神木气田太原组气藏开发低效性主控因素

Dominant factors of the low-efficiency development of the gas reservoir in Taiyuan Formation in Shenmu Gasfield

鄂尔多斯盆地东部的神木气田太原组在储层特征上不同于相邻榆林气田山西组,近年来勘探证实其具有良好开发潜力,但已完钻的气井总体呈低产、低效特征,无阻流量主要分布在(2～4)×104m3/d.为实现神木气田的有效规模开发,根据常规薄片、常规物性分析、压汞曲线特征、岩性描述等系列资料从沉积环境、砂体展布特征及储层物性等方面入手,深层次剖析了该区太原组气藏低效性的原因.认为区域上构造运动,生、排烃时间与储层致密化时间不匹配,沉积相主导下的储层非均质性强,砂岩储层岩屑含量高等因素是导致神木气田太原组气藏低效性的主要因素.在此基础上,通过分析有代表性实验样品的核磁共振结果发现:一定情况下岩性与可动流体饱和度之间存在相关关系.提出水平井是该区有效开发手段之一.

The reservoir characteristics of Taiyuan Formation in Shenmu gasfield are different from those of Shanxi Formation in Yulin gasfield.Exploration data show that Taiyuan Formation in Shenmu gasfield is of favorable development potential,but all of the drilled wells have low yield and low development efficiency.Open flow capacity of the wells is in the range of(2~4)×104 m3/d.In order to effectively develop the gas reservoir,the reasons leading to low development efficiency were analyzed in the aspects of depositional environment,sandbody distribution and reservoir property according to conventional thin section,conventional physical property,mercury penetration curve character,core description,etc.It is held that the main reasons are the mismatching between regional tectonic movements with hydrocarbon generation/ expulsion periods,the severe reservoir heterogeneity caused by sedimentary facies and high content of lithic fragment in sandstone reservoir.It is found that there is some direct correlation between lithology of reservoir and pore mobile liquid saturation according to NMR results of some representative samples.Based on the above,it is held that the technique of horizontal well should be one of measures for the effective development of the studied area.