气体钻井气藏CO2体积分数实时监测方法

气体钻井技术因其在保护与发现储层方面的优势，近年来被应用于国内部分深层致密砂岩气藏的勘探开发;但该技术在钻完井工艺上的变化，导致已成熟应用于液基钻井的防气藏CO2气体腐蚀技术无法实施。这就要求须在气体钻井中随钻评价气藏}z的腐蚀能力，以确定合理的完井方式。为此，由De Waard公式得出将气藏CO2体积分数作为辅助评价气藏CO2腐蚀能力的指标。基于物质守恒定律推导出气藏CO2体积分数与注入气体流量、注入气体}z体积分数、返出气体全烃体积分数、返出气体CO2体积分数的关系，通过在井场进口端与出口端合理位置布局传感器，实现相关参数的采集。现场实例应用表明，计算结果与地层产气规律、邻井资料相符，验证了该方法的准确性。

Method for real-time monitoring CO2 volume fraction of gas reservoir while gas drilling

Because of its advantages at protecting and discovering reservoir, the reservoir gas drilling technology has been used in the exploration and development of partly domestic deep tight sandstone gas reservoirs. However, the changes in the drilling and completion process of this technology make many mature means which are applied to the liquid-based drilling to prevent reservoir CO2 corrnsion ean not be implemented, it is necessary to put forward one method to determine reservoir CO2 corrosion capability while gas drilling for determining reasonable completion ways. For this reason, it is derived from the formula of De Waard that the CO2 concentration of the gas reservoir can be used as the main indicator of the evaluation of reservoir CO2 corrosion capability. The relationship among reservoir CO2 concentration, injecting gas flow; injecting gas CO2 concentration, the total hydroearbon concentration and the CO2 concentration of return gas is deduced based on the law of conservation of matter. The relevant parameters are acquired by arrange sensors at the inlet side and outlet side of well site. Finally, an example is applied in field. The calculation results correspond to the laws of formation gas production and the data of adjacent well, which verifies the accuracy of the proposed method.