Oil Exploitation Research Articles

Dynamic in-situ CT imaging to study meso-structure evolution and fracture mechanism of shale during thermal-mechanical coupling condition

Temperature has a significant impact on the occurrence characteristics and flow properties of oil and gas in shale reservoirs at in-situ conditions. Under thermal–mechanical coupling conditions, the macroscopic deformation instability characteristics and the evolution of the internal microstructure of shale are of great importance for the exploitation of shale oil and gas. However, most studies on the macroscopic and microscopic characteristics of shale only analyze the deformation and instability mechanisms of shale from observations of the post-failure microscopic structures. This paper employs a self-developed THM-CT coupling test system to study the macroscopic deformation characteristics of shale under triaxial compression at real-time temperatures, and simultaneously uses in-situ CT imaging technology to characterize the internal microstructure of shale under different stress levels. Real-time CT porosity obtained via in-situ CT imaging technology represents the mesoscopic structural parameters, together with macroscopic deformation characteristics, delineate the four stages of the entire deformation process in shale: initial compression, linear elastic deformation, yielding deformation, and post-failure. The deformation after peak-stress (σf) in shale is 1–3 times that before peak-stress (σf). The dissolution and softening of clay minerals within the internal micro-lamination of shale, along with the weakening of the internal structure, result in a decline in mechanical parameters such as stress strength (σf) and elastic modulus (E) with increasing temperature. The reconstruction of three-dimensional μCT digital volumes further reconstructs the internal fracture spatial structure under different stress levels during the deformation process, precisely characterizing the dynamic evolution of internal fracture nucleation, expansion, and coalescence during the whole test process. The failure characteristics of shales display notable heterogeneity and anisotropy. Internally, fractures experience a sequence of initiation, formation of vertical and oblique main fractures along the axial direction, and crossing connections between fractures. During test process, multiple occurrences of horizontal secondary micro-fractures extend along weakly cemented lamination, playing a connecting role between the main fractures. Importantly, a real-time quantitative relationship between the macroscopic and microscopic mechanics of rock has been established by linking the mesoscopic damage factor with the applied stress. It was found that the damage factor increases according to a power-law relationship with stress in the yield deformation phase. The variation in the mesoscopic damage factor serves as an intuitive index reflecting the systematic failure of rock, providing an early warning for the impending failure of shale.

An Environmentally Friendly Superhydrophobic Wood Sponge with Photo/Electrothermal Effects Prepared from Natural Wood for All-Weather High-Viscosity Oil–Water Separation

Rapid industrial development has led to increased crude oil extraction and oily wastewater discharge. Achieving oil–water separation and marine oil adsorption in a cost-effective, efficient, and environmentally friendly manner remains a global challenge. In this work, natural wood was chemically treated to prepare a degradable and environmentally friendly wood sponge structure. In situ polymerization and spraying methods were used to produce an environmentally friendly oil–water separation sponge with superhydrophobic and superoleophilic properties (Fe3O4@P-P@WS). Fe3O4@P-P@WS had excellent superhydrophobicity (WCA = 154.2°) and self-cleaning properties. Additionally, Fe3O4@P-P@WS could convert solar and electrical energy into thermal energy, reaching a surface temperature of 74 °C under sunlight irradiation with an intensity of 1.0 kW m−2. When a voltage of 9 V was applied, the surface temperature reached 120.5 °C. Moreover, under the suction of a vacuum pump or the action of gravity, the continuous separation of highly fluid oil substances was achieved. The designed Fe3O4@P-P@WS offers advantages such as easily obtained raw materials, energy efficiency, simple preparation, and the ability to solve secondary pollution issues, providing a new technology for cleaning organic matter in industrial wastewater discharge and for round-the-clock cleaning of high-viscosity crude oil leaked during offshore oil exploitation.

