fractured Monterey Shale itself. In fact, the shale itself has yielded approximately 1 billion bbl of oil since 1900.<ref>Williams, P., 2010, [http://www.oilandgasinvestor.com/Magazine/2010/1/item50371.php Oil-prone shales: Oil and Gas Investor].</ref>

The first example of producible shale oil is taken from the Miocene Monterey Shale, Santa Maria Basin, California (see Appendix immediately following this chapter, location 49 on North American resource map). The Monterey Shale has been the source of substantial amounts of oil in various conventional reservoirs in this basin, but also produces from fractured Monterey Shale itself. In fact, the shale itself has yielded approximately 1 billion bbl of oil since 1900.<ref>Williams, P., 2010, [http://www.oilandgasinvestor.com/Magazine/2010/1/item50371.php Oil-prone shales: Oil and Gas Investor].</ref>

Other examples of open-fractured shale-oil production include the Niobrara, Pierre,<ref>U. S. Geological Survey, 2003, [http://pubs.usgs.gov/fs/fs-002-03/FS-002-03.pdf 2002 U.S. Geological Survey assessment of oil and gas resource potential of the Denver Basin Province of Colorado, Kansas, Nebraska, South Dakota, and Wyoming]: U.S. Geological Survey Fact Sheet FS-002-03, February 2003, 3 p.</ref> Upper Bakken shale-oil systems,<ref name=ND2010>North Dakota Geological Survey, 2010, [https://www.dmr.nd.gov/oilgas/bakkenwells.asp Bakken horizontal wells by producing zone, upper Bakken Shale].</ref> and the West Siberian Jurassic Bazhenov Shale.<ref name=Lptn2003 />

Other examples of open-fractured shale-oil production include the Niobrara, Pierre,<ref>U. S. Geological Survey, 2003, [http://pubs.usgs.gov/fs/fs-002-03/FS-002-03.pdf 2002 U.S. Geological Survey assessment of oil and gas resource potential of the Denver Basin Province of Colorado, Kansas, Nebraska, South Dakota, and Wyoming]: U.S. Geological Survey Fact Sheet FS-002-03, February 2003, 3 p.</ref> Upper Bakken shale-oil systems,<ref name=ND2010>North Dakota Geological Survey, 2010, [https://www.dmr.nd.gov/oilgas/bakkenwells.asp Bakken horizontal wells by producing zone, upper Bakken Shale].</ref> and the West Siberian Jurassic Bazhenov Shale.<ref name=Lptn2003 />

A second Monterey Shale example is a deep Monterey Shale well drilled by Coastal Oil & Gas in a synclinal part of the onshore Santa Maria Basin. The Coastal Oil & Gas (O&G) Corp. 3-Hunter-Careaga well, Careaga Canyon field, flowed 53.9 m3/day (339 bbl/day) of 33deg API oil with 1.85 times 104 m3/day (653 mcf/day) of gas and 15 m3/day (95 bbl) of formation water from the Monterey Shale (scout ticket). It had a reported GOR of 343 m3/m3 (1926 scf/bbl). The well was perforated over numerous intervals from 2740 to 3711 m (8990–12,175 ft) with a maximum flow of 8.2 m3/day (516 bbl/day) and 2.20 times 104 m3/day (778 mcf/day). A geochemical log of this well illustrates its much higher thermal maturity, explaining the high GOR for a Monterey Shale well (Figure 4). The TOC values are variable, ranging from just under 3.00% to less than 0.50%. The highest oil crossover tends to occur where TOC values are lowest, suggesting variable lithofacies, but not open fractures as the oil crossover is marginal, reaching about 100 mg/g (average, 94 mg/g) in the 2793 to 3048 m (9165 to 10,000 ft) interval, with isolated exceptions over 100 mg/g at 3269 to 3305 m (10,725–10,845 ft) and 3580 to 3616 m (11,745–11,865 ft). Based on these data, the optimum interval for landing a horizontal would be in the 2903 to 2940 m (9525 to 9645 ft) zone, although multiple zones with OSI greater than 100 would flow oil. Additional oil likely exists in the pyrolysis (S2) peak because low TOC samples have substantial pyrolysis yields with some of the highest HI values, again indicative of oil carryover into the pyrolysis yield. Thermal maturity, as indicated by vitrinite reflectance equivalency (Roe) from Tmax, suggests maturity values spanning the entire oil window with the early oil window at 2743.2 m (9000 ft) and latest oil window at 3657.6 m (12,000 ft).

A second Monterey Shale example is a deep Monterey Shale well drilled by Coastal Oil & Gas in a synclinal part of the onshore Santa Maria Basin. The Coastal Oil & Gas (O&G) Corp. 3-Hunter-Careaga well, Careaga Canyon field, flowed 53.9 m3/day (339 bbl/day) of 33deg API oil with 1.85 times 104 m3/day (653 mcf/day) of gas and 15 m3/day (95 bbl) of formation water from the Monterey Shale (scout ticket). It had a reported GOR of 343 m3/m3 (1926 scf/bbl). The well was perforated over numerous intervals from 2740 to 3711 m (8990–12,175 ft) with a maximum flow of 8.2 m3/day (516 bbl/day) and 2.20 times 104 m3/day (778 mcf/day). A geochemical log of this well illustrates its much higher thermal maturity, explaining the high GOR for a Monterey Shale well ([[:File:M97Ch1.2FG4.jpg|Figure 4]]). The TOC values are variable, ranging from just under 3.00% to less than 0.50%. The highest oil crossover tends to occur where TOC values are lowest, suggesting variable lithofacies, but not open fractures as the oil crossover is marginal, reaching about 100 mg/g (average, 94 mg/g) in the 2793 to 3048 m (9165 to 10,000 ft) interval, with isolated exceptions over 100 mg/g at 3269 to 3305 m (10,725–10,845 ft) and 3580 to 3616 m (11,745–11,865 ft). Based on these data, the optimum interval for landing a horizontal would be in the 2903 to 2940 m (9525 to 9645 ft) zone, although multiple zones with OSI greater than 100 would flow oil. Additional oil likely exists in the pyrolysis (S2) peak because low TOC samples have substantial pyrolysis yields with some of the highest HI values, again indicative of oil carryover into the pyrolysis yield. Thermal maturity, as indicated by vitrinite reflectance equivalency (Roe) from Tmax, suggests maturity values spanning the entire oil window with the early oil window at 2743.2 m (9000 ft) and latest oil window at 3657.6 m (12,000 ft).

 

This well was perforated over the entire Monterey Shale interval and did produce during a 5 yr period 2.60 times 104 m3 (163,603 bbl) of oil, 6.369 times 106 m3 (224,936 mcf) of gas, and 1.39 times 105 m3 (872,175 bbl) of formation water with the water cut increasing greatly in year 5 when the well was shut in.

This well was perforated over the entire Monterey Shale interval and did produce during a 5 yr period 2.60 times 104 m3 (163,603 bbl) of oil, 6.369 times 106 m3 (224,936 mcf) of gas, and 1.39 times 105 m3 (872,175 bbl) of formation water with the water cut increasing greatly in year 5 when the well was shut in.