Study On Anti Sloughing Characteristics And Strengthening Technology Of Solid Free Flushing Liquid

Small diameter diamond wire line coring drilling is a common method of drilling coring.Because of its technical characteristics,it requires high rheological properties and solid content of drilling flushing fluid.Solid free flushing fluid is a kind of flushing fluid commonly used in small diameter diamond wire line coring drilling because of its characteristics.Due to the complexity of drilling formation,solid free flushing fluid has an irreplaceable role in small diameter diamond wireline core drilling.However,in this drilling method,compared with the low solid flushing fluid,it does not contain solid particles and has insufficient cementation for the formation.The traditional solid-free flushing fluid is difficult to use in many complex geological conditions,which is easy to cause hole wall instability.In some complex formations,the adaptability to the formation is not as good as that of low solid flushing fluid.In order to make the solid-free flushing fluid be used in various complex field and extensive formation conditions,it is necessary to strengthen its anti collapse characteristics.Based on this purpose,this paper studies the anti sloughing characteristics and strengthening technology of solid free flushing fluid.First of all,the characteristics of solid-free washing liquid were analyzed to find the strengthening ideas.Then,based on the polyacrylamide and vegetable gum in the ordinary solid-free washing liquid,the anti sloughing characteristics of different types of solid-free washing liquid were studied through the filtration performance test,rheological test and anti sloughing test.On this basis,three kinds of anti sloughing agents,namely low viscosity synergistic powder,microbubble agent and emulsified asphalt,were selected,and two kinds of solid free flushing fluid of plant gum washing liquid and polyacrylamide emulsion were sloughed down.Through the comparison of anti collapse test,the optimized formula of solid-free flushing liquid with anti collapse strengthening was developed.At the same time,the developed enhanced solid-free flushing solution was applied in the field.Therefore,a set of enhanced solid-free flushing fluid technology system with good anti sloughing characteristics is established,which is suitable for small diameter diamond wire line coring drilling.The main research results are as follows:(1)Solid free washing liquid was prepared with polyacrylamide and plant gum(konjac gum)as the main raw materials.Core soaking test was carried out with two solid free washing liquid.It is found that the expansion of core in polyacrylamide and vegetable gum washing solution is far less than that in clear water,and the collapse time of core is less than that in clear water.It shows that the solid-free flushing fluid has a certain inhibition effect on the core,and has obvious anti collapse effect.Through the comparative analysis of its anti sloughing effect,the optimum dosage of polyacrylamide emulsion and vegetable gum(konjac glucomannan)in two kinds of solid free washing fluids were determined.(2)Standard core,mixed sand core(soil: sand = 2:1)and mixed coal core(soil:Coal = 2:1)are used to simulate different types of formation environment.Through the comparative analysis of the core soaking test data,the final vertical expansion of the latter two in the flushing fluid is less than that of the former,and the final vertical expansion of the mixed sand core is the smallest,so the mixed sand core is selected as the core type of the subsequent enhanced solid-free flushing fluid anti collapse test(core soaking).(3)Three kinds of anti sloughing agents,low viscosity synergist,microbubble agent and emulsified asphalt,were added into two kinds of solid-free washing solutions,namely,polyacrylamide and vegetable gum(konjac gum).The performance of three kinds of enhanced solid-free flushing fluid was evaluated by filtration test,rheological test and anti collapse test.The test results show that the solid free washing liquid prepared by adding microbubble agent into polyacrylamide emulsion has the best anti sloughing effect.On this basis,the optimal dosage of microbubble agent was determined,and the optimum formula for strengthening the solid free washing fluid was determined as follows: 1000 ml H2O+0.7% polyacrylamide emulsion +0.7%WH type microbubble agent.The research results expand the application scope of solid free flushing fluid in small diameter diamond wire line coring,and provide technical support for solving the technical problems of small diameter diamond wire line coring in complex formation from the solid free flushing fluid technical system.