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This study presents a dual-functional system, which is a submerged fluid-filled semi-circular piezoelectric membrane for breakwater and wave energy converter. The mixed Eulerian-Lagrangian method is used to simulate the fully nonlinear waves, deformation of the membrane and variation of voltage on the load . The simulation found that the variation frequency of the strain in the piezoelectric membrane is 2 times of the wave. There exists an optimum resistance of the load that can give the maximum electrical output power. The maximum electrical output power of the piezoelectric membrane occurs as the transmission coefficient of the wave approaches its minimum value.
The utilization of wave energy has been studied by many scholars for several decades. Most of studies focused on the wave energy converter (WEC) with higher wave energy extraction efficiency. This study presents a submerged fluid-filled piezoelectric membrane WEC , which is called SFPMWEC in the following section. Compared with traditional WECs, the wave energy extraction efficiency of SFPMWEC is lower. However, the construction cost of SFPMWEC is much lower than traditional WECs. Other advantages of SFPMWEC are easier maintenance and deployment, non-intrusion and cost sharing with breakwaters. As breakwaters, a submerged fluid-filled flexible membrane has been studied by some scholars. Ohyama et al (1989) had done experiments to study transmission and reflection waves over a submerged bottom-mounted fluid-filled membrane . Phadke and Cheung (1999,2001) studied the response of fluid-filled membrane in linear gravity waves by boundary element method (BEM) coupled with finite element method (FEM). The geometric nonlinearity due to the larger deformation of the membrane is considered in the work of Phadke and Cheung (2003). Das (2009) assumed small amplitude of surface waves and membrane deflection and used the threedimensional, coupled boundary element and finite element model to study the response of a bottom mounted fluid-filled membrane in a wave flume. Liu and Huang (2019) used the mixed EulerianLagrangian method to simulate the fully nonlinear interaction of waves and the submerged fluid-filled flexible membrane. These studies show that the submerged fluid-filled flexible membrane breakwater can reduce the transmission waves greatly at resonance of the membrane system. The resonance of the membrane system means that the maximum response of the membrane occurs as the natural frequency of the membrane system equal to the frequency of the incident wave. Therefore, it is possible to use a submerged fluid-filled piezoelectric membrane as both breakwater and WEC.
Free surface flow around a surface-piercing flat plate operating at incidence is a suitable research subject for marine hydrodynamics, because it includes typical flow features found in marine hydrodynamics such as vortex generation, flow separation, and free surface flows. For those reasons, it is selected by the ITTC committee as a benchmarking case for Stereo PIV(SPIV) test. In this paper, flow past a surface-piercing flat plate is studied by computational fluid dynamics (CFD) simulations. The incident angle is 20 degree and the current velocity is 0.4 m/s. Unsteady Reynolds-averaged Navier-Stokes (URANS) simulation is carried out and compared with the existing experimental data. The hydrodynamic forces on the flat plate, velocity profile in the wake regions are presented and analyzed. In addition, the vortical structures are identified and visualized by the Liutex/Rortex method.
Flow around surface-piercing structures involves interactions between current, wave and body and is of importance for ship and ocean engineering. Wave-induced pressure gradient will affect the boundary layer around the submerged body and vice versa, boundary layer will affect the waves of first order forces and moments (Metcalf et al., 2006). On the other hand, the submerged structures are commonly with truncated free end at the bottom and the tip vortices shed from bottom will interact with free surface (Briggs et al., 2019).
Similar physical problems have been extensively studied. Stern et al. (1987) studied the effects of waves on the boundary layer of a surfacepiercing flat plate with an upstream horizontal foil with variable depth of submergence used for generation of Stokes waves in a towing tank for a range of wave steepness and average Re=1.64×106. They observed wedge shaped, broken and turbulent separation region on the free surface.
Metcalf et al. (2006) experimentally investigated the unsteady freesurface wave-induced boundary-layer separation for a surface-piercing NACA 0024 foil in a towing tank at three different Froude numbers, 0.19, 0.37 and 0.55 and three Reynolds numbers, 0.822, 1.52 and 2.26×106. They provided mean and unsteady far-field wave elevations, mean and unsteady foil-surface pressures and analyzed the frequency components of shear layer, Karman shedding, and flapping instabilities, respectively. However, no PIV measurement is conducted in their study.
