A novel chemical-consolidation method based foam amino resin system of sand control systems in the oilfield is reported. This sand control technique is more superior to the conventional method owing to its advantages such as the outstanding resistance and lower density as well as simple process preparation. The apparent density of the foam resin system ranges from 0.528 g/cm³ to 0.634 g/cm³ at room temperature. Moreover, the system has excellent foaming properties and excellent compatibility with the formation fluids. In addition, the foam amino resin sand consolidation system was optimized and investigated. Simultaneously, the sand-fixing performance of the foam resin system was comprehensively assessed. The optimized conditions are as follows: curing temperature, 60°C; curing time, 12 h; consolidated core compressive strength, 6.28 MPa. Furthermore, the consolidated core showed remarkable resistance to the formation fluids. In summary, the foam resin system effectively met the requirements of the sand control and the horizontal wells in the oilfield.

Sand production has been a shared problem in the development of weakly-cemented sandstone oil reservoirs. Sanding simulation and prediction are of utmost importance for the production optimization of this type of reservoir. For a long time, research on sand production has been centered on “what is produced from the formation,” such as the size and rate of produced sand. However, “what is left inside the formation,” which is the structural change of the rock after sanding, is also another intriguing and important topic for the management of sand-prone reservoirs. Some related studies have been carried out, and they have proposed that wormhole-like pore throat will appear after sand production, but the precise morphological description and formation mechanism are still lacking. A series of sanding simulation experiments are performed to deepen the understanding of the sanding cavity pattern and its mechanism. The experiments are carried out using a visual sanding simulation apparatus. Through this, the complex wormhole sand production patterns are found and classified into single-branch wormhole cavity patterns and multi-branch wormhole cavity patterns. The extension processes of those different patterns are also demonstrated. Besides, this work discusses the change in the reservoir flowability performance in wormhole sanding mode, and the near-well flowability might be improved by actively inducing weakly-cemented sandstone to create a bigger aperture wormhole sanding pattern. Through the visual microscopic system, the sand competitive detachment mechanism that induces wormhole extending is revealed, along with the cavities concurrent extension mechanism that induces multi-branch wormhole extending. Moreover, this work discusses the microscopic detachment forms which help explain the sand-produced rate from weakly-cemented sandstone. This work enhances and creates a novel understanding of the sanding patterns and mechanisms in weakly-cemented heterogeneous reservoirs, which is beneficial to providing direct guidance for sand production prediction and sand control optimization.

In this paper, we have developed a facile MgCl₂-assissted hydrothermal synthesis route to grow tubular aragonite whiskers on a large scale. The products have been characterized by powder X-ray diffraction (XRD), optical microscopy, and scanning electronic microscopy (SEM). The results show the as-grown product is pure tubular aragonite crystalline whiskers with a diameter of 5–10 mm and a length of 100–200 mm, respectively. The concentration of Mg²⁺ plays an important role in determining the quality and purity of the products. Furthermore, the method can be extended to fabricate CaSO₄ fibers. The high quality of the product and the mild conditions used mean that the present route has good prospects for the growth of inorganic crystalline whiskers.

Summary: Successful cases of hydraulic screen-through fracturing (HSTF) in the Bohai oil field highlight the possibility that hydraulic fracturing can be an alternative method for enhancing the productivity of loose reservoirs. However, a portion of the HSTF wells in the Bohai oil field suffer from severe solids production, meaning that proppants and stratum sands are produced in the wellbore during production and cause wellbore plugging and ensuing debilitation of productivity. In this study, fluid flow amid the stratum, fracture, and HSTF well is simulated experimentally, and pressure drop, flow rate of the fracture, and stratum are monitored to investigate mechanisms and influencing factors of solids production from HSTF wells. Perspectives on solids control optimization are put forward for the Bohai oil field. Results indicate that the formation of an erosion cavity on lip-sealing in fracture and a dominant fluid channel near the wellbore in the stratum are two main mechanisms of solids production. The higher the flow rate and fluid viscosity are, the more severe solids production can be. For the Bohai oil field, with 725-psi-strength resin-coated proppant, the minimum proportion of resin-coated proppant in fractures to prevent solids production can be reduced from the previous 65% to 30%. With 1,073-psi-strength resin-coated proppant, it can be further reduced to 20%. Reducing the proportion of resin-coated proppant can help optimize the conductivity of fractures. This study aims to provide preliminary insight on solving the solids production problem of an HSTF well, thus enhancing the applicability of hydraulic stimulation in loose reservoirs.