Study On Dissolution Of Organic Acids To Reservoir Mineral

Interaction between mineral rock and organic acid dissolved in formation fluid,led to the reservoir porosity and permeability change,while the physical properties of the reservoir is directly related to the size of the reservoir and quality.To clarify the controlling factors of reservoir mineral dissolution reaction,this thesis carried out series of simulation experiments to examine the acetic acid,oxalic acid,respectively,and calcite,dolomite and the influence factors of potash feldspar dissolution process;thus detected the reaction concentration in the solution by employing atomic absorption of mineral dissolution rate,scanning electron microscopy(SEM),energy spectrum analysis and X-ray diffraction method,which contribute to the final analysis to changes of the microstructure and composition before and after mineral dissolution.On basis study above,this thesis summarized the main mineral dissolution laws,to predict reservoir space distribution and evaluation into possession of important significance.The experiments showed that Calcite dissolution process in acetic acid system,when reaction temperature between 50 ~ 100℃,its dissolution rate and solubility increases with the rise of temperature,while decrease with temperature rise beyond 100 ℃,and the corrosion rate and corrosion quantity increases with the increase of concentration of acetic acid.In the process of dolomite and the reaction of acetic acid,dissolving rate and solubility increases with the rise of reaction temperature and concentration of acetic acid with no obvious turning point,the dissolubility of magnesium ions in the solution concentration showed higher than that of calcium ions,but under the same conditions were greater than dolomite,calcite dissolution velocity and solubility than calcite dolomite soluble.In the process of oxalic acid and dolomite karst,concentration is low,only calcium oxalate precipitation product;At high concentration,magnesium oxalate and sedimentation will occur.At this time the presence of sodium chloride will increase the solubility of oxalic acid magnesium.Scanning electron microscopy(SEM)were observed before and after corrosion microstructure found that carbonate dissolution mainly along the surface of crystal and crystal fracture union relay weaker place,characterized by selective dissolution.In the process of feldspar reaction with acetic acid and oxalic acid solution,the influence of temperature on the reaction process varies significantly,high concentrations of sodium ions in the early stage of the reaction solution soon after into the stage of slow dissolution;while the dissolution of potassium ion concentration remained relatively stable with no stage changes,but in acetic acid solution the dissolution of sodium ion concentration magnitude higher than potassium ion concentration,and oxalic acid sodium ion concentration in the solution,though higher than that of potassium ion concentration,but on an order of magnitude,sodium feldspar,than potassium feldspar soluble.Silicon ions in the solution of dissolution is relatively slow.Scanning electron microscopy(SEM)and energy spectrum analysis of mineral characteristic changes before and after the reaction,and acetic acid dissolution,sodium feldspar surface has antigenic feldspar,quartz generated;And more intense reaction in oxalic acid solution,in addition to the above secondary mineral,feldspar,clay minerals containing iron and calcium,which can reach an conclusion that oxalic acid shows a higher corrosivity than acetic acid does.