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Steam generation for the purposes of thermal recovery includes facilities to treat the water (produced water or fresh water), generate the steam, and transport it to the injection wells. A steamflood uses high-quality steam injected into an oil reservoir. The quality of steam is defined as the weight percent of steam in the vapor phase to the total weight of steam. The higher the steam quality, the more heat is carried by this steam. High-quality steam provides heat to reduce oil viscosity, which mobilizes and sweeps the crude to the producing wells.
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.
Risk analysis is a term used in many industries, often loosely, but we shall be precise. By risk analysis, we mean applying analytical tools to identify, describe, quantify, and explain uncertainty and its consequences for petroleum industry projects. Typically, there is money involved. Always, we are trying to estimate something of value or cost. Sometimes, but not always, we are trying to choose between competing courses of action. The tools we use depend on the nature of the problem we are trying to solve. Often when we are choosing between competing alternatives, we turn toward decision trees.
Coiled-tubing drilling (CTD) can be very effective in certain situations. Its application is growing as experience defines what it takes to be successful. Coiled-tubing drilling (CTD) has a rather extensive history and received a large amount of press and hype from the 1990s to date, a significant amount being less than positive. There have been numerous highly successful applications of CTD technology in such regions as Alaska and the United Arab Emirates, yet CTD is still considered an immature new technology. One example of exaggerated expectations is CTD's reputation for offering certain advantages, including small footprint, high mobility, and quick operations. However, when more complex CTD services are planned, including directional drilling and cased completions, these advantages may no longer apply. These materials are typically not required for conventional CT services. When including the additional separators and nitrogen-pumping equipment required for underbalanced drilling (UBD), the advantages related to small footprint and high mobility may no longer be the case. Numerous truckloads of equipment can take days to rig up in preparation to drill with CT. Figure 1 shows a purpose-built CTD rig working in Oman.
Acoustic logs provide the primary means for evaluating the mechanical integrity and quality of the cement bond. Acoustic logs do not measure cement quality directly, rather, this value is inferred from the degree of acoustic coupling of the cement to the casing and to the formation. Properly run and interpreted, cement-bond logs (CBL) provide highly reliable estimates of well integrity and zone isolation. Just as filtrate invasion and formation alteration may produce changes in formation acoustic properties, and thus variation in acoustic logs over time, so too, cement-bond logs may vary over time as the cement cures and its properties change. Modern acoustic cement-evaluation (bond) devices are comprised of monopole (axisymmetric) transmitters (one or more) and receivers (two or more). They operate on the principle that acoustic amplitude is rapidly attenuated in good cement bond but not in partial bond or free pipe. Conventional CBL tools provide omnidirectional measurements, while the newer radial cement-evaluation tools provide azimuthally sensitive measurements for channel evaluation. Tool response depends on the acoustic impedance of the cement, which, in turn is function of density and velocity.
Preventing such failures is critical to maintaining well production. Echo amplitude and travel time provide images of the condition of the inside casing surface (e.g., buildup, defects, and roughness such as pitting and gouges) (Figure 1), and travel-time and resonant-frequency analysis provide casing thickness (Figure 1). Holes in the casing are visible in the series of ultrasonic images that are based on amplitude (left) and corrected travel time (right). The center 3D images show the pipe in 90 quadrants. The image shading is generated from the amplitude data (courtesy of SPE). In this example, casing radius and shape are presented as log curves and image maps and deformed casing is easily identified (courtesy of Baker Atlas).
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).
DNV GL is withdrawing from the Nord Stream 2 gas pipeline in response to a possible widening of US sanctions against companies conducting pipeline testing, inspection, or certification services for the project to bring more Russian gas to Europe. The Norwegian provider of pipeline safety and technical verification services announced its withdrawal 4 days after the US Senate voted on 1 January to override a presidential veto of the US National Defense Authorization Act (NDAA). The act threatens new sanctions against companies servicing pipe-laying vessels or otherwise assisting Nord Stream 2 in meeting its goal of carrying first gas by mid-2021. The $11.6-billion project to double the capacity of the existing Nord Stream pipeline is nearly 90% complete with only a final 150-km stretch of pipe left to be laid in deep water offshore Denmark. Given that Gazprom may require international assistance to lay pipe in deep water quickly, US policy makers hope sanctions can deliver a knockout blow to the project for at least the near to medium term given that the NDAA continues the 2019 Protecting Europe's Energy Security Clarification Act prohibiting assistance in laying of pipe at depths of 30.5 m or more below sea level for Nord Stream 2. While the US continues to sound the alarm that Europe will compromise its energy security by increasing its reliance on Russian gas, Russia asserts that US sanctions are less about politics and more about economics; the US simply wants Europe to buy more US LNG, policy makers in Russia and in some European countries assert. Existing US sanctions have already delayed construction for most of 2019 and are estimated to have added $1 billion to the cost of building Nord Stream 2, and together with a possible new round, could affect more than 120 companies from 12 European countries, Reuters reported.