Anisotropy is an inherent property of the formation. In highly deviated wells and horizontal wells, the anisotropy coefficient can be calculated by using the difference information of electromagnetic wave logging curves while drilling. In slightly deviated wells, anisotropy has no obvious influence on resistivity. The traditional method of calculating formation anisotropy coefficients by using difference information is no longer applicable. In this paper, the high-resolution characteristics of micro-resistivity imaging logging and local measurement characteristics in different directions were used to divide the image gray scale, and the equivalent resistivity volume model was established to further calculate the equivalent horizontal resistivity and vertical resistivity, so as to obtain the anisotropy coefficient of the reservoir. The obtained anisotropy coefficient was compared with the anisotropy coefficient calculated with the resistivity while drilling of drilled wells, and the two were in good agreement. In addition, the resolution of the anisotropy coefficient calculated by the micro-resistivity imaging was higher, which could well reflect the anisotropy characteristics of fractures, holes, and heterogeneous well sections, and provide a new method for evaluating the formation anisotropy.

水平井气层孔隙度评价一直是海上气田开发的难题之一,通过核磁共振测井理论分析和岩心侵入实验研究,提出了随钻核磁共振时移测井校正方法.研究认为,在一定时间内,目标区储层的钻井液滤液侵入深度可达10 cm以上,通过随钻核磁共振测井和时移复测,能够求取随钻实时测量时的流体含氢指数Hi.建立Hi与随钻核磁共振孔隙度的关系式,可以对全井段核磁共振孔隙度进行校正,得到相对真实的储层孔隙度;也可以通过直接建立实测孔隙度和复测孔隙度之间的关系式,求取全井段孔隙度值.此方法的优点是在兼顾资料录取质量的同时减少作业时间、降低成本,在多口井应用效果良好,具有一定借鉴意义.

Electromagnetic resistivity logging while drilling is widely used, which has become a required item in the inclined and horizontal offshore wells. However, due to the comprehensive influence of reservoir anisotropy, drilling fluid invasion and other factors, the resistivity measured is distorted, which brings uncertainty to the quantitative evaluation of saturation. Taking Schlumberger electromagnetic resistivity logging tool ARC675 as an example, the simulation is carried out using vector finite element method, to investigate the logging response characteristics under conditions of anisotropy and invasion. Multi-parameter synthetic inversion is realized by step-by-step anisotropy and invasion inversion. Based on this, horizontal and vertical resistivity, invasion depth of drilling fluid and anisotropy are obtained. The above step-by-step inversion method is applied in a highly deviated well, and the results show that the relative error is reduced from 56% to 10% by comparing the measured resistivity and inversion resistivity with the resistivity of the same layer in the adjacent vertical well. This result shows that the method above can provide relatively true formation resistivity for accurate evaluation of reservoir saturation.

东海盆地低渗油气资源丰富,但低渗储层又极其敏感,做好东海低渗储层保护是实现低渗油气资源良好开发的先决条件,为此东海盆地先后使用了两种钻井液体系,分别是反渗透水基泥浆和白油油基泥浆.为了明确两种泥浆体系对低渗储层的侵入特征,开展了(0.1～1)×10?3?μm2、(1～5)×10?3?μm2、(5～10)×10?3?μm2三种类型低渗岩心侵入实验,实验结果表明,水基泥浆和油基泥浆均对岩心存在侵入现象,随着泥浆对岩心的侵入,引起不同程度电阻率的"低侵"和"高侵"特征,利用不同泥浆的侵入特性结合时移电阻率测井可以有效分析泥浆的侵入深度、流体性质以及可动水情况,为低渗储层井筒保护、油气层选段射孔提供有效的技术支持.