The Effect Of Ternary Composite Flooding On Sandstone Reservoirs

The main reservoirs in eastern China are mainly clastic reservoirs.After decades of explorations and developments,these oilfields have been in the late stage.In order to ensure the sustainable development and stabilize the output of oilfield,Da Qing oilfield has got continuous progress in the development technology.Aiming to enhance the recovery rate on the basis of polymer flooding technology,Daqing oilfield further began to study ASP technology and oil displacement mechanism.Pilot test is then conducted.The experimental results show that the ASP flooding oil recovery efficiency can be increased by about 20%on average.But for clastic reservoir,when injecting alkali or alkaline into this kind of reservoir,it must react with reservoir material.Therefore,the dissolution and precipitation will inevitably occur in the process of displacement.These effects will affect the reservoir's physical properties,pore structure and so on,thus causing damage to the reservoir and affecting the displacement effect of this system.This article selects the precipitate problem of ASP flooding as the point of penetration,with a combination of geology and chemical,using a brand-new way of experiment to analog the true circumstance under the ground in which conducting single mineral static immersion and core dynamic displacement experiments.lt analyzes and compares the reaction mechanism and strength of each single mineral in alkali solution by applying 723 model of automatic spectrophotometer to test real time silicon concentration in alkaline/rock reactions.On the other hand,we make core flooding experiment and collect the cores from test site in Saertu Oilfield in Daqing.And we analysis the cores'changes from all aspects before and after displacement by using scanning electron microscopy,casting thin-section,mercury intrusion and X-ray diffraction methods.We also thoroughly studies the reaction rule of alkali-rock and discusses the cause,condition,process,timing and sedimentation sequence of the deposition.The result shows that the reaction of alkaline/montmorillonite and alkaline/kaolinite is the most severe in alkaline/clay mineral reaction.Second,when the calcium concentration in stratum water is too high,a large amount of calcareous deposition is produced after ASP flooding,especially weak base composite displacement agent,entering into the reservoir stratum.Third,mineral components of core are changed after ASP flooding,kaolinite,montmorillonite,quartz and so on all have been dissolved with a large number of ionic group generated.They flow along with fluid and gather,forming amorphous silica gel,then precipitate in the form of clathrate in fluid.The reservoir stratum's heterogeneity is increased after the complex precipitate migrates a certain distance and reaches pore throat to start to settle.According to the above experimental results,the sandstone reservoir corrosion and deposit mechanism in the process of the ASP flooding is built and the precipitate rule is also explored so that these can be provided for the basic theory and reliable geology basis for the further developments of the ASP flooding.