鄂尔多斯盆地马岭地区长81储层成岩作用及孔隙度定量演化

鄂尔多斯盆地马岭地区为三角洲前缘沉积,长8_1油层属于低渗透、特低渗透、超低渗透致密砂岩油藏。综合铸体薄片、扫描电镜、物性等试验资料,深化认识马岭地区长8_1成岩作用特征;利用沉积环境、粘土矿物、古地温、R_o、流体包裹体温度等实验结论开展成岩阶段及成岩序列的研究;在成岩作用阶段中,压实和胶结-交代作用降低了部分孔隙度,溶蚀作用产出的次生孔隙是致密储层的高渗通道,在定性认识的同时设立储层孔隙度定量演化计算,实现了孔隙度演化的定量认识,且定量计算与气测孔隙度误差为3. 2%;通过研究4类样品表明,研究区长8_1属于强烈压实型成岩作用,不同成岩阶段孔隙的差异性直接导致了储层物性的好坏。

Diagenesis and quantitative evolution of porosity in the Chang 81 reservoir in the Maling area,Ordos Basin

The Maling area in the Ordos basin is a delta front deposit. The Chang 81 reservoir is characterized by low permeability, extremely low permeability and extremely low permeability tight sandstone. Based on the experimental data of casty thin-section, scanning electron microscopy and physical properties, we further the understanding of the Chang 81 diagenesis characteristics in the Maling area and stud the diagenesis and diagenetic sequences by using the sedimentary environment, paleo-geothermal temperature, Ro, fluid inclusion temperature and clay minerals. Results show that during diagenesis, compaction and cementation-metasomatism reduced part of the porosity. The secondary porosity produced by dissolution is the hyperosmotic channel of tight reservoirs. Calculating quantitative evolution of reservoir porosity permits to further understanding the evolution of porosity,with errors of porosity between the quantitative calculation and the gas measurement as 3.2%. By studying four types of samples, it is suggested that the Chang 81 reservoir in the study area belongs to strong compaction diagenesis with differences of porosity in different diagenetic stages, which directly determined the physical properties of the reservoir.