Offshore Oil Fields Research Articles

Reservoir Pore Characteristics Based on Depositional Microfacies Control in the Neogene Guantao Formation, Bohai Bay Basin, China

The Neogene Guantao Formation Reservoir in the PLOilfield is a unconsolidated sandstone with high porosity and high permeability. The reservoir diagenesis is weak and dominated by compaction diagenesis. At present, insufficient research into the relationship between the pore characteristics and sedimentary microfacies of shallow delta sandstone reservoirs restricts the prediction of favorable reservoir distribution. This article takes the unconsolidated sandstone reservoir of the Guantao Formation as the research object and analyzes the potential coupling relationship between pore characteristics and sedimentary microfacies. In this study, seven typical sedimentary microfacies were identified and the microscopic characteristics of different sedimentary microfacies reservoirs are described. The results show that the pore structure of various sedimentary microfacies is comprehensively influenced by the sedimentary rock texture, siliceous minerals, and clay mineral distribution. Characterized by more abundant hard quartz and feldspar minerals, positive skewness, and lower pore sorting coefficients, the arenaceous microfacies possess larger pore throat radius and lower pore fractal dimensions than argillaceous microfacies. Finally, due to the difficulty of coring in offshore oilfields and the lack of data on mercury injection experiments, empirical formulas for the porosity, permeability, and pore throat radius of conventional core tests were established, and the pore radius that corresponded to 35% mercury saturation (r35) was used as the characteristic pore structure parameter. The grey correlation method was used to analyze the influence of sedimentary structure factors and mineral content differences on r35 and to determine the main controlling factors.

Production Analysis of Horizontal Wells in a Two-Region Composite Reservoir Considering Formation Damage

The horizontal well is extensively used to exploit oil at the Bohai offshore oilfield, China. It has been proved by practice that formation damage always happens during the production of wells. However, it is a challenging task to evaluate the formation damage for horizontal wells. In this paper, a flow model considering formation damage is established for horizontal wells. The reservoir geometry is divided into two regions: the inner region represents the region of formation damage and the outer region that without damage. The finite element method is used to solve the flow model. The well production rate can be determined by using the material balance method. For different scenarios, such as when the horizontal well is completely in the inner region or when the horizontal well passes through two regions, the effects of some key parameters such as damage radius, damage region permeability, and well position on the oil production rate and pressure distribution characteristics are analyzed. The results show that a smaller damage radius, higher damage zone permeability, and a horizontal well closer to or in greater contact with the outer region result in a higher oil production rate and faster pressure drop propagation. The presented model and obtained results enrich production analysis of horizontal wells in a two-region composite reservoir considering formation damage, which has significance for efficient offshore reservoir development.

Failure Mechanism Analysis of Bonded Joint with Fiber Reinforce Plastic (FRP) Sucker Rod in Offshore Reservoirs

At present, fiber reinforce plastic (FRP) sucker rod has the advantages of high tensile strength, light weight and strong corrosion resistance which gradually applied and popularized in offshore oil and gas field. However, the bonded joint of FRP sucker rod is particularly prone to break and fall off. Current research works mainly focus on the mechanical properties of FRP sucker rod and less consideration was given to adhesive performance. This paper proposed a finite element model (FEM) of bonded joint. The maximum predicted load of bonded joint was acquired and the axial distribution of adhesion stress and slip distance in the bonding interface was studied, which can provide theoretical basic of bonded joint and extend the service life of downhole pumping operation.

