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This paper presents a drilling solution through application of an automated managed-pressure-drilling (MPD) technique proved to identify and react to actual wellbore pressures and detect and control gains and losses while still having the ability to maintain a constant bottomhole pressure (BHP) while drilling through tight windows. The paper demonstrates the successful application of advanced automated MPD technologies on the Dover well close to Fort McMurray, Alberta, Canada. A well in the Dover field had multiple failures in the liner that resulted in excessive sand production, causing the well to be shut in. After reviewing the options of well repair or redrilling the horizontal section to install a new slotted liner, it was determined that redrilling was the best option. After the well-schematic analysis and in collaboration with the operator, the combination of a proprietary control system and MPD techniques was recommended along with a water-based mud (WBM) weight to drill the well and still be able to maintain the BHP required to overbalance the formation. The capability to detect microinfluxes/-losses while drilling, combined with an automated control system covering the drilling parameters [including the surface backpressure (SBP) and constant BHP], allowed the well to be drilled while maintaining the downhole pressure values as required.
Summary Low-melting-point bismuth- (Bi-) based alloys have recently been proposed for plug-and-abandonment (P&A). Previous experiments have shown the feasibility of BiSn [58-wt% Bi and 42-wt% tin (Sn)] and BiAg [97.5-wt% Bi and 2.5-wt% silver (Ag)] alloy plugs in moderate temperature wells, both across shales and across the shale/sandstone sequence. These were validated in linear and cylindrical wellbore cavity geometries for various differential setting pressures for alloy over air. Until now, all of the experiments for setting alloy plugs have been conducted with air as the wetting fluid. Given the lack of adhesion between minerals and alloy, our concept for providing bond strength and integrity has hinged on providing a bicontinuous structure through alloy penetration into the pore network. For shales, with a positive setting pressure, anchors on the surface, in lieu of pores, have proven to be adequate. With results obtained under excess alloy pressure, we have quantified the effect of setting pressure on the alloy/shale bond quality. With brine as the wetting fluid, imposing an excess pressure on the alloy has not been demonstrated previously. This paper is the continuation of our previously published papers (Zhang et al. 2020a, 2020b), and our objective here is not only to show the possibility of forming a plug under brine but also to quantify the plug’s quality with and without an excess alloy pressure. We first describe an apparatus that controls alloy and brine pressures independently through a semipermeable piston assembly and demonstrate forming alloy plugs in a brine-filled borehole cavity. Based on pressure decay tests across the plug, we demonstrate that wellbore integrity is possible only with a positive alloy pressure over that of brine.
Chen, Lei (China University of Petroleum, East China) | Ding, Jinghua (Himile Mechanical Manufacturing (Shandong) Company Limited) | Gao, Junjie (China Waterborne Transport Research Institute) | Ren, Shuyi (China University of Petroleum, East China) | Gao, Jingyang (China University of Petroleum, East China) | Liu, Gang (China University of Petroleum, East China)
Summary Compressibility is a basic property of gelled crude oil, which was always regarded as a constant in the unsteady-pipe-flow process. In this article, the compressibility of gelled crude oil was accurately measured, and some new characteristics were discovered by a new apparatus that was developed using a special sealing method consisting of an elastic film and the Newtonian fluid. There was no leakage in the special hermetical method, and the unexpected seal-ring deformation of the piston in the traditional compression apparatus was also well-avoided. Using the new apparatus, compressibility of the gelled crude oil was tested and it was found that the compressibility of gelled crude oil is strongly time dependent. Introduction Compressibility is one of the most important physical-material parameters. It plays a vital role in the calculation of unsteady flow and the measurement of flow rate. Many scholars have contributed to research into crude-oil compression. Fan and Zhao (1985) tested the compressibility of liquid crude oil in China and developed the compressibility formula that has been widely recognized and adopted. Sun et al. (2006) studied the compressibility of crude oil in the liquid state, but the compressibility of the oil in the gelled state was not considered. The compressibility coefficient of gelled crude oil was regarded as a constant in the literature (Xiao et al. 2012; Kumar et al. 2015, 2016), and the bulk modulus of gelled crude oil was considered to be only related to the water-hammer speed and the density of the crude oil (Xiao et al. 2012; de Oliveira and Negrão 2015; Cheng et al. 2020). The same method was adopted to calculate the oil-compressibility coefficient of gelled crude oil by Davidson et al. (2007). Davidson et al. (2004) and Wachs et al. (2009) stated that the fluid compressibility in the continuity equation should be obtained by the relationship between pressure and volume when investigating the startup process in the viscoplastic and thixotropic fluid pipelines.
