This article describes the chemical make-up and application of the types of gels most commonly used in conformance improvement. Oilfield conformance improvement gels come in a wide range of forms and chemistries. Table 1 provides an overview of various conformance improvement gels. CC/AP gels have an exceptionally robust gel chemistry and are highly insensitive to oilfield and reservoir interferences and environments. They are also applicable over an exceptionally broad pH range. As a result, these gels, when properly formulated, are applicable to the acidic conditions associated with CO2 flooding for which most earlier oilfield polymer gels did not function well.
Early application of polymers for use during oilfield conformance improvement operations was focused on improving volumetric sweep efficiency of waterfloods. More recently, polymers have been used extensively in disproportionate permeability reduction (DPR) and relative permeability modification (RPM) treatments for water shutoff and in conformance improvement polymer-gel treatments. This page discusses polymers used in oilfield operations and how they contribute to conformance improvement. Polymers are large molecules and chemical entities referred to as macromolecules. Polymer molecules are the resultant chemical specie when a large number of relatively small and repeating molecular entities, called monomers, are joined together chemically.
Viscoelastic surfactants (VES) are important gelling agents in well stimulation treatments. Proper job design requires that the additives create the desired viscosity for effective proppant or gravel pack sand transport. Post-stimulation production enhancement partially relies on the thoroughness of gelling agent destruction or removal, known as "breaking" the gel. VES gels are non-damaging and do not create a filter cake, and thus are prone to high leak-off. The leak-off fluid potentially has a high zero-shear viscosity and can be challenging to remove from the formation. We propose a breaker system that comprises a monomer and radical initiator that will travel into to the formation with the VES gel. The resulting polymer will disrupt the worm-like micelles of the VES, creating spherical micelles and reducing the viscosity of the fluid. The breaker system presented here is operable at 200 °F. Rheology measurements show that the VES fluid with monomer and initiator has reduced viscosity and becomes less shear-thinning. Optical transmission and backscattering measurements show that the presence of breaker does not greatly accelerate proppant settling. The reduced viscosity would not adversely affect proppant transport. Core flow experiments compared retained permeability of cores treated with VES and VES with reacted monomer and initiator. The core flushed with broken fluid possessed a retained permeability of 79%, while the unmodified VES left only 44% retained permeability.
Hou, Qingfeng (Key Laboratory of Oilfield Chemistry, Research Institute of Petroleum Exploration and Development, CNPC) | Zheng, Xiaobo (Key Laboratory of Oilfield Chemistry, Research Institute of Petroleum Exploration and Development, CNPC) | Guo, Donghong (Key Laboratory of Oilfield Chemistry, Research Institute of Petroleum Exploration and Development, CNPC) | Zhu, Youyi (Key Laboratory of EOR, Research Institute of Petroleum Exploration and Development, CNPC) | Yang, Hui (Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences) | Xu, Xingguang (Energy Business Unit, Commonwealth Scientific Industrial Research Organization) | Wang, Yuanyuan (Key Laboratory of Oilfield Chemistry, Research Institute of Petroleum Exploration and Development, CNPC) | Chen, Gang (Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences) | Hu, Guangxin (Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences) | Wang, Jinben (Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences)
Stimuli-responsive emulsions have attracted much attention in diverse fields. However, research on the rapid and effective demulsification based on pH-responsive emulsions has barely been reported, although they are viewed as promising canditates for oil-water separation processes after oil recovery. In the present work, we have successfully synthesized a series of pH-responsive emulsions on the basis of a novel polymer containing amphiphilic and protonated moieties. The properties of these pH-responsive emulsions including stability, morphology microscopy, Zeta potential, and interfacial tension have been extensively investigated. We observed that the prepared oil-in-water emulsion could stay stable for more than 24 h within the pH range of 8-10, while it lost 80-90% of the water in 10-20 min if the pH was adjusted to 2-4. The variation in emulsion stability can be attributed to the protonation of poly [2-(N, N-diethylamino) ethyl methacrylate] (PDEA) residues at low pH values. Accordingly the polymers intend to become more hydrophilic and depart from the oil-water interface, leading to an increased interfacial tension. Furthermore, it was found that the applied polymers aggregated at the oil-water interface and that the morphology of aggregations was strongly affected by the pH values. These proposed polymers enabled the formation of emulsion with a controllable response to the pH stimuli. This work is expected to shed light on the development of stimuli-responsive emulsions and may have significant implications in the fields of oil recovery, waste water treatment, and so forth. For example, due to the high w/o interface activity of surfactants such as heavy alkyl benzene sulfonate (HABS) and petroleum sulfonate, severe emulsion has also been found with the alkali-surfactant-polymer (ASP) produced fluid. Currently, rapid breaking of these emulsion fluid is still a big challenge.