The local human capital costs of oil exploitation

This paper explores the local-level impacts of oil exploitation on human capital accumulation in Colombia, a resource-rich developing country. We provide evidence based on detailed spatial and temporal data on oil exploitation and education, using the number of wells to measure treatment intensity at the school level. To derive causal estimates, we rely on an instrumental variable approach that exploits the exogeneity of international oil prices and a proxy of local oil endowments. The results indicate that although oil exploitation does not impact enrollment in higher education, it may negatively affect human capital in Colombia since it generates a delay in the decision to enroll. Furthermore, it incentivizes talent allocation away from STEM and professional degrees. Our results suggest no effect on either the quality of secondary education or tertiary education completion. These results are robust to a number of specification changes, and we stress the role of local markets and spillovers as the main transmission channel. In particular, we find that higher oil production increases formal wages, without finding evidence of a premium to tertiary education enrollment in oil-producing areas, and there is a positive spillover to other economic sectors.

The impact of bedding planes on microwave-induced damage in rock at the field scale: a numerical model

The feasibility of microwave heating-assisted rock breakage technology in geotechnical engineering has been widely explored. However, the limited knowledge of the impact of the contrast properties between different bedding planes and outer formation stresses limits its application at the field scale. In this work, the mechanics of mineral processing, rock breakage, and unconventional gas and oil exploitation were first characterized. A coupled model is subsequently proposed to govern the coupling process of microwave heating and induce inhomogeneous deformation and stress in various bedding planes. Three stress forms are considered in this approach: horizontal stress, normal stress, and shear stress. With the assistance of the finite element method, the stress conditions of bedding planes composed of rock under free swelling, constant stress, and constant volume were addressed. A bedding plane characterized by high microwave adsorption ability is usually compressed by a bedding plane characterized by low microwave adsorption ability. The bedding ore is under the condition of free swelling during mineral processing, whereas in the remaining two scenarios, the bedding rock is stress controlled. The tensile and compressive stresses can reach their maximum values under the condition of free swelling. The outer formation stress reduces the values of tensile and compressive stresses but has little impact on the shearing stresses. Additionally, this work provides criteria for defining an a priori evaluation of the effectiveness of microwave treatment of bedded ore and rock for different geotechnical engineering applications.

Origin of biomarkers (PAH, n-alkane, hopane, estrane) in different colors of plastic resin pellets and surface sediments from coastal area of the Makuran-Oman Sea

The unique attributes of the study area, situated near the Strait of Hormuz—an extensively utilized oil shipping corridor for Iran and neighboring Arabian nations—encompass oil extraction and exploitation, the establishment of an oil export hub, the advancement of petrochemical industries, as well as tourism and transportation activities. This research represents the first examination of the sources of plastic resin pellet release, addressing both local and non-local contributions. To conduct this study, samples of plastic resin pellet and coastal and intertidal surface sediments were collected from seven stations on the shores of the Oman Sea in Hormozgan province (Sirik, Garook, Ziarat, Karpan, Koohestak, Gohardo, and Kargan) with four replications to determine the origin and spatial distribution pattern of hydrocarbons and the diffusion source of plastic resin pellets (offshore or regional). Plastic resin pellets were separated based on color (white, yellow, brown, and black). Soxhlet was used to extract hydrocarbons, two stages of column chromatography were used to separate compounds, and gas chromatography–mass spectrometry (GC–MS) was used to identify and determine their concentration. The total n-alkanes concentration ranged from 2940 to 18,711 (μg/g) in coastal surface sediments, from 19,721–1678 (μg/g) in intertidal surface sediments, and from 11,481.50 to 55,601.41 (μg/g) in plastic resin pellets. A similar trend was found for the total PAH concentration which ranged from 135.57 to 3890.62 (ng/g) in coastal sediments, from 1820.28 to 6579.55 (ng/g) in intertidal sediments, and from 3714.19 to 66/1920451 (ng/g) in plastic resin pellets. According to the sediment pollution criteria, a high pollution level was assessed in most of the stations. In most of the surface sediments and plastic resin pellets, the presence of unresolved complex mixture (UCM), the carbon preference index (CPI) lower than 1, and the diagnostic ratios of PAH, hopane, and sterane compounds indicated petrogenic origin for hydrocarbons. The results of principal component analysis based on 16 diagnostic ratios of PAH, n-alkane, hopane, and sterane compounds showed that brown and black plastic resin pellets were placed in a different group than the coastal and intertidal sediments and white and yellow plastic resin pellets. Most likely, the diffusion source of brown and black plastic resin pellets is different and through open water.

