Determination of Formation Time of Calcareous Cements in Marine Sandstone and Their Influence on Hydrocarbon Accumulation: A Case Study of the Carboniferous Donghe Sandstone in the Hadexun Oilfield, Tarim Basin

Table 3

Carbon and oxygen isotopes, Δ47, and calculated values of calcareous cement in the Donghe sandstone, Hadexun Oilfield.

Well	Depth (m)	No.^1	δ^13C (‰)^2	1 s.d.^3	δ^18O (‰)^4	1 s.d.^5	Δ47 avg^6	1 s.e.^7	δ^18O(‰)^8	1 s.d.^9	value^10
HD4	5070.07	5	-3.1	0.1	-10.6	0.1	0.590	0.021	-3.1	2.8	115.7
HD4	5070.62	5	-3.3	0.1	-9.8	0.3	0.580	0.015	-1.6	2.4	115.7
HD4	5098.52	5	-4.4	0.0	-6.9	0.1	0.545	0.005	3.6	0.8	114.8
HD17	5529.01	5	-4.5	0.0	-6.9	0.1	0.562	0.005	2.4	0.6	114.7
HD17	5529.47	5	-7.8	0.1	-9.0	0.1	0.546	0.020	1.4	0.8	106.9
HD17	5230.13	5	-5.6	0.1	-9.8	0.1	0.572	0.015	-1.1	0.6	111.0

¹Number of replicate runs. ²The δ¹³C (‰) value is the average value of five replicates and output by PDB. ³Standard deviation of δ¹³C. ⁴The δ¹⁸O (‰) value is the average value of five replicates and output by PDB. ⁵Standard deviation of δ¹⁸O. ⁶Δ47 avg. is the average value of five replicates. ⁷Standard errors of regression coefficients of the . ⁸δ¹⁸O (‰) is the average calculated value of the water and output by SMOW. ⁹1 s.d. is the standard deviation of δ¹⁸O. ¹⁰The value was calculated using the formula after Keith et al. [37].