Zhao, Jian. (China University of Mining and Technology) | Wang, Jia-Min (China University of Mining and Technology) | Gao, Wei (China University of Mining and Technology) | He, Man-Chao (China University of Mining and Technology)
Kaolinite is often a cause of deformation in soft-rock tunnel engineering, leading to safety problems. The mechanism of the deformation is closely related to the interaction between kaolinite and water molecules. In order to gain a better predictive understanding of the governing principles associated with this phenomenon, we investigated the adsorption of H2O on the kaolinite (001) surface using the density functional theory within the local-density approximation and a supercell approach at first. The coverage dependence of the adsorption structures and energetics was studied systematically for a wide range of coverage, [from 1/16 to 1 monolayers (ML)], and adsorption sites. The results showed that the preferred adsorption sites on the kaolinite (001) surface for H2O are the threefold hollow site with the adsorption energies ∼1.10 eV. The adsorption energy decreased with coverage, thus indicating the greater stability of surface adsorption and a tendency to form H2O islands (clusters) with increasing coverage. The results further revealed that the H2O does not adsorb on sixfold hollow site of the aluminum (001) face of the third layer of kaolinite, implying that water molecule is difficult to penetrate through the ideal kaolinite (001) surface. In addition, we calculated the energetic barriers for diffusion of H2O between the most stable and next most stable adsorption sites, which range from 0.073 to 0.129 eV. The results also showed that H2O are very easy to diffuse on kaolinite (001) surface. The other properties of the H2O /kaolinite (001) system, including the different charge distribution, the lattice relaxation, and the electronic density of states, were also studied and are discussed in detail.
Soft rocks rich in clay minerals can cause harm to tunnel engineering because, when adsorbing water, the mechanical strength of the clay minerals is reduced, leading to deformation of the rocks. In order to gain a better predictive understanding of the governing principles associated with this phenomenon, the interaction between clay minerals and water molecules requires further investigation (Roland et al., 2011; Croteau et al., 2009). Kaolinite is one of the most abundant components in clay minerals. Understanding the interaction between kaolinite and water molecules is important to researchers in the fields of geophysics and geomechanics (Yoshihiko et al., 1999; He et al., 2009; Gupta and Miller, 2010; Yin and Miller, 2012). Due to the limitations of experimental methods, theoretical analysis of the mechanism from a microscopic point of view will help to solve the engineering problems. Computer simulation based on the density-functional theory (DFT) has been proven to be a powerful and reliable tool to study water-solid interfaces at the molecular level (Yang et al., 2004; Park and Sposito, 2004). The behavior of water at the kaolinite (001) surface using DFT has been investigated (Hu and Angelos, 2008). The adsorption and diffusion behavior of H2O molecules on kaolinite surface have not yet been established. So a deeper insight into the water on kaolinite surface, through detailed first-principles calculations, is needed.
The attachment of marine fouling organisms is harmful to any marine structure such as ship hulls, fishing nets, jetties and platforms. Marine antifouling coating is still the widely commercial used solution for marine antifouling in shipping industry. It is necessary to evaluate the antimicrobial and antifouling performances of marine antifouling coating before formal use. Assessment methods of antimicrobial and antifouling performances are investigated in this study. Based on the antifouling mechanism, flat colony counting test, crystal violet staining test, diatoms static fouling test and diatoms dynamic fouling test are chosen for the laboratory test. With reference to some standards on shallow submerging test for marine antifouling panel, the deficiencies of the current evaluation method are discussed and the corresponding solution is then proposed. The appropriate proportion of the evaluation scale is divided according to the different influences on the antifouling property of the biofouling, and the monomer fouling is selected as the main evaluation scale. A novel calculation method of Fouling Resistance can be proposed and compared with ASTM and SAC standard. An effective assessment system for antimicrobial and antifouling performance of marine antifouling coating is proposed and validated by cases.
Biofouling describes the settlement and the accumulation of marine organisms, such as bacteria, diatom, barnacle and oyster, on the structures immersed in seawater which can cause a variety of problems. On ship hull, it can increase the hydrodynamic drag, lower the maneuverability of the vessel and increase the fuel consumption. This causes increased costs within the shipping industry through the increased use of manpower, fuel, material and dry dock time (Muller, Wang, Proksch, Perry, Osinga, Garderes, and Schroder, 2013; Yebra, Kiil, and Dam-Johansen, 2004). Many studies have been carried out around biofouling, and there are various antifouling methods and antifouling patents, but antifouling coating is the most widely used antifouling method (Amara, Miled, Slama, and Ladhari, 2018; Chambers, Stokes, Walsh, and Wood, 2006).
