Distribution characteristics of gas and water of tight sandstone gas reservoir in upper Triassic Xujiahe formation of Guang 'an gas field

Key words:  Guang 'an gas field  Xujiahe formation  tight sandstone  identification of gas and water  distribution of gas and water

Abstract:

Using high definition array induction logging (HDIL) data, the gas and water layers in upper Triassic Xujiahe formation of Guang 'an gas field were identified qualitatively, and total water saturation was calculated using the improved Archie equation. The irreducible water saturation was estimated using the matching method of NMR experimental data, and movable water saturation is the difference value of total and irreducible water saturation, which could be used to identify the gas layer and water layer of tight sandstone gas reservoir of Xujiahe formation in Guang 'an gas field quantitatively. Based on the above mentioned logging methods, the distribution characteristics of gas and water were studied. The results show that the tight sandstone gas reservoir in study area is a typical lithologic gas reservoir, and there are multiple gas water systems vertically. Inside the systems, the gas is at top and water is at bottom. Macroscopically, gas layers distribute at the structural high positions, and the gas water layers and water layers distribute at gentle slope. Vertical gas water distribution of T_3x⁶ member is complicated relatively, and the most of water layers in T_3x⁴ member are at the lower part. The macroscopic distribution of gas and water is controlled by sedimentary microfacies and affected by structural relief. The heterogeneity of reservoirs determines the microcosmic distribution characteristics of gas and water. Faults, fractures and abnormal pressure have adjustment action to the distribution of gas and water.