Reservoir facies classification based on random forest and geostatistics methods in an offshore oilfield

Machine learning methods are increasingly employed in various seismic and petrophysical methods for parameter estimation, interpretation, prediction, and classification. Reservoir facies classification assists the interpretation of seismic data as an important step in petroleum exploration and production monitoring. In this study, we estimate a reservoir facies model by integrating random forest (RF) algorithms and geostatistics modeling. The Surmeh Formation with the Jurassic age is known as one of the most important hydrocarbon reservoirs in the Middle East. The upper part of the Surmeh Formation is equivalent to the Arab Formation, which includes sequences of evaporitic carbonate facies in the study area. Well log data including DT, GR, RHOB, and PHI are used in the RF method for reservoir facies classification. Cross-validation verifies the high accuracy of our classification, with an average accuracy of 95%. The predicted reservoir facies consistently describe the carbonate and evaporitic facies with the geological information of this formation. The decision tree diagrams of the RF algorithm give valuable information on decision limitations and how to select features for efficient computation. We use the classification results for facies modeling. The comparison between facies models and drilling core data shows that the APE value of the sequential indicator simulation model is less than that of the indicator kriging model.

Synthesis and Performance Evaluation of an Organic/Inorganic Composite Gel Plugging System for Offshore Oilfields.

In this article, we developed a new composite gel for plugging dominant fluid flow channels in offshore oilfields. The composite gel was synthesized by organic and inorganic gel networks interpenetrating into a compact three-dimensional spatial network structure, resulting in a good plugging effect. The performance of the composite gel was evaluated from the aspects of gelling characteristics and gel microstructure, while the plugging effect was evaluated through core experiments. The results showed that the influencing order of each component on gelling was acrylamide > cross-linking agent > urea > initiator > polyaluminum chloride. The initial viscosity of the composite gel was about 5–6 mPa·s, and it had good plugging abilities in different permeability cores. In comparison with inorganic gels (plugging ratio of 77.2%) or organic gels (84.8%), the composite gel system has a plugging ratio of up to 99.5% using a core with water permeability of 4300 mD. Besides, the reservoir applicability of the composite gel was studied, and the results suggested that the composite gel system had good resistance to dilution, mechanical shear, oil corrosion, and aging and could be quickly removed after plugging.

Prediction and classification of faults in electric submersible pumps

As a core component of oil production equipment, electric submersible pumps (ESPs) have been widely used in offshore oil fields to improve oil well production. There is an urgent need for an effective method of predicting and classifying ESP faults in advance because the traditional approach of diagnosis after a fault occurs results in serious economic losses. This paper describes a method for the prediction and classification of ESP faults, combining a backpropagation neural network with artificial feature extraction. To overcome the influence of noise and the small sample size of fault data, overlapping sampling and manual feature extraction are applied to the original data. To predict the occurrence of faults in advance, the fault events are divided into three stages. Experimental results show that the accuracy of fault prediction using samples with feature extraction applied is better than that using only the original samples. Compared with other algorithms, the proposed method obtains better prediction and classification results, demonstrating that artificial feature extraction is indispensable and effective in the process of fault prediction.

Possible Connection Between Recent Seismicity and Fluid Injection in the Offshore Oil and Gas Field Area of Sakhalin Island, Russia

Possible Connection Between Recent Seismicity and Fluid Injection in the Offshore Oil and Gas Field Area of Sakhalin Island, Russia

RESERVOIR PRESSURE MAINTENANCE (RPM) ON OIL DEPOSITS

The article provides a brief analysis of the issue of improving oil recovery as a result of lower formation pressure in offshore oil wells. In the introductory part, the issues of lowering the formation pressure during the operation of oil and gas fields were considered. It is known that during the initial operation of wells, the wellhead pressure is high, so the wellhead is sufficient to transport pressure. However, after a period of operation, a sharp drop in formation pressure is observed, and when the wellhead pressure is less than the pressure in the in-house pipelines, it is not possible to transport the oil or gas obtained through these pipelines. In such conditions, in order to improve the development of oil storage, products from offshore oil and gas fields are transported to the shore through special tanks. The issue of increasing the wellhead pressure of such wells has been widely studied, as the occurrence of such transport leads to the consumption of additional funds. The decrease in formation pressure is observed differently in different wells. This situation mainly varies depending on the operating conditions and service life of the wells. In this case, in order to increase the service life of oil and gas fields, work is underway to artificially increase the formation pressure. Thus, in order to eliminate the problem of reducing the formation pressure, gas or liquid is injected into the well from the outside, which helps to increase the pressure. In wells where the pressure in the pipe mouth space is reduced, the process of applying additional pressure from the outside is carried out continuously during the next operation. Then the pumps used to inject liquid and gas into the reservoir were inspected. Their equipment and various parts are shown through graphs. It was noted that pumps and pumping equipment differ in their characteristics depending on the volume and conditions of liquids and gases injected from the outside as a result of the reduction of formation pressure. In addition, the collection system and transportation process of such wells have been reviewed and explained in detail using graphs and tables. Finally, the generalized results from the considered topic were noted. Keywords: fountain armature, reservoir pressure maintenance, injection pressure, pumping equip-ment, pump station, manifold block.

