Treatment of the oilfield wastewater from the chemical and petroleum industries, often present in the form of emulsion, is one of the major environmental concern in current times. Demulsification is presently the most viable method to separate the oil and water from a rigid, homogenous emulsion especially, chemical demulsi-fication. Mostly, chemical demulsifiers used at high temperature can give enhanced separation efficiency and result in the use of less dosage of expensive chemicals. Mainly, the reservoir conditions also exist at high tem-perature, thus, it is important to consider the effect of temperature for the selection of best choice among available demulsifiers. The review discusses the recent discoveries and modification among the existing demulsifiers such as triblock EO-PO copolymer, non-biodegradable polymers, branched copolymers and others. The major chemical demulsifiers and their upcoming alternatives such as the nanomaterial demulsifiers and ionic liquids have also been discussed in great details. Chemical structure and molecular weight were found to in-fluence the emulsion breaking ability of a demulsifier. The surface properties play an important role in the se-lection of appropriate demulsifier whether hydrophobic or hydrophilic. Method of heating whether microwave or conventional heating, doesn't play a significant role in influencing the emulsion breaking efficiency of polymeric surfactants. However, microwave heating is preferred for demulsification by ionic liquids. Lastly, the whole mechanism of chemical demulsification and few upcoming chemical treatments for demulsification are also well described in brief.
When a gas hydrate reservoir is depressurized for gas production, the production tendency and dissociation behavior may differ depending on conditions such as the bottom hole pressure and depressurization rate. Gas hydrate dissociation is a complex process that involves the transfer of materials and heat, and on-site analysis based on laboratory-scale results is critical. In the present study, a field-scale numerical analysis was performed to reflect the conditions of the Ulleung Basin in the East Sea of Korea. The dissociation behavior, which varies depending on the conditions in the gas hydrate-bearing sediment, was analyzed under various conditions of bottom hole pressure and depressurization rate. This study also identified the effects of depressurization conditions on gas hydrate saturation. As the bottom hole pressure decreased and the depressurization rate increased, the production rate and cumulative production of gas and water increased, and the radius of the pressure propagation effect at the beginning of production increased. In sediments with a gas hydrate saturation of ≥70%, the pressure propagation was unstable and the dissociation rate was low. These results can serve as preliminary data for the field production of gas hydrates in the Ulleung Basin.
We apply Massively Parallel Interface for MPFA-O scheme with state-of-the-art Operator-Based Linearization (OBL) approach for multiphase flow in porous media. The implementation of MPFA-O scheme enhances the modelling capabilities for non-K-orthogonal mesh. A fully implicit scheme is applied to guarantee the stability of solutions when a mass-based formulation is involved to keep the flexibility of the framework for general-purpose reservoir simulation. As the MPFA-O introduces more non-zeros elements in the Jacobian matrix than the traditional TPFA, massively parallel computations via Message Passing Interface (MPI) in this work help to guarantee competitive computational efficiency for high-fidelity geological models. Concerning the Jacobian assembly hassle, we apply the OBL approach which introduces operators combining the fluid and rock properties in the conservation equations and discretizes the operators in the physical parameter space. By computing values and derivatives of the operators via a multilinear interpolation, the assembly of Jacobian matrix and residual vector could be drastically simplified. Another benefit of the OBL is that by only evaluating operator values on the predefined nodes in the physical parameter space, the overhead related to complex phase behavior and property evaluation is significantly reduced. In the end, we present several benchmark cases to rigorously demonstrate the accuracy, convergence, and robustness of the framework and two challenging field-scale cases to further prove its computing performance and parallel scalability.
Breakthroughs in shale gas exploration in the Upper Ordovician-Lower Silurian strata of the Upper Yangtze Platform have attracted interest in its sedimentary-tectonic evolution, but the tectonic background of the northern margin of the Upper Yangtze Platform remains unclear. In this paper, the Wufeng-Longmaxi formations on the northern margin of the Upper Yangtze Platform were investigated. Based on geochemical and mineral-ogical analyses of the tuffs/K-bentonites of the Wufeng Formation and the barite in the Longmaxi Formation, as well as previous research results, it was concluded that the northern margin of the Upper Yangtze Platform was in an extensional tectonic background during the Late Ordovician-Early Silurian. Detailed analysis revealed that, (1) the U-Pb zircon age of the tuff in the Bajiaokou section in South Qinling is 443.91 +/- 0.92 Ma. The Zr/ TiO2-Nb/Y diagram of the tuffs/K-bentonites indicates that their protoliths were alkaline-subalkaline basalt and andesite series rock. Based on the Th-Hf/3-Ta, Th-Tb*3-Ta*2, and TiO2-Nb/3-Th diagrams, there are undis-covered intraplate tension calc-alkaline basalts in the northern Yangtze Platform or the southern Qinling region, which provided volcanic clastic materials to the Ziyang, Lan'gao, Chengkou, Yichang and other regions. (2) Scanning electron microscopy revealed that the barite crystals in the Longmaxi Formation exhibit dissolution features and have a large particle size. Energy spectrum analysis of these barite crystals revealed that they have C, O, S, and Ba contents of 8.48 wt%, 22.98 wt%, 13.09 wt% and 55.44 wt%, so they are speculated to have been formed via cold methane seep genesis in a weak extensional tectonic setting. The 87Sr/86Sr ratios of the barite revealed that different types of barite were simultaneously formed in this area under the influences of hydro-thermal and cold methane seeps. (3) The analysis of the heavy minerals in the Lower Silurian strata in the Bajiaokou section revealed that the provenance in the South Qinling area changed significantly during the late Early Silurian. Based on the above analyses, the northern margin of the Upper Yangtze Platform was in an extensional tectonic setting during the Late Ordovician-Early Silurian. The distribution of the total organic carbon content indicated that the extensional tectonic background provided good conditions for the enrichment and preservation of organic matter. The results of this study provide an understanding of the regional sedimentary-tectonic pattern and evolution of the Yangtze Platform during this period, as well as a reference for future shale gas exploration in this region.
Significant natural fractures develop in deep sandstone reservoirs. However, the previous numerical simulation for matrix acidizing in sandstone rocks always focused on the reactive flow in porous media. A series of responses between multiple types of acids and minerals in fracture and matrix pores have been a significant setback for seeking the mechanism of acid flow in fractured sandstone rocks. This paper, established a multistage reactive-transport model for fractured sandstone rocks based on the two-scale continuum model to explore the effects of fractures on the reactive flow. The weak forms of fluid flow and solute transport equations are derived using the Galerkin method to couple the matrix and fracture domains, and the extended finite element method was used to solve the discretization model. Additionally, we presented numerical simulations under 2D linear flow conditions with specific and sensitive analyses about fracture and matrix properties. Numerical cases showed that the wormhole-shaped structure generated by acid dissolution is hard to develop even in highly heterogeneous fractured sandstone rocks due to the low reaction rate between mud acid and minerals. However, fractures that are not parallel to the flow direction can accelerated acid flow in the formation and reduced Si(OH)4 precipitation. Increasing the injection rate can not change the dissolution patterns of sandstone, but expanded the acid diffusion range and decreased Si(OH)4 precipitation in fractured sandstone.
