The Background Value Of Abnormal Mechanism Of Carbon Dioxide In Drilling Conditions

It is found that there is no CO₂ gas when gas measuring CO₂ in high anomaly Hole in oil and gas exploration of Hailar Basin in some wells;Also there is a large number of CO₂ gas in low abnormal or not abnormal Hole in the gas test. This phenomenon can also be found in some other oil fields in China. The purpose of this study tries to explore the causes of this phenomenon.There is more or less CO₂ found in the Hailar Basin strata through the formation water analysis. Degassing reservoir rock analysis shows that there is generally higher CO₂ concentration in CO₂ gas output extrusion gas reservoir rocks. Four kinds of Degassing of drilling fluid commonly show that CO₂ content of gas drilling get out of prolapse than those in saline high levels of gas in the CO₂. And the gas CO₂ content of oil-based drilling fluids reaching 19.9% shows that drilling could have an impact on CO₂ gas.Also we have some closed heating experiments on the mixture of drilling fluid and different reservoir rock . The results show that under the condition of 100℃, there is basically non-gas output, and under the condition of 150℃there is gas output, in which the content of CO₂ and N₂ gas is associate with the type of drilling fluid. In most cases under the conditions of formation temperature drilling fluids does not produce CO₂ reactting with the rock. According to this article and others integrated research results we consider that the main reason of abnormal test in gas-oil-free gas production should be that the reservoir have low gas-bearing. And the reason why no abnormal test oil gas measuring a large number of CO₂ production is that mainly due to the impact of drilling.