North Coles Levee field

The highest concentrations of dicarboxylic acid anions are those reported by MacGowan and Surdam (1988) for the 12-31 well in the North Coles Levee field, San Joaquin Basin. They reported an oxalate concentration of 95 mg/1 and a malonate concentration of 2540 mg/1 in formation water from the 12-31 well. MacGowan and Surdam (1988) reported similarly high concentrations of oxalate and malonate for other wells in the San Joaquin and Santa Maria basins. Another analysis of organic acid concentrations in formation water from the 12-31 well was tabulated by MacGowan and... 

Boles JR (1991) Plagioclase dissolution related to oil residence time. North Coles Levee field, California. Am Assoc Pet Geol Bull 75 544 (Abstr)... 

Figure 1 shows the location of the hydrocarbon reservoirs discussed in this paper and Table 1 references the data sources. Table 2 contains the new isotopic data from the basin. Numerous studies of the North Coles Levee have been published (Boles Ramseyer, 1987 Schultz et al., 1989 Wood Boles, 1991), but only sparse data have been published from other fields in the area (e.g. Paloma and Lakeside fields see Fischer Surdam, 1988). The new data in Table 2 add seven new areas to the central basin database, including South Coles Levee, Canal, Paloma, Landslide, Rio Viejo, San Emidio Nose and Yowlumne fields. 

Fig. 6. Isotopic composition of calcite cements from North Coles Levee, South Coles Levee and Canal fields. North Coles Levee dolomite cements shown for comparison. North Coles Levee data from Schultz et al. (1989) South Coles Levee and Canal data from Table 2. Increasingly negative 5 OpDB and lower Sr ratios are correlated with higher temperatures of crystallization. Strontium ratio decrease is attributed to Sr from plagioclase alteration. Shaded box shows calculated composition of calcite in equilibrium with present pore water at Coles Levee fields based on fluid temperature and composition in Fisher Boles (1990) and Sr isotopic data in Feldman et al.( 993).

One would expect thermogenic carbon sources to become increasingly important as the sands are buried. However, the late carbonate cements at North Coles Levee (after about 4 Ma) have carbon isotopic values in a very restricted range (-2%o to -4%o), as if they were buffered by some process taking place in the reservoir (Fig. 9 in Wood Boles, 1991). Similarly, late calcite cements forming in the Rio Viejo, Yowlumne and San Emidio Nose fields (Table 2) also have relatively heavy carbon values, between -5 and 0. The timing of the buff-... 

Data from South Coles Levee and Canal fields (Table 2) confirm the positive correlation between oxygen and Sr isotopes, as noted at North Coles... 

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