Advanced seals have been applied to numerous turbine machines over the last decade to improve the performance and output. Industrial experiences have shown that significant benefits can be attained if the seals are designed and applied properly. On the other hand, penalties can be expected if brush seals are not designed correctly. In recent years, attempts have been made to apply brush seals to more challenging locations with high speed (>400 m/s), high temperature (>650 °C), and discontinuous contact surfaces, such as blade tips in a turbine. Various failure modes of a brush seal can be activated under these conditions. It becomes crucial to understand the physical behavior of a brush seal under the operating conditions, and to be capable of quantifying seal life and performance as functions of both operating parameters and seal design parameters. Design criteria are required for different failure modes such as stress, fatigue, creep, wear, oxidation etc. This paper illustrates some of the most important brush seal design criteria and the trade-off of different design approaches.
Advanced seals have been applied to numerous turbine machines over the last decade to improve the performance and output. Industrial experiences have shown that significant benefits can be attained if the seals are designed and applied properly. On the other hand, penalties can be expected if brush seals are not designed correctly. In recent years, attempts have been made to apply brush seals to more challenging locations with high speed (>400 m/s), high temperature (>650 °C), and discontinuous contact surfaces, such as blade tips in a turbine. Various failure modes of a brush seal can be activated under these conditions. It becomes crucial to understand the physical behavior of a brush seal under the operating conditions, and to be capable of quantifying seal life and performance as functions of both operating parameters and seal design parameters. Design criteria are required for different failure modes such as stress, fatigue, creep, wear, oxidation etc. This paper illustrates some of the most important brush seal design criteria and the trade-off of different design approaches.
Formation evaluation (FE) while drilling is an established technique in horizontal well orientations for unconventional reservoirs such as the Barnett Shale. Due to constrained well economics, special care is taken to acquire cost-effective information quickly to maximize lateral wellbore effectiveness. Real-time data and rapid analysis provide rock parameters impacting completion decisions. New technologies are discussed that further benefit our understanding of the reserve potential and improve asset economics. In particular we will discuss innovative applications of LWD imaging, LWD magnetic resonance (MR), and full-bore coring. One key evaluation technology to optimize stimulation design is imaging-while-drilling to determine natural fracture system orientation and density and to distinguish J1 and J2 fracture sets and fractures that are potentially open. Images also provide input into geomechanical models that are used to plan stable wellbores and optimize stimulation treatments. Innovation in LWD NMR applications allows quantification of porosity, irreducible and clay bound water in real-time. When combined with LWD bulk density, the total organic carbon content and static rock mechanical properties can also be computed optimizing well placement and completion design. It is shown that the integration of LWD imaging, MR and other LWD logs can improve the understanding of unconventional reservoirs. Introduction Unconventional resources, as exemplified by gas and oil-bearing shales, show wide variations in mineralogy, rock properties, volumes of free, absorbed, and adsorbed gas (Jacobi et al., 2008), even in the same basin (Soeder, 1988). Recent developments in wireline methods (Jacobi et al., 2008) to determine these properties have led to completion and production strategies based on these properties. LWD measurements (obtained while drilling a well) have the advantage of determining at least some of these properties in real-time, so that completion decisions can be made rapidly and wells can be be steered using the real-time data (Stamm et al., 2007). Finding the correct LWD measurements for subsequent analysis that approximate some of the results of these new wireline methods would be a benefit to the overall design of logging programs, the wells's impact on production, and the completion method and design, especially in horizontal wells. Desirable qualities for shale gas production may be analogous to the Barnett shale (Leonard et al., 2008): brittle rock for ease of forming hydraulically stimulated fracture clusters, natural fractures or at least planes of weakness for fracture propagation upon stimulation; a stress field where the horizontal stresses are similar; a considerable quantity of organic carbon with free gas and potential release of adsorbed gas; relatively easily-drilled formations of competent rock to avoid borehole breakout and hole collapse such that horizontal wells can be drilled to open more rock to release gas; and, finally, at least some portion of the basin where barriers to water encroachment from below allow containment of water ingress (Gale et al., 2007, Leonard et al., 2007). The Marcellus shale is reported as varying considerably from other upper Devonian shales in the same basin, exhibiting a variation of shale petrophysical and geochemical properties. Core samples of the Huron shale taken from wells in Ohio and Kentucky (Soeder, 1988) exhibit very low proportions of porosity to nitrogen gas (< 0.2 %) while the Marcellus shale had by comparison much higher values (8 to 9 % although acquired in only one well). Likewise, permeabilities were much larger in the Marcellus sample (6 to 19 md) versus the Huron shale (generally < 0.03 md with some sample values as high as 8md). Both porosity and permeability measurements were obtained at two values of net confining stress, 1,750 and 3,000 psi for the Huron and 3,000 and 6,000 psi for the Marcellus. These kinds of differences highlight the need for a definitive method of analysis since clearly all gas-bearing shales are not alike.
