Threats to cybersecurity continue to increase in number and appear from unexpected new angles due to an increasing sophistication of cyber-attacks. A novel methodology is required not only for data protection but also to achieve safe and reliable operations at sea. The first step towards securing control systems is to make sure they are designed and operated per recognized international standards and recommendations, such as the ISO (International Organization for Standardization) 27000 series, the IEC (International Electrotechnical Commission) 62443 family of standards, the NIST (National Institute of Standards and Technology) framework, or the IADC (International Association of Drilling Contractors) cybersecurity guidelines. In addition, testing and probing these systems and their associated networks for possible vulnerabilities and robustness under high traffic loads are important to verify that the implementation of the design is safe, secure and carried out in accordance with the vendor’s or the system integrator’s documentation.
This paper provides tangible examples of findings from cybersecurity and network health tests performed on various vessels and installations, such as shuttle tankers, drilling rigs and FPSOs (floating production, storage and offloading), by DNV GL Marine Cybernetics Advisory. Typical pitfalls of on-board cybersecurity are discussed, such as inadequate protection mechanisms, installation failures and mismatches between documentation and installation, vulnerabilities in controllers, and insufficient network capacities.
So far, off the coast of Brazil, steel catenary risers (SCRs) are only used in the subsea gathering system when connected to a semi-submersible FPU (Floating Production Unit) or a Buoy Supported Risers system (BSR). This paper presents a technical feasibility study for the use of SCRs in the ultra-deepwaters of Pre-salt field (Santos Basin) connected to a spread-moored FPSO (Floating Production Storage and Offloading).
Environmental loads acting on FPSOs cause higher movements than on other types of FPUs (such as semi-submersible, SPAR and TLP). The wave-induced floater motions under the harsh conditions of Santos Basin may generate high fatigue damage at the riser TDZ (touchdown zone). In addition, extreme events may cause a significant compression load on the SCR, inducing global buckling in the same region and, thus, making the TDZ a region of special interest for the design.
To address the issues mentioned above, advanced engineering techniques and effective technologies available in the offshore industry were employed. The study considered different safety classes along the riser, allowing greater flexibility for the definition of safety requirements, and calibrated the fatigue safety factors according to a risk-based methodology. The proposed configuration made use of hydrodynamic dampers and fatigue performance improvement techniques such as upset end pipes and stress relief on critical welds.
The study results indicate the feasibility of SCRs for the operational conditions considered. The use of SCRs potentialy enhances the competitiveness of rigid riser systems for the Pre-Salt fields of Santos Basin when compared with Steel Lazy Wave Risers (SLWRs).
This work describes a methodology that evaluates the Discrete Latin Hypercube with Geostatistical Realizations (DLHG) sample size for complex models in the history matching under uncertainties process with application to the Norne Benchmark Case. The sample size affects the time demanded and results accuracy in a history matching process because a small sample size can yield inaccurate risk quantification and a high sample size can demand excessive time to reach good results. Both factors should be evaluated in order to improve the project's efficiency and to obtain reliable results. Such evaluation gains greater importance in complex reservoir models because the number of tests to determine the reservoir scenarios that match dynamic data can be high due to the level of complexity. The methodology presented in this work is divided in three steps. First, we evaluate the ability of DLHG to produce output cumulative distribution functions (CDF) that replicate a more exhaustive sampling technique (Monte Carlo) using the Kolmogorov-Smirnov test. The output is the misfit between observed and simulated production rates; then, we compare the influence and correlation matrices obtained with DLHG and Monte Carlo samples. The influence matrix shows the impact of the uncertainty variation on the outputs and the correlation matrix measures the strength of the dependence between the uncertainty attributes and outputs. Finally, we perform the stability test. The methodology was applied to the Norne benchmark case; a field located in the Norwegian Sea. The main characteristics of the methodology are: (1) it uses a statistical technique to compare the output CDFs from the reference and DLHG samples and (2) it evaluates the ability of the DLHG sample to identify the reservoir attributes that affect the history match results. We evaluated DLHG sample sizes of 20, 50, 100 and 200, and considered a MC sample size of 5,000 to the Norne benchmark case. The DLHG CDFs for the 100 sample size was able to accurately replicate the corresponding MC CDFs, however it did not replicated the behavior of the influence and correlation matrices. The DLHG sample size of 200 was able to reproduce the CDFs outputs, the influence and correlation matrices and it was considered stable. The study showed that even if the sample size is able to represent the CDFs outputs from a reference solution, the influence and correlation matrices should be evaluated. The methodology presented can be incorporated into usual history match routines.
