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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.
Introduction The three primary functions of a drilling fluid--the transport of cuttings out of the wellbore, prevention of fluid influx, and the maintenance of wellbore stability--depend on the flow of drilling fluids and the pressures associated with that flow. For example, if the wellbore pressure exceeds the fracture pressure, fluids will be lost to the formation. If the wellbore pressure falls below the pore pressure, fluids will flow into the wellbore, perhaps causing a blowout. It is clear that accurate wellbore pressure prediction is necessary. To properly engineer a drilling fluid system, it is necessary to be able to predict pressures and flows of fluids in the wellbore. The purpose of this chapter is to describe in detail the calculations necessary to predict the flow performance of various drilling fluids for the variety of operations used in drilling and completing a well. Overview Drilling fluids range from relatively incompressible fluids, such as water and brines, to ...
To evaluate a given casing design, a set of loads is necessary. Casing loads result from running the casing, cementing the casing, subsequent drilling operations, production and well workover operations. Mechanical loads are associated with casing hanging weight, shock loads during running, packer loads during production and workovers, and hanger loads. In tubing and over the free length of the casing above top-of-cement (TOC), changes in temperatures and pressures will have the largest effect on the ballooning and temperature load components. The incremental forces, because of these effects, are given here.
Abstract Torque and drag models have been used for many decades to calculate tensions and torques along drill-strings, casing strings and liner strings. However, when applied to sand-screens, it is important to check that all the initial hypotheses used for torque and drag calculations are still valid. In particular, it should be checked whether the buoyancy force on a perforated tube may differ from the one applied to a plain tube. The buoyancy force applied on a pipe, contributes to the sum of efforts at the contact between the pipe and the borehole and therefore influences torque and drag calculations. This contact force is local and should account for localized effects as well as the material internal forces, torques and moments on each side of the contact. As the buoyancy force is the result of the gravitational component of the pressure gradient on the surface of the pipe that is in contact with the fluid, the presence of holes in the pipe also influences the buoyancy force. When applied to a portion of a pipe, buoyancy does not have contributions at the end caps of that portion of the drill-stem since these end caps are not in contact with the fluid, except at positions with a change of diameter. Therefore, one shall be cautious when calculating the local buoyancy force either on a plain or a perforated tube. The paper describes how to calculate the local buoyancy force on a portion of a drill-stem by application of the Gauss theorem accounting for the necessary corrections arising from the end caps not being exposed to the fluid. An experimental setup has been built to verify that the tension inside a pipe subject to buoyancy does follow the derived mathematical calculations. With complex well construction operations, for instance during extended reach drilling or when drilling very shallow wells with high kick-off rates, the slightest error in torques and drag calculations may end up in jeopardizing the chance of success of the drilling operation. It is therefore important to check that all initial calculation hypotheses are still valid in those contexts and that for instance, sand-screens may be run in hole safely after a successful drilling operation.
In a dynamic calculation, there are two effects not considered in steady flow: fluid inertia and fluid accumulation. In steady-state mass conservation, flow of fluid into a volume was matched by an equivalent flow out of the volume. In the dynamic calculation, there may not be equal inflow and outflow, but fluid may accumulate within the volume. For fluid accumulation to occur, either the fluid must compress, or the wellbore must expand. When considering the momentum equation, the fluid at rest must be accelerated to its final flow rate.
Casing and tubing strings are the main parts of the well construction. All wells drilled for the purpose of oil or gas production (or injecting materials into underground formations) must be cased with material with sufficient strength and functionality. Casing is the major structural component of a well. The cost of casing is a major part of the overall well cost, so selection of casing size, grade, connectors, and setting depth is a primary engineering and economic consideration. Conductor casing is the first string set below the structural casing (i.e., drive pipe or marine conductor run to protect loose near-surface formations and to enable circulation of drilling fluid).
The three primary functions of a drilling fluid depend on the flow of drilling fluids and the pressures associated with that flow. These functions includes: The transport of cuttings out of the wellbore, prevention of fluid influx, and the maintenance of wellbore stability. If the wellbore pressure exceeds the fracture pressure, fluids will be lost to the formation. If the wellbore pressure falls below the pore pressure, fluids will flow into the wellbore, perhaps causing a blowout. It is clear that accurate wellbore pressure prediction is necessary. To properly engineer a drilling fluid system, it is necessary to be able to predict pressures and flows of fluids in the wellbore.
Several designs for autonomous inflow-control devices (AICDs) are available. One forces inflowing fluids to enter gates, depending on inertial and viscous forces of the various fluids. Another is an autonomous valve in the shape of a free-floating disk that restricts the flow rate of low-viscosity fluids and is primarily used to choke gas and water inflow. Recently, a device with water-swellable rubber inside the nozzle has been proposed, but it is not yet commercially available. The comparative properties and abilities of these designs are the focus of this paper.