Novakovic, Vladimir (Maritime Research Institute Netherlands (MARIN) / Delft University of Technology) | Costas, Juan José (Delft University of Technology) | Schreier, Sebastian (Delft University of Technology) | Kimmoun, Olivier (IRPHE, École Centrale de Marseille) | Fernandes, Ashwin (Maritime Research Institute Netherlands (MARIN)) | Ezeta, Rodrigo (Maritime Research Institute Netherlands (MARIN)) | Birvalski, Miloš (Maritime Research Institute Netherlands (MARIN)) | Bogaert, Hannes (Maritime Research Institute Netherlands (MARIN))
The intricate physical mechanisms involved during sloshing impacts in LNG tanks lead to biases in sloshing model tests when the impact loads are predicted. In order to increase the understanding of these biases, a new state-of-the-art facility dubbed the Multiphase Wave Lab (MWL) has been established. In the MWL, impact tests are performed within an autoclave (15 m long x 2.5 m diameter), whose purpose is to provide an accurately controlled environment in which the pressure, temperature and gas composition can be controlled and monitored. Wave impact tests are performed by generating waves in a flume which is located inside the autoclave. In this paper, we present the capabilities of the MWL to control the temperature, ullage pressure and gas composition in the autoclave. We study also the quality of the global flow repeatability by means of a breaking wave which is created with a wave-focusing technique. We quantify the repeatability of the waves with a Sobolevnorm-like criterion on the frequency domain and evaluate the repeatability for different ullage pressures. Preliminary experiments show a good degree of repeatability, in accordance with high-speed recordings of the impacting waves. INTRODUCTION Ships that transport liquefied natural gas (LNG), floating units that produce or re-gasify LNG and ships that use LNG as a fuel need to be equipped with dedicated tanks to hold the LNG and minimize the heat transfer between the LNG and the environment (LNG is stored at -162°C at atmospheric pressure). In terms of containment, membrane LNG tanks such as the NO-line and the Mark-line tanks (GTT, France) are widely used because they utilize the hull space efficiently. However, these structures are more sensitive to sloshing impacts inside the tanks. Thus, it becomes of great importance to quantitatively assess the magnitude of these impacting forces in the design stage. Currently, this is done by performing sloshing model tests at reduced scale (Gervaise et al., 2009). These tests, however, are inherently biased. Empirical scaling factors based on feedback at sea are then used to account for these biases. Dedicated measurements on-board LNG carriers have shown that the long-term statistics of the impact loads as defined by the prevailing sloshing assessment methodology are conservative (Lund-Johansen et al., 2011; Pasquier & Berthon, 2010). However, the short-term statistics derived from the tests do not consistently represent reality (Karimi et al., 2014). Resolving this inconsistency between the scaled and the full-scale measurements would lead to optimized tank designs in terms of strength and thermal capacity, as well as to increasing the operating envelope of the vessels (e.g. operating with partially-filled tanks).
Nguyen, Anh-Dan (Chonnam National University) | Kim, Young-Sang (Chonnam National University) | Kang, Gyeong-O (Honam Regional Infrastructure Technology Management Center, Chonnam National University) | Kim, Hui-Jin (Chonnam National University)
ABSTRACT The main aim of this paper is to assess behavior of existing caisson type quay wall, which is upgraded by deepening front water depth, using numerical analysis. To upgrade the quay wall, the rubble mound under the front caisson toe is solidified by grouting and then cut until the design level. The numerical analysis is carried out by the finite element method (FEM) program (PLAXIS 2D-2018). From the results, the change of stress in the rubble mound before and after upgrade can be evaluated. Besides, the analysis also indicates the difference of quay wall displacement estimated from distinct soil models. INTRODUCTION Quay walls are earth retaining structures at which ships can berth. They are usually equipped with bollards to provide moorings for ships and fendering to absorb the impacts of the vessels. The quay walls are used for the transshipment of goods by cranes or heavy equipment that moves alongside the ships (De Gijt and Broeken, 2005). The quay walls used in reality are very distinct from structure types, but in general, they can be classified into four basic types including gravity walls, sheet pile walls, structures with relieving platform and open berth quays as shown in Fig. 1. Nowadays, with the significant increase of big vessels, the requirement for transportation of goods and passengers by waterway is also rising rapidly. This leads to the demand for the deep-water ports to become more and more necessary to berth these ships. However, many existing quay walls were built in the history having low front water depth. These mooring facilities are becoming backward and cannot meet current development. Besides, because of the high cost and the environmental problem, the total demolition of these existing quay walls and construction the new structures are not a reasonable option. Thus, upgrading by increasing the front water depth of the existing quay walls is a suitable solution from both engineering and economic views.
