Author Contributions
Funding acquisition, F.S.; Investigation, W.D., R.L., Y.W., D.Z., Y.C., Z.S. and F.Z.; Methodology, F.S., R.L., Y.W., D.Z., Y.C., Z.S. and F.Z.; Project administration, F.S.; Supervision, W.Y. and X.L.; Writing—original draft, W.D.; Writing—review & editing, W.Y. and X.L. All authors have read and agreed to the published version of the manuscript.
Figure 1.
Tectonic outline map of northern Guizhou Province (modified after [
34]).
Figure 1.
Tectonic outline map of northern Guizhou Province (modified after [
34]).
Figure 2.
Pore extraction software flow.
Figure 2.
Pore extraction software flow.
Figure 3.
Mineral composition characteristics of the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province. (a) Siliceous mineral composition (quartz, plagioclase, and potassium feldspar); (b) calcareous mineral composition (calcite, dolomite, and anhydrite); (c) clay mineral composition (kaolinite, chlorite, illite, and il/montmorillonite mixed layer); (d) total mineral composition (siliceous minerals, calcium minerals, and clay minerals).
Figure 3.
Mineral composition characteristics of the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province. (a) Siliceous mineral composition (quartz, plagioclase, and potassium feldspar); (b) calcareous mineral composition (calcite, dolomite, and anhydrite); (c) clay mineral composition (kaolinite, chlorite, illite, and il/montmorillonite mixed layer); (d) total mineral composition (siliceous minerals, calcium minerals, and clay minerals).
Figure 4.
Lithofacies distribution characteristics of samples between the Wufeng-Longmaxi Formation and the Niutitang Formation in northern Guizhou Province [
41].
Figure 4.
Lithofacies distribution characteristics of samples between the Wufeng-Longmaxi Formation and the Niutitang Formation in northern Guizhou Province [
41].
Figure 5.
Scanning electron microscopy characteristics of pores in shales of the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province. (A,B,G) Intergranular microfractures of clay minerals, (C) calcite dissolution pores, (D) intergranular pores of mylonitic mineral grains, (E) intergranular pores of clay minerals partially filled with pyrite, (F) intergranular pores of clay minerals, (H) organic matter filled with pyrite, (I) intergranular pores plugged by organic matter and mud, (J) organic matter pores developed within organic matter, (K) organic matter uniformly distributed in intergranular micropores, and (L) feldspar particles surrounded by barite.
Figure 5.
Scanning electron microscopy characteristics of pores in shales of the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province. (A,B,G) Intergranular microfractures of clay minerals, (C) calcite dissolution pores, (D) intergranular pores of mylonitic mineral grains, (E) intergranular pores of clay minerals partially filled with pyrite, (F) intergranular pores of clay minerals, (H) organic matter filled with pyrite, (I) intergranular pores plugged by organic matter and mud, (J) organic matter pores developed within organic matter, (K) organic matter uniformly distributed in intergranular micropores, and (L) feldspar particles surrounded by barite.
Figure 6.
Capillary pressure curves of the Wufeng-Longmaxi Formation and Niutitang Formation shales in northern Guizhou Province based on high-pressure mercury intrusion.
Figure 6.
Capillary pressure curves of the Wufeng-Longmaxi Formation and Niutitang Formation shales in northern Guizhou Province based on high-pressure mercury intrusion.
Figure 7.
Nitrogen adsorption–desorption curves for the Wufeng-Longmaxi and Niutitang Formation shales in northern Guizhou Province.
Figure 7.
Nitrogen adsorption–desorption curves for the Wufeng-Longmaxi and Niutitang Formation shales in northern Guizhou Province.
Figure 8.
Organic matter pores in the shales of the Wufeng-Longmaxi Formation and Niutitang Formation in northern Guizhou Province. (a) DY1-S86 of the Wufeng-Longmaxi Formation; (b) ZY1-S39 of the Niutitang Formation; (c) ZY1-S74 of the Niutitang Formation; (d) DY1-S86 organic matter pore extraction of the Wufeng-Longmaxi Formation; (e) ZY1-S39 organic matter pore extraction of the Niutitang Formation; (f) ZY1-S74 organic matter pore extraction of the Niutitang Formation.
