Characteristics, formation and evolution of pre-salt dolomite reservoirs in the fifth member of the Ordovician Majiagou Formation, mid-east Ordos Basin, NW China

FU Siyi,ZHANG Chenggong,CHEN Hongde,CHEN Anqing,ZHAO Junxing,SU Zhongtang,YANG Shuai,WANG Guo,MI Wentian

Table 1 Geochemical analysis data of the pre-salt dolomite samples.

Well Depth/m Formation Lithology SiO2 content/% Al2O3 content/% TFe2O3 content/% CaO content/% MgO content/% MnO content/% 87Sr/86Sr δ13C δ18O J-12 3 660.17 M57 Dolomicrite 1.39 0.22 0.26 32.01 19.05 0.022 0.709 647 1.2 -5.17 J-6 3 552.50 M57 1.42 0.43 0.21 31.80 18.73 0.007 0.709 601 0.47 -5.55 J-6 3 573.37 M57 2.76 0.63 0.36 31.14 18.46 0.009 0.709 844 1.55 -5.05 Y-9 2 444.30 M56 3.38 0.61 0.39 27.11 14.60 0.005 0.709 651 0.76 -6.18 J-12 3 632.18 M57 Crystalline dolomite 3.67 0.81 0.30 30.40 17.88 0.008 0.710 153 0.32 -5.30 J-12 3 653.80 M57 3.24 0.71 0.37 30.74 18.02 0.012 0.710 054 1.52 -6.43 J-12 3 674.10 M59 1.10 0.15 0.15 32.62 18.64 0.007 0.710 045 1.20 -5.96 J-6 3 520.74 M56 0.86 0.23 0.18 32.18 19.05 0.007 0.709 420 0.34 -6.02 J-6 3 576.59 M57 1.29 0.28 0.22 33.00 18.04 0.007 0.708 892 1.86 -5.61 J-6 3 578.40 M57 0.73 0.18 0.16 32.71 18.43 0.008 0.709 237 1.56 -5.66 J-6 3 613.17 M510 1.95 0.43 0.29 32.55 17.55 0.007 0.708 981 1.38 -5.65 LT-2 2 652.70 M57 3.87 0.90 0.45 32.10 16.06 0.010 0.709 786 -0.08 -7.05 YT-1 2 530.60 M57 1.59 0.30 0.30 32.04 19.14 0.010 0.710 717 -0.57 -7.31 J-12 3 647.32 M57 Dolarenite 0.94 0.26 0.16 29.44 17.11 0.007 0.709 253 0.43 -5.65 J-12 3 662.13 M58 2.67 0.52 0.31 31.64 17.55 0.008 0.708 815 0.35 -5.27 J-12 3 672.43 M58 0.71 0.16 0.12 27.65 15.36 0.006 0.708 323 -0.30 -5.74 J-6 3 562.17 M57 0.70 0.17 0.24 31.76 16.47 0.016 0.709 602 0.17 -6.05 J-6 3 585.07 M58 0.76 0.16 0.14 29.73 16.76 0.008 0.709 476 1.06 -4.12 J-6 3 622.38 M510 1.19 0.21 0.21 33.86 17.21 0.009 0.708 903 0.83 -4.89