Wang, Xin-long (National University of Defense Technology) | Wei, Gang (National University of Defense Technology) | Du, Hui (National University of Defense Technology) | Wang, Shao-dong (National University of Defense Technology)
The internal waves wake will be generated when an underwater vehicle sails in stratified ocean. Such internal waves signals could be detected by synthetic aperture radar (SAR). The characteristics of the internal waves depend on vehicles, stratified fluid and motion properties. The SAR images of the internal wave are also affected by the magnitude and direction of the sea surface wind. The internal waves generated by an underwater vehicle in a two-layered fluid were simulated based on a hydrodynamic theoretical model. The rough sea surface influenced by wind were simulated by the P-M wind wave spectrum. The SAR images were calculated based on the internal wave signals under rough sea surface by the two-scale method. The numerical simulation shows that the internal wave wake could be identified in the SAR images under appropriate speed and depth of the vehicle. As the ship speed increases, the internal wave wake tends to be close to the center axis of the track. The visibility of the wake is also related to the wind speed. At low wind speed, the wake has high visibility. Under moderate sea conditions, the wake can be identified by removing noise caused by surface wind waves, while the wake is difficult to recognize at high wind speed.
When a submerged vehicle sails in ocean, it will produce hydrodynamic wakes similar to those of ships, which are difficult to eliminate for a long time. The types of wakes can be divided into Kelvin waves, Internal waves and Turbulent wakes (Zhang et al. 2003). And in synthetic aperture (SAR) radar remote sensing images, the wake often lasts for a long time and has a wide range, and may still exist even under moderate sea conditions (Lyden et al.1988). The SAR imaging of wakes can be influenced by various factors, such as marine environmental factors (sea conditions, stratification, terrain, etc.), submersible factors (speed, depth, etc.), radar factors (polarization mode, angle of incidence) (Yeremy et al. 2001).
Cheng, Zhong (Xi'an Shiyou University and CNOOC Ener Tech-Drilling & Production Co.) | Xu, Rongqiang (CNOOC Ener Tech-Drilling &Production Co.) | Yu, Xiaolong (CNOOC Ener Tech-Drilling &Production Co.) | Hao, Zhouzheng (CNOOC Ener Tech-Drilling &Production Co.) | Ding, Xiangxiang (CNOOC Ener Tech-Drilling &Production Co.) | Li, Man (CNOOC Ener Tech-Drilling &Production Co.) | Li, Mingming (CNOOC Ener Tech-Drilling &Production Co.) | Li, Tiantai (Xi'an Shiyou University) | Gao, Jiaxuan (Xi'an Shiyou University)
Upstream Oil & Gas industry recognizes that there are significant gains to be had by the implementation of new digital technologies. For offshore exploration and development, the goal is to bring together all domains, all data, and all engineering requirements in a seamlessly interconnected solution. The industry is putting significant efforts into using instrumentation and software to optimize operations in all domains for exploration and production (E&P) to move towards the digital oil field of the future. an innovative digital solution has been designed and implemented to cover all different aspects of the well planning and engineering workflows, delivering a step change in terms of capabilities and efficiency.
As part of this transformation process, CNOOC have implemented integrated data management project of geological engineering for covering all different aspects of the well engineering workflows, delivering a step change in terms of capabilities and efficiency. The objective is to provide a continuous improvement platform to users for:
Digitalization can reduce the time spent with daily documentation and simultaneously increase the quality by removing an error prone way of work.
Technological solution enabling real-time data transmission from all rigs to CNOOC onshore headquarters and enabling real-time visualizations of the drilling data. This includes workload, number of needed rigs, daily performance, key performance indicators and even operation time forecasts based on real data.
Engineering solution to transform expert experience and accident cases into information to easily identify the areas of operational improvement allowing to implement specific measures to reduce intangible loss time (ILT) and non-productive time (NPT) which can help in reducing costs.
This project has also provided a real geological drilling environment where high frequency real-time drilling data is utilized along with low frequency daily drilling report data to provide better insights for well planning and generate ideas for improving performance and reducing risk.
This paper presents a full description of a new industry standard digital well construction solution that has the potential to transform the well operation process by providing a step change in collaboration, concurrent engineering, automation, and data analytics. Furthermore, the cloud-deployed solution challenges will be briefly discussed.
The learned lessons and gained experiences from this project construction presented here provide valuable guidance for future demands E&P and digital transformation.