Figure 8.
Organic matter pores in the shales of the Wufeng-Longmaxi Formation and Niutitang Formation in northern Guizhou Province. (a) DY1-S86 of the Wufeng-Longmaxi Formation; (b) ZY1-S39 of the Niutitang Formation; (c) ZY1-S74 of the Niutitang Formation; (d) DY1-S86 organic matter pore extraction of the Wufeng-Longmaxi Formation; (e) ZY1-S39 organic matter pore extraction of the Niutitang Formation; (f) ZY1-S74 organic matter pore extraction of the Niutitang Formation.
Figure 9.
Extraction of pore features from shales of the Wufeng-Longmaxi and Niutitang Formations in Guizhou Province. (a–c) The original images of intergranular pores corresponding to “a’ to c’”; (a’–c’) Extraction of intergranular pore features, (d,e) The original images of intergranular microfractures corresponding to “d’ to e’”; (d’,e’) extraction of intergranular microfracture features; (f) The original images of dissolution pores corresponding to “f’’; (f’) extraction of dissolution pore features.
Figure 9.
Extraction of pore features from shales of the Wufeng-Longmaxi and Niutitang Formations in Guizhou Province. (a–c) The original images of intergranular pores corresponding to “a’ to c’”; (a’–c’) Extraction of intergranular pore features, (d,e) The original images of intergranular microfractures corresponding to “d’ to e’”; (d’,e’) extraction of intergranular microfracture features; (f) The original images of dissolution pores corresponding to “f’’; (f’) extraction of dissolution pore features.
Figure 10.
Microfractures in shale reservoirs of the Wufeng-Longmaxi Formation and Niutitang Formation in northern Guizhou Province. (a) DY1-S77 microfracture; (b) ZY1-S87 microfracture.
Figure 10.
Microfractures in shale reservoirs of the Wufeng-Longmaxi Formation and Niutitang Formation in northern Guizhou Province. (a) DY1-S77 microfracture; (b) ZY1-S87 microfracture.
Figure 11.
Multi-scale pore size distribution curves from the Wufeng-Longmaxi and Niutitang Formations. (a) Pore size distribution calculated by high pressure mercury; (b) Pore size distribution calculated by low temperature nitrogen adsorption.
Figure 11.
Multi-scale pore size distribution curves from the Wufeng-Longmaxi and Niutitang Formations. (a) Pore size distribution calculated by high pressure mercury; (b) Pore size distribution calculated by low temperature nitrogen adsorption.
Figure 12.
Correlation between Ro, clay content, TOC, and pore structure parameters. (a) Correlation map between Ro and Plane porosity of Wufeng-Longmaxi and Niutitang Formations; (b) Correlation map between Clay content and Plane porosity of Wufeng-Longmaxi and Niutitang Formations; (c) Correlation map between TOC and Plane porosity of Wufeng-Longmaxi and Niutitang Formations; (d) Correlation map between TOC and Mesoporous surface area of Wufeng-Longmaxi and Niutitang Formations.
Figure 12.
Correlation between Ro, clay content, TOC, and pore structure parameters. (a) Correlation map between Ro and Plane porosity of Wufeng-Longmaxi and Niutitang Formations; (b) Correlation map between Clay content and Plane porosity of Wufeng-Longmaxi and Niutitang Formations; (c) Correlation map between TOC and Plane porosity of Wufeng-Longmaxi and Niutitang Formations; (d) Correlation map between TOC and Mesoporous surface area of Wufeng-Longmaxi and Niutitang Formations.
Figure 13.
Relationship between tectonic preservation parameters and pore structure of the Wufeng-Longmaxi Formation and the Niutitang Formation in northern Guizhou Province (The blue bars represent the Wufeng-Longmaxi Formation, and the red bar represent the Niutitang Formation).
Figure 13.
Relationship between tectonic preservation parameters and pore structure of the Wufeng-Longmaxi Formation and the Niutitang Formation in northern Guizhou Province (The blue bars represent the Wufeng-Longmaxi Formation, and the red bar represent the Niutitang Formation).
Figure 14.