Assessment of the Potential for CO2 Storage and Utilization in the Fractured and Porous Reservoir of the Cambrian Sandstones in West Lithuania’s Baltic Basin

Cambrian sandstones comprise a large and saline-only aquifer that can be utilized for CO2 geological storage in the Baltic basin, including Lithuania. The two prospective storage sites with the most potential are located in west Lithuania. Despite the larger area of the Gargždai elevation (233 km2), the Syderiai uplift (62 km2) is characterized by the largest storage volume. The most significant difference between the studied structures is primarily related to the much higher reservoir quality of the Cambrian sandstones at the Syderiai site. The sandstones’ average porosity is 16% and their permeability measures 310 mD, while the Gargždai site is characterized by poor reservoir quality (average porosity of 7% and permeability as low as 10 mD in the sandstone). The main controlling parameter for the sandstones is authigenic quartz cementation. The reservoir type is classified as the porous sandstone type for the Syderiai site and as the fractured reservoir type for the Gargždai site. The storage volumes of CO2 of the sites were assessed as 56.7 Mt and 31.3 Mt, respectively. The present study determined that the Syderiai uplift was the prospective site with the most potential for the geological storage trapping of CO2, owing to its high reservoir quality, while the Gargždai elevation is characterized as a potential alternative for CO2 storage combined with EOR technology for oil exploitation, despite its poor reservoir quality.

Preparation and characterization of quartz ceramic proppant replacing natural quartz sand by solid waste silica fume

AbstractThe improper disposal of industrial wastes will cause environmental pollution and economic losses due to the loss of active ingredients. Solid waste silica fume and pyrolusite powder were used to synthesize quartz ceramic proppant by pelleting and sintering to replace natural quartz sand for unconventional oil and gas exploitation. The effects of pyrolusite powder content and sintering temperature on the apparent density, breakage ratio, and acid solubility of the proppant were thoroughly studied. The phase composition and microstructure of the proppant were characterized by X‐ray diffraction and scanning electron microscopy, respectively. The results revealed that the main crystal phase of the proppant prepared without pyrolusite was cristobalite, while that with pyrolusite was cristobalite and quartz, and the content of quartz phase increased gradually with increasing the pyrolusite content. The addition of pyrolusite remarkably increased the density and improved the performance of the proppant due to the resulting glass phase at high temperatures and the presence of andradite. As adding 20% pyrolusite, the apparent density of the proppant sintered at 900°C was 2.26 g/cm3, while the breakage ratio under 28 MPa closed pressure and acid solubility reached the minimum, 9.89% and 5.3%, respectively, meeting the industrial standard requirements.

Different mechanisms of two oil-soluble additives to reduce heavy crude oil viscosity

The depletion of light crude oil resources necessitates the efficient development of heavy crude oil, characterized by high density and viscosity. In this work, we used molecular dynamics (MD) simulations to investigate the mechanisms by which two oil-soluble viscosity reducers (VRs) reduce the viscosity of heavy crude oil. Our results reveal that direct interaction between VRs and asphaltene (ASP) aggregates is not the sole pathway for viscosity reduction. Instead, targeting resin (RES) emerges as a critical strategy. The first kind of VR (VR1), with its polar acrylamide head, binds effectively to ASP, reducing the exposure of ASP to other heavy oil components and thereby decreasing the friction between ASP and these components. In contrast, the second kind of VR (VR2), with a maleic anhydride head, tends to disperse away from ASP aggregates, reducing viscosity by weakening the intermolecular interactions between RES and lighter components. These findings elucidate distinct mechanisms by which VRs mitigate the viscosity of heavy crude oil and provide insights for the design of more effective oil-soluble VRs for future heavy oil exploitation.