Sharma, Ayush Sharma (University of Petroleum and Energy Studies) | Raj, Kriti Raj (University of Petroleum and Energy Studies) | Patidar, Atul Kumar Patidar (Department of Petroleum and Earth Sciences, University of Petroleum and Energy Studies)
Interpretation of subsurface lithology has been an integral part of bottom-hole investigation while drilling a well for hydrocarbon exploration. Conventional methods such as mud logging and open-hole logging have proven to be effective in this aspect. But there arises a need of the real time interpretation of subsurface drilling lithologies to have a better control over desired well path and economics, which is very limited through available conventional methods. This paper aims to provide a classifier that can deliver a justified chance of success in lithology estimation based on input matrix provided to the classifier. The dataset is taken from open source platform (Equinor), which provided the drilling history of 15_9_F_15_D well of North Sea Basin along with the interpreted lithology. This dataset is used to prepare the input matrix and the corresponding output used for the classifier. It incorporates seven drilling parameters, i.e. rate of penetration (ROP), weight on bit (WOB), bit rotation per minute, total bit rotations, corrected drilling exponent, mud flow & mud weight and the corresponding recorded subsurface lithology for each foot. It is made sure that the chosen drilling parameters have a direct impact on the rate of penetration with changing physical characteristics of the formations being penetrated. The formations are calibrated with the integer values from 1 to 5 for easier numerical computations. The prepared dataset is divided into two components i.e. training Set (80%), and test Set (20%) with feature scaling implemented. The most intuitive classification model among all the tested classification algorithms i.e. multiple classification algorithm, artificial neural network, and KNN search method is stated based on their individual F (1) score on the test set. It is observed that the cost function for the multiple classification model stopped reducing after the first few iterations irrespective of learning rate value alterations, which induced a limit on the accuracy provided by the chosen algorithm. It is observed that the performance of ANN is quite good for the lithology present in majority, such as claystone. However, the performance degrades exponentially for the lithologies occurring in minorities such as sandstone, dolomite, marl and limestone. The results obtained from KNN classification model not only provides an accuracy of 95% in claystone, 92% in sandstone and 89% in marl which makes this model the most appropriate classifier to be used among the three.
The preliminary results, through the comparison among the three classifiers not only provides the most intuitive model for subsurface lithology prediction using real-time drilling data, but also gives an idea about the most appropriate classifier to be used in the future reference, be it any basin, given that the same set of drilling parameters are used as the input matrix for training the classifier.
Sajjad, Farasdaq Muchibbus (PT Pertamina Hulu Energi) | Wirawan, Alvin (PT Pertamina Hulu Energi) | Chandra, Steven (Institut Teknologi Bandung) | Ompusunggu, Janico Zaferson Mulia (PT Pertamina Hulu Energi) | Prawesti, Annisa (PT Pertamina Hulu Energi) | Suganda, Wingky (PT Pertamina Hulu Energi) | Muksin, M. Gemareksha Jamaluddin (PT Pertamina Hulu Energi) | Amrizal, Amrizal (PT Pertamina Hulu Energi)
Tubular engineering design is essential for production operation, especially in the mature oil and gas fields. The complex interaction among oil, natural gas, and water, complemented with wax, scale, inorganic compound, and deformation brings complexity in analyzing tubular integrity. This challenging problem will be more severe if the wells are located in offshore environment, therefore finding the cause of tubing deterioration is a challenging.
Field X, which has been in production for 30 years, cannot avoid the possibility of tubular thinning and deformation. The degradation is slowly developed until severe alterations are observed on the tubing body. The current state of the wells is complicated since the deformation inhibits the fluid flow and increases the risk of wellbore collapse and complications during sidetracking, infill drilling, workover, and other production enhancement measures. The risks can be harmful in the long run if not mitigated properly.
The current condition encourages us to conduct more comprehensive study on tubular degradation. It is to model the multiple degradation mechanisms, such as corrosion, scaling, and subsidence, under the flowing formation fluid. The model is then coupled with reservoir simulation in order to provide a better outlook on tubular degradation. We used multiple case studies with actual field data to identify the dominant mechanism on tubular degradation. The case study cover various reservoir and fluid characteristics and also operations problems to develop general equation and matrix for risk analysis and field development considerations.
We present the degree of tubular degradation and its effect to overall field performance and economics. Current field practices do not encourage a thorough tubular assessment during early life of the wells, which create complex problem at later stage. The study indicates that a proper planning and preventive action should be performed gradually before tubular degradation becomes severe. The paper presents a field experience-based model and guideline matrix that is useful in developing new areas from the perspective of well and facilities integrity, so that the degradation-related issues could be recognized earlier.
