Research progress and application of deep in-situ condition preserved coring and testing

With the depletion of shallow resources, the exploration of deep earth resources has become a global strategy. The study of the different patterns in the physical mechanical properties of rocks at different occurrence depths is the basis for exploring deep into the earth, with the core and premise being the acquisition and testing of deep in-situ core specimens. Based on the original idea of deep in-situ condition preserved coring (ICP-Coring) and testing, combined with theoretical modeling, numerical analysis, test platform development, indoor testing and engineering application, the principles and technologies of deep ICP-Coring are developed. This principle and technology consists of five parts: in-situ pressurepreserved coring (IPP-Coring), in-situ substance-preserved coring (ISP-Coring), in-situ temperaturepreserved coring (ITP-Coring), in-situ light-preserved coring (ILP-Coring), and in-situ moisturepreserved coring (IMP-Coring). The theory and technology of temperature and pressure reconstruction at different occurrence depths and in different environments are proposed, and prototype trial production was completed by following the principle of displacement and tests based on the in-situ reconstructed environment. The notable advances are as follows: (1) Deep in-situ coring system: A pressure-preserved controller with an ultimate bearing capacity greater than 140 MPa, highperformance (temperature-resistant, pressure-resistant, and low thermally conductive) temperaturepreserved materials, an active temperature control system, and high-barrier quality-preserved membrane materials were developed; a deep ICP-Coring capacity calibration platform was independently developed, a deep in-situ coring technology system was developed, and the acquisition of deep in-situ cores was realized. (2) In-situ storage displacement system: Following the dual-circuit hydraulic design idea, a single-drive source push-pull composite grabbing mechanism was designed; the design of the overall structure for the deep in-situ displacement storage system and ultrahigh pressure cabin structure was completed, which could realize docking the coring device and core displacement in the in-situ reconstructed environment. (3) Test analysis system: A noncontact acoustic-electric-magnetic test system was developed under the in-situ reconstructed environment, and the errors between the test results and traditional contact test results were mostly less than 10%; a detachable deep in-situ core true triaxial test system was developed, which could perform loading tests for deep in-situ cores. The relevant technological achievements were successfully applied to the exploration and development of deep resources, such as deep mines, deep-sea natural gas hydrates, and deep oil and gas. The research results provide technical and equipment support for the construction of a theoretical system for deep in-situ rock mechanics, the development of deep earth resources and energy, and the scientific exploration of different layers and occurrence depths (deep and ultradeep) of the Earth.(c) 2023 Published by Elsevier B.V. on behalf of China University of Mining & Technology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).