Study on Influence of Heavy Oil Reservoir Damage Caused by Multi-Component Thermal Fluid Huff and Puff

Multi-component thermal fluid (MCTF) huff and puff technology is an innovative heavy oil development technology widely used in China offshore oilfields. MCTFs mainly include steam, N2 and CO2. Under high temperature and high pressure, the physical and chemical reactions between thermal fluids and rocks occur, damaging the reservoir permeability and production effect. In this paper, 16 groups of core comparison experiments were carried out by MCTF device, the influence of original permeability, temperature and component on reservoir damage was quantitatively studied, and a mathematical model was established. Finally, the influence of reservoir damage on heavy oil development was investigated through numerical simulation. The experimental study reveals that MCTF has an obvious damage effect on the reservoir, where temperature and PV dominate the damage degree; with the increase of MCTF injection volume (PV), the core permeability rapidly decreases initially and stabilizes later (>6 PV). The numerical simulation results show that reservoir damage could lead to a recovery drop by 6.9% during MCTF development; on the premise of considering reservoir damage, MCTF huff and puff will further improve oil recovery by 9.68% compared with pure steam. The research is of great significance for understanding the production law of MCTF huff and puff and helpful for promoting the development of offshore heavy oil reservoir.

Experimental Research on Cationic Surfactants in the Drag Reduction of Water Injection Pipeline

Summary To achieve the throughput increase and drag reduction of the water injection pipeline for offshore oil fields, this paper takes the cationic surfactant solution as the research object and explores the feasibility of applying the additive drag reduction technology to the water injection pipelines through the rheological test and drag reduction simulation device. The experimental results show that the cetyltrimethylammonium chloride (CTAC) selected initially has excellent thixotropy, and the viscosity recovery rate within 300 seconds can reach more than 97%. In addition, CTAC/NaSal (sodium salicylate) solution has strong oil resistance and salt tolerance. As the oil concentration increases from 0 to 6,000 ppm, the viscosity only decreases by 8.24%; as the salt concentration increases from 0 to 6,000 ppm, the maximum viscosity growth rate is 87.08%. Furthermore, the CTAC/NaSal has good temperature resistance, which enhances with the increase of concentration. The recommended concentration of drag reducer is 400 ppm, and the maximum drag reduction rate, throughput increase rate, pressure drop reduction rate is 74.19, 76.76, and 67.99%, respectively. Therefore, the CTAC/NaSal solution has broad application prospects in the drag reduction of water injection pipelines.

OPTIMAL IN THE NATIONAL ENERGY SECTOR DIRECTIONS OF FORMATION OF INFRASTRUCTURE COMPLEX

OPTIMAL IN THE NATIONAL ENERGY SECTOR DIRECTIONS OF FORMATION OF INFRASTRUCTURE COMPLEX

Synthesis and characterization of AM/AMPS/DMDAAC/AAC tetrapolymer for application in drilling fluid / Síntese e caracterização do tetrapolímero AM/AMPS/DMDAAC/AAC para aplicação em fluido de perfuração

Petroleum is an important raw material. The first step in the construction of the oil well is drilling, in which drilling fluid is used to support the well wall, to cool the drill bit, among other functions. In its formulation, additives such as polymers are used, which serve to guarantee its properties. This work aims to synthesize a new water-soluble polymer for possible application in drilling fluids. The tetrapolymer synthesis was carried out in an inert atmosphere and used the monomers acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), dimethyldiallylammonium chloride (DMDAAC) and acrylic acid (AAC). Fourier Transform Infrared Spectrometry (FTIR) and thermogravimetric (TGA) analyzes were performed to characterize the product obtained. The synthetized tetrapolymer was stable up to a temperature of 230ºC, a result obtained by TGA, which suggests that it is able to keep its structure stable at high temperatures, and can be used in onshore or offshore oil fields.