The implementation of a well integrity management system in a mature liquid hydrocarbon storage field brought to light essential questions about the present condition and likely evolution of the barrier elements in the years to come. Are there defects in the cement sheaths that were not detected at the time of site construction more than 50 years ago? Are there aging processes, such as casing corrosion or cement degradation, that could limit the field's useful life or even present an immediate risk? And, finally, what were the exact properties of cement and casing, given that the information available in drilling reports is very limited?
At the start of the campaign, the perceived need and available technology meant using a logging tool requiring pressure, and therefore the inspection would typically involve 2 workovers and a period of 3 weeks. However, tool selection focused on the actual aging risks, together with the use of new transmitters and relentless operational optimization improved operational efficiencies allowing two wells to be logged in two consecutive days, with important savings in direct and indirect cost as well as minimization of operational risk. The cost reduction did not come at the expense of actionable information: the wireline tools selected, together with detailed preparation and carefully supervised execution led to outstanding data quality being collected.
The implementation of a consistent method of absolute log calibration and quantitative evaluation allowed us to characterize cement properties and defects, as well as their evolution with time. A salient signature, common to most storage sites in salt, is high cement quality across the salt, with a sudden unexpected, partial loss of bond across the anhydrite that overlies the rock salt formation. This was recognized as a benign form of "sulfate attack": The precipitation of secondary ettringite within the cement matrix results in expansion and thus debonding across the stiff anhydrite, whereas creeping salt pushes cement back on the casing. Lead cement densification was also observed near shallower aquifers, also rich in sulfates, with clamping provided by marls in this case. After optimizing the logging suite, it was concluded that there was no risk of erosion, wear or corrosion, external as well as internal. The analysis also improved understanding of cement behavior across salt and the role of creeping formations.
A streamlined approach at integrity assurance, whereby the right questions are asked by the management system, optimum inspection protocols are selected and carefully carried out, and acquired data is processed using advanced quantitative techniques, allowed us to understand characteristics and dynamics of barrier elements and to conclude that safe operation of the site is possible and that there is no fixed life span.
Sand production in unconsolidated formations during sampling can lead to poor quality of samples being acquired due to plugging of flow lines and sealing issues at the probe. Formation pressure and mobility measurements can also be affected by sand production which may cause plugging inside the tool or at the tool inlet and result in increased operational time. Predicting sanding potential thus becomes critical to achieve both operational and formation characterization objectives, especially in deep-water environments, where operation costs are high. Calculating "Critical Draw Down" (CDD) pressure and predicting the sanding envelope through geomechanical-sanding analysis provide insights critical to successful testing and sampling operation.
A fit for purpose geomechanical model has been developed based on petrophysical data along with regional knowledge of geomechanical conditions. With the geomechanical model, analytical sanding evaluation is used to calculate a range of CDD values for the likely testing and sampling points using well logs from offset wells. Logs from the studied well are analyzed in real time to update CDDs. The zones least prone to sand production are identified and prioritized for testing and sampling. The pre-drill sanding risk assessment is also used to optimize operational parameters including selection of the best pump and packer types while the real time updated CDD values is incorporated to limit the flowing (drawdown) pressures during the sampling and testing operations.
A case study from a deep-water field in India is highlighted where the mentioned workflow developed post logging for a pilot wellbore has helped to optimize decisions in real time during formation pressure testing and sampling in its sidetrack wellbore, thus adding value to reservoir characterization objectives and reducing nonproductive time (NPT). Based on the pre-drill sanding assessment, CDD was found to be in the range of 0 - 500 psi below the formation pore pressure in some of the sand bodies. Also, a large face packer was recommended to enhance sealing efficiency by increasing the contact area with the formation. Pump rate was regulated during pressure testing and sampling to ensure that the pressure never exceeded the pre-defined CDD values thus preventing sand production. Multiple fluid samples were collected successfully without any plugging. This integration of geomechanical assessment with operation contributed to 32% increase in success rate for good quality pressure testing and acquisition of representative samples in the sidetrack wellbore, benefitted from a systematic adaptation of pre-job assessment and real time optimizations compared to the pilot wellbore.
The pre-drill petrophysical and geomechanical evaluations provide critical insights to assist in real time optimization of pressure testing and fluid sampling operations in unconsolidated reservoirs. Workflow presented in this paper has proven to be valuable in obtaining reliable formation pressure data and contamination-free formation fluid samples for accurate reservoir and fluid characterization in unconsolidated formations during wireline logging testing and sampling operations.
