322 



Economic Aspects 



of active seeps contain bits of tar and 

 globules of oil. In deeper basin sediments 

 small masses of tar (Fig. 245) have some- 

 times been found. These were probably in- 

 cluded in the asphaltic fraction analyzed in 

 the cores, but they should not have affected 

 the hydrocarbon analyses. 



The obvious presence of submarine oil 

 seeps off known oil fields on land led to 

 early exploitation of the seaward parts of 

 the fields. The first wells drilled in the off"- 

 shore region were in 1896 at Summerland, 

 30 years after the first well was drilled on 

 land in southern California near Ventura 

 (Carter, 1954). Several offshore rigs were 

 built atop pilings and wharves extended out 

 from shore. Most offshore production, 

 however, has been from wells drilled at the 

 shore and whipstocked seaward so that 

 their bottoms are located as far as 4 km 

 from the well heads. Spectacular numbers 

 of closely spaced wells lined up along the 

 shore may be seen at Huntington Beach 

 and Wilmington. Since 1950 use has been 

 made of drilhng barges, Texas towers (Fig. 

 246), and man-made islands (Monterey Oil 

 Company's 1954 island 2.5 km off Seal 

 Beach, Richfield Oil Corporation's 1958 

 island 0.8 km off Rincon, and Standard- 

 Humble's 1958 platform 3.5 km off Sum- 

 merland). Although the islands cost 3 or 4 



million dollars each, there is enough space 

 on each to drill 25 to 70 wells. In 1958 the 

 ultimate method was approached when 

 patents were issued to a group of four 

 companies (Continental, Union, Shell, and 

 Superior) for a method of drilling wells in 

 very deep water. This method has been 

 used to depths of nearly 500 meters, and it 

 involves positioning the drilling equipment 

 (including blowout preventers and mud 

 pumps) on the sea floor and guiding the 

 drill bit to the desired location with flexible 

 cables (Fig. 247). In contrast to the 1 1 per 

 cent success of wildcat wells on land in the 

 United States, a much higher percentage of 

 success has been attained in drilling the off- 

 shore region of southern California (98 per 

 cent), Louisiana (27 per cent), and Texas 

 (23 per cent), owing largely to the great care 

 required by the high cost. 



Total production in the offshore area to 

 the end of 1957 amounted to 549 million 

 42-ganon barrels (Table 31), more than four 

 times the total ofl'shore production in the 

 Gulf of Mexico (Thomasson, 1958). Pro- 

 duction for the year 1957 was 31.9 million 

 barrels, or 9.4 per cent of the total produc- 

 tion of Cahfornia — 339.1 million barrels 

 (Popenoe, 1958), or 1.2 per cent of the total 

 United States production (Bureau of Mines, 

 1958). Reserves for California are about 



Figure 245. Small masses of 

 tar found occasionally in basin 

 cores. These are believed to 

 have floated from distant seep 

 areas and, after partial oxida- 

 tion, to have sunk to the bot- 

 tom. Diameters are about 

 2 mm. 