A novel application for pressure transient analysis aimed to identify the characteristic pressure response of fault reactivation in a compartmentalized reservoir, where fluid injection/extraction creates a pressure differential across the fault that leads to fault-seal breach, is presented. The analytical solution to two producer wells separated by a sealing segmenting fault is presented. Fault reactivation is incorporated into the model as a fault transmissibility enhancement occurring at the onset of fault reactivation (
The low contrast between formation oil and oil-based mud (OBM) filtrate as well as noise associated in the signal can cause the T2 distribution for the different fluids to resemble each other, making it difficult to identify the formation fluid using nuclear magnetic resonance (NMR) data. One challenges is to quantify the remaining oil volume and estimate the formation fluid proprieties using the diffusion map (T2D) from two-dimensional (2D) inversion. Consequently, it is important to determine new methodologies that can properly enhance the evaluation of such environments.
This paper presents an application of blind deconvolution with a maximum likelihood algorithm processing applied to enhance the NMR diffusion map (T2D), helping to identify, quantify, and characterize the remaining oil volume in an invaded zone. The blind deconvolution algorithm is effective even when no information about the noise is known, making it possible to enhance the T2D map, deconvoluting the point-spread function (PSF) from the signal. After the enhancement, a multiple asymmetric Gaussian fit is used to generate a modeled distribution of the formation oil to estimate the remaining formation oil volume and its T2Intrisic logarithmic mean.
The methodology using the blind deconvolution over the T2 diffusion map was tested. Promising results provided a formation oil distribution consistent with expected fluid properties measured.
End-of-well operations can improve drilling performance through selection of the proper tools to optimize rig time and tailoring solutions. For deepwater projects, it is necessary to optimize costs without compromising safety and quality while delivering maximum efficiency. An innovative technique is presented for placing a long cementing plug using sacrificial tubing and a special tool. This method also allowed checking the top of cement (TOC) after a short waiting on cement (WOC) period. Plugging and abandonment operations were performed in deepwater wells in the Caribbean Sea, saving up to two days of rig time by using a single intervention to isolate the openhole length from 600 to 1500 m and allowing continued, timely operations. A case study of this operation is presented that discusses the experience and lessons acquired, which should be beneficial for the industry.
Conventional balanced plugs are not efficient in openhole lengths greater than 500 ft because of operational limitations and design considerations. In such scenarios, fit-for-purpose downhole tools can provide reliable solutions, such as using a release mechanism to safely place a cement plug of the necessary length with proper thickening time distributed along the volume pumped. This technique avoids the long WOC times necessary to achieve adequate compressive strength. The release tool enables running sacrificial pipe; placing cement through the sacrificial pipe; displacing cement slurry with a dart, which provides an indication of its latching at the surface; and disconnecting to retrieve the landing string. In the laboratory, a 500-psi slurry compressive strength was obtained after 6 hours and 15 minutes. This allowed the TOC to be tagged after 6 hours of WOC. Because this procedure does not require the 3 1/2-in. stinger to be pulled out of the plug, the risk of spacer contamination in the slurry was reduced. Based on laboratory results, three operations using the release tool and discussed design considerations were performed successfully for the first time in the Caribbean Sea, with no nonproductive time (NPT) or quality issues experienced, saving up to USD 500,000 for the operator. Laboratory tests, such as compressive strength, provided a good indication of the time necessary to tag the TOC, which met the operation objectives. The tool capabilities and operational and design considerations can be used as a reference for projects in similar environments that require alternatives with proven solutions. The main benefit was reduced operator costs for rig daily charges resulting from placing one plug rather than several balanced plugs. This was also beneficial for the mud company because a large spacer volume was not incorporated into the mud. Another benefit was allowing tagging of the plug in the same operation because of the short WOC.
Barros, P. M. (Petrobras) | Fonseca, J. S. (Petrobras) | Silva, L. M. (Petrobras) | Maul, A. (Petrobras) | Yamamoto, T. (Petrobras) | Meneguim, T. (Petrobras) | Queiroz, L. E. (Petrobras) | Toribio, T. (Petrobras) | Martini, A. F. (Petrobras) | Gobatto, F. (Petrobras) | González, M. (Paradigm)
Geomechanical models need to incorporate a more reliable geological model concerning the overburden as well as the underburden sections. These aspects are more important when considering the flow simulation model and the injection and/or production of the field due to the surrounding rocks behavior and their responses against those ratios (injection/producing).
Therefore, a 3D model is needed and the oil industry faces a great challenge: how to build this reliable model without seismic information? Or, how to use seismic properties with all their ambiguity to derive this 3D model?
Special attention is necessary when observing the salt-section above the pre-salt reservoir in Santos Basin, Brazil, since the amplitude response is heavily influenced by the velocity model used for the migration process.
The majority of these velocity models are considered non-geological as the main reasoning for them is only to produce a good image. To build a good seismic image, reproducing the geology is not needed: the only condition imposed on the model is that the migration operators applied using that model will focus the image. In other words, we could see a completely alien model regarding geology that focuses the image, and that model would be considered correct.
