冀中坳陷奥陶系多期岩溶发育特征

冀中坳陷奥陶系岩溶储层发育，但在不同的层位和不同的地区岩溶孔洞缝的发育程度差别很大，表明岩溶发育的主控因素不同。通过显微镜下和露头剖面对裂缝产状和切割关系的分析，识别出了至少三期裂缝。研究表明:这三期裂缝分别对应于印支期、燕山期和喜马拉雅期的岩石破裂事件。通过露头、镜下对孔洞缝形态的研究，结合胶结物的阴极发光特征，认为冀中坳陷奥陶系存在同生期岩溶、埋藏期岩溶和表生期岩溶。多期的岩溶作用形成了目前奥陶系的岩溶储层。不同时期的构造活动对冀中坳陷的岩溶作用影响不同。在近地表环境下，奥陶系经历的构造活动越强烈，溶洞发育率越高。对比冀中坳陷内各岩溶古地貌类型和放空漏失的数据，表明岩溶洼地也是有利的古地貌类型，分析认为这种岩溶洼地为不积水的岩溶洼地。岩溶高地、岩溶斜坡和岩溶洼地在垂向上具有不同深度范围的水平岩溶分带，对应于不同地貌类型下的渗流带和潜流带。在靠近深大断裂带附近，有大量的钻具放空和泥浆漏失，并且流体包裹体均一化温度表明有热液的存在。在岩溶作用较弱、溶洞发育率低的区域，白云岩和石灰岩的薄互层段是有利的岩溶发育层段。

Multi-phase Karst Development Characteristics in the Ordovician of the Jizhong Depression

Ordovician karst reservoirs in the Jizhong Depression are well developed,but the development of vugs, caverns and channels varies greatly in each stratum and in each area,indicating different main karst controlling factors. At least three phases of fracture occurrence and cutting relationship were identified by microscopy analysis and at the outcrop. The study suggests that the phases correspond to the rock rupture events of the Indosinian,Yanshan and Himalayan movements. The outcrop and microscopy study of the shape of the pores,and the cathodoluminescence of the cement,indicated that the Jizhong Depression developed syngenetic karsts,burial karsts and epigenetic karsts during the Ordovician. The present karst reservoirs in the Ordovician were formed by multi-phase karstification. The tectonic activities of different periods resulted in different forms of karstification in the Jizhong Depression:the strongest near-surface tectonic activity resulted in the most rapid development of dissolution pores. A comparison of karst paleogeomorphology data and drilling breaks and mud losses in the Jizhong Depression shows that karst depressions are a favorable paleogeomorphological type. It is considered that such karst depressions were non-water storage structures. The karst highlands,slopes and depressions have horizontal karst zones of different vertical depth,which correspond to the vadose and phreatic zones that existed in different paleogeomorphologies. Large numbers of drilling breaks and mud losses occur near deep fault zones,and the homogenization temperature of fluid inclusions indicates the existence of a hydrothermal fluid. Thin interbedded sections of dolomite and limestone are favorable karst-development sites in areas with weak karstification and a low development rate of dissolution pores.