Mohiuddin, Mohammad A. (Oceans Graduate School, The University of Western Australia) | Hossain, Muhammad S. (Oceans Graduate School, The University of Western Australia) | Ullah, Shah N. (School of Engineering and Technology, Central Queensland University) | Kim, Youngho (Oceans Graduate School, The University of Western Australia) | Hu, Yuxia (Environmental and Mining Engineering, The University of Western Australia)
Field tests suggest that the T-bar factor may vary over a large range for calcareous soils. As the T-bar penetrates very deep into soft soil, a full flow-round mechanism is formed around the T-bar. Examining the stress states around this mechanism suggests that soil elements are subjected to a varying stress state, and the element behaviour represents a combination of triaxial compression, simple shear, and triaxial extension conditions. This paper reports results of T-bar penetrometer tests performed at an elevated gravity of 150-g (where g is earth's gravity) in a geotechnical centrifuge on a calcareous silty sediment collected from the North West Shelf of Australia. Once the centrifuge tests were completed, a tube sample was cored from the centrifuge strongbox. Two specimens were prepared from two reference depths, and undrained monotonic simple shear tests were carried out. The undrained shear strengths obtained from the simple shear tests were used to back analyse the T-bar bearing factor (NT-bar). A mean T-bar factor of 9.92 was found for the calcareous silt tested. A threedimensional large deformation finite element analysis was conducted to find out the T-bar factor in an ideal soil, showing the potential for undertaking further parametric analyses using an appropriate constitutive model to develop a robust interpretation framework for Tbar test data. T-BAR PENETROMETER AND BEARING FACTOR Full-flow penetrometers (such as the T-bar, ball) are increasingly practiced both in laboratory environments (e.g. Purwana et al., 2005; Hossain et al., 2011) as well as in field investigations offshore (Erbrich & Hefer, 2002; Erbrich, 2005) due to its ability in: (i) providing a continuous resistance profile that can be directly interpreted to the corresponding soil strength profile; and (ii) eliminating the necessity of overburden pressure corrections needed for the cone penetrometer (Lu et al., 2004; Zhou & Randolph, 2009). The T-bar penetrometer was first implemented by Stewart & Randolph (1994), and identified as advantageous for investigating fine-grained sediments due to the large projection area ratio (5∼10 times larger than the cone penetrometer) leading to high resolution of soft seabed resistance. T-bar penetrometer tests allow any stratigraphy variance to be captured through measurements of the load through an attached load cell located just above the T-bar (Fig 1a). Depending on the penetration speed of the Tbar both undrained and drained strength can be inferred from the measured load (Finnie & Randolph, 1994).
Summary The cyclic solvent injection (CSI) process has recently shown to be a promising method for enhanced heavy oil recovery in Canada. Laboratory testing is often run before development of field pilots to assess the effect of parameters, such as solvent choice and process conditions, on the CSI response. However, differences between laboratory results vs. field applications have been observed. CSI laboratory studies work for only two to three cycles due to low incremental oil in subsequent cycles, whereas field pilots continue for years over multiple cycles. This experimental study is intended to capture the production mechanisms responsible for heavy oil production in CSI. Primary production and CSI tests were conducted using sandpack models saturated with live heavy oil of 9530 mPa·s viscosity. The experiments were conducted in horizontal and vertical mode injection at high- and low-pressure depletion rates using two solvent mixtures of CH4 and C3H8. The sandpacks were scanned after every cycle to analyze the evolution of gas and oil saturations using computed tomography (CT). Three cores were used to study the effect of several parameters: gravity forces, pressure depletion rate, solvent composition, and initial oil saturation on the performance of CSI processes. CSI cycles run after primary production in horizontal systems produced negligible incremental oil for both slow and fast drawdown rates due to the large void space and high free gas saturation inhibiting the pressure buildup to push the solvent-diluted oil. These CSI experiments were only initially successful in dead oil systems, in which the initial oil saturation was higher and appropriate pressure gradient was generated through fast depletion rates. During the vertical alignment, CSI cycles exhibited higher incremental oil recovery per cycle. Slow depletion cycles were more efficient in terms of pressure and incremental recovery per cycle; however, faster depletion cycles performed better as a function of time. These results are more in line with the repeated recoveries measured over multiple cycles in field CSI pilot studies. More volume of diluted oil was drained out of the core when the solvent mixture with higher propane (C3H8) content was injected. These results demonstrate the importance of gravity drainage in the CSI process and its significance on successful oil recovery rates. This study illustrates the limitations of previous horizontal laboratory tests and shows an improved test configuration for modeling and prediction of the improved response observed in CSI pilots.
At a given temperature, the vapor pressure of a pure compound is the pressure at which vapor and liquid coexist at equilibrium. The term "vapor pressure" should be used only with pure compounds and is usually considered as a liquid (rather than a gas) property. For a pure compound, there is only one vapor pressure at any temperature. A plot of vapor pressures for various temperatures is shown in Figure 1 for n-butane. The temperature at which the vapor pressure is equal to 1 atm (14.696 psia or 101.32 kPa) is known as the normal boiling point.