东海盆地A凹陷主要以低孔低渗储层发育为主,经生产实践证实,该类储层运用常规直井或低角度定向井(产能低)难以实现商业产能,因此,渗透率各向异性和储层"甜点"攻关显得尤为重要.碎屑岩储层各向异性特征普遍存在,基于全直径岩芯360°分扇区各向异性实验(渗透率、声波时差)结果表明:6个扇区的水平渗透率分布范围为(3.7～17.3)×10?3μm2,轴向90°渗透率为0.06×10?3μm2,渗透率各向异性分布范围为62～288,其中水平优势方向的渗透率是非优势方向的3～5倍,且渗透率高值与纵波时差、横波时差低值存在较小夹角.进一步利用成像测井资料与区域地应力分析证实,最大水平主应力方向与构造裂缝发育方向(渗透率优势方向)存在较小夹角,结合"甜点"储层展布形态,并垂直于最大水平主应力方向布井有利于产能释放,助力低渗储层的经济有效开发.

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 The traditional method of calculating formation anisotropy coefficients by using difference information is no longer applicable.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.

东海地区低渗-致密储层的岩性及孔隙结构复杂、物性非均质性强,储层含水饱和度的准确计算一直是该类储层测井评价中的难点.提出了2种储层含水饱和度计算方法.一是基于岩心三维纳米CT扫描实验的变m值计算方法,根据数字岩心样品连通孔隙度与胶结指数m理论值,回归拟合出随孔隙度变化的变m值计算公式,建立数字岩心变m值西门度模型求取储层含水饱和度;二是利用核磁测井资料或RC50与渗透率的相关关系式得到RC50的值,进而通过地层因素F与RC50的负相关关系及地层因素F与储层含水饱和度的关系式求取储层含水饱和度.以东海地区X凹陷Y区低渗-致密砂岩储层实际井为例,分析了本文提出的2种模型和定m值西门度模型的计算结果,结果表明本文提出的2种模型的计算结果与密闭取心饱和度更加匹配,说明本文模型更加适用于东海地区低渗-致密储层.

随钻测井技术可提供地质实时导向,保持砂体产层高钻遇率.在缺少探井资料的井区,基于水平井随钻探边工具,利用方位等信息以及电阻率反演模型准确定位井眼轨迹,刻画砂泥岩性边界、油气水流体边界,再对包含了界面信息的轨迹线抽稀成点,弥补稀疏井网背景下约束井点不足的缺陷,实现高精度构造成图.该方法扩展了随钻测井技术在油气藏精细描述、储层建模中的应用,在东海某气田中的应用验证了方法的可行性.

The paper introduces a method to solve the problems in sweet spot identification and production prediction in coalbed methane wells by using conventional well logging data.Taking No.3 coal seam in southern Shizhuang block of Qinshui basin as an example and starting from the average daily gas production in individual CBM wells,the paper discusses the logging response characteristics of the coal seam and calculates the key parameters of the coal seam such as coal texture index,productivity index,gas content,gas saturation,critical desorption pressure and coal roof & floor features by using caliper,natural potential,gamma-ray,deep lateral resistivity and density logging curves.The paper establishes a composite coal-seam quality parameter by using coal texture index and productivity index,builds up criteria to identify CBM sweet spot with logging data by integrating the composite quality parameter,gas content,critical desorption pressure and coal roof & floor features,and predicts CBM production by using gas content and gas saturation in coal seams,and production scale coefficient.The application results from 97 CBM wells in the study area show that the accuracy rate of the prediction method can reach 84％.