Proposed conceptual model for elaborating differential reservoir-forming mechanisms for the Lower Paleozoic Wufeng-Longmaxi and Niutitang Formations. (a) Wufeng-Longmaxi Formation; (b) Niutitang Formation.
Figure 14.
Proposed conceptual model for elaborating differential reservoir-forming mechanisms for the Lower Paleozoic Wufeng-Longmaxi and Niutitang Formations. (a) Wufeng-Longmaxi Formation; (b) Niutitang Formation.
Table 1.
Ro and TOC of the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Table 1.
Ro and TOC of the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Well | Formation | Sample ID | Depth/m | Ro/wt% | TOC/wt% |
---|
DY-1 | Wufeng-Longmaxi | DY1-S11 | 381.26 | 0.90 | 0.23 |
DY1-S41 | 521.11 | 1.56 | 0.54 |
DY1-S61 | 564.3 | 1.68 | 0.86 |
DY1-S66 | 570.5 | 1.66 | 1.50 |
DY1-S71 | 573.5 | 1.65 | 3.17 |
DY1-18 | 576.56 | 3.20 | 3.19 |
DY1-S77 | 577.7 | 1.86 | 2.60 |
DY1-S82 | 580.7 | 1.77 | 2.76 |
DY1-S86 | 583.1 | 1.95 | 3.78 |
DY1-S91 | 586.1 | 2.04 | 3.44 |
DY1-S95 | 588.8 | 2.18 | 4.11 |
DY1-S106 | 597.15 | 1.83 | 3.92 |
ZY-1 | Niutitang | ZY1-S37 | 970.675 | 2.50 | 6.55 |
ZY1-S43 | 978.02 | 2.52 | 6.20 |
ZY1-S53 | 984.905 | 3.25 | 6.41 |
ZY1-S73 | 999.25 | 2.51 | 4.65 |
Q130114 | 1006.16 | 2.19 | 5.36 |
Q130116 | 1010.05 | 2.04 | 7.70 |
Q130117 | 1010.71 | 2.58 | 9.55 |
Q130118 | 1011.51 | 2.45 | 8.09 |
Q130119 | 1013.91 | 2.82 | 7.95 |
Q130120 | 1018.35 | 2.37 | 8.62 |
Q130123 | 1022.01 | 2.64 | 19.29 |
Q130124 | 1022.71 | 3.40 | 12.22 |
Table 2.
Kerogen microscopy in the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Table 2.
Kerogen microscopy in the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Well | Sample ID | Formation | Depth/m | Sapropel Group/wt% | Vitrinite/wt% | Inert Mass Group/wt% | Type |
---|
Type Index | Type |
---|
DY-1 | DQ1 1-1 | Wufeng-Longmaxi | / | 12 | 3 | / | 52 | II1 |
DQ1 2-1 | / | 10 | 2 | / | 53 | II1 |
DQ1 3-1 | / | 16 | 1 | / | 57 | II1 |
DQ1 4-1 | / | 9 | 2 | / | 52 | II1 |
DQ1 5-1 | / | 6 | 5 | / | 47 | II1 |
DQ1 6-1 | / | 10 | 3 | / | 51 | II1 |
ZY-1 | ZY1 1-1 | Niutitang | / | 98 | 2 | / | 96.5 | I |
ZY1 2-1 | / | 99 | 1 | / | 98.25 | I |
ZY1 3-1 | / | 98 | 0 | 2 | 96 | I |
ZY1 4-1 | / | 97 | 3 | / | 94.75 | I |
ZY1 5-1 | / | 99 | 1 | / | 98.25 | I |
ZY1 6-1 | / | 97 | 3 | / | 94.75 | I |
ZY1 7-1 | / | 96 | 4 | / | 93 | I |
ZY1 8-1 | / | 99 | 1 | / | 98.25 | I |
ZY1 9-1 | / | 99 | 0 | 1 | 98 | I |
ZY1 10-1 | / | 97 | 1 | 2 | 94.25 | I |
ZY1 11-1 | / | 99 | 1 | / | 98.25 | I |
ZY1 12-1 | / | 98 | 1 | 1 | 96.25 | I |
Table 3.
Mineral compositions and contents of the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Table 3.
