| With the earth’s shallow resources gradually exhausted,marching into the earth’s deep has become a key scientific and technical strategy for energy exploitation across the world.However,in comparison to shallow resource exploitation,deep resource development is hampered by extreme engineering factors such as high geotemperature,high crustal stress,high osmotic pressure,and strong disturbance,which severely limit the efficient and safe exploration and development of deep resources.At the moment,the fundamental ideas underlying geological exploration,mineral development,and oil and gas extraction across the world are still based on classical theories such as material mechanics and elasticity.It is difficult to effectively describe or even blank the mechanical behavior differences of rocks under different depths and in-situ environmental conditions.It is necessary to break through the traditional theoretical framework and innovate the scientific theory of rock mass mechanics in deep in-situ environment.The current rock mechanics system is mainly based on the classical rock mechanics theories and experimental methods of “ordinary” standard core,classical real-time loading path and elastic-plastic constitutive relationship.However,almost all“ordinary” standard core samples have lost their in-situ stress and storage environment,and cannot truly reproduce their original state.Therefore,the core and key of innovating deep in-situ rock mass mechanics is how to obtain in-situ core under deep environmental conditions,and how to obtain deep original in-situ condition preserved core has become a technical problem that needs to be broken through around the world.Therefore,we proposed “Five Preservation” coring concept as pioneer,and innovatively developed the in-situ condition-preserved coring(ICP-Coring)technology to realize in-situ maintenance of the deep rock samples’ storage environment,which can provide technical support for innovating the scientific theory of rock mass mechanics in deep in-situ environment.This innovative technology has been granted by China National Natural Science Foundation(NO.51827901).The project consists of three systems: in-situ condition-preserved coring system,in-situ condition-preserved transferring system and in-situ condition-preserved testing system.Additionally,the system is divided into six functional modules: in-situ pressurepreserved coring,in-situ temperature-preserved coring,in-situ quality-moisture-light preserving coring,calibration platform,in-situ environment reconstruction and in-situ testing system.In-situ pressure-preserved coring(IPP-Coring)is one of the core functional modules of ICP-Coring.This paper focuses on the extreme operating environments such as high temperature,high pressure,strong disturbance and small space of deep drilling,furthermore,a pressure controller assembly with self-tightening sealing characteristics and composite sealing function was proposed,so as to ensure the sealing stability and reliability of ICP-Coring operation in deep extreme environment.The main research contents are as follows:(1)Based on the working mechanism of ICP-Coring system,the composite seal design idea and the sealing interface characterization method of pressure controller are proposed.The pressure controller with spatial intersecting geometric characteristics and self-tightening compound sealing principle is innovatively designed,and the spatial geometric motion model of the sealing interface is constructed to eliminate the risk of geometric interference in the working process of the pressure controller;The sealing interface is reconstructed by two-dimensional digital filtering algorithm,and the quadratic interpolation method is used to fit it to obtain a smooth numerical surface;Based on the error analysis of statistical parameters of rough surface,the parameter accuracy of fitting surface model is verified.(2)Taking the contact area ratio and contact load as evaluation parameters,the effects of surface randomness,contact morphology and surface texture on the micro contact characteristics and surface morphology are studied.The research shows that the random characteristics of rough surfaces have little influence on the results of numerical simulation.Under the same statistical parameters,any group of rough surfaces can be selected for calculation and analysis.In the range of ideal elastic deformation,compared with the contact analysis results of isotropic surface and anisotropic surface,the general change law of contact characteristics is basically the same,and the numerical difference is small,but the surface morphology is quite different,which has an important impact on the formation of metal seal.Considering the plastic parameters of materials,when the isotropic surface and anisotropic surface reach the critical sealing conditions within the selected roughness range,the corresponding contact loads of the same material under different roughness and surface texture characteristics are almost the same.When the sealing interface adopts the processing technology of anisotropic surface,the better sealing performance can be obtained by distributing the flow direction of hydraulic medium perpendicular to the texture direction.(3)Combined with numerical simulation and laboratory test,the seal form evolution law of the pressure controller with initial configuration is studied,and the reason why it cannot realize composite seal is disclosed.The motion characteristic test was carried out for the pressure controller with specific configuration parameters,and the motion stability of the pressure controller forming a composite seal in a narrow space was tested.Based on the design principle of selftightening composite seal and the design manual of high pressure vessel,the critical evaluation criteria for the formation of initial rubber seal and metal seal are put forward respectively.Through numerical simulation and laboratory test,the sealing ability of the pressure controller with current configuration is verified,the causes of composite seal failure are analyzed and the optimization direction is proposed.(4)The pressure controller with the characteristics of single contact composite seal and bending resistant composite seal is innovatively designed,and the approximate solution method of micro inclined plane contact problem based on non-uniform contact is proposed.Aiming at the key problem that the pressure controller cannot realize the composite seal,the sealing interface design idea of single contact composite seal is proposed,and the continuous contact of metal sealing area is realized through the optimization of interface parameters.According to the contact form of single contact seal interface,the micro inclined plane contact problem is approximately solved based on the theory of contact mechanics.By analyzing the failure causes of single contact seal,the pressure controller with bending resistant configuration is innovatively designed,and the characteristics of composite seal before and after optimization are compared through numerical simulation to verify the feasibility of seal in theory.(5)The effectiveness of the composite seal of the bending resistant pressure controller is tested through laboratory tests,and the contact characteristics of its sealing interface in the process of bearing are analyzed.Based on the process analysis and control of the preparation process,the prototype of the pressure controller is processed.The dimensional machining accuracy and sealing interface matching accuracy are verified by morphology measurement and hydrostatic test.The laboratory test of pressure controller’s sealing performance with 100 MPa are completed,which proves the reliability of its composite seal.By comparing the changes of the micro morphology of the sealing interface and the macro configuration size of the bonnet before and after the test,the formation mechanism of the composite seal is revealed,and its safety in the deep high-pressure environment is proved. |
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