延川南区块致密砂岩气测井识别与评价技术

Logging identification and evaluation of tight sandstone gas in the southern Yanchuan block

致密砂岩气储层具有孔隙度较低、渗透性较差、孔隙结构复杂、非均质性较强等特征,地层骨架对测井信息的影响远大于孔隙流体的影响,基于体积模型的中—高孔渗储层参数评价方法不适用于该类储层。为有效评价鄂尔多斯盆地东南缘延川南区块的致密砂岩气,优选了2种基于常规测井资料的视弹性模量系数法和三孔隙度比值法气层识别方法,两者结合能有效识别气层;根据储层特征与岩-电响应关系分析,应用密度-中子加权平均法、粒度中值回归法及变岩-电参数的Archie公式计算致密砂岩储层的孔隙度、渗透率、饱和度,实现了延川南区块致密砂岩气储层参数的高精度定量评价。该方法也适用于其他地区致密砂岩气储层参数的评价。

The tight sandstone gas reservoir has the characteristics of low porosity and low permeability, complex pore structure and strong heterogeneity, which makes the reservoir evaluation difficult. The conventional methods based on volume model in medium-high porosity and permeability reservoir is not suitable for this kind of reservoir due to much more contribution of sandstone framework to logging. Two methods of gas-bearing iden- tification were optimized based on conventional loggings： apparent elastic modulus coefficient method and three porosity ratio method. The combination of the two methods can effectively identify gas layers. According to reser- voir characteristics and relationship analysis of rock electricity and response, the porosity, permeability and satu- ration of tight sandstone reservoir were calculated by using neutron-density weighted average, median grain size linear regression and parameter variable Archie＇ s equation methods, completing the high precision quantitative evaluation of tight sandstone gas reservoir in the southern Yanchuan block. These methods are also applicable to evaluate tight sandstone gas reservoir in other area.