Analyzing the Origin of Low Resistivity in Gas-Bearing Tight Sandstone Reservoir

Table 4

Field fast water analysis data of X-A-3.

Sample sequence	Unit	Mud filtrate	3882.0 m sample	3902.3 m sample	3913.5 m sample
Sample depth	m	—	3882	3902.3	3913.5
Pumping time	min	—	315	570	735
Total anion	mg/L	59964	45957	44977	45163
Total cation	mg/L	56760	45471	39571	38576
Total salinity	mg/L	116724	91428	84548	83158
Na^+/K^+ ratio	—	1.58	1.57	1.36	1.41