Oil Exploitation Research Articles

Study on the Influencing Factors on the Effectiveness of Liquid Nitrogen Fracturing Technology

Liquid nitrogen fracturing technology is a new fracturing and permeability enhancement technology for reservoirs unsuitable for hydraulic fracturing, and its ultralow temperature, high compression ratio, high freezing and expansion force, and low viscosity characteristics are expected to provide a program for fracturing and permeability enhancement in low-permeability reservoirs. The paper systematically analyzes the influencing factors restricting the effect of liquid nitrogen fracturing, aiming to provide theoretical basis and technical support for the efficient and environmentally friendly exploitation of low-permeability oil and gas fields.

Study on the Mechanism of Coal Fracturing by Liquid Nitrogen

As a fracturing medium with excellent properties, liquid nitrogen has multiple fracturing effects on coal, and its potential application in coalbed methane mining has become a hot spot in current research. In this paper, the key scientific problems of fracturing and penetration enhancement by liquid nitrogen in low-permeability coals are discussed in depth, and the pore fracturing process and its fracturing mechanism of low-temperature fracturing coal are analyzed. It is found that the ultra-low-temperature fluid fracturing process has the effect of high-energy fluid fracturing to break the rock, and also has the coupled fracturing effect of low-temperature fracturing and phase-change fracturing to increase the energy-driven replacement. It aims to provide theoretical basis and technical support for the efficient and environmentally friendly exploitation of low-permeability oil and gas fields.

Coconut shell-derived green synthesised carbon nanotubes for clean-up of crude oil spills

Abstract The global economy has led to an increase in oil transportation and exploitation, posing a threat to aquatic and terrestrial ecosystems. Crude oil spilled water purification is a major challenge worldwide. Researchers are focusing on finding adsorbents that improve oil adsorption capability. In the present study the adsorption of crude oil using synthesized carbon nanotubes (CNTs) prepared from coconut shell was investigated by batch adsorption experiments under varying parameters (adsorbent dosage and contact time) after analytical techniques (UV–vis, FTIR and SEM) confirmed the formation of the CNTs. The morphological modification significantly increased the hydrophobicity of the adsorbent, thus creating a synthesized CNTs with a much better adsorption capacity for crude oil removal having a maximum adsorption capacity of 4855.8 mg/g. The experimental results showed that the percentage of crude oil removal increased with an increase in adsorbent dosage and the contact time respectively. According to the correlation coefficient (R 2 = 0.9801) value obtained from the adsorption isotherm investigations, the isotherms were found to fit the Freundlich isotherm somewhat better than the Langmuir isotherm model, which is consistent with the findings reported in the literature. These findings have made the synthesised CNTs an attractive, useful, and environmentally friendly adsorbent for controlling crude oil spill.

Organosiloxane-Modified Auricularia Polysaccharide (Si-AP): Improved High-Temperature Resistance and Lubrication Performance in WBDFs.

This study introduces a novel organosilicon-modified polysaccharide (Si-AP) synthesized via grafting and comprehensively evaluates its performance in water-based drilling fluids (WBDFs). The molecular structure of Si-AP was characterized using Fourier-transform infrared spectroscopy (FTIR) and 1H-NMR experiments. Thermalgravimetric analysis (TGA) confirmed the good thermal stability of Si-AP up to 235 °C. Si-AP significantly improves the rheological properties and fluid loss performance of WBDFs. With increasing Si-AP concentration, system viscosity increases, API filtration rate decreases, clay expansion is inhibited, and drilling cuttings hydration dispersion is suppressed, especially under high-temperature conditions. Additionally, mechanistic analysis indicates that the introduction of siloxane groups can effectively inhibit the thermal degradation of AP chains and enhance their high-temperature resistance. Si-AP can form a lubricating film by adsorbing on the surface of clay particles, improving mud cake quality, reducing the friction coefficient, and significantly enhancing the lubricating performance of WBDFs. Overall, Si-AP exhibits a higher temperature-resistance limit compared to AP and more effectively optimizes the lubrication, inhibition, and control of the filtration rate of WBDFs under high-temperature conditions. While meeting the requirements of drilling fluid systems under high temperatures, Si-AP also addresses environmental concerns and holds promise as an efficient solution for the exploitation of deep-seated oil and gas resources.

