陕北地区延长组长6段高伽马砂岩储层参数确定方法

陕北地区三叠系延长组长6段是石油勘探开发的重要层位,该段普遍发育高自然伽马砂岩,该类储层与常规储层测井响应特征不同,给长6段储层物性参数及含水饱和度测井计算带来一定的难度。在高伽马储层与邻近常规储层测井特征对比分析基础上,建立了陕北地区延长组长6段高伽马储层孔隙度、渗透率、泥质含量计算公式,并进一步讨论了该类储层在平面上的含油性。高伽马储层岩心分析饱和度与邻近常规储层相差不明显,但是,由于高伽马储层电阻率数值下降明显,造成高伽马储层与邻近常规储层利用测井资料计算出来的含水饱和度相差较大,因此对高伽马储层饱和度计算公式进行了修正。在储层分类基础上,分析认为影响陕北地区长6段储层饱和度测井计算的主要因素是高伽马储层电阻率和孔隙度变化,并进一步建立了该地区长6段复杂储层含水饱和度计算公式。

Determination of High Gamma Sandstone Reservoir Parameters for 6th Member of Yangchang Formation in North Shaanxi

The 6th member of Yanchang Formation of Jurassic System in the northern region of Shaanxi is an important layer for oil exploration and development. High natural gamma sandstone is widespread in this layer. Such reservoir is different from conventional one in terms of logging response characteristics, thus causing some difficulties for calculation of physical property parameters and water saturation logging for the 6th member of the formation. Based on comparison and analysis of logging characteristics between the high gamma reservoir and its neighbor conventional reservoir, the formula is established to calculate porosity, permeability and mud content for the 6th member of Yangchang Formation. This paper also further discusses the horizontally oil-beating property of such reservoir. High gamma reservoir is nor obviously different from its neighboring conventional reservoir in terms of core analysis of saturation. However, high gamma reservoir is quite different from its neighboring conventional well in terms of water saturation calculated by using logging data, because the resistivity value of high gamma reservoir decreases significantly. Therefore, the saturation calculation formula of high gamma reservoir is revised. Based on classification of reservoirs, this paper regards changes of resistivity and porosity of high gamma reservoir as the main factor to affect saturation calculation of the 6th member of Yanchang Formation in the northern region of Shaanxi. The formula is further perfected for saturation calculation of the complicated 6th member of Yanchang Formation in this region.