特低渗储层微观孔隙结构与可动流体赋存特征--以二连盆地阿尔凹陷腾一下段储层为例

Characteristics of micro pore structure and movable fluid of extra-low permeability reservoir:a case study of lower Et1 reservoir in A'er Sag,Erlian Basin

为了明确二连盆地阿尔凹陷腾格尔组腾一下段储层微观孔隙结构和可动流体赋存特征,开展了扫描电镜、铸体薄片、X射线衍射、高压压汞、恒速压汞和核磁共振等实验研究。结果表明:①腾一下段储层微观孔隙结构分为3种类型,不同孔隙结构具有不同的可动流体赋存特征。②Ⅰ类大孔喉结构,孔喉组合主要为粒间孔-孔隙缩小型喉道和粒间孔-缩颈型喉道,喉道半径大,孔喉半径比小,核磁共振T2谱主要为左低右高双峰型,可动流体饱和度高;Ⅱ类孔隙结构,主要为粒间孔-片状喉道组合与溶蚀孔-片状喉道组合,T2谱主要为左高右低双峰型,可动流体饱和度中等;Ⅲ类孔隙结构,主要为粒间孔-片状喉道组合、溶蚀孔-片状喉道组合和晶间孔-管束状喉道组合,喉道半径小,T2谱为左单峰型,可动流体饱和度低。③储层物性、微观孔隙结构、黏土矿物含量对可动流体赋存具有重要影响,其中喉道特征是影响可动流体赋存的最主要因素,喉道半径越大,大喉道越多,可动流体饱和度越高。该研究成果对阿尔凹陷腾一下段储层的高效开发具有指导意义。

In order to make clear the micro pore structure and the occurrence characteristics of movable fluid of the lower Et1 reservoir in A'er Sag,Erlian Basin,the experimental studies such as SEM,casting slice,X-ray diffraction,high pressure mercury injection,constant velocity mercury injection and NMR were carried out.The results show that:(1)There are three types of micro pore structure of the lower Et1 reservoir,and different pore structures have different characteristics of occurrence of movable fluid.(2)The pore structure of typeⅠis mainly composed of intergranular pore-pore shrinking throat and intergranular pore-necking throat,with large throat radius and small pore throat radius ratio.Its T2 spectrum of NMR is mainly left low right high bimodal type,and movable fluid saturation is high.The pore structure of typeⅡis mainly composed of intergranular pore-flaky throat and dissolved pore-flaky throat,and its T2 spectrum is mainly left high right low bimodal type,with medium movable fluid saturation.The pore structure of typeⅢis mainly composed of intergranular pore-flaky throat combination,dissolved pore-flaky throat combination and intercrystalline pore-bundle throat combination.The throat radius of typeⅢis small,with T2 spectrum of left single peak type and low movable fluid saturation.(3)The physical properties,micro pore structure and clay mineral content of the reservoir have an important influence on the occurrence of movable fluid.The characteristics of throat are the main factors affecting the occurrence of movable fluid.The larger the throat radius is,the more the large throat is,the higher the saturation of movable fluid is.The research results have guiding significance for the high-efficiency development of lower Et1 reservoir in A'er Sag.