The interfacial behavior of surfactants exerts a considerable impact on the chemical flooding-produced liquid treatment project. For circumventing the limitations of model simplification and single-factor simulation of previous molecular dynamics (MD) studies, this paper based on the experimental results of crude oil-phase and water-phase composition constructed different simulation systems of “crude oil/SDBS/mineral water” considering the concentration of sodium dodecyl benzene sulfonate (SDBS). The impact of SDBS concentration on the stability of the crude oil–mineral water interfacial film was explored, and the simulation results were verified by comparing with the simulation system of “crude oil/SDBS/pure water” and interfacial tension experiments. The simulated results showed that the SDBS molecules in the system exist in the form of a monolayer film after dynamic relaxation equilibrium, and with the increase in concentration, the number of SDBS molecules per unit area of the film increases, and the molecular chain bending characteristics are weakened. The order of the effect of inorganic cations on the aggregation degree of SDBS is Ca2+ > Na+ > K+ > Mg2+. When the concentration of SDBS increased from 0.15 to 0.70 mol/L, the total oil water interfacial film thickness increased from 1.433 nm in the crude oil/SDBS/mineral water system and 1.272 nm in the crude oil/SDBS/pure water system to 2.125 nm in the crude oil/SDBS/mineral water system and 2.398 nm in the crude oil/SDBS/pure water system. The absolute value of interface formation energy increased from 1223.59 and 1236.32 to 2739.19 and 3033.64, respectively, which are also basically consistent with the experimental results of interface tension. Furthermore, inorganic ions will weaken the performance of the surfactant SDBS and detrimentally affect the structural strength and stability of interfacial films. These results offer useful insights into the stabilization mechanism of oil–water emulsions. In particular, they provide a basis for the design and optimization of new pathways for oil–water emulsion instability in oilfield development.

As the global oil market continues to tighten, there is an increasing focus on enhancing oil recovery. However, enhanced oil recovery technologies require the addition of chemical components such as surfactants, alkalis, and polymers to the oil reservoir. These chemical components change the interface structure and affect fluid flow characteristics and phase interactions through adsorption and other behaviors, thus affecting the production efficiency and energy consumption of oil recovery, gathering, processing, and transportation. Particularly, a stable interface is formed during oil recovery that can sharply increase the difficulty of phase separation during oil gathering and processing, thereby considerably decreasing the separation efficiency. Therefore, it is crucial to understand the effect of the interface structure and behavior on fluid flow characteristics and phase interactions for the advancement of the petroleum industry. Herein, the application and regulation of interfaces in the petroleum industry for fluid flow characteristics and phase interactions are reviewed, approaches for characterizing interface characteristics are critically analyzed and discussed, mechanisms of various factors influencing interface formation and stability through phase interactions are investigated, and methods of interface inhibition and destruction are summarized. Moreover, the latest techniques for applied interface formation in the petroleum industry are discussed, and the challenges and research prospects related to interfaces are summarized, providing references for enriching theoretical research in the field of interfaces within the petroleum industry and efficiently optimizing the production and operation of the petroleum industry.

Wax deposition during crude oil transmission can cause a series of negative effects and lead to problems associated with pipeline safety. A considerable number of previous works have investigated the wax deposition mechanism, inhibition technology, and remediation methods. However, studies on the shearing mechanism of wax deposition have focused largely on the characterization of this phenomena. The role of the shearing mechanism on wax deposition has not been completely clarified. This mechanism can be divided into the shearing dispersion effect caused by radial migration of wax particles and the shearing stripping effect caused by hydrodynamic scouring. From the perspective of energy analysis, a novel wax deposition model was proposed that considered the flow parameters of waxy crude oil in pipelines instead of its rheological parameters. Considering the two effects of shearing dispersion and shearing stripping coexist, with either one of them being the dominant mechanism, a shearing dispersion flux model and a shearing stripping model were established. Furthermore, a quantitative method to distinguish between the roles of shearing dispersion and shearing stripping in wax deposition was developed. The results indicated that the shearing mechanism can contribute an average of approximately 10% and a maximum of nearly 30% to the wax deposition process. With an increase in the oil flow rate, the effect of the shearing mechanism on wax deposition is enhanced, and its contribution was demonstrated to be negative; shear stripping was observed to be the dominant mechanism. A critical flow rate was observed when the dominant effect changes. When the oil flow rate is lower than the critical flow rate, the shearing dispersion effect is the dominant effect; its contribution rate increases with an increase in the oil flow temperature. When the oil flow rate is higher than the critical flow rate, the shearing stripping effect is the dominant effect; its contribution rate increases with an increase in the oil flow temperature. This understanding can be used to design operational parameters of the actual crude oil pipelines and address the potential flow assurance problems. The results of this study are of great significance for understanding the wax deposition theory of crude oil and accelerating the development of petroleum industry pipelines.

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When wax deposition behavior occurs, gas condensate well suffers from moderate to serve reduction of productivity, even wellbore region blockage. For the operation and maintenance of a gas condensate well production system, a new methodology is needed to understand the wax deposition pattern in the wellbore region and assess the wax prevention under wellbore conditions. This paper establishes a phase envelope relationship in phase-behavior of typical condensate gas flow. The experiments map the potential deposition location in the wellbore region and capture the chemical wax inhibition performance in terms of wax appearance temperature (WAT), wax crystal morphology, and wax inhibiting rate, etc. The fluid component in wells for determining the envelope relationship in phase-behavior was corrected based on the gas-oil ratio of the actual gas condensate well and the carbon number distribution of the produced condensate oil-gas. The cold finger apparatus and dynamic wax inhibition measurement apparatus were designed to test wax deposition characteristics and evaluate chemical wax inhibition performance. The main test unit comprises a fully-closed high-pressure autoclave and cold finger capable of a maximum temperature of 285 °F and a maximum pressure of 16000 psi. The condensate mixtures were sampled from the wellbore region by downhole fluid sampling method. Starting from chemical wax prevention in wellbore flow, the wax crystal-improved wax inhibitor, which was mainly composed of long-chain hydrocarbons and polymers with polar groups, was employed. The temperature difference, intake pressure, stirring rate, and amount of wax inhibitor were controlled in the experiments. The wax content, WAT, and wax crystal structural characteristics of condensate systems showed noticeable differences from well to well. Using the matched component by the simulation, the wellbore temperature and pressure profiles are reliably predicted, and the envelope relationship in phase behavior of condensate gas flow is reasonably determined. Thermal and molecular diffusion are still the main mechanisms for driving wax deposition behavior in wellbore regions. The critical conditions for wax precipitation, wax deposition characteristics, and potential impact of wax deposition pattern are formulated. With the combined wellbore temperature and pressure profiles, the universal relationship schema for identifying deposition location is derived. The wax deposition location obtained from the schema agrees well with what was detected in actual production. Chemical wax prevention is an effective way to inhibit wax deposition. A maximum WAT reduction of 80% and a wax inhibiting rate of 90% could be achieved with the wax crystal improved wax inhibitor at a concentration of 0.25 wt.%. Understanding the wax deposition pattern in the wellbore region is significant for flow assurance and well operation. It provides evidence for wax prevention in wellbore flow and promotes deep condensate gas reservoir development and production efficiency.