Gas storage reservoirs are crucial infrastructures for strategic reserves, emergency peak regulation, and safeguarding national energy security. However, the complex injection and production processes and frequent pressure fluctuations pose severe challenges to safe production. The through-tubing retrievable packer, as a key downhole equipment for through-tubing operations, has the advantages of high efficiency, low risk, and simple operation. It shows the great application potentialities in the fields of temporary plugging and seal verification of immobile pipe strings. However, the through-tubing packer with the traditional laminated steel sheet structure cannot meet the on-site requirements for the super-expansion sealing of using 4-1/2 tubing to seal the 7-inch casing in gas storage reservoirs. It is urgent to solve the problem of sealing a large-diameter casing with a small-diameter tubing while taking into account the sealing performance and strength requirements of the rubber element.Here, this paper innovatively put forward a design scheme for a new corrugated-skeleton through-tubing retrievable packer. It determined the size parameters and material selection of the corrugated skeleton, three-rubber-element structure and other key components. By establishing the setting mechanical models of through-tubing packer, the setting mechanism was elucidated and the effective setting conditions for downhole operations were defined. The 3rd-order Ogden model was selected to conduct a hyperelastic constitutive analysis on the polyurethane rubber element, and the ABAQUS finite element simulation software was adopted to simulate the super-expansion process of the packer. The results indicated that the overall complete super expansion could be achieved within 30 seconds, verifying the feasibility of the super expansion behavior. On this basis, the geometric size parameters of the corrugated skeleton and sealing rubber element of the super-expansion corrugated-skeleton through-tubing retrievable packer were further optimized. The simulation results showed that when the profile expression of the corrugated skeleton is y=3sin1.5x and the outer diameter of the outer rubber element is 84 mm, the overall stress change of the packer is smooth, the setting performance is good, and thus the stress concentration can be effectively reduced, and the sealing performance and setting effect can be improved. This super expansion corrugated-skeleton through-tubing retrievable packer can meet the pressure-bearing requirements of the complex working conditions of gas storage reservoirs, reduce the stress concentration of the sealing rubber element, extend the service life of the downhole tool, and provide theoretical support and design reference for the design of super expansion through-tubing retrievable packers in gas storage reservoirs.

Because the magnetic signal information of pipeline defects obtained by magnetic flux leakage detection contains interference signals, it is difficult to accurately extract the features. Therefore, a novel pipeline defect feature extraction method based on VMD-OSVD (variational modal decomposition - optimal singular value decomposition) is proposed to promote the signal to noise ratio (SNR) and reduce aliasing in the frequency domain. By using the VMD method, the sampled magnetic signal is decomposed, and the optimal variational mode is selected according to the rate of relative change (VMK) of Shannon entropy (SE) to reconstruct the signal. After that, SVD algorithm is used to filter the reconstructed signal again, in which the H-matrix is optimized with the phase-space matrix to enhance SNR and decrease the frequency domain aliasing. The results show that the method has excellent denoising ability for defect magnetic signals, and SNR is increased by 21.01%, 24.04%, 0.96%, 32.14%, and 20.91%, respectively. The improved method has the best denoising effect on transverse mechanical scratches, but a poor denoising effect on spiral welding position. In the frequency domain, the characteristics of different defects are varied, and their corresponding frequency responses are spiral weld corrosion > transverse mechanical cracking > girth weld > deep hole > normal pipe. The high-frequency band is the spiral weld corrosion with f₁ = 153.37 Hz. The low-frequency band is normal with f₂ = 1 Hz. In general, the VMD-OSVD method is able to improve the SNR of the signal and characterize different pipe defects. And it has a certain guiding significance to the application of pipeline inspection in the field of safety in the future.

The sleeve sealing ball seat is one of the important components in the multistage fracturing process of horizontal wells. The erosion and wear of the surface will decrease the sealing performance of the fracturing ball and the ball seat. This leads to pressure leakage during the fracturing process and fracturing failure. In this paper, combined with the actual ball seat materials and working conditions during the fracturing process, the erosion tests of ductile iron and tungsten carbide materials under different erosion speeds, angles, and mortar concentrations are carried out. Then the erosion test results were analyzed by mathematical fitting, and a set of erosion models suitable for sliding sleeve setting ball seat materials were innovatively established. For the first time, this paper combines the erosion model obtained from the experiment and the computational fluid dynamics (CFD) with Fluent software to simulate the erosion of the ball seat. Based on the simulation results, the morphology of the sliding sleeve seat ball after erosion is predicted. Through analysis of the test and simulation results, it is showed that the erosion rate of tungsten carbide material is lower and the wear resistance is better under the condition of small angle erosion. This research can offer a strong basis for fracturing site selection, surface treatment methods, and prediction of failure time of ball seats.

Friction is widespread in almost every field in the oil and gas industry, and it is accompanied by huge energy losses and potential safety hazards. To deal with a series of questions in this regard, biomimetic surfaces have been developed over the past decades to significantly reduce economic losses. Presently, biomimetic surface engineering on different scales has been successfully introduced into related fields of the oil and gas industry, such as drill bits and the inner surfaces of pipes. In this review, we focused on the most recent and promising efforts reported toward the application of a biomimetic surface in oil and gas fields, indicating the necessity and importance of establishing this disciplinary study. Regarding the oil and gas industry, we mainly analyzed and summarized some important research results into the following three aspects: (i) applications in reducing the wear of exploration production equipment and its components, (ii) separation and drag release technologies in oil/gas storage and transportation, and (iii) functional coatings used in oil and gas development in oceans and polar regions. Finally, based on an in-depth analysis of the development of biomimetic surface engineering in the fields of oil and gas, some conclusions and perspectives are also discussed. It is expected that biomimetic surface engineering can be used in oil and gas fields more widely and systematically, providing important contributions to green development in the near future.