GDI (IoT-Based Gas Detector) As an Appropriate Technology for Gas Leak Detection in Tarakan City, North Kalimantan

Tarakan City, as the center of oil and gas resource exploitation in North Kalimantan Province, faces significant challenges related to safety and security concerning potential natural gas leaks. With its large population and the presence of 1,400 oil and gas wells, as well as being the largest consumer of natural gas networks in Indonesia with 32,000 consumers, the risk of gas leaks is a major concern. Previous gas leak incidents have demonstrated serious impacts, including fires and explosions resulting in significant losses for the community and the environment. To address these challenges, the 5.0 technology offers a potential solution, particularly implementing the Internet of Things (IoT). Based on this technology, developing an IoT-Based Gas Detector involves surveying potential tools, analyzing economic, social, and environmental factors, assembling the tools, and applying the product. IoT Gas Detectors have an advantage by utilizing connected sensor technology. The IoT-Based Gas Detector can be utilized to detect gas leaks in real-time, providing swift responses and reducing the potential impacts of gas leaks. Consequently, it can increase safety, security, and the efficient use of natural resources. The IoT-based Gas Detector (GDI) program supports several Sustainable Development Goals (SDGs), including: [1] No Poverty, [3] Good Health and Well-being, [7] Affordable and Clean Energy, [9] Industry, Innovation, and Infrastructure, [11] Sustainable Cities and Communities, [17] Partnerships for the Goals.

High-Temperature, Salt-Resistant, and High-Strength-Controlled Consolidated Resin Slurry for Fracture Plugging during Oil and Gas Well Drilling

Summary The temperature and pressure of deep and ultradeep plugging are gradually increasing, resulting in higher requirements for the performance of plugging materials. In this study, a resin slurry plugging system that can be used to plug lost channels of fractures of different scales in the process of oil and gas exploitation was prepared, and the factors affecting the consolidation of the system under different conditions were studied. The resin slurry plugging system was initially consolidated in 2 hours and completely consolidated in 6–9 hours. It exhibited good viscosity recovery ability and excellent thixotropy characteristics of shear thinning and static thickening, which help realize strong residence and plugging in the fracture. The resin slurry plugging system prepared with 200 000 mg/L salinity water could still achieve good consolidation at 140°C, and the consolidating strength was higher than 5.0 MPa. In addition, the 7.10-MPa consolidation strength of the resin slurry plugging system with aging at 140°C for 15 days could satisfy the long-term plugging needs. Furthermore, the pressure-bearing plugging capacity and degradability of the resin slurry plugging system were investigated. The resin slurry plugging system could be fully filled in the steel wedge-shaped fractured core at 140°C, and the pressure-bearing plugging capacity was up to 13.07 MPa. The resin slurry plugging system could achieve a strong residence in the sand-filling pipe model, forming a high-strength plugging layer, and the pressure-bearing plugging capacity could reach 10.73 MPa. The acid dissolution degradation rate at 140°C was 97.69%, indicating a low degree of damage to the reservoir and meeting the requirements for subsequent plug removal. The excellent properties of the resin slurry plugging system, such as high temperature, high salt resistance, and pressure plugging, provide a new solution for plugging lost formations of fracture cave carbonate rocks.

Study on displacement units for water flooded low-permeability oil reservoirs

Understanding the reservoir feature changes is essential for optimizing oil exploitation throughout the development lifecycle. This paper proposed an analytical displacement unit method to character the features of water-flooded, low-permeability oil reservoirs. The method hinges the ratio of fluid flux to area and average water saturation, providing a fine description of reservoir dynamics. It has been implemented in a case study of a five-spot waterflooding scheme. The reservoir can be categorized into sixteen distinct unit types, each with specific attributes. This paper delves into the evolution of these displacement units and the key factors that influence their behavior. The findings provide insights into the degree of waterflooding and oil distribution following continuous waterflooding. Furthermore, the proposed method offers a valuable framework for analyzing the development of dominant water flow channels and exploiting the residual oil.

