低渗透率气藏岩石电性参数特征及影响因素

On Rock Electrical Parameters Characteristics in Low-permeability Gas Reservoir and Its Influential Factors

低渗透率气藏岩电参数特征与理论值有明显差异,对用测井资料计算含气饱和度有较大影响。通过室内岩电实验,对低渗透率气藏岩石电性参数特征进行研究,并分析了测定过程中的主要影响因素。研究表明,低渗透率气藏岩石电性参数与理论值相比呈现大a小m的趋势;饱和岩心电阻率总体上是随着渗透率的增加而降低的;含水饱和度60%是电阻率指数变化快慢的分界点;当地层水矿化度大于10000 mg/L时,饱和岩心电阻率随地层水矿化度的增加呈指数递减关系;由于饱和不完全造成的孔隙度变化,经过校正后可使a值大约增加14.62%。

The rock characteristics and electrical parameters have a significant difference from the theoretical value in the low-permeability gas reservoir, which brings great impact on calculating gas saturation by log data. Studied are the rock characteristics and electrical parameters in lowpermeability gas reservoir by means of laboratory experiment, and the main influential factors are analyzed. The experiment result shows that： compared with the theoretical value, low-permeability gas reservoir rocks electrical parameters present a trend of bigger a and smaller m. With the core permeability increases, the saturated core electrical resistivity reduces as a whole. It is a cutoff point in the changing velocity of resistivity index when the water saturation reaches 60%. When the formation water salinity is greater than 10 000 mg/L, the saturated core electrical resistivity decreases with the increase of formation water salinity according to an exponential relationship. The partial saturation caused by the porosity changes can make the value of a increases about 14. 62% after adjustment.