六盘山盆地固页1井白垩系马东山组泥页岩储层特征

以六盘山盆地固页1井白垩系马东山组泥页岩为研究对象,通过岩心编录、铸体薄片鉴定、X衍射、扫描电镜及等温吸附等手段,对六盘山盆地固页1井白垩系马东山组泥页岩储层特征进行综合研究。结果表明:马东山组泥页岩具有丰富的岩相组合,包括页岩相、泥质碳酸盐岩相、白云岩相、含碳酸盐质泥岩相、含白云质泥岩相、白云质泥岩相及灰质泥岩相;其中含白云质泥岩相和碳酸盐质泥岩相TOC含量最高。马东山组泥页岩为低孔低渗类储层,其矿物组成以黏土矿物含量低、长石类和碳酸盐类矿物含量高为特征,易于压裂。镜下及扫描电镜观察显示,马东山组泥页岩孔裂隙可概括为顺层分布、网状分布、溶蚀和粒间4种微裂缝与粒间、晶间和溶蚀3种孔隙;其孔隙具有丰富的溶蚀现象,且溶蚀孔多被炭质、方解石、白云石、斜长石、伊利石及石膏等充填,形成丰富的粒间孔、晶间孔、溶蚀孔及晶体间微裂缝;孔隙大小集中分布于2~10μm,个别可达10~33μm。等温吸附表明,马东山组泥页岩最大甲烷吸附能力介于0.96~4.6 m^3/t,均值2.29 m^3/t;Langmuir压力中等偏低,变化范围为1.27~2.21 MPa,平均1.74 MPa,显示马东山组泥页岩具有较强的储气能力。总之,马东山组泥页岩储层孔裂隙发育丰富、泊松比低、脆性好、储气能力好且易于压裂,是良好的页岩油气储层。

Shale Reservoir Characteristics of Cretaceous Madongshan Formation of Well Guye 1 in Liupanshan Basin

Shale samples from the Cretaceous Madongshan Formation (Fm.) (Well Guye 1) in the Liupanshan Basin were used for reservoir characterization via core logging, thin section petrography, X-ray diffraction (XRD), scanning electron microscope (SEM) imaging and isothermal adsorption. The results show a variety of lithologic facies, such as shale, argillaceous carbonates, dolomite, carbonate-/dolomite-bearing or calcareous/dolomitic mudstone. In particular, the carbonate-/dolomite-bearing mudstone have higher TOC contents than the other rock types. The shale reservoir, with characterizing low porosity and low permeability of the Madongshan Fm., have a low clay content and relatively high feldspar and carbonate mineral contents. Optical microscopic and SEM petrographic observations reveal four kinds of microfractures (i.e.stratiform, stockwork, dissolution and intergranular fractures) and three kinds of pores (i.e.intergranular, dissolved and intergranular pores). The dissolved pores are filled by carbonaceous material, calcite, dolomite, plagioclase, illite and gypsum. The pore and fracture sizes vary mainly from 2 to 10 μm, and locally from 10 to 33 μm. Isothermal adsorption shows that CH₄ adsorption capacity of the Madongshan Fm. shale is between 0.96 and 4.6 m ³/t (average 2.29 m³/t). The Langmuir pressure is between 1.27 and 2.21 MPa (average 1.74 MPa). It is suggested that the Madongshan Fm. shale has a strong gas storage capacity but is difficult to be desorbed. To summarize, the Madongshan Fm. shale is a potential good oil and gas reservoir, characterizing by its abundance of pores and fractures, low poisson ratio, high brittleness, relatively good gas storage ability and readiness in development.