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The application of fiber in the completion fluid can improve the rheological properties of the completion fluid and the plugging quality of the production layer by the completion fluid and reduce the damage of the filtrate to the reservoir formation. However, there are few studies on the influence of fibers on the rheological properties of completion fluids and the flow behavior in pores. In this paper, plant fiber, mineral fiber, and synthetic fiber are discussed. Carbon fiber, bamboo fiber, polypropylene fiber, and polyester fiber are selected as research objects. The dependence of the rheological property of polymer solution on fiber type, fiber concentration, temperature, and shear rate is evaluated. The evaluation is carried out by observing the microscopic state of the fiber through a microscope and a scanning electron microscope, testing the rheological property parameters of the fiber with an OFITE 900 rheological tester, and fitting with the Herschel−Bulkley model. The results show that polypropylene fiber and carbon fiber have the best dispersion in polymer solution. The higher the fiber content, the greater the influence of fiber on the rheological properties of the solution. Compared with the other three fibers, carbon fiber has the greatest influence on the rheological properties of polymer solution. When the temperature is lower than 70 °C, the influence of the fiber on the rheological properties of the solution is not affected by the temperature. When the temperature exceeds 70 °C, the carbon fiber and polypropylene fiber are affected by the temperature, and the viscosity of the polymer solution is increased. The flow behavior of fiber suspensions in pores varies with the flow factor n. Carbon fiber suspensions are most conducive to the transition of polymer solution to plate laminar flow, which can improve the bearing capacity of plugging materials.

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Offshore oil- and gas-field development is shifting from shallow water to deepwater on a large scale. Deepwater shallow bentonite slurry drilling fluid has a single composition and a simple structure. Therefore, the bentonite slurry drilling fluid has been neglected for the shallow wellbore strengthening ability. Based on the shallow geological characteristics and bentonite hydration mechanism, considering the economy and application effect, the optimization of bentonite slurry drilling fluid from four aspects of viscosity enhancement, adsorption, trapping, and physical plugging to carry out deepwater shallow wellbore strengthening research has been undertaken. For an indoor simulation of bentonite slurry and its drilling slurry-making process using a 2–10% mass concentration of bentonite slurry drilling fluid, laser particle size analysis found an interesting phenomenon different from the traditional understanding: for every 5% increase in particle size accumulation in the range of 0.1–100 μm, the bentonite slurry particle size increases linearly. Based on this interesting phenomenon, the basic performance of drilling fluids with different concentrations of bentonite slurry was evaluated. Experiments were conducted to introduce cationic emulsified asphalt as a deformation filler and to explore a new inexpensive drilling and wellbore strengthening material, AEH-P. The effectiveness of deepwater shallow strengthening was evaluated for AEH-P and cationic emulsified asphalt from both mechanistic and experimental aspects. It is obvious that the wellbore strengthening effect is the result of both particle settling and particle size matching. By exploring the relationship among bentonite slurry hydration dispersion, the charged nature, particle concentration, and the wellbore strengthening effect, a set of low-cost deepwater shallow bentonite slurry drilling fluids with a good wellbore strengthening effect are constructed. The research results provide a method to strengthen the wellbore for the subsequent fast and efficient drilling of deepwater shallow wells, further improving the drilling efficiency.

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The method of plugging while drilling has been one of the commonly used methods to control formation loss during drilling. The damage to materials for plugging while drilling to MWD has become a complex problem. For many years, field engineers had insufficient knowledge of the passing performance of materials for plugging while drilling in measurement while drilling (MWD). In the existing research, the blocking mechanism of materials for plugging while drilling to mud screen during the flow process is still unclear. In this study, we use computational fluid dynamics coupled with discrete element method (CFD–DEM) to investigate materials’ plugging mechanism while drilling. The results show that the migration process of lost circulation materials (LCMs) in the mud screen can be divided into three stages, displacement, retention, and accumulation of LCMs. The blocking mechanism of LCMs on the mud screen comes from two aspects. One is from the bridging of LCMs with larger particle size in the holes of the mud screen. Another source is the difference between the entry speed and the overflow speed of LCMs. The particle size and mass fraction of LCMs and the viscosity and displacement of the fluid affect the flow properties of LCMs from these two factors, respectively.

In China’s unconventional oil drilling, horizontal wells are one of the main forms of drilling, water-in-oil drilling fluid have been widely used due to their stable performance and excellent lubricating properties. To reduce the high cost of water-in-oil drilling fluids at the drilling site, further reduce the pressure of cuttings processing, and meet the requirements of environmental protection, an oil-based drilling fluid system with a low oil-water ratio was developed. Based on the research of key emulsifiers and the introduction of nanomaterials, it helps the drilling fluid system maintain the performance of the drilling fluid while increasing the water-phase ratio, and further enhances the fluid loss performance of the drilling fluid. The developed low oil-water ratio oil-based drilling fluid has been applied in the horizontal section of Jiaoye 5-3HF and Jiaoye 21-S2HF, two wells in the Fuling shale gas block in China, and successfully drilled to the designed well depth. The Marsh funnel viscosity of the drilling fluid is controlled from 63s to 78s, the plastic viscosity is lower than 40 mPa·s, the dynamic shear force is maintained at 3.5–7 pa, the high temperature and high pressure water loss is controlled below 2.6 ml, and the demulsification voltage is stable above 600v; the properties of the drilling fluid Excellent, meeting the requirements of on-site drilling construction. Compared with the conventional oil-water ratio system, the oil-based drilling fluid system with low oil-water ratio can greatly reduce the oil content, which can meet the requirements of on-site drilling and save the cost of oil-based drilling fluid to a large extent. It can reduce the pressure of environmental protection to a certain extent.