Research On Pump-suction Local Reverse Circulation Coring Drilling Tool In Unconsolidated Fractured Formation

Mineral resources are basic material resources needed for human survival and development.The exploration of mineral resources is of great importance to people's livelihood.In order to understand the reserves and grade of mineral resources,coring drilling technology is the most effective method.Coring drilling in China's eastern Kunlun WuLong Gou mine is often encountered with complex formations such as unconsolidated and fractured,using normal circulation coring tools,single pipe or double pipe drilling tool in these strata,it is difficult to obtain ideal cores.When adopting the current local reverse circulation coring drilling tool at the bottom of jet-type drilling fluid to carry out coring drilling,the core recovery rate has been improved,but this still can not meet the requirements on the coring quality in the mining area.In view of the above problems,this paper carried out research on coring technology in unconsolidated and fractured formations.The purpose of this paper is to drill and core in unconsolidated and fractured formations,based on previous research on coring drilling tools,a new type of bottom hole local reverse circulation coring drilling tool structure has been proposed,the feasibility of local reverse circulation coring of core drilling was analyzed in theory,function test of the coring drilling tool was designed,a new type of local reverse circulation coring drilling tool and its parts' structures were designed based on pump suction principle with the use of Solidworks,AutoCAD and CAXA software,analysis of the impact of coring drilling tool key parts structure parameters on the reverse circulation coring effect and optimization of the structural parameters of key parts of coring drilling tool were carried out using fluid dynamics software(CFD),the coring tools developed for the reverse circulation effect test and drilling test were analyzed before and after optimization of coring using laboratory equipment.Finally,the main conclusions and innovations of this paper are summarized,and the shortcomings and future research directions are pointed out.The paper is divided into seven chapters.Main contents are as follows:The first chapter analyzes the status quo of research on coring technology of oil drilling,geological exploration drilling and scientific drilling,especially coring technique and its feature in drilling complex formations such as unconsolidated and fractured formation,which is followed by main technical problems,research objectives,research content and key problems yet to be solved in complex formations such as unconsolidated and fractured formation faced by core drilling researchers.The second chapter discusses the circulation mode and working principle of different drilling fluid in coring drilling,especially the characteristics of reverse circulation coring drilling technology and the local reverse circulation coring drilling technology at the bottom of the hole.Based on previous studies on core drilling structure design and combining single rotary and double Tube coring tool and external gear pump structure and working principle,this paper put forward a kind of local reverse circulation core drilling tool based on the pump-suction principle,and then theoretically analyzed and calculated the negative pressure produced by the negative suction parts.In the third chapter,the position of negative suction parts in coring tools is discussed.The function test of coring tools is designed to verify that the coring tool is capable of realizing the local reverse circulation of drilling fluid at the bottom.Test on the negative suction effect of the current jet-type reverse circulation drilling tool has been carried out.Comparison and analysis of the coring tool and the existing jet-type reverse circulation drilling tool's negative suction effect were made in this paper which lays foundation for further design and optimization of coring tools.In the fourth chapter,the overall design of the pump-suction local reverse circulation coring drilling tool at the bottom of hole is carried out,and the functions of each part are discussed.Then,the standard parts used in coring tools are expounded and selected.Finally,other parts of the coring tool are designed;the structure charts and engineering drawings are drawn and the parts are machined and manufactured.In the fifth chapter,the numerical simulation of the structural parameters of key parts of coring drilling tool is carried out,which analyzes the technical characteristics of CFD software.According to the actual situation,the analysis software Fluent is chosen to simulate the flow field inside the negative suction parts,which gives conclusion on the influencing rule of changing key parameters of negative suction parts towards pressure difference.In the sixth chapter,according to previous research,the optimized structure and parameters are used to reprocess some parts,and the negative suction effect test and the drilling test of the coring tool are carried out.Based on the analysis of the test results,the conclusion is obtained that the negative suction effect is obviously improved and the coring requirement within complex formations such as loose and broken formations can be satisfied.The seventh chapter summarizes the main research contents,research conclusions and innovation points,and points out the inadequacies of the paper and future research directions.Through theoretical analysis,structural design,numerical simulation and experiment of the above problems,the main conclusions and understandings are as follows:(1)The local reverse circulation coring drilling tool which is based on the pump suction principle can produce negative pressure inhalation effect and complete the target of drilling fluid local reverse circulation at the bottom of the hole.Also the feasibility of the method is proved by the function test of the coring tool.(2)This paper designed the local reverse circulation coring drilling tool,drew the three dimensional drawings and engineering drawings of the coring tool,completed the machining of coring drilling toolparts,forming a complete set of methodabout drilling tool design and manufacturing,laying the foundation for follow-up research and providing reference.(3)The numerical simulation of three key parameters(Ry,D and N)affecting the negative suction effect of coring tools is carried out by using fluid dynamics software.The parameter combinations for designing the model P91 are optimized.(4)Test results show that after optimizing the structure and parameter of the new coring tool,the negative suction effect increased to about 100%~360% under different pump capacity.The negative suction effect of the new coring drilling tool after optimizing the structure and parameters is better than that of current jet-type reverse circulation coring drilling tool,with negative suction effect increased by 17%~328% in different pump capacity.In the test of drilling,the coring drilling tool with new structure can meet the coring requirement in the target formation.