Research On Hole Protection Technology Of Recoverable Reusable Screen Pipe In Soft Coal Seam

The lower hole-protecting screen is an effective measure to prevent hole collapse.However,due to factors such as the deviation of the drilling trajectory and the deformation and necking of the hole wall,the downpipe resistance is large or even the downpipe fails.The problem of ineffective recovery after mining has resulted in high cost of hole protection,which severely restricts the large-scale promotion and application of screen pipe hole protection.In order to effectively increase the distance between the lower pipe of the protection pipe and realize the recycling and reuse of the protection pipe,this paper adopts the method of combining theoretical analysis,numerical simulation,and surface and downhole tests,and the drilling protection pipe for gas drainage in soft coal seams is fed and reused.Research on the changing law of pushing and pulling force in the process of pulling out.Analyzed the force situation of the protective hole pipe during the extubation and the factors affecting the pushing and pulling force:(1)The factors affecting the pushing and pulling force required for the protective hole pipe to be pulled out mainly include the geological conditions,the trajectory of the extraction hole and the drilling hole.Hole body structure;(2)The force analysis model of the hole-protecting pipe in the drilling is established,and the push-pull force equation of the hole-protecting pipe in the process of pulling in and out is solved.The characteristics of commonly used pipes were compared and analyzed,and the influence of slope inclination and horizontal offset distance of boreholes on the propulsion resistance of the hole protection pipe was studied by ground tests:(1)PE and PVC pipes have good resistance to torsion deformation,compression deformation and resistance tensile and shear strength,it can be used as a protective hole pipe;(2)The thrust required for the delivery tube is generally increasing,and the increase in slope is increasing,the thrust required for the delivery pipe is also increased;(3)The change of the horizontal offset distance has little effect on the propulsion resistance.Numerical simulation studies the influence of factors such as the deflection angle of the hole,the diameter of the hole,the diameter of the protective hole,and the pipe material of the protective hole on the push-pull force required for the protective hole to be fed and pulled out of the hole:(1)The large diameter pipe is in The thrust mutation point will occur during the propulsion process.The thrust is divided into three stages:linear increase,rapid increase and linear increase;the small diameter pipe protection hole does not produce thrust mutation,and is affected by the bending and sinking of the protection hole,the thrust is divided into linear There are three stages of increase,slow increase and slow decrease;(2)The diameter of the borehole has a significant influence on the thrust at the beginning of the second stage,and the effect is significant in the third stage;(3)When the tube is extubated,the pulling force varies with the extubation The distance change can be roughly divided into two stages,the drawing force decreases rapidly in the early stage,and the rate of decrease in the latter drawing force is slow;(4)From the point of view of material,the protective hole pipe with a small elastic modulus is easier to bend and deform in the bending section of the borehole,and the required push-pull force is small;(5)The deflection angle of the borehole has a significant influence on the thrust force in the later stage of pipe feeding,generally It is more than 2/3 of the distance between drilling and pipe feeding.The influence of deflection angle on the pulling force is mainly in the early stage of extubation,and there is no effect after more than 1/2 of the extubation distance.Based on the required push-pull force of the hole-protecting pipe obtained by simulation,a pneumatic integrated pipe feeding and pulling-out integrated machine was developed.The field test investigated the gas drainage effect and the effective recovery rate of the hole-protecting pipe with different diameters:(1)The lowering diameter is50 mm and 40 mm borehole pipes have the best gas drainage effect,while the 32 mm diameter protector pipe has a poor gas drainage effect;(2)the 32 mm and 40 mm diameter protector pipes can achieve 100% effectiveness However,the recovery rate of the 50 mm protective pipe is only 60%,and the 40 mm protective pipe can effectively reduce the gas drainage compliance time by 50.3%,which is the optimal downpipe diameter.This thesis has 76 pictures,14 tables,and 92 references.