中文摘要：

沉积物成岩作用中碳酸盐胶结物的形成和溶解直接关系到岩石孔隙体积及其连通性，对石油、天然气等的储集和运移具有重要影响。通过纵向对比分析发现库车坳陷的克拉2气田储集岩层的孔隙度和渗透率值与碳酸盐含量呈反相关关系。即碳酸盐含量越高，孔、渗值越低。引起碳酸盐含量变化的正是其中的方解石胶结物的变化。岩石显微结构表明，方解石随深度的变化是通过粒间胶结物的早期沉淀、深埋时的溶解及晚期再胶结而发生的，并且导致本区K201井3800nl深处的孔、渗高异常带。伴随方解石在深度上的含量变化，地下水也呈现出纵向上的分带性。基于水岩作用热力学相平衡及质量守恒理论，利用相关的热力学数据库和溶液模型，模拟方解石的溶解度与水型之间的关系得出，方解石的溶解度与地下水中[ΣCO2]-[Ca^2＋]值密切相关，该值越小越有利于方解石的溶解，否则发生沉淀。克拉2气田中Na2SO4型水的[ΣCO2]-[Ca^2＋]≈0，是典型的方解石饱和溶液，方解石与这种溶液呈平衡态，既无大量的沉淀，也无明显的溶解；NaHCO3型水的[ΣCO2]-[Ca^2＋]〉0，是一典型的过饱和溶液，这种地下水所在的岩石中出现大量方解石肢结物的沉淀，孔、渗值很低；CaCl2型水的[ΣCO2]-[Ca^2＋]〈0，代表了典型的欠饱和溶液，与其对应的储层内不但无方解石沉淀，而且早期的方解石胶结物也要被彻底溶解，形成大量的次生孔隙，导致孔、渗值增高，从而成为本区天然气的最有利储集层段。

英文摘要：

Precipitation and dissolution of carbonate cements within elastic rocks are directly related to pore volume and permeability of the rocks,and also have an important impaction on reserves and transportation of oil and gas. On the basis of vertical examination,this study reveals that there is an inverse relation between the porosity, permeability and the carbonate cements in the reservoir from the Kuche depression of the Tarim Basin,that is,the more the carbonate cement content is,the lower the porosity and permeability is. It is the calcite cementation that results in the variation of carbonate mineral contents. The microstructures of the elastic rocks indicate that the variation of calcite with depth is resulted from the early intergrain precipitation of calcite,the dissolution during deep burial and then the later recementation. Moreover,the calcite cement dissolution produced the abnormally high porosity and permeability zone around the depth of 3 800 m in the well K201. There are ground water type zones on the vertical direction with the variation of calcite content. Based on the water-rock interaction thermodynamic phase equilibrium theory and the mass conservation law,the relation between calcite solubility and water types was discussed in this study. It is showed that the calcite solubility depends on the value of [ΣCO2]- [Ca^2＋] of the ground water. The lower the water [ΣCO2]- [Ca^2＋] is,the higher the calcite solu bility is. The Na2SO4 type water with [ΣCO2]- [Ca^2＋]≈0 is a typical saturated fluid in which calcite content is stable,so neither precipitation nor dissolution happens. The NaHCO3 type water, [ΣCO2]- [Ca^2＋]〉0,is a typical supersaturated fluid ,and a large volume of calcite cement precipitates resulting in the decrease of porosity and permeability of rocks. The CaCl2 type water, [ΣCO2]- [Ca^2＋]〈0,represents a kind of unsaturated fluid in which no calcite precipitates and the early calcite cement can be dissolved so that a large quantity of secondary pore space can be formed