Diagenetic Evolution of Marine Carbonate Reservoirs: A Case Study from M5_1-2 Submember of Middle Ordovician Majiagou Formation in SE Ordos Basin, China

Table 1

Summary of δ¹⁸O and δ¹³C values for different types of carbonate of Ordovician in Yan’an area.

Rock type	Sample numbers	δ^13C (‰)		δ^18O (‰)
		Range	Average	Range	Average
Bulk rock	59	−6.30‰ to 1.01‰	−1.15‰	−11.36‰ to −6.54‰	−8.58‰
Mud powder crystalline dolomite	22	−4.33‰ to 4.26‰	1.86‰	−10.50‰ to −1.12‰	−5.98‰
Dissolution pores filled with dolomite	6	−6.30‰ to 1.05‰	0.34‰	−11.90‰ to −2.05‰	−7.08‰
Dissolution pores filled with calcite	7	−11.06‰ to −2.67‰	−1.95‰	−17.08‰ to −3.89‰	−11.84‰