Mineral compositions and contents of the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Well | Sample ID | Formation | Depth/m | Quartz/wt% | Potassium Feldspar/wt% | Plagioclase/wt% | Calcite/wt% | Dolomite/wt% | Pyrite/wt% | Anhydrite/wt% | Thenardite/wt% | Clay Minerals/wt% |
---|
DY-1 | DY1-S11 | Wufeng-Longmaxi | 381.26 | 40 | 0 | 14 | 5 | 0 | 0 | 0 | 6 | 35 |
DY1-S21 | 469.365 | 35 | 0 | 13 | 14 | 6 | 0 | 0 | 0 | 32 |
DY1-S31 | 504.45 | 32 | 3 | 12 | 16 | 4 | 0 | 0 | 0 | 33 |
DY1-S41 | 521.11 | 34 | 5 | 11 | 8 | 4 | 3 | 4 | 0 | 31 |
DY1-S47 | 534.89 | 36 | 4 | 19 | 11 | 8 | 3 | 0 | 0 | 19 |
DY1-S53 | 546.6 | 40 | 0 | 15 | 8 | 5 | 0 | 0 | 0 | 32 |
DY1-S57 | 555.64 | 39 | 5 | 14 | 7 | 5 | 0 | 0 | 0 | 30 |
DY1-10 | 560.585 | 42 | 4 | 13 | 6 | 4 | 0 | 0 | 0 | 31 |
DY1-S61 | 564.3 | 44 | 4 | 14 | 8 | 6 | 0 | 0 | 0 | 24 |
DY1-S66 | 570.5 | 45 | 6 | 21 | 5 | 3 | 0 | 0 | 0 | 20 |
DY1-S71 | 573.5 | 48 | 3 | 9 | 6 | 7 | 5 | 0 | 0 | 22 |
DY1-18 | 576.625 | 44 | 3 | 11 | 7 | 5 | 5 | 0 | 0 | 25 |
DY1-S77 | 577.7 | 50 | 4 | 13 | 7 | 7 | 4 | 0 | 0 | 15 |
DY1-S82 | 580.7 | 42 | 3 | 10 | 7 | 4 | 7 | 0 | 0 | 27 |
DY1-S86 | 583.1 | 48 | 4 | 12 | 3 | 3 | 8 | 0 | 0 | 22 |
DY1-S91 | 586.1 | 63 | 4 | 10 | 2 | 2 | 4 | 0 | 0 | 15 |
DY1-24 | 588.365 | 39 | 5 | 14 | 2 | 14 | 5 | 0 | 0 | 21 |
DY1-S95 | 588.8 | 42 | 7 | 18 | 3 | 7 | 6 | 0 | 0 | 17 |
DY1-S99-1 | 591.9 | 76 | 2 | 6 | 4 | 2 | 0 | 0 | 0 | 10 |
DY1-S103 | 594.775 | 55 | 4 | 10 | 2 | 6 | 0 | 0 | 0 | 23 |
DY1-S106 | 597.15 | 41 | 5 | 16 | 3 | 5 | 0 | 0 | 0 | 30 |
ZY-1 | ZY1-1 | Niutitang | 946.38 | 47 | 0 | 23 | 2 | 0 | 0 | 0 | 0 | 28 |
ZY1-5 | 960.43 | 31 | 0 | 21 | 2 | 25 | 4 | 0 | 0 | 17 |
ZY1-11 | 969.50 | 36 | 0 | 31 | 6 | 5 | 9 | 0 | 0 | 13 |
ZY1-13 | 974.30 | 42 | 11 | 18 | 5 | 4 | 5 | 4 | 0 | 11 |
ZY1-16 | 978.20 | 38 | 11 | 24 | 5 | 0 | 5 | 4 | 0 | 13 |
ZY1-17 | 979.30 | 42 | 10 | 17 | 5 | 0 | 6 | 4 | 0 | 16 |
ZY1-19 | 981.50 | 48 | 9 | 17 | 3 | 3 | 5 | 0 | 0 | 15 |
ZY1-23 | 984.50 | 61 | 9 | 20 | 3 | 2 | 5 | 0 | 0 | 0 |
ZY1-27 | 990.43 | 44 | 7 | 23 | 8 | 2 | 7 | 0 | 0 | 9 |
ZY1-S69 | 996.15 | 33 | 13 | 31 | 4 | 3 | 6 | 0 | 0 | 10 |
ZY1-34 | 1000.20 | 45 | 10 | 21 | 3 | 0 | 4 | 3 | 0 | 14 |
Table 4.
