致密砂岩气藏储层物性下限及控制因素分析

长庆油田苏里格气田东区盒8、山1 段致密砂岩储层具有典型的低孔–低渗及多层系含气特征。储层下限标准的研究是划分有效储层的基础，砂岩储层的储集性能受控于沉积环境、岩石组成、沉积埋藏史及在埋藏过程中的成岩作用。采用多种方法对该区储层物性下限进行研究，通过产能模拟法验证了物性下限值，探讨了有效储层的控制因素及各因素间的主次关系。结果表明：盒8 砂岩孔隙度下限为5.0%，渗透率下限为0.100 mD，含气饱和度下限为45%。山1 段孔隙度下限为4.0%，渗透率下限为0.075 mD，含气饱和度下限为45%。岩性、沉积微相起主控作用；机械压实作用是造成砂岩孔隙度下降的重要因素；溶蚀、蚀变作用的强弱决定着砂岩储集性能的好坏；砂体厚度对有效性的控制作用较小。

Methods to Determine the Lower Limits and Controlling Factors of the Effective Reservoir of Tight Sand Gas Reservoirs

The tight sand reservoirs of the east of Sulige Area in Changqing Oilfield is typical of relatively lower porosity andmuch lower permeability in gas reservoirs area. Research of lower limit of reservoir set is the base for distinguishing effectivereservoirs from non-effective ones. We have researched the lower limit of reservoir by several methods. The lower limits ofeffective porosity and permeability for reservoirs are determined by productivity simulation technique. On the basis of theresearch，the controlling factors of effective reservoirs are discussed. Our research indicates that the low limit of porosity andpermeability is 4.0%5.0% and 0.0750.100 mD，respectively. And the lower limit of gas saturation is 45%. The property ofreservoirs in east Sulige Gas Field is mainly controlled by lithology and sedimentary microfacies. The mechanical compaction isthe key factor which caused the porosity decreasing. Quality of sandstone reservoirs is controlled by the efficiency of corrosionand alteration. Thickness of sandstone has less influence on the reservoir effectiveness.