This paper describes the deployment of a new circumferential ultrasonic tool for cement evaluation used in a thick-casing environment. The operation was performed in a deepwater well, where massive loads often require heavier linear-weight casings with thicknesses greater than 1.0 in. A new-generation, circumferential, ultrasonic cement-evaluation tool was run in combination with a cement bond-log (CBL) tool to evaluate a primary cementing operation and assure zonal isolation in an ultradeepwater well with 10 3/4-in. casing set in the 14 3/4-in. hole section. Casings with thicknesses greater than 1.0 in. are outside the operating range of current circumferential ultrasonic tools. The improvement features, main specifications, and measurement physics comparing the new tool with previous-generation technology are presented. The operation was performed in a well containing two sizes of 10 3/4-in. casing in the same casing string. Both 85.3 lbm/ft (0.8-in. thick) and 109.0 lbm/ft (1.0-in. thick) casing sections were present and evaluated in the same pass. The sonic/circumferential ultrasonic combination was able to effectively evaluate the quality of the primary cementing operation behind both casing weights, as well as positively detect the top of cement (TOC). The combination of the ultrasonic tool with traditional bond-log technology provides independent and complementary measurements of cement bond quality. This presented the operator with the ability to radially analyze the zonal isolation using an image map and to identify cement quality issues, such as channeling and the presence of microannuli. In addition, the casing integrity was evaluated in the same pass using the ultrasonic tool. The new ultrasonic tool makes it possible to achieve confirmation of well integrity in complex, deepwater environments, clearly identifying zones ranging from free pipe to fully cemented conditions, including radial mapping. Improvements in the measurement physics enables the analysis of the annulus in cases of heavy, thick-walled tubulars, as well as in the presence of heavier drilling fluids.
The assessment of annulus cement barriers is critical in well Plug and Abandonment (P&A) planning and execution. For wells with 10 to 30+ producing years, the data from well construction may be unavailable, incomplete, or not fully compliant with current industry good cementing practices. This case study presents a methodology for assessing qualification and credibility of annular hydraulic isolation, highlighting the challenges involved in the process. The engineering workflow starts by data mining from well construction regarding casing and cementing operations, drilling fluids, pumping schedule, wiper plugs events, casing centralization, washer, spacer, and cement slurry design in addition to anomalous events occurred. A mapping of the cement quality is then performed in representative wells which have availability of data with uniform criteria to establish key performance metrics. Finally, a novel statistical imputation methodology is then performed to overcome missing data followed by modeling and simulations, and a credibility analysis resulting in the qualification degree of the annulus cement – qualified permanent barrier, unqualified or failed. The methodology was applied for subsea wells in P&A campaigns in Campos Basin offshore Brazil, by using this credibility & criticality assessment in the B-annulus hydraulic isolation as an input for the P&A design and resulted in increased applicability of Through Tubing scope - without the necessity to remove the production tubing – and eliminated the need of additional evaluation of the production casing cement through logging tools or pressure testing. Consequently, a 5-day average reduction in P&A intervention was obtained. The analysis showed that the cementing strategies performed in well construction dates, despite different from current practices, provide sufficient cement quality in many scenarios. The studies conducted also show the correlation between cement evaluation logs and modeling of existing cement jobs with data imputation techniques to compensate for missing data in cement-job data. New methodologies and technologies for the assessment of annular isolation in wells to be plugged and abandoned are of relevant interest for the industry and taking in consideration the uncertainties and field experience into the qualification process of existing barriers is a challenge. This paper provides insight on how uncertainty levels may be reduced to still provide quantitative results and allow the selection of an optimized P&A design.
Drilling wells with TOT-3P design consists of optimizing (reducing) the steps of well construction. Drilling takes place in 3 sections (3P=3 phases) and the completion, sand containment screen plus production column (upper and lower), is performed in a single trip (TOT = True One Trip). The construction of wells in 3 sections is only possible with the deepening of the casing of the second section of the well and the capacity of this casing to have the function of surface and production. Some challenges stand out this project, such as the gain of inclination, cleaning and stability of the open well in a riserless phase, in addition to the need to return cement to the mud line for structural purposes and guarantee the solidarity set of barriers. Because drilling has only three sections, the shoe surface/production casing should be deepened in such a way that it is competent to withstand the production loadings, the pressure influence of injector wells and compose the solidary set of barriers (SSB) for abandonment, as well as enable the installation of components of the tubing at the required depth, such as the gas lift mandrel (GLM). To analyze the feasibility of the TOT-3P project, some points are studied: Analysis of flow potential of the shallow sands crossed in section II;Surface/production casing shoe racing analysis for well construction and for well productive life;Depths of tubing modulates (PDG, chemical injection mandrel and gas lift mandrel) to meet production monitoring, combat fouling and well production. Thus, integrated strategies for Drilling, Fluids and Cementation were defined in order to obtain the objectives mentioned through a bore caliper with diameter that allows a good cementation to be performed and obtained a satisfactory result in the cementation evaluation profiles, leading to the return of cement to mud line and composition of 2 solidary sets of barriers in annular above the reservoir.
