|Theme||Visible||Selectable||Appearance||Zoom Range (now: 0)|
The most important mechanical properties of casing and tubing are burst strength, collapse resistance and tensile strength. These properties are necessary to determine the strength of the pipe and to design a casing string. If casing is subjected to internal pressure higher than external, it is said that casing is exposed to burst pressure loading. Burst pressure loading conditions occur during well control operations, casing pressure integrity tests, pumping operations, and production operations. The MIYP of the pipe body is determined by the internal yield pressure formula found in API Bull. This equation, commonly known as the Barlow equation, calculates the internal pressure at which the tangential (or hoop) stress at the inner wall of the pipe reaches the yield strength (YS) of the material.
Summary In this paper we present a methodology to superimpose the American Petroleum Institute (API) uniaxial and triaxial limits on tubular design limits plots (API TR 5C3 2018). Complications caused by a recent change of axis are resolved, producing a practical design limits plot that avoids the horizontal shift of the API vertical limits, which is currently the industry standard. The commonly used slanted ellipse is compared against an adaptation of the circle of plasticity in the form of a horizontal ellipse, showing the convenience of this last one with examples. After the current official collapse formulation was made part of the main body of standard API TR 5C3 (2018), the horizontal axis on the standard industry well tubular design limits plot changed. The present study evaluates this redefinition of the horizontal axis. One consequence of this modification is a difficulty plotting the API tension and compression limits. The API horizontal limits (uniaxial burst and collapse) are found to be independent of load situation, whereas the API vertical design limits (uniaxial tension and compression) are dependent on inside and outside tubular pressures. The approaches used by commercial software and industry publications to solve this challenge are reviewed. A new design methodology is developed to link API uniaxial limits to the triaxial theory. One main objective of the study is to establish a mathematical relationship between API tubular design limits and the von Mises triaxial theory (API TR 5C3 2018). A methodology that allows plotting the API uniaxial force limits on the design limits plot is developed. The study also shows that the results obtained from the industry standard slanted ellipse are identical to those obtained from the horizontal ellipse and circle. One important difference is that the slanted ellipse is based on the zero axial stress datum, whereas the horizontal ellipse/circle uses the neutral axial stress datum. The horizontal ellipse/circle is well suited for calculations involving buckling, compatible with the information used in field operations, and its formulations are less complicated than the tilted ellipse. Therefore, attention is called to the use of the horizontal ellipse/circle in well tubular design.
Teigland, Andreas (Norwegian University of Science and Technology) | Brechan, Bjørn (Norwegian University of Science and Technology) | Dale, Stein Inge (Norwegian University of Science and Technology) | Sangesland, Sigbjørn (Norwegian University of Science and Technology)
Summary As wells in modern operations are getting longer and more complex, assessing the effect of casing wear becomes ever more crucial. Degradation of the tubulars through mechanical wear reduces the pressure capacity significantly. In this paper, we use the finite element method (FEM) to analyze the stress distribution in degraded geometries and to assess reduction in collapse strength. A model for the collapse strength of the casing with a crescent-shaped wear groove is developed and its performance evaluated in relation to experimental data. The model was created by using the Buckingham Pi theorem to make generalized empirical expressions for yield and elastic collapse of tubulars. Finite element analysis (FEA) of 135 geometries was used in the development of the model. The results show that the generalized expressions capture the trends observed in the FEA accurately and match the experimental data from six tubular collapse tests with an average relative difference in collapse pressure of 5.2%. Introduction External pressure on tubulars may cause collapse, depending on the magnitude of the pressure, the material properties, and the geometry of the tubular.
In situations in which predrill analysis reveals high risk but has a large uncertainty, it is possible to mitigate that risk by carrying out geomechanical analysis in real time. Performing real time assessment requires acquisition of a variety of data while drilling. The measurement can also be used to show where transient pressure events such as surging and breaking the gel strength of the mud exceed fracture pressure, or where swabbing reduces the pressure below the pore or collapse pressure of the wellbore. Direct pore-pressure measurements while drilling can provide critical data to calibrate pore-pressure predictions in permeable formations. Extended leakoff tests are strongly recommended.