Turning a brownfield from industrial to residential or commercial use has been a trend in recent years. Even more so when land has become valuable, like many of the former manufactured gas plants (MGP) which lie in today’s hearts of the cities. Prior to landuse alternation, land contamination assessment is required in order to ensure that health and environmental risks to receptors are in compliance with legal regulations. Conventional site characterizations based on soil and groundwater sampling may involve significant uncertainties due to insufficient sampling density under limited budgets. Estimations of free phase product (NAPL) spatial extensions might be highly affected by traditional sampling schemes, which often may happen to miss the contaminant bodies. Applying a denser sampling grid may be not feasible due to time and cost constraints (large sites, accessibility issues, depth specific problems). High resolution methods like Membrane Interphase Probe (MIP), Laser Induced Flurescence (LIF), Hydraulic profiling Tool (HPT), Electrical Conductivity (EC) respectively Cone Penetration Testing (CPT) are recognized as rapid, low-invasive and cost-efficient site characterization methods in terms of contamination, hydraulics and lithology. This paper displays best practice scenarios to cope with oil contaminated sites when reaching amazing economical efficiencies (up to more than 100m per day) and preserving at the same time the vertical high-resolution capabilities.
A Dual LIF site characterization system was developed by combining a UVOST, and a TarGOST system under a single Dual LIF probe coupled afterwards to a CPT cone. The combined system was deployed at a Swedish site. The site main contaminants are oil-related with reports over coal-tar specific type of NAPL. A no. of 45 UVOST-TarGOST-CPT profiles down to around 10m bgl were carried out indoor, and outdoor of site facilities. They revealed the type, spread, and intensity of site contamination. For calibration, and validation aims, several soil samples were recovered by depth oriented MacroCore sampling.
As high-resolution site characterization method, LIF displays significant advantages over traditional characterization techniques. Especially for NAPL detection and delineation, a LIF deployment followed by complementary target-oriented soil sampling delivers the key to reliable site models. A combined use of UVOST and TarGOST under a CPT environment proved to potentiate the high-resolution methodology by enforcing validation resp. resolution capabilities in terms of contaminants (heavy vs light contaminant classes, different saturation degrees, vertical differentiation of NAPLs), and geotechnical parameters (lithology, soil density and consistency). This combined UVOST-TarGOST-CPT methodology applied for the first time in Europe, illustrates the need for site specific screening methods able to provide reliable images of the site under cost efficiency requirements. Moreover, reliable site models open the perspective of successful remediation strategies, and land redevelopment scenarios.
Comparisons of site characterization campaigns display significant cost, and time savings using environmental high resolution techniques against conventional methods of drilling/sampling/testing, with direct reflection into the bottom-line profitability of projects. Analyzed scenarios point out, that cost reductions above 30% and time reductions above 20% are fully reachable added-value objectives.
For many unconventional reservoirs, the initial oil saturation is extremely low (around 30 %). In such circumstances, it is necessary to use alternative geological and hydrodynamic simulators to forecast production levels. A novel adaptive modeling approach based on cascades of fuzzy logic matrices was proposed and implemented for a mature carbonate oil reservoir in the Permian basin of Texas where next generation waterflooding was considered to revive development process and increase oil recovery.
The proposed approach is a variant of machine learning to solve the classical analysis and synthesis problem. At the analysis stage, the input and target parameters are normalized in order to equalize their significance. For each pair of input parameters, a fuzzy-logic matrix is formed and populated with actual values of the target parameter. The set of matrices forms a cascade in which every component is characterized by its own membership function. At the synthesis stage, forecasted results of the target parameter are calculated taking into account all membership functions and correspond to the maximum values of their superposition.
By means of the proposed approach, geological and hydrodynamic models of the unconventional reservoir were successfully created, which made it possible to estimate the distribution of its initial and remaining oil reserves for all reservoir formations. The options for further reservoir development were also considered including the reactivation of non-operating wells, drilling new wells, and initiation of waterflooding. The obtained results confirmed that waterflooding was able to enhance the cumulative oil production of the reservoir compared with the base case without waterflooding, and its role became more significant as the number of operating production wells increased. The calculated results also showed that the proposed approach was quite sensitive to the changes of input parameters, for example, to the number of production and injection wells. The cumulative oil production varied several times depending on the considered option. The calculated results justified the ability of the proposed approach to forecast the development results and to choose the proper strategy for the reservoir reviving. A distinctive feature of the proposed approach was its ability to adapt to any of geological and field conditions, such as the extremely low initial oil saturation that most reservoir simulators do not take into consideration.