基于高温高压电性实验的压溶气藏总含气量评价方法OA

Overpressure-dissolved gas,as a novel resource primarily composed of dispersed free gas and saturated dissolved gas,is widely distributed in the Yinggehai and Qiongdongnan basins with significant resource potential.However,existing petrophysical experiments and logging evaluation models don't take into account the influence of dissolved gas on formation water and rock resistivity under high temperature and high pressure,and the quantitative evaluation methods for gas contents are insufficient.In this study,a petrophysical experimental platform was constructed for overpressure-dissolved gas.Electrical experiments were conducted on formation water containing dissolved gas and cores containing overpressure-dissolved gas to analyze the effects of different occurrence states and methane contents on the resistivity of formation water and cores.Thus,an evaluation method for total gas content was established.The following results are obtained.First,formation water resistivity increases exponentially with the increase of dissolved methane.Second,an empirical expression for formation water resistivity and dissolved methane under arbitrary temperature,pressure and formation water salinity are innovatively established based on the electrical experimental results.Third,a relationship model between rock resistivity and gas abundance is established by employing gas abundance to represent total content of dissolved gas and free gas in rocks,and introducing the newly built expression of formation water resistivity into the classical electrical model of gas saturation.This model can be used to calculate the total gas content of overpressure-dissolved gas reservoir.Fourth,the model verification indicates that the maximum relative error of calculated gas abundance to core experimental result is≤10%,confirming that the method is valid and reliable.The proposed method provides a key technical support for resource evaluation of overpressure-dissolved gas reservoirs,and assists the exploration and development progress of such gas resources.