Drag reduction performance of slick water is one of the key factors affecting fracturing, but the physical mechanism has still not been clearly identified. This paper aims to build a drag reduction modeling of polymer additives dissolved in hydrocarbon in pipe flow on the basis of Giesekus constitutive equation, which was validated by the loop experiment later. The model was applied to calculate the drag reduction rate of polyacrylamide tetrapolymer additive (DR800) in turbulent flow. Indoor loop experiments were introduced for parameter validation and model verification. Although the physical mechanism has still not been clearly identified, the modeling was aimed to explain the contribution of different components: viscous shear stress, Reynolds shear stress and viscoelastic shear stress. It turned out that as the complexity of the flow increased, the viscous contribution and viscoelastic contribution decreased while the turbulence contribution increased. In low Reynolds numbers, viscoelastic shear stress contributed most to friction coefficient while the turbulence can be neglected. In high Reynolds numbers, the contribution of turbulence increased rapidly thus to be the dominating part of the overall contribution, followed by viscoelasticity, and the least was viscous shear stress. By performing consistent comparisons between modeling and experimental results, it can be seen that the model can predict the drag reduction rate of DR800 in a range, which can be used for field production and guidance.

Non⁃ionic surfactants, fluorinated cationic surfactants, and fluorocarbon polymers have been evaluated for their ability to alter wettability and injectivity in tight sandstone reservoirs through contact angle tests and injectability tests. The results showed that, compared with other chemical agents, the fluorocarbon polymer CRS⁃850 had better gas wetting inversion effect, and the contact angle of the core surface increases from 45.6° to 92.1°; the self⁃absorption of salt water before wettability changing was 0.360 8 g, the self⁃absorption after treatment dropped to 0.020 6 g, the core self⁃aspiration decreased by 98.85%, and the max self⁃suction rate decreased from 0.053 g/min to 0.002 g/min. The wet reversal agent increased the liquid⁃phase percolation capacity of the coreand the gas⁃driving permeation rate significantly, and the recovery effect of core gas drive permeability is remarkable, which increases by 501.69% to 673.91% on the basis of the gas flooding brine, indicating that the gas⁃wetting reverser has beneficial to remove liquid⁃phase damage in tight sandstone reservoirs.

The Bozi block of the Tarim Oilfield is a typical tight sand condensate gas reservoir with serious wax plugging. So it is necessary to study the phase behavior and the wax deposition pattern of well fluids in Bozi gas reservoir, which will provide the phase enveloping diagram of the condensate gas and then help to control the paraffin deposition. In this study, the PVT tester and the self⁃designed microscopic solid deposition tester with visualized windows are used to get the phase enveloping line of the condensate gas of Well Bozi 104. The condensate oil and wax precipitation are analyzed based on the results of software simulation and production data. The results show that in the process of condensate gas changing with temperature and pressure, different phase states are produced, such as gas phase region, gas⁃liquid two phase region, gas⁃solid two phase region and gas⁃liquid⁃solid three phase region. The experimental results are used to correct the software simulation results to obtain different temperature and pressure phase. The state envelope is used to predict the conditions for liquid and wax precipitation when the production wells are in different production stages; the condensate and wax deposition areas of the Bozi 104 wells are located on the ground transmission pipelines, and appropriate anti⁃wax measures should be made