Image designed from Figure 1b in the article. The objective of the complete paper is to accurately determine horizontal-shale-well estimated ultimate recovery (EUR) for an area integrating geology, machine learning, pattern recognition, and statistical analysis by use of various parameters of nearby producing horizontal shale wells as inputs. The work uses local geological information followed by execution of machine learning to identify critical well parameters that lead to better production. Then, a pattern-recognition step is performed while making sure the number of wells in each category is statistically significant. The conclusions are verified using available literature on correlation between well production and various well parameters.
Nedwed, Tim (ExxonMobil Upstream Research Company) | Kulkarni, Kaustubh (ExxonMobil Upstream Research Company) | Jain, Rachna (ExxonMobil Upstream Research Company) | Mitchell, Doug (ExxonMobil Upstream Research Company) | Meeks, Bill (ExxonMobil Development Company) | Allen, Daryl P. (Materia Inc.) | Edgecombe, Brian (Materia Inc.) | Christopher, J. Cruce (Materia Inc.)
Industry maintains well control through proper well design and appropriate controls and barriers. This has made loss of well control a very low probability event. Currently the final barrier to maintain control is a valve system (blowout preventer or BOP) located on top of wells capable of sealing around or shearing through obstructions that might be in the well (e.g. drilling pipe and casing) to isolate the well. Although the risk is low when proper drilling practices and design are employed, there are still concerns about well control especially for operations in sensitive environments. Adding an additional barrier could alleviate these concerns.
One scenario for well control loss is if the BOP fails to seal allowing drilling fluids and reservoir fluids to flow. We are currently evaluating a concept to respond to such an event and seal leaking BOPs by injecting a liquid monomer and a catalyst below a BOP leak point to form a polymer-plug seal.
Mixtures of dicyclopentadiene (DCPD) and other monomers mixed with a ruthenium-based catalyst cause a rapid polymerization reaction that forms a stable solid. These reactions can occur under extreme temperatures and pressures and withstand significant contamination from other fluids and solids.
Lab studies have shown that DCPD-based polymer plugs can withstand axial stress of 15,000 psi without significant deformation even at temperatures of 200°C and with 20% drilling fluid contamination. For well control, one option is to preposition monomer mixes and catalyst into pressurized cannisters located at or near subsea BOPs while drilling high-complexity wells. Connecting the pressurized cannisters to appropriate ports on the BOP will allow rapid transfer. During a well-control event, actuating valves would rapidly force the monomer mixes and catalyst from the cannisters into the BOP to initiate polymerization. Polymerization reactions can be as short as a few seconds depending on the monomer mix and catalyst. The resulting solid polymer plug will block the leak path to potentially seal the well.
This paper describes the concept details and summarizes the current status of research.
Smart scale management techniques are of great demand in nowadays oil and gas industry. The formation of zinc, iron and lead sulphide scales can cause severe damages of production equipment which ultimately results in loss of productivity.
Johnson, Leah M. (RTI International) | Shepherd, Sarah D. (RTI International) | Rothrock, Ginger D. (RTI International) | Cairns, Amy J. (Aramco Services Company: Aramco Research Center-Houston) | Al-Muntasheri, Ghaithan A. (Aramco Services Company: Aramco Research Center-Houston)
Acid stimulation, for both oil and gas wells, greatly supports the industry as a versatile means of enhancing production. Although acids enhance carbonate reservoir permeability to hydrocarbons, the reaction rates of the acid [e.g., hydrochloric acid (HCl)] with the rock often are too rapid at high temperatures, leading to a reduction in acid penetration. Several methods exist to improve the effectiveness of acidizing in high-temperature reservoirs (e.g., greater than 120°C), including the use of conventional emulsified-acid systems, mixtures of HCl and organic acids, and gelled acids. Many of the aforementioned techniques are effective forms of treatment; however, they hold significant limitations such as reduction in acid efficiency, poor control over penetration depth, and the requirement of corrosion inhibitors. Accordingly, encapsulated HCl holds potential as an attractive alternative to address these shortcomings because its prolonged release profile would permit transport of acid deep within the reservoir. In addition, when successfully encapsulated, this technology could eliminate, or at the very least minimize, the use of corrosion inhibitors. Herein, we demonstrate the design and preparation of highly modular core/shell particles comprising concentrated HCl encapsulated within an acrylate-based thermoset polymer shell. We show that the shell-generation mechanism (i.e., photopolymerization of acrylate monomers) is compatible with concentrated HCl and further detail the encapsulation process. Our results demonstrate that the acid-release profiles are dictated by the properties of the shell material, enabling a prolonged delivery of HCl in laboratory studies. This is a first step toward the design of particle-shell systems that can tolerate harsh reservoir conditions, including high temperatures, pressures, and salinity of mixing water. A tunable core/shell delivery system that encompasses a sufficient amount of strong mineral acid is well-poised to address the unmet need of deeper penetration of HCl into the reservoir, enabling greater stimulation efficiency.