During the formation of oil-gas and migration process, some soluble trace elements in the sedimentary organic matter will be separated and dissolved in the associated water. Some soluble trace elements in oilfield water and crude oil will dissolve in water and migrate with water to the near-surface place. Through analyzing variation of soluble anions in near-surface soil, we can track the oil-gas information underlying strata. A study of variation of near-surface soluble anions in the Xinchang gas field, Changde gas field and Pingfangwang oil field show that soluble anions in oilfield water mainly migrate in the form of water carriers, the upward migration passage of oilfield water determines the anomaly shape and pattern at the top of oil and gas reservoirs, and soluble anions have a certain indicating significance for oil and gas reservoirs in the underlying strata.