Exploring subsea dynamics: A comprehensive review of underwater pipelines and cables

The development of marine resources is intrinsically linked to the utilization of various marine equipment. Among these, marine pipelines and cables are crucial for the exploitation of deep-sea oil and gas resources. Mooring cables, marine towed cables, marine umbilical cables, submarine cables, and marine pipelines are typical slender and flexible marine components. These slender marine flexible members present various dynamic challenges during laying, installation, and in-position operation. Facing these challenges, scholars from China and around the globe have explored theoretical, numerical, and experimental solutions to these challenges. The conclusions need to be condensed to improve their practical and academic value for engineering applications. This paper summarizes the explorations and provides general design methods and concepts of marine pipelines. Additionally, this paper looks forward to the future development trend of marine pipelines in engineering applications as well as theoretical research. The aim is to provide a reference for the research of underwater pipelines and cables.

Experimental study on the rock breaking effect of different tooth shapes of inserted teeth in a hobbing-cone hybrid PDC bit under complex stress environment

The hobbing-cone hybrid PDC bit has emerged with the increasing exploitation of deep oil and gas resources. As an important component of new bits, studying the mechanism of toothed fracturing of deep rocks is crucial for improving rock-breaking efficiency. In this paper, the spherical teeth and conical teeth were used to intrude sandstone under different confining pressures, and the brittleness index (BIm), specific energy (SE), and average fragment size (dm) were used to analyze the rock-breaking effect. The 3D contour scanner quantitatively analyzed the crushing pit area. Finally, the in-situ CT scanning and discrete element numerical simulation were used to summarize the crack propagation law. The results show that with the increase of confining pressure, the BIm of inserted teeth increases continuously, and the growth rate of conical teeth increases, while that of spherical teeth decreases. The SE and dm exhibit a symmetrical distribution with a confining pressure of 10MPa as the axis of symmetry. When the difference in principal stress is 5MPa, the SE is the lowest point, the rock-breaking efficiency is the highest, and the corresponding dm is at the highest point, but the curve trend is the opposite. When the stress difference is 5MPa, it is conducive to propagating surface cracks, thus forming a larger crushing area and the highest rock-breaking efficiency. Based on CT results, the dense particle core is formed near the inserted teeth, and that of the spherical teeth is located below. In contrast, that of the conical teeth is located on the side, which is also the reason for the difference in crack propagation between different tooth shapes.

Study on pressure fluctuation characteristics of the mixed-flow pump with the tandem misaligned blade structure

Abstract As supporting equipment for deep-sea oil and gas resource exploitation, how to improve the transmission performance and stability of the impeller of the mixed-flow pump (MFP) has become a key technical problem. This paper focuses on studying the impeller blade of the MFP. Based on the blade optimization technology, four different tandem misaligned blade (TMB) angle schemes of α=0°,15°,45°,75° are proposed. The SST k-ω turbulence model is used to simulate the different blade angles under the pure liquid condition. The pressure pulsation of the MFP and the blade load distribution are studied. This result show that the TMB structure increases the pressure fluctuation inside the MFP. The pressure coefficient inside the impeller exhibits a more consistent pattern at an angle of α=45° compared to other angles, and the internal flow field of the MFP exhibits most stable. From this analysis of blade load distribution, TMBs have a greater effect on the pressure surface of the front blade of the MFP. When α=15°, the best pressurization performance of the MFP. This study may serve as a benchmark for subsequent iterations of optimizing the MFP’s model and hydraulic design.

Study on Wellbore Stability of Shale Oil Drilling

Abstract With conventional oil and gas development entering the middle and late stage, unconventional oil and gas development is the focus of resource replacement and stable production. The South China Sea is rich in shale oil resources and has great development potential. However, the experience of shale oil exploitation in the South China Sea is not enough. The performance of oil shale rock in the target block is unclear, the anisotropy caused by bedding has great influence, the formation has abnormal high pressure, and various factors affect the wellbore stability. In the process of drilling, complex conditions occur frequently, which seriously limits the efficiency of exploration and development. Therefore, this paper studies the wellbore stability of shale oil drilling in the South China Sea, carries out rock mechanics experiments, analyzes the strength of oil shale rock, and studies the influence of oil-based drilling fluid and anisotropy caused by bedding on rock strength. Combined with logging data, the change law of formation caving pressure is analyzed and formation pressure is predicted. The research shows that the oil shale rock in this area has low strength, the core is hard and brittle, and the core is anisotropic under the influence of bedding. The strength weakening law of oil shale soaked in oil-based drilling fluid is studied, and the formation collapse pressure variation law is further obtained. The fracture pressure, caving pressure and pore pressure of the proposed drilling are predicted, which provides technical support for the safe and efficient drilling of shale oil drilling in the South China Sea.