Prediction of slug length distribution in horizontal large-diameter gas/liquid pipeline systems

Large-diameter (ID ≥ 0.1524 m) pipeline network systems are widely used in the food industry for grain transportation, in the chemical and nuclear industries for steam/water thermal distribution systems, in the oil and gas industry for crude oil transportation and exploitation, and in urban water supply and drainage systems. Due to the favorable operational and geometrical conditions in surface gas/liquid pipelines, slug flow often prevails, dominating the horizontal and slightly inclined flow pattern map. Formed liquid slugs at large-diameter pipeline entrances and dip can grow, accelerate, and overtake other slugs, resulting in high-momentum and long slugs ranging in length from a few meters to a few hundred meters. The discrepancy of current mechanistic models to predict slug length in large diameter pipes, and the scarcity of large diameter slug length data motivated this work to propose a combined mechanistic and empirical approach to predict full slug length distribution in large diameter surface pipeline systems. A first-principle mechanistic mean slug length model is improved by optimizing its closure relationships using a large-diameter lab and field slug length database. Furthermore, an empirical large-diameter slug length standard deviation dimensionless model is proposed and statistically validated. The proposed mean and standard deviation slug length models are combined to construct a probability distribution and maximum slug length models. Validation of the proposed model revealed an absolute average error of 27% and 31% for the mean and maximum slug lengths, respectively, vastly outperforming all existing models.

Impact of oil price, economic globalization, and inflation on economic output: Evidence from Latin American oil-producing countries using the quantile-on-quantile approach

This research examines the impact of oil prices, economic globalization, and inflation on the economic output in oil-producing countries in Latin America. We employ advanced time series techniques to achieve precision in findings and reliability of policy inferences. We use cointegration techniques with and without structural breaks because oil prices are highly volatile, and the economies analyzed are unstable in the face of political and social changes. Additionally, we performed a sensitivity analysis using standard quantile and the newly developed quantile-on-quantile regressions to measure the impacts of the covariates on real per capita output. Finally, we use causality Fourier techniques to identify the direction of causal relationships between the series. We found that the oil price, economic globalization, inflation, and output have a long-term equilibrium relationship in the presence of structural breaks. Likewise, quantile models show that the impacts of inflation, economic globalization, and oil prices on economic output are extensively non-linear across the quantile distribution. We found a negative connection between inflation and economic output in the surveyed territories. We propose that those responsible for energy policy in the countries studied should rethink crude oil policies to maximize the benefits of oil exploitation under stagnant globalization and growing inflation.

Nanocellulose/scleroglucan-enhanced robust, heat-resistant composite hydrogels for oilfield water plugging

In an oil exploitation process, hydrogel plugging agents can effectively reduce the water-oil intermixing, decrease water extraction volume, and enhance oil recovery rate. The practical applications of traditional polyacrylamide (PAM) hydrogel plugging agents in oilfield are limited by their non-biodegradability, poor mechanical performance, and inferior temperature-resistance. This work developed a mechanically stable and high-temperature-resistant composite hydrogel (STP) by incorporating biodegradable scleroglucan (Slg) and TEMPO-oxidized cellulose nanofibers (TOCN) in the PAM hydrogel. The addition of Slg conferred heat resistance to the PAM hydrogel, while TOCN reinforced the mechanical strength. Anti-aging analyses revealed that the STP endured for 108 h in a saline environment at 140 °C. In the water flooding characterization, the STP displayed a breakthrough pressure of 42.10 psi/ft. at a flow rate of 0.75 cm3/min. Under these extreme conditions, the plugging pressure reached 14.74 psi/ft., meeting the essential criteria for oilfield water plugging. This research demonstrates the potential of polysaccharides in the preparation of sustainable, tough, and heat-resistant water plugging materials.

