In December 2021, the international journal Petroleum Science published the original paper "Research on in-situ preserved coring and testing systems" by Xie Heping's team, which systematically introduced the significant original results of "deep in-situ preserved coring and fidelity testing systems" achieved by Xie Heping's team. The research on in-situ preserved coring and testing systems" was introduced by Xie Heping's team.

The new concept of "five-preserved" (preserved pressure, preserved quality, preserved moisture, preserved light) coring was proposed for the first time, and was the first to define "preserved pressure coring (IPP-Coring), preserved quality coring (ITP-Coring), preserved quality coring (ISP-Coring), preserved moisture coring (IMP-Coring), preserved light coring". The company has defined a series of proprietary terms such as "IPP-Coring", "ITP-Coring", "ISP-Coring", "IMP-Coring" and "ILP-Coring", and has rigorously defined their connotations to establish an original, world-leading "deep in-situ fidelity coring and fidelity testing and analysis system".

Fig. 1 Schematic diagram of the deep rock in-situ fidelity coring and fidelity test analysis system

Through deep in-situ fidelity coring and fidelity test analysis to obtain real "living" samples from the deep Earth, the system will realise the test analysis of rock material, composition, structure and behavioural characteristics under deep in-situ environmental conditions. The system will provide a means and platform for constructing new theories of deep engineering science, improving access to deep resources, exploring new mysteries of the deep Earth, and obtaining new data on the variability of rock characteristics in in-situ environments at different depths. The work was approved by the National Natural Science Foundation of China in 2019 as a major scientific research instrument project (recommended by the department) "Deep Rock In-situ Fidelity Coring and Fidelity Test Analysis System (51827901)".

Fig. 2 Schematic diagram of fidelity environment rock sample loading test

Focusing on the three core technical difficulties of the system: deep in-situ pressure and insulation coring (a world problem), deep in-situ quality and moisture preservation and light preservation coring (a technical gap) and deep in-situ fidelity loading testing (a technical gap), the team innovated independently and achieved a breakthrough from 0 to 1 in principle conception, testing platform and technical equipment. Among them, in the fidelity of the core system innovation proposed a self-triggered gravity-type pressure-holding control technology, active-passive enhanced coupling insulation technology and in-situ solid film preservation quality moisture and light preservation technology. It has now achieved 100 MPa pressure-holding limit load-bearing strength, 0.97% temperature control accuracy and more than 98% quality and moisture preservation and light preservation rate; in addition, the pressure control accuracy for reconstructing the in-situ environment of the transfer and storage system is as high as 1% and the steady-state temperature control accuracy reaches ±0.2°C; the recording error of the non-contact test system is 6% smaller than that of the contact test. The predetermined research objectives associated with this project have been exceeded.

Fig. 3 Schematic design of the insulation structure of the corer

Fig. 4 Schematic diagram of the sealing film with composite nano-fillers to achieve the principle of quality, moisture and light retention

The research and development of this major scientific instrument will truly obtain the parameters, characteristics and laws of deep in-situ environment in real state, crack the core problems of deep rock mechanics "in-situ" research, fill the gaps in the principle, technology and equipment of deep in-situ rock mechanics research, which is conducive to re-understanding deep resource reserves and exploring the mystery of deep life, and will also greatly promote the high-level development of deep earth, deep sea and deep space fidelity prospecting and coring technology in China.