Short-term interactions between Longmaxi shale and carbon dioxide-based fracturing fluids

The shale is a dense quarried rock material containing abundant shale oil/gas. Extracting shale gas usually requires fracturing the rock formation to speed up gas desorption and migration. Supercritical carbon dioxide fracturing, as an environmentally friendly and waterless fracturing technique of reservoir stimulation, gains increasing recognition in commercial exploitation of shale oil and gas. However, there is insufficient understanding on the interaction between carbon dioxide-based fracturing fluids and shale, as well as its influence on the mechanical parameters of shale, which are pivotal for determining injection parameters and forming the fracture network. This study focuses on the injection of carbon dioxide-based fracturing fluids to enhance shale gas extraction and carbon dioxide sequestration. Simulation tests of injection were conducted to investigate the influence of different fracturing fluids (deionized water, gaseous/supercritical carbon dioxide, gaseous/supercritical carbon dioxide mixed with brine) injected into shale reservoirs on the microstructure and mechanical properties of shale after short-term physicochemical interaction. This article adopts research methods such as uniaxial compression and uniaxial tensile mechanical experiments based on acoustic emission monitoring and various physical characterizations such as scanning electron microscopy, X-ray diffraction, X-ray fluorescence spectrometer, etc. Results show that following treatment with different carbon dioxide-based fluids, the uniaxial tensile/compressive strength, elastic modulus, fractal dimension of pore structure, and the brittleness index of shale exhibit varying degrees of decrease compared to those of dry untreated shale samples. After interacting with different carbon dioxide-based fracturing fluids, the mechanical parameters and brittleness index of shale decrease more significantly than that of the others as the addition of brine. This study shows that the water in carbon dioxide-based fracturing fluids is a controlling factor affecting the elastic modulus of shale. Additionally, the ductility of the shale increases and the acoustic emission emitting lag due to the coupling effects of brine and carbon dioxide. The change law of the elemental and mineral composition of the shale is consistent with the mechanical strength; and the change of element content and mineral composition is the most significant. Compared to gaseous carbon dioxide, the supercritical carbon dioxide has a greater impact on mineral composition of the shale. The change of mechanical strength and microstructure evolution mechanism caused by the short-term interactions between the shale and fracturing fluids provide theoretical references and implications for the determination of injection parameters and permeability transformation of the Longmaxi shale reservoirs.

Experimental study of foam stability and interfacial behaviour of cellulose nanocrystals-enhanced C22-tailed zwitterionic betaine surfactant

The intrinsic thermodynamic instability of foam systems significantly constrains their effectiveness in enhancing oil and gas recovery from unconventional reservoirs. This study investigated the foam properties and interfacial rheological characteristics of the EDAB/CNC/APG system, analyzing the influence of various factors including temperature, pH, and inorganic salts. The results indicated that the optimal concentration ratio for CNC-surfactant system consists of 0.3 % EDAB, 1.5 % CNC and 0.5 % APG by mass fraction. In this system, the addition of CNC forms a three-dimensional network structure at the gas–liquid continuous interface, significantly extending the drainage half-life of the system. At elevated temperatures, the intense molecular thermal motion disrupts the interactions between CNC and EDAB. This disruption leads to a decrease in surface tension and the viscoelastic modulus of interfacial expansion, resulting in an increase of foam volume but a decline in foam drainage half-life. Foam performance and interfacial rheological characteristics are optimal under neutral pH conditions and manifest higher stability in alkaline conditions compared to acidic conditions. In highly mineralized reservoirs (≥5.0 % salt concentration), inorganic salt ions shield the attraction between CNC and oppositely charged surfactants. This shielding weakens the cross-linking within CNC-surfactant systems, altering the structure of the liquid film interface and causing a sharp decrease in foam half-life. The C22-tailed zwitterionic betaine surfactant EDAB, enhanced by CNC, provides a novel, environmentally friendly, efficient, and safe approach to the exploitation of complex, low-permeability oil and gas reservoirs.