Spatial Cumulative Assessment of Impact Risk-Implementing Ecosystem-Based Management for Enhanced Sustainability and Biodiversity in the Black Sea

Marine ecosystems are becoming increasingly vulnerable to cumulative anthropogenic effects and pressures. Therefore, various methodological approaches and tools have been designed to apply cumulative impact appraisal schemes and better assess the dynamics and interactions among pressures affecting marine ecosystems. This study aims to apply the Spatial Cumulative Assessment of Impact Risk for Management (SCAIRM) tool for the Black Sea coastal waters considering human activities, pressures, and effects on different ecosystem components coupled with one management scenario development for actual and new emerging sectors. According to the SCAIRM, the primary pressure on the marine ecosystem was identified as introducing or spreading non-indigenous species from shipping. Additionally, when considering cumulative impact, activities related to coastal defense and flood protection, particularly beach nourishment works, were found to have the highest impact. This is due to the cumulative scores associated with the physical loss from permanent alteration or removal of seabed substrates, and temporary or reversible physical disturbances to the seabed. The scenario development indicated that after shipping, oil and gas exploitation is anticipated to become the second-highest risk sector for additional impact in the Romanian Black Sea. Additionally, the increased military activities related to the war in Ukraine present escalating risks that must be considered in EBM strategies. The results assess the possible effects of human activities and the associated pressures to direct management toward achieving sustainability, biodiversity protection, and the marine ecosystem’s integrity.

Sensor fault estimation based on ellipsoid bundles for dynamic point-the-bit rotary steerable systems

The dynamic point-the-bit rotary steerable system (DPRSS) achieves high-performance trajectory control in oil and gas exploitation. However, the sensor faults significantly degrade the reliability of the DPRSS. In this paper, the problem of sensor fault estimation for the DPRSS is investigated. Firstly, the DPRSS is modeled by a descriptor system with unknown but bounded uncertainties, which include measurement noises, model perturbations, and unknown inputs. Next, by integrating the decoupling technique, a sensor fault estimator is put forward based on the ellipsoid bundles. Besides, order reduction and bound calculation methods are proposed to derive intervals of the states and faults. Then, with a defined minimization criterion of the ellipsoid bundle, a sufficient condition is presented to design the parameters of the estimator. Finally, numerical simulations and experiments on a DPRSS prototype are provided to demonstrate the effectiveness of the proposed fault estimation method.

Performance of a Composite Inhibitor on Mild Steel in NaCl Solution: Imidazoline, Sodium Molybdate, and Sodium Dodecylbenzenesulfonate

Mild steel corrosion is a significant challenge in oil and gas exploitation. Inhibitors are frequently employed to minimize the corrosive impact on mild steel. Mixing corrosion inhibitors is an effective method in reducing the dosage of toxic compounds and expanding the potential applications of inhibitors in NaCl solutions. Herein, a mixed corrosion inhibitor composed of imidazoline (IM), sodium molybdate, and sodium dodecylbenzenesulfonate (SDBS) for mild steel in a 3.5 wt% NaCl solution are investigated by orthogonal experimental design and electrochemical measurement. The imidazoline compound was synthesized and identified using Fourier transform infrared (FTIR) spectroscopy. The inhibitory effect is improved by higher concentrations of sodium molybdate and is further enhanced with the addition of 10 mg/L of SDBS. The electrochemical impedance spectroscopy indicates that the combination of IM (100 mg/L), sodium molybdate (50 mg/L), and SDBS (100 mg/L) results in excellent performance with electrochemical impedance (1.8 kohm·cm2). The mild steel surfaces after electrochemical measurement were analyzed using scanning electron microscopy (SEM). The information can contribute to the development of corrosion inhibitors with high performance or to understand the influence of mixing inhibitors on corrosion processes of mild steels.

Preparation and performance evaluation of intelligent plugging agent for thermo‐sensitive water‐based drilling fluid

AbstractIn the process of unconventional oil and gas exploitation, the invasion of a large amount of drilling fluid into the formation is one of the most critical reasons leading to wellbore instability. A temperature‐sensitive polymer (AOS) was synthesized from acrylamide, oligo (ethylene glycol) methyl ether methacrylate (OEGMA), and sodium p‐styrene sulfonate by emulsion polymerization. The material is a solid‐free fluid with good fluidity at room temperature, after injection into the formation, the fluid is gradually transformed into hard gel above the lower critical solution temperature (LCST) (90°C), thus blocking micro‐fractures and improving wellbore stability. Infrared and NMR characterization confirmed the successful preparation of the target product. The transmittance of AOS with ambient temperature was measured by UV–vis spectrophotometer, and the LCST behavior of AOS was verified by rheological and viscoelastic measurements. The interaction mechanism between AOS and sodium bentonite was evaluated according to the American Petroleum Institute standard. The results show that after aging at 180°C, the filtration loss is reduced by 93%, and the medium permeability (100, 200 mD) formation is effectively plugged, with a plugging efficiency is as high as 74.7%.

