Abstract: Dedolomitization is very common in the strata, but it is still in dispute about its formation environment，influencing factors，mechanisms，and the role in reservoir and so on.The recognition marks was analyzed，and detailed classification of dedolomitization from 3 aspects was given: Retaining the original crystal form or not，occurrence mode and forming environment，the manifestation in diagenesis.Dedolomitization can occur in various environments，from the near-surface settings to shallow burial and deep burial environments，even in hypergene deposit and lacustrine environments.The factors influencing dedolomitization mainly include the dolostones chemical constituents and physical properties，degree of order，fluid characters（concentration of SO^2-₄，Ca/Mg ratio，temperature，pH and partial pressure of CO₂）and Fe content of the dolostone. Cathodeluminescence and geochemical analysis can be used to study the dedolomitization mechanism in near-surface，mixed seawater and freshwater，burial and other environments.Dedolomitization process can be divided into two steps, including dissolution of dolomite and the precipitation of calcite. Only the first step occurs to form the rhomb-moldic pore; the two steps take place at the same time; only one step happens or the two the two steps take place in different order.Dedolomitization mostly begins from the core of the dolomite or the interface between the core and the rim，because there are deficits during the growth process and the Ca content is high.Dedolomitization can be considered as a kind of process that the Mg²⁺ is gradually released.The studies of calcite-dolomite-solution system can help to investigate the transforming condition between calcite and dolomite and the influencing factors.The near-surface dedolomitization is generally relevant to the dissolution of gypsum or anhydrite and the meteoric water of vadose zone and phreatic zone.It is confirmed that the laterally continuous distribution of dedolomitization can indicate unconformity.The study of dedolomitization products can reflect the diagenetic stages and the source of the fluid.Dedolomitization can enlarge the modic pore and inter-crystal pore and improve the reservoir quality，but there is close relationship between the increasing porosity of dedolomitization and latter eluviation.Without the latter leaching，maybe the late burial dedolomitization relevant to calcite precipitation will destroy the primary pores.

Key words: dedolomitization, influencing factors, mechanisms, calcite-dolomite-solution system, reservoir

摘要： 去白云石化作用在地层中普遍发育，但对其形成环境、影响因素、形成机理以及对储集层的作用等的认识一直存在争议。文中分析了去白云石化的识别标志，从是否保留原始晶形、产出状态及形成环境以及成岩作用中的表现形式3个方面对去白云石化作用进行了详细的分类。去白云石化形成环境广泛，从近地表受大气淡水影响的环境，直到浅埋藏、深埋藏等环境，甚至表生矿床、湖相环境中都可以发育去白云石化。影响去白云石化的因素主要有：原始白云石的化学成分与物性、有序度、流体性质（包括流体中SO^2-₄浓度、Ca/Mg值、温度、CO₂分压和pH值等）以及原始白云石是否含Fe等。利用阴极发光与地球化学分析等手段，可有效界定近地表、海水与淡水混合以及埋藏等不同环境下去白云石化的形成机理。去白云石化的过程可以被分为两个步骤：（1）白云石的溶解；（2）方解石的沉淀。这两个步骤可能仅发生其中之一或前后顺序不同。去白云石化多从白云石晶体核心或边缘与核心之间的界面处开始，这是由于这些地方在白云石生长过程中有缺陷或Ca含量较高。去白云石化可以被认为是Mg²⁺逐渐释放的过程。方解石—白云石—溶液体系的研究有助于探讨方解石、白云石之间相互转化的条件及影响因素。近地表去白云石化常常与膏盐溶解和渗流带/潜流带大气淡水有关。横向上连续分布的去白云石化地层可指示不整合面。研究去白云石化作用产物的特征，可以反映成岩作用期次及流体来源。去白云石化可增大溶模孔和晶间隙，改善储集性能，但去白云石化贡献的孔隙多与后期淋滤有关，如果缺乏后期淋滤，晚期埋藏形成的去白云石化方解石对于储集层孔隙是破坏性的。

关键词: 去白云石化, 影响因素, 机理, 方解石—白云石—溶液体系, 储集层

CLC Number: 

• P588.2