PRACTICAL METHOD FOR ASSESSING RESERVOIR PERFORMANCE TO REVIVE CLOSED OIL WELLS

Efficiency is the key issue in reinstating of closed oil wells to production. The goal of this work is to develop practical workÀow for assessing reservoir performance to revive closed wells. The workÀow are generating the set of criteria, valuing the criteria, and making a ranked list of wells to be revived. Application to an offshore oil field, which under consideration to start producing again shown that the results are found to be reliable and consistent with the historical production performance. From the nine wells assessed, found that Well 3 and Well 7 are not recommended to be revived due to low remaining reserves and less predicted additional recoverable oil. The proposed methodology focus on petrophysical and production performance analysis associated with the wells probed rather than integrating static-dynamic reservoir data, well data, and operational issues as the commonly used one.,. Application of this methodology are expected to be beneficial to companies involved in field operations because the cost associated with the time spent for these types of processes could be reduced considerably.

Asia’s oceanic Anthropocene: How political elites and global offshore oil development moved Asian marine spaces into the new epoch

AbstractThe Anthropocene epoch, characterized by human-caused planetary-scale transformations like climate change and ocean acidification, today is usually associated with the period beginning in the mid-twentieth century. Taking an oceanic perspective on the Anthropocene in Asia, the article argues that oceanic and terrestrial energy regimes synchronized since the 1950s when, for the first time in history, oceanic ghost acres turned marine spaces into a major fuel source. Despite global connections between offshore oil regions located in North America, Asia, and other places going back to the late nineteenth century, Asia’s contingent offshore oil field locations and their physical geographies, combined with political factors, inhibited large-scale offshore drilling before the 1950s. These characteristics of marine spaces meant that Asian political elites and their developmentalist agendas became the guiding force in exploring offshore fields, a process that was hardly dominated by corporate capitalism or structural choice limitations due to the legacies of colonialism.

Impact of Integration of the Production Systems and Reservoir of a Benchmark Based on Carbonate Fields

AbstractIntegrating production system and reservoir is used in several studies of offshore oilfield development and management for improved production forecasts through more realistic boundary conditions. This study evaluates the influence of the parameters in a production strategy of a reference model (carbonate oil reservoir) on financial and production performance. We first considered nonintegrated system (NI) with the reservoir and fixed boundary conditions for well and gathering system. We then considered integrated system (I) with the variable boundary conditions for the wells and gathering system. Finally, we compared both systems. Our analysis involved several steps to define the best production strategy for both systems based on net present value (NPV) and how integrated modeling helps define production strategy. For NI, three stages were considered: number of wells, placement of wells, and platform capacity. For I, five stages were evaluated (all NI parameters) with diameters and gas lift evaluation, and platform placement. The results are similar, but the simplifications (NI) may affect financial performance. The cross analysis indicated (in the hypothesis that the integrated system is closer to reality) that integrating the NI case resulted in considerable financial and production differences and may be useful in simplified systems. Since the main aspects of the object-function financial return were related to reservoir model behavior, one can first apply the nonintegrated optimization cycles, then add the integrated cycles, obtaining an intermediate time of the integrated model optimization in similar cases.

