实验技术与管理2025，Vol.42Issue(7)：43-50,8.DOI:10.16791/j.cnki.sjg.2025.07.006
柴达木盆地第四系盐湖岩心样品的体重、湿度、孔隙度和给水度试验方法
Test methods for bulk density,moisture content,porosity,specific yield of Quaternary salt lake core samples in the Qaidam basin
摘要
Abstract
[Objective]The physical properties of salt lake core samples,such as bulk density,moisture content,porosity,and specific yield,are fundamental parameters for exploring potash deposits.These properties are crucial for evaluating brine deposits and calculating salt and brine reserves.Due to their highly heterogeneous structure and susceptibility to external forces,salt-lake core samples often deviate from their original state,cause structural deformation.In addition,their strong hygroscopicity leads to the loss of crystallized water,altering their composition.During the drilling process,brine inevitably drains from the salt core samples,complicating the measurement of brine volume discharged under gravity.This makes conventional methods unsuitable for determining porosity and specific yield.[Methods]After extracting the salt-lake core samples from the drill rods,brine is drained under gravity.Bulk density is determined using Archimedes'principle,while moisture content is measured at 45℃,including the crystallized water from thenardite(sodium sulfate)and borax.After measuring bulk density,the sample is placed in a siphon test bottle filled with brine from the same borehole and depth.A vacuum pump creates negative pressure,allowing brine to infiltrate the sample's pores for the specific yield test.The volume of brine injected equals the volume that would be discharged under gravity,and the ratio of injected brine volume to the total sample volume defines the specific yield.Porosity is calculated by adding the volume of brine discharged(specific yield)to the volume retained(water retention)and dividing by the total sample volume.Porosity is further calculated through water retention and K-value tests(The K-value represents the ratio of the volume of brine that the sample cannot discharge under the action of gravity to the volume of water adsorbed by the sample).The specific yield and porosity data are validated by field pumping tests,with good agreement.[Results]The experiment uses brine from the same location and depth as the sample,which better reflects the actual conditions of Quaternary salt lake strata.Experimental temperatures are strictly controlled to prevent the loss of crystallized water from salts other than thenardite and borax.Specific yield is determined using the siphon test bottle,and porosity is calculated more accurately by determining the K-value and the content of adsorbed water.The specific yield data shows less than 10%variation compared to unsteady flow pumping test results.[Conclusions]The proposed method is simple,straightforward,cost-effective,and fast.Using brine as the medium better matches actual formation conditions.The specific yield data aligns well with field pumping test results and can be used for reserve estimation of Quaternary salt lake liquid mineral layers.However,due to reliance on low negative pressure backfilling,this method is unsuitable for more compact salt-lake core samples from the Tertiary period.Since the test is destructive and the samples are heterogeneous,it cannot be repeated.Therefore,equipment calibration,environmental control,personnel training,and measures to preserve sample integrity during field sampling,storage,and transportation are essential.The test requires two people to cooperate in operation and two people to check the recorded data.Dual-operator procedures are also used to ensure data accuracy and reliability.关键词
盐湖岩心样品/湿度/孔隙度/给水度/抽水试验Key words
salt-lake core samples/moisture content/porosity/specific yield/pumping test分类
天文与地球科学引用本文复制引用
刘梁,殷录成,贾建团,肖玉萍,赵玉祥,韩光,祝云军,李海明..柴达木盆地第四系盐湖岩心样品的体重、湿度、孔隙度和给水度试验方法[J].实验技术与管理,2025,42(7):43-50,8.基金项目
国家重点研发计划项目(2022YFC2904301) （2022YFC2904301）
