川南深层页岩气藏含气量及可压性测井评价方法

Log Evaluation Method for Gas Bearing and Fracability of Deep Shale Gas Reservoirs in Southern Sichuan

川南深层页岩气藏相对于中-浅层页岩气藏具有埋藏深、温度高及压力高的特点,影响了深层页岩气的游离气/吸附气含量占比及地层可压性。深层页岩气藏的游离气/吸附气含量占比增大、地层岩石塑性增加,使得单一页岩脆性指数不能准确表征地层可压性,因此,深层页岩气藏游离气含量的准确评价是深层页岩气藏含气性评价的关键。基于储层孔隙度、泥质含量与TOC多元回归方法下的饱和度计算模型,解决了深层页岩气藏含气性测井评价难题;同时建立基于页岩地层岩石力学脆性与断裂韧性指数结合的深层页岩地层可压性测井评价方法,有效地评价了页岩气藏高温高压下的储层可压性,在川南深层五峰组-龙马溪组页岩气藏测井评价中取得了良好的应用效果。

Compared with the middle shallow shale gas reservoir,the deep shale gas reservoir in southern Sichuan has the characteristics of deep burial depth,high temperature and high pressure.Those affect the free/adsorption ratio of gas content and the formation fracturing ability.The free/adsorption ratio of deep shale gas reservoir increases and the formation rock plasticity increases,which makes the single shale brittleness index unable to accurately characterize the formation fracturing.Therefore,the accurate evaluation of free gas is the key to the gas content evaluation of deep shale gas reservoir.This paper establishes a multiple regression method for saturation calculation based on reservoir porosity,shale content and TOC,which solves the problem of gas bearing log evaluation for deep shale gas reservoirs.At the same time,established the fracturing log evaluation method with the rock mechanical brittleness and fracturing toughness index,the reservoir fracability with deep burial depth,high temperature and pressure is effectively evaluated.It has achieved good application effect in log evaluation of deep shale gas reservoirs for Wufeng and Longmaxi formation in southern Sichuan.