Comparative Analysis of Satellite and Regulatory based Gas Flare Volumes in the Niger Delta Region

Associated gas flaring leads to severe environmental issue, and the importance of effective monitoring and accurate recording of this operation has been a subject of discussion in the petroleum industry. This research used statistical methods to compare the flare volume of both Regulatory Agency records and Satellite-based estimates to determine the accuracy and reliability of estimates. Seven prolific offshore oilfields from the Niger Delta region were considered for this research and the monthly records of flare volume for 2016, 2017, 2020 and 2021 were used to investigate the comparative relationship that exists. The result revealed that the mean flare volumes of four oilfields (Agbara, Bonga, Erha and Usan) did not differ significantly but Abo and Akpo oilfields revealed that estimates from the satellite were significantly greater than the regulatory reports, while the estimates from Agbami oilfield supported the contrast. The Pearson correlation analysis also revealed that a moderately strong positive relationship exists between the estimates for the sampled oilfields. The study further examined the discrepancies between both methods of gas flare measurements and proffered solutions on how these discrepancies could be resolved and recommended a strategy for monitoring natural gas venting.

Value Improving Practices in Production of Hydrocarbon Resources in the Arctic Regions

The relevance of the article is due to the fact that as the ice melts, the Arctic Ocean is becoming increasingly available. This fact has renewed the interest in Arctic mineral resources. The purpose of this article is to study special aspects of the development of Arctic hydrocarbon resources, which can boost the economic growth of the Russian economy in the medium term, and to identify approaches to enhance the economic value of these processes. The purpose was achieved by the solution of the following objectives: analysis of the current state of the Arctic resources, as well as the situation on both the global and Russian markets for hydrocarbon resources; study of the special part played by Arctic marine hydrocarbons; and substantiation of the development of transport infrastructure as an important factor in enhancing the economic efficiency of the production of offshore hydrocarbon resources in the Arctic Regions. The methodological framework of the article is formed by the fundamental provisions of economic theory, national economy, economic, environmental and energy security, as well as discoveries and developments by foreign and domestic scientists to ensure the economic efficiency of offshore hydrocarbon production in the Arctic Regions. The author’s sequence of stages for calculating the technical and economic potential of offshore oil and gas fields in the Arctic is proposed, which, unlike the existing ones, is based on an integral indicator combining financial, technical, climatic and service-infrastructure characteristics of fields, which makes it possible to make a rating of fields to determine the order and priority of the beginning of their development. The necessity of taking into account a wide list of factors in the comparative analysis of oil and gas fields in the Arctic in order to make strategic management decisions on the priority of field development is proved. The article suggests that the organizational structure and legal support be differentiated by management levels (mega-level, macro-level, meso-level, and micro-level), as it pertains to the extraction of marine hydrocarbon resources in the Arctic Regions and the development of the transport infrastructure of the Northern Sea Route.

Efficient demulsification of cationic polyacrylate for oil-in-water emulsion: Synergistic effect of adsorption bridging and interfacial film breaking

The development of reverse demulsifier is an urgent need for the increasing amount of produced liquid in oilfield. Synthesis of reverse demulsifier containing multiple characteristics is an effective method. In view of this, this study reports a series of cationic polyacrylates as the reverse demulsifiers, which were prepared by using 3-chloro-1-propanol to modify the copolymer of acrylate and N-[3-(dimethylamino) propyl] methacryamide (DMAPMA). The properties and performance tests showed that the PMD1 prepared by using methyl acrylate (MA) as monomer (mass ratio of MA to DMAPMA was 2:1) has well water solubility, high interfacial activity, and the best demulsification efficiency. For treating the produced liquid from an offshore oilfield, demulsification efficiency of PMD1 was 94.7% with 50 mg/L dosage, which was much higher than that of the reagent in use (15.7%). Furthermore, the demulsification mechanism of PMD1 was studied by oil-water partition coefficient experiment, zeta potential measurement, optical tweezers method, elastic modulus measurement, and coalescence kinetics experiment. Prominent demulsification ability of PMD1 was attributed to the synergistic effect of adsorption bridging via cationic group and oil/water interfacial film breaking by acrylate group. The cationic polyacrylate combines the advantages of polyacrylate and polycation reverse demulsifiers, which display a great application prospect in the petroleum industry.

