沥青对储层特征的影响及测井定量评价

以塔中志留系塔中11井区为例,通过对沥青砂岩进行洗油盐洗沥青前后物性、压汞、核磁共振配套实验,分析沥青对储层物性、孔隙结构、电性影响及不同离心力核磁共振实验与T_2截止值优选。岩样洗油盐后比洗沥青后孔隙度增加得多,说明孔隙空间中稠油含量高于干沥青含量;干沥青主要分布在大孔喉中,洗沥青后大孔喉分布孔隙结构变好;物性差岩样洗沥青后的导电能力变好,干沥青会导致中低渗透储层电阻率升高。在实际核磁共振资料处理中提出采用变T_2截止值,变T_2截止值是可动流体和束缚流体分界点。沥青砂岩在建模时,应考虑油胶质沥青在粒间孔所占的体积,精确计算沥青含量,有助于准确进行流体性质识别。

Asphalt Influence on Reservoir Characteristics and Quantitative Evaluation

In order to clarify the impact of bitumen on the properties of the reservoir,this paper takes the 11 well area of Silurian in central Tarim basin as an example to analyze the effects of bitumen on reservoir physical properties,pore structure,and electrical properties.In addition, the changes in T2spectrum obtained by NMR experiments under different centrifugal force conditions were also analyzed to optimize the T2cutoff.All of these analyses are based on experimental results from bituminous sandstone before and after washing oil,washing salt,and washing asphalt.It is found the porosity measured after washing oil and salt is bigger than the porosity after washing asphalt,which indicates that the content of heavy oil in pore space is higher than that of dry asphalt.Since the dry asphalt is mainly distributed in large pore throats, the pore structure after asphalt washing becomes better;moreover,the dry asphalt will increase the resistivity of the middle and low permeability reservoirs,but after washing asphalt,the conductivity of the rock samples become better.According to the results of NM R experiments,it is suggested to use varying T2cut-off in actual NM R data processing to determine the volume of the movable fluid volume and the bound fluid volume.In order to accurately calculate the content of bitumen,the volume occupied by the oily gum bitumen in the interparticle pores should be taken into consideration when constructing the model,which will help to identify the fluid prop-erties.