Effect of Pseudomonas aeruginosa on Corrosion Behavior of X65 Carbon Steel.

X65 pipeline steel is widely used in the field of offshore oil and gas exploitation due to its excellent performance. However, due to the complex environment in the ocean, X65 pipeline steel is faced with a great risk of microbial corrosion failure. Therefore, it is of great significance to study the corrosion mechanism of X65 pipeline steel by microorganisms. In this paper, the corrosion effect of Pseudomonas aeruginosa (P. aeruginosa) secreting phenazine compounds on X65 pipeline steel was studied by the weight loss method, biofilm scanning electron microscopy analysis, surface corrosion morphology observation, electrochemical testing and medium pH test corrosion products. The results showed that the inoculation of P. aeruginosa accelerated the corrosion of X65 steel. After knocking out the phzM and phzS genes that regulate the synthesis of PYO, P. aeruginosa can still produce biofilms on the surface of X65 steel consistent with the morphology of wild-type P. aeruginosa, but the corrosion of X65 steel is significantly reduced. It is proved that PYO plays an important role in the corrosion process of P. aeruginosa on steel.

A Methodology to Evaluate the Real-Time Stability of Submarine Slopes under Rapid Sedimentation

Rapid sedimentation is widely recognized as a crucial factor in initiating the instability of submarine slopes. Once the slope fails, the subsequent landslide poses a significant threat to the safety of underwater infrastructures and potentially leads to severe damage to seabed pipelines, offshore foundations, and oil and gas exploitation wells. However, there is currently a lack of numerical methods to effectively assess the real-time stability of submarine slopes under rapid sedimentation. This study firstly employs a calibrated finite element (FE) model-change approach to reproduce the rapid sedimentation processes and proposes a concise method to calculate the safety factors for the real-time stability of sedimenting submarine slopes. Further, a parametric analysis is carried out to evaluate the effect of varying sedimentation rates on slope stability, and the critical sedimentation rate is numerically solved. Moreover, the effect of seismic events with different occurring times on the stability of rapidly sedimenting slopes is investigated in depth, and the most critical seismic loading pattern among various acceleration combinations is achieved. The results indicate that the presence of weak layers during sedimentation is a critical factor contributing to slope instability. The introduced rate of decrease in the safety factor proves valuable in assessing slope safety over a specific period. As the occurrence time of seismic events is delayed, the seismic resistance of the slope decreases, increasing the likelihood of shallower sliding surfaces. The findings offer insights into the mechanisms by which rapid sedimentation influences the stability of submarine slopes and provide valuable insights for predicting the potential instability of rapidly sedimenting slopes under specific seismic activity levels.

Hydro-mechanical analysis of particle migration in fractures with CFD-DEM

Particle migration driven by fluid flow is presented in many geological and geotechnical contexts, such as sand production in oil exploitation, internal erosion in dikes or dams, and proppant movement in petroleum engineering. In this study, fluid flow-induced particle migration in rock fractures has been investigated by coupling the computational fluid dynamics (CFD) and the discrete element method (DEM), focusing on the particle movements and the associated migration mechanisms. To fit the fracture roughness, tetrahedral grids were used to generate the fluid mesh in CFD analysis. The CFD-DEM model was first calibrated against experimental and analytical results, then a series of simulations was conducted to analyze the effects of fracture roughness (defined by the joint roughness coefficient, JRC), size ratio between fracture aperture and particle diameter, and hydraulic gradient on the migration of particle assemblies. Three modes of particle movement were obtained, i.e., the movement of particle assemblies as a whole, the separation of large particle assemblies into smaller ones, and the detachment of particles at assembly boundaries. Additionally, the velocity of a particle assembly passing through the fracture was negatively related to the aggregation of particles while positively related to the erosion rate of particle assemblies within the fracture. An equation to calculate the time of a particle assembly to pass through a fracture was proposed.