The pursuit of hydrocarbon reserves and increased oil production means that operators continue to look to prolific high-permeability, clastic reservoirs that can be found in basins around the world. The use of high-deviation and horizontal well trajectories in these fields increases the amount of reservoir contacted by the wellbore, which improves productivity but increases the challenges of sand control. Practical sand-control options for these wells include gravel packs, standalone screens, and slotted liners. The lower flux rates in extended-reach wells, and the high cost of gravel packing mean that operators are increasingly turning to standalone screens as the solution. However, the choice of screen will depend on the particular application to ensure that the well completion can retain the sand, avoid plugging and erosion, and maintain mechanical integrity.
The offshore industry anticipates the need for production-riser systems in ultradeepwater fields. The development of these fields [this paper considers a field located in the central Gulf of Mexico (GOM)] leads to many challenges with respect to the selection of the riser concept; in some instances, such applications may require extending riser technology beyond its current limits. This paper evaluates the feasibility of a number of production- and export-riser configurations for ultradeepwater applications. Please note that riser-design criteria, methodology, and data (riser functions and associated pipe sizes; riser internal-fluid properties; and riser-strength assessment) are provided in the complete paper. Steel-catenary-riser (SCR) wall-thickness sizing is initially carried out when considering X65 line pipe. For a design pressure of 5 ksi, the wall thickness of the production riser is primarily driven by collapse because of external hydrostatic pressure.
This work is a study of collapse pressure of perforated pipes to evaluate the effect of lateral perforations on the radial resistance of pipes under external pressure. These types of pipes represent a simple and economical technology widely used as sand-control meshes or perforated liners. One of the most common challenges to high flow rates in mature fields is the migration of sand to the well. High rates of oil production together with maximum sand retention is the optimal result. In accomplishing this complex goal, perforated pipes play a vital role because they are a simple and inexpensive application, and they are widely used in the industry.
Recently, well design engineers attempted to replace traditional API 5CT pipes with cheaper UOE steel pipes in the downhole wellbore construction. The UOE method for producing longitudinally welded large-diameter pipes creates typically weaker pipes in terms of collapse resistance. The standard API 5C3 collapse design procedure no longer meets safety requirements. A practical solution to this issue is discussed.
UOE pipe casing can be designed based on the new collapse strength envelope, which is established by modifying the API RP1111 collapse strength model. The original API RP1111 collapse strength model was intended for pipeline design, not downhole tubular design. It is comprised of the elastic collapse term and yield collapse term, with the latter being proportional to material yield strength. However, the deration effects of temperature, tension, and internal pressure are not included. For downhole wellbore tubular design, yield strength is replaced with equivalent yield strength (from API 5C3 new addendum), which is a function of temperature, axial stress, and internal pressure.
A new casing design workflow has been implemented in the computer program, and case studies were performed to verify the collapse design results. A new collapse pressure envelope was generated using the computer program integrated with a commercial tubular design tool and was compared to the traditional API 5C3 collapse pressure envelope. As expected, the new collapse strength values, calculated using the modified API RP1111 collapse model, are typically much lower than the estimated values using the API 5C3 collapse formula.
Results of the collapse safety factor and maximum allowable wear are also compared between the modified API RP1111 collapse model and the traditional API 5C3 collapse model. Typically, UOE pipe using the modified API RP1111 collapse model generates lower safety factor and maximum allowable wear values, as expected.
The API RP1111 collapse strength model has been modified to include the deration effects of downhole conditions. Implementing this model in the commercial tubular design tool enables the cost-effective design of wellbore casing strings using cheaper UOE-manufactured steel pipes.
