Research On Drilling Technology Of Multilateral Horizontal Well Reinforced By Grouting In Coal Seam Floor

Water inrush from the floor of the coal seam restricts the safe and efficient exploitation of coal resources in the North China coalfield.The research and application of the drilling technology of multilateral horizontal grouting wells are of great significance in solving the water disaster management problems of this type of mine.In the face of the complexity and diversity of the current stratigraphic conditions and hydrogeological characteristics in different mining areas,the influence of the complicated construction in Zhaogu No.1 Coal Mine leads to increased difficulty in the design and construction of multilateral horizontal wells and the formation of wells,This article takes the design of multilateral horizontal well trajectory,technology of fault drilling and precise control of well trajectory as the research object.In order to solve the problem of unsatisfactory grouting in the management area,the surface horizontal directional multilateral wells are set as the grouting channels,the wellbore grouting is implemented to transform aquifers,and water-conducting fractures are blocked.Through collecting,analyzing and studying the relevant domestic and international research,the author integrates the actual circumstances of horizontal directional multilateral wells practical application,adopts several methods such as theoretical analysis research,numerical simulation,and on-site drilling tests,focusing on the design of multilateral horizontal grouting wells and well trajectory control.The main researches are as follows:(1)Study the track types and design models,summarize the design principles suitable for multilateral horizontal wells for floor grouting in coal seams,and choose a reasonable 2D track profile and 3D track design method for branch wellbores.(2)Properly simplify the structural characteristics of fractures,use COMSOL Multiphysics software to simulate the flow pattern of grouts in fractured formations,study the grouting process under different fracture characteristics by selecting formations and grouting parameters,and obtain the effective diffusion range of the grouts so as to provide a theoretical basis for branch wellbores reasonable layout space.(3)Research on phenomenon of the main wellbore during the completion of drilling under the influence of fault structure,such as the instability of the well wall,collapsed blocks,and drilling sticking.Research is also made to probe into drilling safety and cementing measures caused by unsatisfactory well cementation in shattered and missing areas.The impact of different types of faults on drilling is analyzed.Thetypes of faults that may be encountered are analyzed and the technical methods of finding target limestone aquifers after the wellbore trajectory passes through the fault.(4)Determine the applicable branch side drilling and branching technology.The bedding trajectory control method based on geosteering technology is studied after ensuring that each branch wellbore smoothly enters the limestone aquifer.Both the subjective and objective factors are taken into consideration,combining logging information and the characteristics of the change in the gamma logging curve while drilling,all of which provides guidance for precise control of the wellbore trajectory.Through the research and field test application in this thesis,a series of key technologies for efficient drilling of multilateral horizontal wells suitable for coal floor grouting reinforcement have been formed.Such technologies can effectively reduce or even avoid a series of difficulties and problems encountered in the process of drilling under the complex geological conditions of the coal mine area.What's more,this set of technologies can improve the drilling efficiency,provide a reference for the construction of the same type of multilateral wells and have wide application value as well as broad prospects.