To optimize drilling efficiency, some presalt wells in the Santos basin, Brazil, had their project modified to a configuration in which the entire well is drilled, cased, and cemented in only three phases, in contrast to the usual four phases, thus saving approximately 12 to 15% on the total drilling time. The saline and production zones are cased and cemented in the same phase, requiring a cement slurry design that minimizes salt dissolution and, at the same time, has specific properties for production zone isolation. The quality of this cement job is key for the success of the project, given that poor cementation could lead to direct exposure of the wellhead to the reservoir fluids, making the three-phases project unviable due to associated risks. It is important, then, to understand and control all aspects that can influence the cement job success. The presalt reservoir is formed by carbonate rocks that present a variable ratio of gases such as CO2 and H2S. To avoid future risk of gas migration through the cement sheath, the slurry used in the cementing operation must be formulated with gas-migration-control additives to reduce cement matrix permeability. The salt section is composed of layers of different salt types, with the tachyhydrite and carnallite the most soluble. The results of research conducted with salt rock cores from this basin indicated that the best salt concentration added to the cement slurry, to avoid salt dissolution, is either 15 to 20% sodium chloride or 3 to 5% potassium chloride. It is well known that the addition of salt to cement slurry impairs the slurry properties, especially free fluid and compressive strength, two important parameters to determine a successful cement evaluation. Several laboratory tests were performed until the ideal formulation was defined. The spacers were also optimized to promote superior mud removal. Cementing techniques and best practices such as effective casing centralization, mud removal, losses mitigation, and slurry density control are imperative to ensure job objectives are achieved. To the time this paper has been written, four wells had been successfully drilled and cemented using the new configuration. Fluids design and flawless execution of the job provided an excellent cement logging evaluation, proving that it is possible to enhance the well construction to save rig time and, consequently, lower the well costs.
Drilling time and resources for casing and cementing the wellbore represent a significant cost in oil well construction. Therefore, slender wells have been targeted to be constructed with less phases and higher efficiency reducing costs by half. The objective of this paper is to present how a fit-for-purpose foam cement system contributed to delivering a dependable barrier for a True-One-Trip Ultra-Slender well, where a single barrier shall provide wellbore mechanical integrity and competent isolation from the reservoir to seabed. The methodology for this foam cement job involved, initially, hydraulic and thermal modeling, followed by lab testing, such as thickening time, compressive strength, and foam stability tests. The pumping schedule included 4 different tailored systems that were pumped to maximize probability of returns at the mudline. By using the constant-nitrogen-rate technique, the foam quality was optimized to help ensure slurry and foam stability at downhole conditions. Proper energized fluid selection and casing centralization were placed to guarantee a slurry system application with improved mud removal capacity and optimized standoff to avoid slurry contamination attributed to channeling. During execution, no issues were observed until reaching the final depth. The open hole diameter was estimated based on volumetric determination by pumping a tracer and a scavenger slurry, to be visualized at the mudline. Based on that information, further volumes were fine tuned and pumped to ensure appropriated foam cement quality and density along the wellbore section. As one of the major objectives of the job, returns could be achieved at mudline and the final differential pressure was higher than expected, indicating a cement sheath in the annulus had extensive length. Cement job evaluation was performed after the job using sonic and ultrasonic tools to confirm the quality of the barrier placed in the annulus. Additionally, an advanced Cement Evaluation was executed and showed excellent isolation for the slurries placed in the well. The results from this unprecedented operation in Brazil have proven the features and benefits of using foamed cement in ultra-slender wells for specific challenges, such as: requirement of returns at mudline, application in long length zonal isolation operations, and the necessity of high-strength low-density solutions near the mudline. After this job, similar wells have been constructed in the same area, and the applied technique has continuously proven to be a dependable and sound solution for similar scenarios. Based on the successful case history presented in this paper, the application of foam cement technology in ultra-slender wells represent an innovative and dependable solution for the actual and future high-efficiency wellbore geometries. By reducing the risks of having a single cement sheath in the entire well, it enables the oilwell industry to reduce time and risks during wellbore construction and helps enhance its productivity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.