渗透回流模式白云石化作用对碳酸盐岩储层的影响

A Study of the Effect of the Dolomitization on the Carbonate Reservoir in the Seepage Reflux Mode

白云石化作用对含油气的碳酸盐岩储层有明显的改造作用,而前人的研究大部分是针对白云石的成因模式,未对其形成过程给出具体描述,更未对白云石化作用对储层的改造程度做出定量分析。针对白云石化中的"渗透回流模式",建立了白云石化作用的一维模型,利用多组分、多相流溶质运移模拟软件TOUGHREACT,研究渗透回流模式对储层物性影响的深度范围。结果表明,当高Mg/Ca比的浓缩海水进入含水层后,导致方解石溶解,白云石沉淀,储层孔隙度与渗透率均比初始值大,模拟5万年时,依靠重力作用,渗透回流白云石化作用能够影响到50 m深的储层范围,产生一定规模的白云岩储层。

Dolomitization has a significant influence on the carbonate rock reservoirs which contain oil and gas resources.Previous studies mainly focus on formation models of the dolomite,however,a fair description of its formation process is quite rare,needless to say a reasonable quantitative analysis for the transformation level of the reservoir by dolomitization.In this paper,a 1 -D model was set up based on the seepage reflux dolomitiza-tion model.Under the comprehensive advantage of TOUGHREACT,a multicomponent multiphase flow and sol-ute transport simulation software,the exploration on the transformation of the reservoir by dolomitization is fully re-alized.As the obvious results illustrate：when the concentrated sea water with high Mg/Ca ratio intrudes into the aquifer,calcite dissolution and dolomite precipitation are inevitable and actually happen in this case.The porosity and permeability are greater than the initial value.In 50,000 years,by force of gravity,seepage reflux dolomiti-zation can affect 50 m depth of the reservoir resulting in the formation of a certain scale dolomite reservoir.