Preparation and Application of CO2-Resistant Latex in Shale Reservoir Cementing

With the application of CO2 fracturing, CO2 huff and puff, CO2 flooding, and other stimulation technologies in shale reservoirs, a large amount of CO2 remained in the formation, which also lead to the serious corrosion problem of CO2 in shale reservoirs. In order to solve the harm caused by CO2 corrosion, it is necessary to curb CO2 corrosion from the cementing cement ring to ensure the long-term stable exploitation of shale oil. Therefore, a new latex was created using liquid polybutadiene, styrene, 2-acrylamide-2-methylpropanesulfonic acid, and maleic anhydride to increase the cement ring’s resistance to CO2 corrosion. The latex’s structure and characteristics were then confirmed using infrared, particle size analyzer, thermogravimetric analysis, and transmission electron microscopy. The major size distribution of latex is between 160 and 220 nm, with a solid content of 32.2% and an apparent viscosity of 36.8 mPa·s. And it had good physical properties and stability. Latex can effectively improve the properties of cement slurry and cement composite. When the amount of latex was 8%, the fluidity index of cement slurry was 0.76, the consistency index was 0.5363, the free liquid content was only 0.1%, and the water loss was reduced to 108 mL. At the same time, latex has a certain retarding ability. With 8% latex, the cement slurry has a specific retarding ability, is 0.76 and 0.5363, has a free liquid content of just 0.1%, and reduces water loss to 108 mL. Moreover, latex had certain retarding properties. The compressive strength and flexural strength of the latex cement composite were increased by 13.47% and 33.64% compared with the blank cement composite. A long-term CO2 corrosion experiment also showed that latex significantly increased the cement composite’s resilience to corrosion, lowering the blank cement composite’s growth rate of permeability from 46.88% to 19.41% and its compressive strength drop rate from 27.39% to 11.74%. Through the use of XRD and SEM, the latex’s anti-corrosion mechanism, hydration products, and microstructure were examined. In addition to forming a continuous network structure with the hydrated calcium silicate and other gels, the latex can form a latex film to attach and fill the hydration products. This slows down the rate of CO2 corrosion of the hydration products, enhancing the cement composite’s resistance to corrosion. CO2-resistant toughened latex can effectively solve the CO2 corrosion problem of the cementing cement ring in shale reservoirs.

Oil Exploitation in the Niger Delta: A Case Study of Environmental Costs and Responsibilities

Oil Exploitation in the Niger Delta: A Case Study of Environmental Costs and Responsibilities

Multi-stage development process and model of steam chamber for SAGD production in a heavy oil reservoir with an interlayer.

Steam-assisted gravity drainage (SAGD) is an efficient thermal recovery technique for oil sands and extra heavy oil exploitation. The development of steam chamber goes through multi-stage physical processes for SAGD production in a heavy oil reservoir with an interlayer. In this study, considering the situation that an interlayer is located directly above a pair of horizontal wells, we analyzed the whole process of steam chamber development. We divided the whole process into stages I-V, which are the first rising stage, the first lateral expansion stage, the second rising stage, the second lateral expansion stage and the confinement stage, respectively. Particularly, we further divided stage II into 2 periods and stage IV into 3 periods. These stages and periods can help us understand the development process of steam chamber dominated by an interlayer more profoundly. Based on the divided stages and periods, we established different models of SAGD production by assuming different geometric shapes of steam chamber in different stages and periods. Oval shape was assumed in stages I and III, and inverse triangle shape was hypothesized in stages II, IV and V. The formulas of the front distance of steam chamber and the oil production rate of SAGD were deduced from the established models for different development stages. At the end, we performed two example applications to SAGD production in heavy oil reservoirs with an interlayer. The real oil production rates were matched very well with the theoretical oil production rates calculated by the deduced formulas, which implies the multi-stage development model of steam chamber is of reliability and utility.