Zhang, Jinwu (CNPC GreatWall Drilling Company) | Hua, Jiqing (CNPC GreatWall Drilling Company) | Xiong, Xiaolin (CNPC GreatWall Drilling Company) | Liu, Jinxia (CNPC GreatWall Drilling Company) | Li, Mingbo (CNPC GreatWall Drilling Company) | Gui, Feng (Baker Hughes) | Ghosh, Amitava (Baker Hughes) | Ong, See Hong (Baker Hughes) | Huang, Xingning (Baker Hughes) | Deng, Lichuan (Baker Hughes)
The shale revolution has extended the life cycle of the oil and gas industry, promoted the growth of global oil and gas reserves and production, and changed the energy's strategic pattern of various countries. At present, the national shale-gas demonstration area of PetroChina Changning and Weiyuan is in the stage of large-scale production. Horizontal well and hydraulic fracturing are two key technology that have proven to provide an effective way to economically develop medium to high maturity shale gas resources. However, due to geological complexity of the shale-gas demonstration area, and the lack of robust analysis and research on overpressure mechanism and wellbore instability characteristics, drilling events such as stuck pipes, lost circulations and inflows occurred frequently during horizontal well drilling. These non-productive events greatly restricts the wellbore construction cycle time and the production of shale gas reservoir. A comprehensive geomechanical study was carried out from which the three pressure profiles required for drilling, i.e., pore pressure, collapse pressure and fracture gradient, are established. The study also clarified the spatial distribution of overpressure across the field. The improved pore pressure and geomechanical understanding of the field provides the necessary inputs for an integrated, multi-disciplinary approach carried out during pre-drilled analyses, real-time monitoring and post-drilled evaluation to manage the stability of horizontal wells. The safe mud weight window derived from geomechanics provides the basis for mud weight and mud formulation designs that can be continuously optimized to improve wellbore stability and reduce drilling risks. The integrated approach has been applied for 4 horizontal wells in Weiyuan's shale gas field. One of the wells, Wei202-H34-3, has the horizontal section length of 2500m, making it the longest horizontal section recorded in the block. Drilling performance analyses of the well showed that the overall drilling risk, the wellbore construction time, and the drilling costs were substantially reduced by optimizing the drilling operations through geomechanics integrations and applications. The experience and knowledge obtained from this integrated workflow will provide guidance and serve as reference for the efficient development of unconventional oil and gas reservoirs in China.
Polish Oil and Gas Company (POGC) is in the process of appraising tight gas discoveries in the Polish part of the European Southern Rotliegend Basin. Encouraged by the results and experience of directional wells, it planned to assess the feasibility of drilling a horizontal well using underbalanced drilling technology. For this evaluation, an understanding of the geomechanical setting was needed, and thus constructing a field-specific geomechanical model was the underlying aim of the study. Two constitutive models were used in order to obtain a range of safe mud weights and to assess the effects of under- or near-balanced drilling operations on wellbore stability in the reservoir sands: an elastic and a poroelastic model. The two models did not agree, so we tried to assess the model quality based on which model best described the failures observed in the offset wells during drilling. The data was not sufficient to determine the best model, so we have two possible answers. If the elastic model is correct then a higher mud weight is needed to safely drill the horizontal well. If our assumptions about poroelasticity are correct, then the horizontal well can be drilled with much lower mud weights.
Underbalanced drilling (UBD) is a valuable method for optimization of multiple drilling objectives including: minimizing formation damage caused by drilling fluid invasion, increasing the rate of penetration and reducing drilling time, increasing bit life, performing early detection of hydrocarbons, dynamic testing of productive intervals while drilling, and minimizing lost circulation (
The primary aim of this study was to determine the feasibility of underbalanced drilling in a horizontal appraisal well through the Permian age Rotliegend sandstone target in the Wielkopolska Province, onshore Poland. Deposition of the Upper Rotliegend occurred in arid and semi-arid continental conditions, and therefore the basin contains Aeolian, fluvial, and playa deposits. Continental Rotliegend sedimentation was terminated by the Zechstein transgression, which caused partial redeposition of poorly consolidated, porous, and permeable Aeolian sands. They are topped with the Zechstein Limestone deposits and then by the PZ1 evaporites (