盐效应和共同离子效应对方解石溶解度的影响及其地质意义  

Effect of salts and common ions on solubility of calcite and its geological implications

作　　者：陈勇 王淼 刘庆[3] 卓勤功 张学军[3] 陈小兰[5] 

机构地区：[1]中国石油大学地球科学与技术学院,山东青岛266580 [2]海洋国家实验室海洋矿产资源评价与探测技术功能实验室,山东青岛266071 [3]中国石油化工股份有限公司胜利油田分公司勘探开发研究院,山东东营257015 [4]中国石油勘探开发研究院,北京100083 [5]山东科技大学地球科学与工程学院,山东青岛266590

出　　处：《中国石油大学学报（自然科学版）》2016年第6期33-39,共7页Journal of China University of Petroleum(Edition of Natural Science)

基　　金：国家自然科学基金项目(41172111);国家科技重大专项(2016ZX05006-001);中央高校基本科研业务费专项(SD2013211151;16CX05005A)

摘　　要：储层矿物的生长和溶解受控于成岩流体,在恒定温度条件下,对不同盐度和离子类型溶液体系中的方解石溶解特性进行实验研究。结果表明,在低盐度(<20%)条件下,方解石溶解度随盐度增加而增大,但盐度过高会导致方解石溶解度降低,方解石溶解度最大值的盐度区间对应了高孔隙发育带;在相同浓度条件下,MgCl_2体系中方解石的溶解度最大,NaCl体系中次之,KCl中最小,说明Mg^(2+)的盐效应大于Na^+和K^+的盐效应,能促进方解石的溶解;Ca^(2+)会因为共同离子效应而抑制方解石的溶解,反而有助于方解石沉淀(生长),其结果有助于地层保持良好的封闭性;Na_2SO_4的盐效应不明显,随浓度增大,方解石的溶解度快速降低;硫酸根对方解石溶解的抑制作用强于氯离子,表明Na_2SO_4水型可能不利于储层溶蚀次生孔隙的发育。Growth and dissolution of minerals in petroleum reservoirs are controlled by the diagenesis fluids. The solubility characteristics of calcite in different salt and ions aqueous systems at stable temperature were investigated using experiments. The experimental results show that the solubility of calcite increases with the salinity rising （ salinity〈20%） . However, it de-creases under high salinity condition. And it is found that the fluids in reservoir contain salinity corresponding to the maxi-mum solubility of calcite with high porosity. The solubility of calcite is the highest in MgCl2-H2 O system, middle in NaCl-H2O system, lowest in KCl-H2 O system at the same mole concentration of salt. This implies that the Mg2＋ has stronger salt effect on solubility of calcite than Na^＋and K^＋, which improves the dissolution of calcite. The Ca^2＋shows constraint on dissol-ving of calcite due to the common ion effect;however it may lead to growth of calcite, resulting in improving sealing ability of strata. The salt effect of Na2 SO4 is not remarkable, and the solubility of calcite decreases quickly with Na2 SO4 content in-creasing. The sulfate ion shows more constraint on dissolution of calcite than Cl^-, which indicates that it is not suitable for forming of secondary porosity in reservoir containing Na2 SO4 .

关 键 词：方解石 溶解度 生长 盐效应 共同离子效应 储层物性 

分 类 号：P592[天文地球—地球化学]