曲折度电阻率模型在大庆G地区低渗储层评价中的应用  

Application of tortuosity resistivity model in low permeability reservoirs in G area of Daqing oilfield

作　　者：宋延杰[1] 王楠[1,2] 唐晓敏[1] 

机构地区：[1]东北石油大学地球科学学院,大庆163318 [2]中石油长城钻探地质研究院,盘锦124010

出　　处：《地球物理学进展》2012年第5期2008-2015,共8页Progress in Geophysics

基　　金：黑龙江省自然科学基金项目"低阻油层通用有效介质电阻率模型研究"(TE2005-24)资助

摘　　要：大庆G地区P油层孔渗较低、泥质含量较高,属于中低孔特低渗、高含泥储层,利用压汞实验资料对该区储层特征进行分析,研究结果表明该区储层分选性较差、孔喉不均、微观孔隙结构复杂.复杂的孔隙结构会引起导电路径的复杂化,影响储层的电性特征.经典阿尔奇公式由于没有考虑孔隙结构变化对岩石电阻率的影响,不能准确描述孔隙结构复杂的低孔、渗储层的导电规律,因而建立一种适合于低孔、渗复杂储层的电阻率模型成为当务之急.针对P油层具有更复杂的孔隙结构,本文利用曲折度岩石体积物理模型建立了岩石孔隙结构和岩石电阻率之间的联系及关系式.该式表明,孔隙度一定时,孔隙通道越弯曲,孔隙结构越复杂,孔隙曲折度越大,岩石的地层因素值也越大.为了使该关系式实用化,本文提出在曲折度电阻率模型中引入结构系数,解决孔隙曲折度的表征问题,实现对岩石孔隙结构复杂程度的定量计算,从而建立了新的地层因素公式.利用压汞和岩电等实验数据对新的地层因素公式进行验证,证实地层因素和结构系数存在着幂次关系,岩石的孔隙结构越复杂,结构系数越大,地层因素越高.针对研究区泥质含量较高、地层矿化度较低的特点,选用能够描述饱含水地层电阻率与地层水电阻率之间弯曲关系的DOLL方程作为饱和度基本方程,并将新的地层因素公式引入DOLL方程中,建立了该区低孔、渗泥质砂岩饱和度方程.实际处理结果表明,该导电模型在一定程度上考虑了孔隙结构变化对电阻率的影响,计算的含水饱和度平均相对误差小于8%,精度满足低孔、渗储层开发生产的需要.It has been shown that reservoirs in P formation of Daqing G area have the characters of high shale content, low porosity and permeability. After further study on pore structure characters of reservoirs from mercury injection data, we know that the reservoirs have bad sorting features, heterogeneous pore-throat distribution, and complex microscopic pore structure. Since the complex pore structure always leads to the complexity of conductivity pathway, it will change the electrical characteristics of reservoirs. However, Archies equation is not suitable for the evaluation of water saturation in low porosity and permeability reservoirs, because the equation ignores the effectof variation of pore structure in low porosity and permeability reservoirs on rock resistivity. Thus, it becomes the most important issue to establish a resistivity model for low porosity and permeability reservoirs. Considering the P formation has more complicated pore structure, an equivalent tortuosity volume model is used. In the model, pore volume and the conductivity path of the rock are considered to be a tortuous tube. And the matrix and formation water is conducting current in parallel. By the equivalent volume model, a resistivity equation is derived in which the relationship between resistivity of the rock and pore structure is established. According to the resistivity equation, the more tortuous pore pathway is, the more complex pore structure is, then the greater pore tortuosity is, and the higher formation factor becomes. In order to make this equation be applied practically, a new parameter i. e. structure coefficient is introduced in the equation to describe the level of pore tortuosity, which also makes possible quantitative representation of the pore tortuosity. As a result, a new formation factor equation is established with structure coefficient. The analysis of experimental data of mercury-injection and core resistivity demonstrates that power function relationship between formation factor and structure coefficient does exi

关 键 词：低孔、渗储层 孔隙结构 曲折度电阻率模型 结构系数 地层因素 

分 类 号：P631[天文地球—地质矿产勘探]