Marine shale lithofacies division scheme.
Table 4.
Marine shale lithofacies division scheme.
Lithofacies Types | Mass Fraction of Mineral Components/wt% |
---|
Siliceous | Calcium | Clay |
---|
Siliceous shale facies | 50~75 | <30 | 10~50 |
Clayey shale facies | 25~50 | <30 | 50~75 |
Calcareous shale facies | <30 | 50~75 | 25~50 |
Mixed clayey–siliceous shale facies | 30~50 | <33 | 30~50 |
Mixed clayey–calcareous shale facies | <33 | 30~50 | 30~50 |
Mixed calcareous–siliceous shale facies | 30~50 | 30~50 | <33 |
Table 5.
Pore structure parameters of shale in the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province based on the high-pressure mercury intrusion method.
Table 5.
Pore structure parameters of shale in the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province based on the high-pressure mercury intrusion method.
Well | Sample ID | Formation | Depth/m | Pore Volume/cm3 | Specific Surface Area/(m2/g) | Hg Porosity/% | Average Throat Radius/μm |
---|
DY-1 | DY1-2 | Wufeng-Longmaxi | 545.99 | 0.08 | 9.69 | 1.71 | 21.04 |
DY1-6 | 554.84 | 0.17 | 190.96 | 1.46 | 22.40 |
DY1-9 | 559.51 | 0.15 | 58.51 | 1.18 | 20.45 |
DY1-16 | 572.15 | 0.1 | 4.51 | 0.84 | 25.38 |
DY1-23 | 586.15 | 0.15 | 157.46 | 1.27 | 27.24 |
ZY-1 | ZY1-4 | Niutitang | 958.25 | 0.05 | 330.80 | 1.48 | 0.03 |
ZY1-13 | 974.30 | 0.07 | 856.26 | 0.48 | 6.91 |
ZY1-25 | 987.30 | 0.14 | 3498.24 | 1.16 | 15.90 |
ZY1-36 | 1002.73 | 0.05 | 864.45 | 0.56 | 0.01 |
Table 6.
Pore structure parameters of shale in the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province based on the N2 adsorption method.
Table 6.
Pore structure parameters of shale in the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province based on the N2 adsorption method.
Well | Sample ID | Formation | Depth/m | Specific Surface Area/(m2/g) | Pore Volume/(mL/g) | Average Pore Diameter/nm |
---|
DY-1 | DY1-S61 | Wufeng-Longmaxi | 564.300 | 15.237 | 0.014 | 3.623 |
DY1-S71 | 573.500 | 13.083 | 0.015 | 3.824 |
DY1-18 | 576.630 | 14.931 | 0.035 | 3.773 |
DY1-S77 | 577.700 | 13.678 | 0.016 | 3.811 |
DY1-S82 | 580.700 | 14.172 | 0.017 | 4.683 |
DY1-S106 | 597.150 | 9.968 | 0.013 | 3.811 |
ZY-1 | ZY1-11 | Niutitang | 969.500 | 3.357 | 0.030 | 6.282 |
ZY1-S37 | 970.675 | 7.769 | 0.009 | 3.731 |
ZY1-17 | 979.300 | 6.260 | 0.019 | 3.702 |
ZY1-S53 | 984.905 | 8.608 | 0.008 | 3.589 |
ZY1-S73 | 999.250 | 12.970 | 0.012 | 3.733 |
Table 7.
The gas content of shale reservoirs in the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Table 7.
