方解石在成岩环境中的溶解度与地下水化学特征、温度等有着极为密切的关系.通过CaCO3溶解沉淀反应平衡以及地下水中的Ca2+活度可以确定不同温压的地下水条件下方解石的溶解趋势.地下水溶液的pH值和温度是方解石溶解度最直接的控制因素.方解石溶解趋势可以通过CaCO3电离反应的吉布斯自由能(△G)来判断:△G＜0时,反应向溶解方向进行；△G＞0时,反应向沉淀方向进行.根据方解石的水岩反应理论,对塔河油田34口井的奥陶系地层水进行了△G的统计计算.结果显示:塔河油田现今地下水条件有利于方解石的溶解,西部地区较东部溶解趋势强,北部地区溶解趋势相对较弱.这为定量了解塔河地区埋藏岩溶趋势及该地区的储层评价预测提供了理论依据.%The solubility of calcite in the diagenesis is closely related to the chemistry of groundwater and the temperature. According to the reaction equilibrium of CaCO3 and activity of Ca2+ in groundwater, the solubility of calcite in different temperatures and pressures could be calculated. The pH value and the temperature of solution are the main factors to control the solubility of calcite. The dissolving tendency of calcite could be judged by the Gibbs free energy. The condition with △G<0 in the solution is favorite to dissolution of calcite and that with △G>0 is favorite to deposit of calcite. The AG of groundwater in thirty-four wells are calculated, Tahe oilfield. The results show that: present groundwater conditions favor the dissolution of calcite, the calcite tends to dissolute more in west and south area. This water-rock reaction theory can be used to quantitative understand the burial karst tendency and support the reservoir evaluaterating.
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