Comparative Study on the Reservoir Characteristics and Development Technologies of Two Typical Karst Weathering-Crust Carbonate Gas Reservoirs in China

Table 1

Basic information of the Lower Paleozoic gas reservoir in the Jingbian gas field and the Sinian gas reservoir in Gaomo area.

Parameters	Gas reservoir
	Lower Paleozoic reservoir in the Jingbian gas field	Sinian reservoir in the Anyue gas field
Geographical location	Across Shanxi and Inner Mongolia	Suining and Ziyang in Sichuan and Tongnan in Chongqing
Basin	Ordos Basin	Sichuan Basin
Position for geological structures	Shanbei slope	Leshan-Longnvsi paleouplift
Time of discovery	1989	2010
Burial depth (m)	300~3765	4953~5535
Target formation	Ordovician Ma-51	Sinian Deng-4 and Deng-2
Reservoir rock type	Dolomite reservoir with dissolved pores and vugs	Fractured-vuggy dolomite reservoir
Gas reservoir type	Composite stratigraphic-lithologic trap	Composite stratigraphic-lithologic trap
Cumulative gas-bearing layer average thickness (m)	8.4	63
Average porosity (%)	5.47	3.3
Average permeability (10^-3 μm^2)	2.63	0.5
Gas-bearing area (km^2)	9640	1085
Proven GIIP (10^8 m^3)	5477	4084
Reserve abundance (10^8 m^3/km^2)	0.5682	3.12
Quantity of completed wells	736	67
Average daily gas production per well (10^4 m^3)	3.26	17.3
Relative density of natural gas	0.59~0.63	0.59~0.64
Average CH4 content (%)	93.42	91.98
Average CO2 content (%)	5.12	5.77
Average H2Scontent (/m^3)	1489.57	1.24%
Formation water type	CaCl2-type	CaCl2-type
Average formation pressure (MPa)	30.24	59.65
Average formation pressure coefficient	0.91	1.13
Average temperature (°C)	105.85	153.55
Average geothermal gradient (°C/100 m)	3.05	2.6