Lordejani, Sajad Naderi (Eindhoven University of Technology) | Abbasi, Mohammad H. (Eindhoven University of Technology) | Velmurugan, Naveen (MINES ParisTech) | Berg, Christian (Kelda Drilling Controls) | Stakvik, Jon Å. (Kelda Drilling Controls) | Besselink, Bart (University of Groningen) | Iapichino, Laura (Eindhoven University of Technology) | Di Meglio, Florent (MINES ParisTech) | Schilders, W. H. A. (Eindhoven University of Technology) | van de Wouw, Nathan (Eindhoven University of Technology and University of Minnesota)
Summary Automated managed-pressure drilling (MPD) is a method to enhance downhole pressure-control performance and safety during drilling operations. It is becoming more common to use model-based simulation for the evaluation of pressure-control systems designed for MPD automation before using those in the field. This demands a representative hydraulics-simulation model that captures the relevant aspects of a drilling system. This paper presents such a model and an approach to numerically implement that model for simulation studies. The complexity of this simulation model should be limited, first, to support effective numerical implementation and, second and most importantly, to allow for the analysis of the behavior and performance of the automated pressure-control systems during the controller-design phase. To this end, aspects of a drilling system that can considerably affect the performance of the automated MPD system are captured in the model. This hydraulics model incorporates both the distributed and multiphase-flow nature of a drilling system. Moreover, it captures nonlinear boundary conditions at the inlet of the drillstring, at the drill bit, and choke manifold, and also the variations in the cross-sectional area of the flow path. Model validations against field data from real-life MPD operations and simulations of industry-relevant scenarios indicate that these aspects are effectively captured in the model and preserved during the numerical implementation. Introduction Conventionally, the task of pressure control is accomplished by changing the mud density during drilling operations. However, this method of controlling the pressure is slow and inaccurate, and it lacks a means of compensating and responding to transient pressure fluctuations (e.g., occurring during pipe-connection operations or drilling into high-pressure formations). Besides, this method cannot be used for drilling deep wells with narrow drilling windows because of its low accuracy. To overcome such drawbacks of conventional pressure-control methods, MPD has been introduced. A main objective of MPD is to provide a means of fast, accurate, and efficient control of the bottomhole pressure, as opposed to conventional methods.
Cong, Xin (College of Civil Engineering, Tongji University) | Kuang, Cuiping (College of Civil Engineering, Tongji University) | Dong, Zhichao (College of Civil Engineering, Tongji University) | Gong, Lixin (The Eighth Geological Brigade of Hebei Geological Prospecting Bureau) | Liu, Huixin (The Eighth Geological Brigade of Hebei Geological Prospecting Bureau) | Zhu, Lei (The Eighth Geological Brigade of Hebei Geological Prospecting Bureau)
Based on Qilihai lagoon, an idealized two-dimensional coupled hydrodynamic and sediment transport numerical model was established to simulate morphological evolution under 7 different widths of tidal inlet. The morphological stability was discussed and main results are that 1) a major tidal creek forms at the lagoon entrance, then divides into multiple bypass tidal creeks; 2) tidal prism increases with the width from 100 m to 350 m, meanwhile the unit width discharge and mean current speed in tidal inlet decrease as tidal inlet widening; 3) the time to reach equilibrium state has a higher correlation with tidal prism.
Coastal lagoon is located in the transition area between sea and land, where the natural environment is complex and changeable. It has multiple values of ecology, tourism and bank protection, etc. However, due to changes of natural environment, e.g. sea level rise and storm surge, and over exploitation and utilization (Ran et al., 2019), ecological balance has been broken, ecological environment has been deteriorating, and lagoon wetland resources have been shrinking. Lagoon system's hydrodynamic environment is controlled by various dynamic conditions such as runoff, tidal current and wind. Tidal inlets connecting lagoon system and open sea directly determine hydrodynamic conditions and control the stability of lagoon system.
Tidal inlet stability was explained in two different ways by Gao (1988). One is the dynamic equilibrium relationship between dynamics and morphology. Escoffier (1940) proposed a relation curve between the maximum bottom shear stress of the channel and its sectional area, which was similar to the P-A (tidal prism - cross-sectional area) relationship proposed by O'brien (1931). Other one is the change rates of geomorphic elements such as plane position and form, section shape and section area of tidal inlets, which depend on the comparison between the factors keeping inlets open and making inlets tend to close (Bruun, 1978).