ISOLATION WORKS AGAINST IRRIGATION WITH GEL COMPOSITION IN OIL RESERVES AT THE FINAL STAGE OF PROCESSING

At a time of high demand for energy carriers, it is important for the dynamic and long-term development of the oil industry of the country to increase the oil yield of long-term wells using various new methods of impact, along with the discovery, development and development of new and promising facilities. For the intensive development of the economy of the Republic of Azerbaijan, it is important to increase gas and oil production from oil fields in the Caspian Sea basin and onshore. In this regard, it is important to increase the efficiency of oil production in offshore and onshore fields, to improve the development system, work with the well fund, as well as the application of artificial impact methods. Due to the complications that occurred during the development of oil fields in the country, some of the wells are either temporarily or completely removed from the exploitation fund. One of these complications is the watering of the well product. Experience in the development of oil fields with different geological and physical properties shows that premature irrigation of existing wells, geological structure of fields, ratio of oil and water viscosity in the extracted fluid, heterogeneity of layers, oil composition, volume of injection and discharge affect. At present, there is a decrease in the amount of oil in the production of offshore and onshore oil fields, and an increase in water. Although many irrigated wells are insulated and repaired to prevent irrigation, the economic and technological efficiency of these wells is insufficient. Therefore, the creation of new and effective technologies to prevent the flow of water into wells remains relevant. Premature watering of oil wells results in reductions in oil production, reduced interval between repairs in wells, and corrosion of underground and surface equipment of wells. Many researchers have noted that it is not advisable to use long-term, large-scale and economically inefficient methods to increase oil production, so the development of more layers with local impact technologies is considered promising. These methods have significant results in the isolation of irrigated areas with higher permeability. This problem can be solved in two ways: 1) Isolation of water channels with injection wells 2) Isolation of water flow to production wells Numerous studies have shown that isolating water flow in wells gives better results. The contradiction in pumping oil with injection wells is that, on the one hand, oil production must be maintained high, and on the other hand, a well with high oil production must be irrigated prematurely and subsequently reduce the phase permeability of oil. Most of the oil fields in the Republic of Azerbaijan are in the final stages of development. As a result, it is important to increase the efficiency of the development of complex oil fields by reducing the volume of associated water and increasing oil production from partially irrigated formations. The effectiveness of isolating water-washed areas with different compositions is ambiguous. Using a 10% solution of liquid glass and hydrochloric acid as the base material, it is possible to prepare an elastic buffer material to strengthen the wellbore area. It is also possible to create a gel with adjustable setting time by adding a certain amount of a third component to the initial base mixture. Preliminary studies with the added third reagents have shown that an elastic binding composite can be formed by adding urea, laprol and chromium salts to the liquid glass and hydrochloric acid solution. In subsequent studies, 0.1 to 10% Na2SiO3 and 10% HCl solution; Viscosity was measured by adding CO(NH2)2, CrCl3, KMS and Laprol at 0.5 and 1% by mass. Keywords: related water, watering rate, gel, liquid glass, urea, laprol, chromium salts, hydrochloric acid

Forecasting the transition to undesirable gas-liquid two-phase flow patterns in pipeline-riser system: A method based on fast identification of global flow patterns

The level of flow assurance for gas-liquid two-phase pipeline-riser system in offshore oil and gas fields will be significantly improved once the transition to undesirable flow patterns can be forecasted before its occurrence. In this study, experiments of gas-liquid two-phase flow in a pipeline-riser system were performed at both steady and transient inlet flow conditions, through which the forecast method was investigated. Two mechanisms for the transition to undesirable gas-liquid two-phase flow patterns were discovered; and the feasibility of forecasting was demonstrated by the response of differential pressure signals to the change of inlet flow rates. The forecast method was a combination of a fast identification model and special forecasting rules. The formation position of the liquid slug was also qualitatively predicted. All the cases of the transition to undesirable flow patterns in the experiments were successfully forecasted at least 30 s ahead of the formation of undesirable flow patterns, which proved enough for the response of flow control systems through an additional experiment. False positives were also discussed.