A new method for the wettability evaluation of solid particles
[Objective]Wettability not only controls fluid flow and distribution in unconsolidated sandstone reservoirs but also affects particle migration.Therefore,accurate evaluation of the surface wettability of solid particles is crucial for effectively controlling reservoir particle wettability.This holds great importance for the prevention and control of particle migration damage.However,existing evaluation methods mainly target the macroscopic scale of the solid plane above a centimeter,which fails to accurately evaluate the surface wettability of sand particles at the nanoscale in unconsolidated sandstone reservoirs.[Methods]In this study,we analyze the advantages and disadvantages of modem methods for evaluating the wettability of solid particles.The measurement of the contact angle is the most common way to characterize the wettability of a flat solid.However,the influence of particle shape and uniformity often results in large measurement errors in the contact angle.The activation index method can effectively evaluate the wetting degree of the particles within a certain range.However,an activation index H of 100％does not correspond to the maximum hydrophobic degree.Under ideal conditions,both the activation index and the contact angle can accurately characterize the particle wettability with minimal error.The relationship between the activation index and the contact angle should be approximately linear.In this study,the activation index values measured by all samples in the modification experiment of unconsolidated sandstone particles are fitted with the corresponding contact angle values.We found that the contact angle increases as the activation index increases.Data within the 30％range deviated more from the fitting curve,indicating a lower activation index value.However,when 30％≤H＜100％,the correlation between the contact angle and activation index is quite strong.We propose a new method for evaluating the surface wettability of solid particles,the wettability index(R).This method combines the activation index with the contact angle measurement method of the pressed plate.To illustrate this new method of wettability evaluation more intuitively,we designed an experiment using six types of modifiers under optimal modification concentration.[Results]The experimental results show that the optimal concentration for most modifiers is 0.6％,except for GH20,which is 0.4％.Sand particles modified with GB80 have an R value of 0.65,indicating weak hydrophobicity.Those modified with GB60 have an R value of 0.51,suggesting neutral wetting.The activation indexes and contact angles of GA20 and GA60 modified sand follow a similar trend,with R values of 0.88 and 0.90,respectively,indicating a strong hydrophobic state.Sand particles modified with the silane coupling agent GH20 have an R value of 0.65,showing weak hydrophobicity,while GF13-modified sand particles have an R value of 0.54,indicating moderate wetting.By comparing the wettability of the mud and sand particles corresponding to the three types of modifiers,we can clearly discern the modification effect.Considering the limitations of current methods for evaluating particle wettability,the new method can effectively address the shortcomings of the activation index method,particularly within a narrow range of values.An experiment was conducted in the laboratory to compare the results derived from the activation index method,contact angle measurement method,and the new wettability index method.[Conclusions]The outcomes demonstrated that this novel wettability evaluation method,based on the wettability index R,can accurately assess particle wettability.This method offers several advantages:it is simple to implement,data processing is convenient,and its application scope is broad.
万方数据
维普