In this paper, we will illustrate a way to build plausive velocity models fitting both the geology and the mathematics of the migration for a good seismic image. This allows for the use of the amplitude response for many purposes, including (but not limited to) deriving geomechanical properties, predicting the lithologies inside the evaporitic section and recursively building a new, more realistic velocity model.
Workover vessel operations in offshore oil fields are crucial to recovering productivity and helping ensure safety. Because of economic constraints, the number of workover vessels is often limited, and logistics optimization has significant relevance. This paper provides a methodology for increasing efficiency with regards to the operational management of these vessels.
The method to address logistics optimization for a fleet of vessels should consider fleet and operational constraints to help determine the most economic routes to perform tasks in different geographic locations. This paper presents a solution to a workover operation routing problem performed by a heterogeneous fleet of vessels with different load capacities and limited abilities to perform different operations. Decisions were necessary to determine which boat should perform each task scheduled for a location at a specific time. The model was developed using operational historical data integrated into an optimization workflow, based on genetic algorithms, to determine which itinerary and tasks each vessel should execute.
This work evaluated two fleet scenarios characterized by vessel capacity and potential ability to perform specific tasks. The results reveal the possibility of a significant reduction in the total time necessary for the fleet to perform the same group of tasks. For both configurations evaluated, the total time reduction was 20 and 40%, respectively. This reduction in total time could result in an increase in tasks performed within a given time period, improved operational economics attributed to reducing downtime, and less production loss caused by the absence of these services. Another benefit provided by this methodology is the capability to generate a new optimized schedule, as necessary.
In the current scenario of high economic variation and uncertainties and reduced oil prices, increasing operational efficiency is a primary challenge. The study results illustrate the importance of an improved method to optimize fleet logistics, thus improving key performance indicators (KPIs) of interest to stakeholders, such as reduced navigation time, improved economics, and improved operator satisfaction. Furthermore, the general methodology presented can be adapted to other routing problems encountered within the petroleum industry.
This paper describes a new Intelligent Well Completion (IWC) configuration used in Brazilian pre-salt fields. It also presents the first application of this new design and the future benefits expected. The conventional IWC design used in Brazilian pre-salt areas comprises cased hole wells. The casing perforation is performed before installing the completion, which does not provide a separation between upper and lower completion. The production string is installed in a single run from its lower part to the tubing hanger and does not include a disconnection element to allow the upper completion retrieval. The new design adds a separated lower completion that can temporarily isolate the formation during the upper completion installation and heavy workover operations.
In the development of the new openhole IWC design some features have been considered critical: maximum flow area, minimum complexity, CAPEX reduction, improved well safety, flexibility with single zone completion configuration and compatibility with workover. The introduction of a lower completion system added some complexity to the wells, at the same time as it provides reservoir isolation during upper completion installation. Other benefits observed are the decrease of the wellbore size required to drill into the reservoir as an openhole completion is to be installed instead of a case hole. In instance, the use of one of the casings is not required anymore. The proposed alternative was initially applied in one well for qualification and was capable of delivering a dual zone completion where initially an openhole single zone completion was planned. The use IWC in this well was an important feature for reservoir management due to the significant difference between the injectivity of the zones completed. The new design proved to be a success in this initial application.
The new solution developed has set a new completion philosophy for pre-sal wells. Other benefits of using a lower completion in IWC is the ability of quickly isolating the reservoir, what is especially important when major fluid losses are expected during drilling and completion phases. One of the major benefits of this approach is the possibility of installing the lower completion using Managed Pressure Drilling (MPD) techniques.
Leite Cristofaro, R. A. (SimWorx Engineering R&D) | Longhin, G. A. (SimWorx Engineering R&D) | Waldmann, A. A. (Petrobras) | de Sá, C. H. M. (Petrobras) | Vadinal, R. B. (Petrobras) | Gonzaga, K. A. (Petrobras) | Martins, A. L. (Petrobras)
Fluid losses are still today one of the most challenging problems in well construction. The scenarios faced by operators during development and exploratory campaigns in the deep water pre-salt area are characterized by natural fractures, vugs and caves. Therefore, problems related to loss of circulation are critical, increasing the non-productive time and consequently, well construction costs. Additionally, in several situations, conventional drilling limitations prevent the reaching of the well target.
The present study proposes the application of a methodology to define optimum loss control material (cross-linked pills, fluid loss squeeze, bridging agents, cement), among those available for each situation, to minimize lost circulation events during drilling operations.
An Artificial Intelligence strategy based on Supervised Learning was defined to generalize data collected from five hundred lost circulation events over a three years period. Human Computer Interaction principles were used on the development of an interface where the field engineer can interact with training data while having little to no Machine Learning knowledge.
The use of empirical analysis and learning strategies as tools to assist the decision making process in the form of lost circulation countermeasures is described by this paper. The method was validated on data collected from several different wells in the Santos Basin, Brazil, pre-salt area. The strategy was already applied in two real cases resulting in a six days well construction time saving.