Review on the Study of Microscopic Pore Structure and Seepage Characteristics

Pore structure, as the focus of researchers, is also one of the main contents of reservoir geological research, and the characteristics of percolation depend on the micro-pore structure of the reservoir. The study of the characteristics of fluid percolation in the reservoir plays an important role in formulating a reasonable oil and gas exploitation scheme. Understanding the micro pore structure of the reservoir, analyzing the pore throat structure inside the oil and gas reservoir, and systematically studying the micro seepage characteristics of the reservoir have far-reaching influence and great significance for the exploration and development of oil and gas fields.

Nano-enhancing polymer as a fluid loss additive for ultra-high temperature cementing

The exploitation of ultra-deep oil and gas wells is accompanied by technical problems of ultra-high temperature, especially in the cementing process, which will directly deactivate many admixtures. By in-situ polymerization of the monomers and Nano-SiO2 to improve the temperature resistance, the resulting high temperature resistant composite polymer slurry system can show high efficiency in reducing fluid loss under the high temperature environment of 240℃. The synthesis of the high temperature resistant polymer was characterized by IR and 1H NMR, and its physicochemical properties were analyzed by DLS, GPC, TEM and Cryo-SEM. The synergistic mechanism of Nano-SiO2 on the high temperature resistance of the polymer was revealed by TGA. Using DLS, SEM and EDS, a series of cement slurry systems were used to analyze and compare the effect on fluid loss reduction of different adding methods of Nano-SiO2 in cement slurry at high temperature. The results showed that the grafted Nano-SiO2 polymer maintained effective adsorption capacity at high temperature without degradation, and its fluid loss reduction ability was significantly improved at high temperature. The high temperature resistant composite polymer is strongly adsorbed between cement particles to form a dense and robust spatial network structure. The CSH gel structure is optimized by the particle size gradation of the system, so as to obtain a dense cement cake, which is expected to be applied in high temperature cementing.

Spillover effects of natural resources on the attractiveness of foreign direct investment in ECOWAS countries

The economies of Economic Community of West African States (ECOWAS) countries are linked by geography and by a policy of capital mobility. Consequently, the attractiveness of foreign direct investments (FDI) in one country is likely to be influenced by factors that explain FDI in neighboring countries, such as the endowment of natural resources. However, previous empirical studies have overlooked the spatial interaction effects of natural resources on the attractiveness of FDI in ECOWAS countries. In addition, natural resources are factors of production that can justify the location of a Multinational Enterprise in one country at the detriment of another, due to differences in the availability of natural resources. Thus, the main objective of this research is to fill this research gap by analyzing the spatial interaction effects of natural resource exploitation on the attractiveness of FDI in ECOWAS countries. Therefore, the dynamic Durbin Spatial Model (SDM) estimation method with a distance matrix was used for the analysis, covering 12 ECOWAS countries over the period 2007–2020. In addition, the use of the distance-inverse matrix with the dynamic SDM was used to analyze the spatial effects of different types of natural resources in order to test the robustness of the results. In terms of the results obtained, the findings show that the further ahead a country is in exploiting its natural resources, the more it negatively influences the attractiveness of new FDI in its bosom to the benefit of its neighboring countries, which are relatively behind in exploiting their natural resources. Specifically, the mining and forestry exploitation generates positive spillover effects, while oil and natural gas exploitation has negative spillover effects on the attractiveness of FDI from neighboring countries. A synchronization policy and a policy of compensating for the negative externalities linked to the exploitation of natural resources between ECOWAS countries would therefore make it easier to attract FDI and stimulate economic and social development.