The gas content of shale reservoirs in the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Well | Formation | Depth/m | Gas Content/(m3/t) |
---|
DY-1 | Wufeng-Longmaxi | 553.56 | 1.84 |
559.20 | 0.04 |
580.90 | 0.07 |
589.90 | 2.20 |
592.70 | 2.69 |
595.80 | 2.03 |
ZY-1 | Niutitang | 1003.31 | 1.36 |
1006.16 | 1.28 |
1008.05 | 1.20 |
1010.05 | 1.18 |
1010.71 | 1.09 |
1011.51 | 1.37 |
1013.91 | 0.90 |
1018.35 | 0.97 |
1018.89 | 2.05 |
1020.34 | 1.11 |
1022.01 | 1.56 |
1022.71 | 1.30 |
Table 8.
Gas components of the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Table 8.
Gas components of the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Well | Formation | Depth/m | CH4/vol | N2/vol | O2/vol | CO2/vol | C2H6/vol | C3H8/vol | H2/vol |
---|
DY-1 | Wufeng-Longmaxi | 589.90 | 78.36 | 15.97 | 4.37 | 0.87 | 0.43 | 0 | - |
592.70 | 88.91 | 7.56 | 2.39 | 0.68 | 0.46 | 0 | - |
595.80 | 47.22 | 40.01 | 10.18 | 1.04 | 1.55 | 0 | - |
ZY-1 | Niutitang | 1011.51 | 5.27 | 57.32 | 0.00 | 0.43 | 0.01 | 0.00 | 36.98 |
1022.71 | 8.09 | 65.42 | 0.00 | 1.77 | 0.01 | 0.00 | 24.70 |
Table 9.
Organic matter pore morphology parameters of shale in the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Table 9.
Organic matter pore morphology parameters of shale in the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Sample ID | Formation | Depth/m | Plane Porosity | Pore Diametermax/nm | Pore Diametermin/nm | Pore Diameter AVG/nm | Roundness | Convex Degree | Elongation | Fractal Dimension |
---|
DY1-S86 | Wufeng-Longmaxi | 583.1 | 0.026 | 85.559 | 74.188 | 79.873 | 5.007 | 15.941 | 1.554 | 1.151 |
ZY1-S39 | Niutitang | 974.64 | 0.007 | 168.873 | 115.138 | 142.006 | 7.298 | 19.030 | 2.057 | 1.184 |
ZY1-S74 | Niutitang | 1000.05 | 0.011 | 227.897 | 157.464 | 192.681 | 8.747 | 46.964 | 1.778 | 1.199 |
Table 10.
The plane porosity of the intergranular pores in the Wufeng-Longmaxi Formation and Niutitang Formation.
Table 10.
The plane porosity of the intergranular pores in the Wufeng-Longmaxi Formation and Niutitang Formation.
Well | Sample ID | Formation | Depth/m | Plane Porosity/% |
---|
DY-1 | DY1-S61 | Wufeng-Longmaxi | 564.3 | 4.10 |
| DY1-S71 | | 573.5 | 7.10 |
| DY1-18 | | 576.63 | 6.70 |
DY1-S77 | 577.7 | 9.30 |
DY1-S82 | 580.7 | 7.20 |
ZY-1 | ZY1-S21 | Niutitang | 954.665 | 6.80 |
ZY1-S29 | 964.07 | 3.04 |
ZY1-S36 | 969.965 | 3.70 |
ZY1-S53 | 984.905 | 5.90 |
ZY1-S62 | 992.45 | 6.40 |
ZY1-S73 | 999.25 | 3.80 |
Table 11.
Comprehensive evaluation of the tectonic preservation conditions of the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Table 11.
Comprehensive evaluation of the tectonic preservation conditions of the Wufeng-Longmaxi and Niutitang Formations in northern Guizhou Province.
Evaluation Parameters | Daozhen Syncline | Xieba Anticlinorium |
---|
Target Stratum | Wufeng-Longmaxi Formation | Niutitang Formation |
---|
Cover thickness | 220 | 135 |
High-quality shale thickness/m | 28 | 8 |
Number of natural fractures | 6 | 25 |
Stratum dip/° | 19.5 | 65 |
Average depth/m | 2800 | 650 |
Formation breakthrough pressure/MPa | 20.4 | 19.5 |
Fractures | Undeveloped | Well developed |
Fold | NE, NNE | NE, NNE |
Denudation degree | Weak | Intense |
Comprehensive evaluation | Good | Poor |