Many fields currently being drilled by the petroleum industry require the use of high angle, extended reach wells to access remote hydrocarbon deposits. Although pre-drill geomechanical modeling efforts are often carried out to define the mud weight window, many wells still experience significantly elevated drilling costs due to non-productive time (NPT) associated with wellbore instability. This can be attributed to many factors but is predominantly due to the lack of appropriate data while drilling. Since rock properties, stresses and pore pressure often vary from the pre-drill model predictions, critical wells frequently require real-time updating of the geomechanical models using relevant logging while drilling (LWD) data to facilitate accurate, real-time decision-making. In this paper, a case history is presented where memory-quality; high-definition LWD image logs were obtained via high-speed telemetry systems and used to assess wellbore conditions in real time. The high-resolution LWD images were used to detect faults/fractures, breakout and general hole enlargements. Relog images over known unstable sections were also obtained to ascertain the extent of time-dependent wellbore failure. These logs were successfully used to delineate the failure zones and apply the appropriate mitigating actions in real time. Introduction In today's petroleum industry, pre-drill geomechanical modeling efforts are routinely undertaken in fields where significant wellbore instabilities are known to exist. In many cases, comprehensive and robust pre-drill models can be developed that provide great value in that they can be used to design a well and drilling fluid program to mitigate wellbore instability (Evans etal. 2003). However, it is not always possible to construct a robust pre-drill model due to a variety of reasons (e.g., insufficient useful data). This combined with the fact that significant geological uncertainties may still exist, may limit the effectiveness of pre-drill geomechanical models when applied to a current drilling campaign. This fact is borne out by a Gulf of Mexico study (Dodson et al. 2004) suggesting that wellbore integrity-related incidents (hole collapse, kicks and lost circulation) represent a major source of non-productive rig time (despite the development of sophisticated geomechanical modeling capabilities). The study indicated that 37% of the total drilling NPT stems from geomechanical and pressure-related downtime, which consume 24 to 27% of the total drilling costs. Standifird & Keaney (2004) suggested that as much as 40–50% of all NPT is attributable to pore pressure, fracturing and hole instability. This costs the industry an estimated US$26 billion annually (Sweatman 2006). It is our contention that to effectively reduce or even eliminate this NPT, diagnosing wellbore failure in real time (and applying the appropriate mitigating action while drilling) is the key. This is most easily accomplished using high definition LWD image logs. Discussion of Image Logs LWD borehole images provide critically useful information in terms of borehole quality and position within the reservoir (Janwadkar et al. 2007; Lindsay et al. 2006; Lofts et al. 2005; Morris et al. 2006a, 2006b; Onu et al. 2008; Ritter et al. 2004; Stamm et al. 2007). When used in real time, these images can help with making decisions on drilling hazard mitigation and well placement during drilling (Lindsay et al. 2007; Morris et al. 2008). Recent advances in telemetry rates (Hernandez et al. 2008) show that higher resolution image quality, approaching or equaling that of memory data, is now available in real time. This technology has enabled the visualization of geomechanical features at sufficient resolution to be useful for real-time decision-making applications.
fax 01-972-952-9435. AbstractHigh angle wells drilled into finely laminated shale are often found to be less stable than comparable wells drilled into nonlaminated rock. This can be attributed to a variety of factors including, but not limited to, well trajectory, the in-situ stress field, rock strength anisotropy, shale reactivity issues, chemical imbalances between the drilling fluid and shale pore fluid, and many others. However, due to the lack of available data some of these mechanisms are difficult to quantify and therefore are typically not accounted for during well planning. This can result in significant wellbore instability issues that substantially elevate drilling operation costs.In this paper, a comprehensive approach to account for many of these wellbore instability mechanisms is outlined. A plane-of-weakness model is utilized to account for the effects of weak bedding planes and other discontinuities. The model uses parameters that are obtained by curve fitting triaxial strength test results conducted at various angles with respect to bedding. Additionally, traditional mechanical and chemical effects were also addressed and incorporated into the pre-drill model to assist in well planning. The model was then implemented at the Terra Nova field for the case of a highly deviated wellbore drilled through finely laminated shale nearly parallel to bedding.Real-time monitoring of measurement and logging while drilling data was key to identifying the unstable sections so that the root cause of instability could be diagnosed. The appropriate remedial action was then applied and wellbore instability problems were mitigated.Both mechanical and chemical borehole instability models were applied in a case history to evaluate the potential for wellbore instability. In particular, bedding-plane related and chemically-induced instability were addressed and overcome through comprehensive modeling and the deployment of modified operational procedures.
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.