A novel shell-like structure Zn-5Mn alloy with high strength and high plasticity for degradable oil fracturing tools

Fracturing tools for oil and gas exploitation require high mechanical properties and degradability. Zn alloys are possible to have good mechanical properties and much lower cost than widely used rare-earth Mg alloys, so it is worthy to develop Zn alloys as alternative materials. In this paper, a novel shell-like microstructure of Zn-5Mn alloy has been realized by bottom circulating water cooling. MnZn9 phase appears by the first time in Zn-Mn alloys with Mn < 6.4 wt%. This phase leads to the formation of hard MnZn9/MnZn13 core/shell structure with a high volume fraction of 76 %, dispersed uniformly in soft Zn phase. The alloy has excellent compressive properties without fracture even when stress and strain reach 2776 MPa and 80 %, respectively. Its ultimate uniform compressive stress and strain are 865 MPa and 56 % respectively, beyond widely used dissoluble Mg alloys. Weight loss rate of the Zn-5Mn alloy is two times that of pure Zn, immersed in 3 wt% KCl solution at 93°C. The shell-like Zn-5Mn alloy provides guiding significance of applying Zn alloys in fracturing tools for oil and gas exploitation.

Synthesis and Kinetics of CO2-Responsive Gemini Surfactants.

Surfactants are hailed as "industrial monosodium glutamate", and are widely used as emulsifiers, demulsifiers, water treatment agents, etc., in the petroleum industry. However, due to the unidirectivity of conventional surfactants, the difficulty in demulsifying petroleum emulsions generated after emulsification with such surfactants increases sharply. Therefore, it is of great significance and application value to design and develop a novel switchable surfactant for oil exploitation. In this study, a CO2-switchable Gemini surfactant of N,N'-dimethyl-N,N'-didodecyl butylene diamine (DMDBA) was synthesized from 1, 4-dibromobutane, dodecylamine, formic acid, and formaldehyde. Then, the synthesized surfactant was structurally characterized by infrared (IR) spectroscopy, hydrogen nuclear magnetic resonance (1H NMR) spectroscopy, and electrospray ionization mass spectrometry (ESI-MS); the changes in conductivity and Zeta potential of DMDBA before and after CO2/N2 injection were also studied. The results show that DMDBA had a good CO2 response and cycle reversibility. The critical micelle concentration (CMC) of cationic surfactant obtained from DMDBA by injecting CO2 was 1.45 × 10-4 mol/L, the surface tension at CMC was 33.4 mN·m-1, and the contact angle with paraffin was less than 90°, indicating that it had a good surface activity and wettability. In addition, the kinetic law of the process of producing surfactant by injecting CO2 was studied, and it was found that the process was a second-order reaction. The influence of temperature and gas velocity on the reaction dynamics was explored. The calculated values from the equation were in good agreement with the measured values, with a correlation coefficient greater than 0.9950. The activation energy measured during the formation of surfactant was Ea = 91.16 kJ/mol.

Shock wave generated by composite energetic material driven by electrical non-penetrating wire explosion plasma.

Underwater shock wave technology can realize dynamic rock fracture, which is helpful to increase oil and gas reservoir permeability. It can realize the efficient exploitation of medium and low maturity oil and gas resources. In practical application, the shock wave parameters require not only high intensity but also safety and controllability. To meet these requirements, insensitive composite energetic materials driven by electrical wire explosion plasma were proposed, which is one of the most promising methods. However, when in use, the load assembly process containing wires and energetic materials is complex. In this paper, a new type of energetic material load is proposed, using non-penetrating wire to drive composite energetic material. It can simplify the production process of the energetic load and produce acceptable shock wave parameters. The test results show that both the energy deposition of the wire and the shock wave intensity decrease under a non-penetrating wire structure. However, the shock wave intensity is still higher than that of the underwater electrical wire explosion. Based on schlieren diagnosis, it is found that the composite energetic material is gradually driven, and the energy release is not concentrated. In addition, the "non-wire" structure driving condition was discussed in contrast. Under this condition, the process of ionization channel establishment in composite energetic materials is random. The shock wave intensity is weak because the composite energetic material is in the process of slow detonation.