基于有机质富集差异的湖相未熟富有机质泥页岩导电机理与解释模型

The organic-rich shale was researched the electrical conductivity in practice application prior to theory for the moment. The solid organic matter (OM) as a part of non-conductive rock matrix has been widely accepted to research its conductivity separately. OM and minerals represent complex physical and chemical natures, leading to variously combined patterns and difference of conductive behavior. The lacustrine immature organic-rich shale, which is the research target, develops in the Upper Cretaceous of the Songliao Basin. We prefer to probe into the conductive mechanism and interpretation model of lacustrine immature organic-rich shale, based on accumulation difference of OM. According to the occurrence and the distributional difference of OM, various patterns of OM accumulation are analyzed by the reactions of OM and minerals. The conductive mechanism of immature organic-rich shale could be revealed by the analytical interrelations of organic matters of various patterns withrock physical properties, electrochemical properties, and rock electricity. We establish conductive interpretation model of immature organic-rich shale, based on the rock physical model and the contributions from organic matters of various patterns responding to the conductive behavior of different porosities. Thus, our research shall be crucial for understanding the conductive behavior and interpretation model of organic-rich shale in theory, improving the traditional conductive mechanism and model. Our findings will be provided a scientific basis for putting forward an effective approach of the logging evaluation of lacustrine organic-rich shale.

富有机质泥页岩导电性的理论研究滞后于其实践应用，把固态有机质作为不导电岩石骨架一部分而单独研究其导电性存在局限性。有机质和无机矿物特别是粘土矿物具有复杂的物理化学性质，使两者呈现多种结合方式而引起导电行为差异。本项研究将针对松辽盆地上白垩统湖相未成熟富有机质泥页岩，从有机质富集差异的角度，探讨未熟富有机质泥页岩的导电机理与解释模型。根据有机质的赋存状态及分布差异，分析有机-无机相互作用下有机质富集方式的差异性。通过分析不同赋存状态有机质与岩石物理性质、电化学性质、岩石电性之间的相互关系，揭示富有机质泥页岩的导电机理。基于岩石物理建模，结合不同富集方式有机质对不同类型孔隙度导电行为所起贡献，建立富有机质泥页岩的导电解释模型。因此，本项研究有助于从理论上深化未成熟富有机质泥页岩的导电行为与解释模型，从而完善传统导电认识与解释模型，为提出湖相富有机质泥页岩有效的测井评价方法提供科学理论依据。

为了揭示富有机质泥页岩的电阻率测井响应机理并建立解释模型，本项研究主要从有机质与矿物相互作用的角度深入探讨。研究表明，有机质赋存方式包括五种类型，其中结合固态有机质与粘土化学吸附可溶有机质构成的粘土结合有机质占绝对优势，推断粘土结合有机质是有机质的主要赋存方式。据此可知，有机质赋存状态对微观孔隙结构分布具有重要作用，大颗粒生物碎屑有机质主要赋存于大孔，小颗粒粘土结合固态有机质主要赋存于中孔，粘土化学吸附可溶有机质主要赋存于微孔。有机质不同发育阶段岩石导电能力控制因素存在差异，从低有机质的粘土附加导电性主控逐渐过渡到高有机质的孔隙流体离子导电主控岩石导电能力。因此，不同赋存状态有机质在不同类型孔隙中对泥页岩导电行为起到不同贡献，提出“有机质结合粘土阳离子”改变粘土附加导电性、“有机质置换孔隙水”改变孔隙大小分布、“不导电有机质”改变“岩石骨架”含量是富有机质泥页岩的内在导电机理。