Studies On Solidification Treatment Of Waste Slurry

Significant amounts of waste slurry are produced from in the oilfield during the drilling process,which contain many harmful substances such as crude oil and chemicals.The harmless treatment or resource utilization of waste slurry has become an urgent problem in oilfields.It is an effective way for their resource utilization to make the water plugging and profile control system by mixing waste slurry with curing agents,and the key is to select the suitable curing agents.There are many commonly used curing agents such as cements and resins,and their solidification performance for specific waste slurry needs to be investigated.Layered double hydroxides(LDHs)are a kind of inorganic layered materials,which can form the gel structure under suitable conditions.It is worth exploring whether LDHs gels can be used to solidify waste slurry.In the current work,the waste slurry from Shengli Oilfield was chosen,and the solidification performances of Portland cement,urea formaldehyde(UF)resin,and Mg2Al LDHs gel for the waste slurry were evaluated.The effects of various factors on the properties of the solidified bodies were investigated.It is expected to provide valuable information for the solidification treatment and resource utilization of waste slurry.The main research contents and conclusions of this paper are as follows:(1)Mg2Al LDHs gels were synthesized in ethanol aqueous solutions using MgCl2,AlCl3,propylene oxide,and acetylacetone as raw materials.The effects of ethanol content,acetylacetone dosage,temperature,and salt(NaCl)addition on the structure,morphology,and mechanical property of the gels were determined.It is expected to understand the features of LDHs gels and to provide information for the follow-up research on the solidification of waste slurry.The results show that an increase in ethanol content has no obvious influence on the structure and morphology of LDHs particles as well as the appearance of gels while leads to a decrease in the compressive strength of gels.The addition of acetylacetone results in a decrease of the size of LDHs particles,and the compressive strength of gels decreases with an increase in its dosage.The reaction temperature has an obvious impact on the compressive strength of gels.The increase of temperature from 25 to 80? results in a decrease in the compressive strength,and no gels are formed at temperature higher than 120?.The addition of NaCl has no obvious impact on the compressive strength of gels.(2)The solidification performances of Portland cement,UF resin,and LDHs gel for waste slurry were evaluated.The effects of various factors such as curing agent dosage,curing time,and cement additives on the compressive strength and water resistance of the solidified bodies were investigated.The results show that the three kinds of curing agents all can solidify the waste slurry,and the compressive strengths of the so-obtained solidified bodies can reach about 1250 kPa under the studied conditions.With an increase in the cement and LDHs dosage,the compressive strength of solidified bodies increases.However,with an increase in the UF resin content,the compressive strength of solidified bodies initially increases and then decreases,with an optimum dosage of?15%.Sodium silicate and sodium carbonate as cement additives can enhance the early compressive strength,and the greater the cement dosage,the more obvious the effect.After soaking in water,the compressive strengths of the solidified bodies formed by the three kinds of curing agents all obviously decrease,but there exists an obvious difference in the residual compressive strength among the samples.After soaking for 14 days,the order of compressive strength of solidified bodies is LDHs(?250 kPa)>cement(-200 kPa)>>UF resin(?100 kPa).The immersion water of the UF resin solidified body turns black obviously,indicating the crude oil seeps into the immersion water.On the contrary,no obvious change in the color of the immersion water for the LDHs solidified body was observed,indicating that the crude oil is well sealed in the solidified body.LDHs solidified body exhibits higher compressive strength and stronger water resistance,indicating that the LDHs gel system as a curing agent or gelling agent has potential applications in the water plugging and profile modification.