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Abstract In this case study, we apply a novel fracture imaging and interpretation workflow to take a systematic look at hydraulic fractures captured during thorugh fracture coring at the Hydraulic Fracturing Test Site (HFTS) in Midland Basin. Digital fracture maps rendered using high resolution 3D laser scans are analyzed for fracture morphology and roughness. Analysis of hydraulic fracture faces show that the roughness varies systematically in clusters with average cluster separation of approximately 20' along the core. While isolated smooth hydraulic fractures are observed in the dataset, very rough fractures are found to be accompanied by proximal smoother fractures. Roughness distribution also helps understand the effect of stresses on fracture distribution. Locally, fracture roughness seems to vary with fracture orientations indicating possible inter-fracture stress effects. At the scale of stage lengths however, we see evidence of inter-stage stress effects. We also observe fracture morphology being strongly driven by rock properties and changes in lithology. Identified proppant distribution along the cored interval is also correlated with roughness variations and we observe strong positive correlation between proppant concentrations and fracture roughness at the local scale. Finally, based on the observed distribution of hydraulic fracture properties, we propose a conceptual spatio-temporal model of fracture propagation which can help explain the hydraulic fracture roughness distribution and ties in other observations as well.
Fakher, Sherif (Missouri University of Science and Technology) | Elgahawy, Youssef (University of Calgary) | Abdelaal, Hesham (University of Lisbon) | Imqam, Abdulmohsin (Missouri University of Science and Technology)
Abstract Carbon dioxide (CO2) injection in low permeability shale reservoirs has recently gained much attention due to the claims that it has a large recovery factor and can also be used in CO2 storage operations. This research investigates the different flow regimes that the CO2 will exhibit during its propagation through the fractures, micropores, and the nanopores in unconventional shale reservoirs to accurately evaluate the mechanism by which CO2 recovers oil from these reservoirs. One of the most widely used tools to distinguish between different flow regimes is the Knudsen Number. Initially, a mathematical analysis of the different flow regimes that can be observed in pore sizes ranging between 0.2 nanometer and more than 2 micrometers was undergone at different pressure and temperature conditions to distinguish between the different flow regimes that the CO2 will exhibit in the different pore sizes. Based on the results, several flow regime maps were conducted for different pore sizes. The pore sizes were grouped together in separate maps based on the flow regimes exhibited at different thermodynamic conditions. Based on the results, it was found that Knudsen diffusion dominated the flow regime in nanopores ranging between 0.2 nanometers, up to 1 nanometer. Pore sizes between 2 and 10 nanometers were dominated by both a transition flow, and slip flow. At 25 nanometer, and up to 100 nanometers, three flow regimes can be observed, including gas slippage flow, transition flow, and viscous flow. When the pore size reached 150 nanometers, Knudsen diffusion and transition flow disappeared, and the slippage and viscous flow regimes were dominant. At pore sizes above one micrometer, the flow was viscous for all thermodynamic conditions. This indicated that in the larger pore sizes the flow will be mainly viscous flow, which is usually modeled using Darcy's law, while in the extremely small pore sizes the dominating flow regime is Knudsen diffusion, which can be modeled using Knudsen's Diffusion law or in cases where surface diffusion is dominant, Fick's law of diffusion can be applied. The mechanism by which the CO2 improves recovery in unconventional shale reservoirs is not fully understood to this date, which is the main reason why this process has proven successful in some shale plays, and failed in others. This research studies the flow behavior of the CO2 in the different features that could be present in the shale reservoir to illustrate the mechanism by which oil recovery can be increased.
Summary Linear network models are promisingly simple progressive cavity pump design tools. Current linear network models are difficult to use in the design process because they require calibration against experimental data or computationally intensive simulation. In this paper we present new approaches for implementing linear network progressive cavity pump models and provide new methods to accurately and quickly estimate the values of each resistor in the model from pump geometry for both laminar and turbulent flows. This paper also argues that sealing-line flow transitions from laminar to turbulent at orders of magnitude smaller Reynolds numbers than described in the literature thus far. We propose a new hypothesis for the point of transition to turbulent performance.
Arabi, A. (SONATRACH, Direction Centrale Recherche et Développement, and University of Sciences and Technology Houari Boumediene (USTHB)) | Azzi, A. (University of Sciences and Technology Houari Boumedien (USTHB)) | Kadi, R. (SONATRACH, Direction Centrale Recherche et Développement) | Al-Sarkhi, A. (King Fahd University of Petroleum and Minerals) | Hewakandamby, B. (University of Nottingham)
Summary Intermittent flow is one of the most complex flow regimes in horizontal pipes. Various studies have classified this regime as two distinct subregimes: plug and slug flow. This classification has been made based on flow observations. In this work, the behavior of several flow parameters that characterize plug and slug flow are presented. Data from eight published works in the open literature were collected and studied to explain the behavior of both regimes. These data include pressure drop, void fraction, and slug frequency, as well as the lengths of liquid slugs and elongated bubbles for slug and plug regimes. It is observed from the evolution and analysis of these parameters that plug and slug flows have several different distinct features and should be considered as two separate regimes for the empirical modelization of the hydrodynamic parameters. The mixture Froude number, and to a lesser extent the liquid superficial velocity to gas superficial velocity ratio, seem to have significant impacts on the plug-to-slug flow transition. Introduction A variety of fluids (oil, natural gas, water, condensates, and condensed vapor) in the petroleum and gas industry can form two-phase flow.
Abdul-Majeed, Ghassan H. (University of Baghdad (Corresponding author) | Arabi, Abderraouf (email: firstname.lastname@example.org. Now with Al-Mashreq University)) | Soto-Cortes, Gabriel (University of Sciences and Technology Houari Boumediene)
Summary Most of the existing slug (SL) to churn (CH) or SL to pseudo-slug (PS) transition models (empirical and mechanistic) account for the effect of the SL liquid holdup (HLS). For simplicity, some of these models assume a constant value of HLS in SL/CH and SL/PS flow transitions, leading to a straightforward solution. Other models correlate HLS with different flow variables, resulting in an iterative solution for predicting these transitions. Using an experimental database collected from the open literature, two empirical correlations for prediction HLS at the SL/PS and SL/CH transitions (HLST) are proposed in this study. This database is composed of 1,029 data points collected in vertical, inclined, and horizontal configurations. The first correlation is developed for medium to high liquid viscosity two-phase flow (μL > 0.01 Pa·s), whereas the second one is developed for low liquid viscosity flow (μL ≤ 0.01 Pa·s). Both correlations are shown to be a function of superficial liquid velocity (VSL), liquid viscosity (μL), and pipe inclination angle (θ). The proposed correlations in a combination with the HLS model of Abdul-Majeed and Al-Mashat (2019) have been used to predict SL/PS and SL/CH transitions, and very satisfactory results were obtained. Furthermore, the SL/CH model of Brauner and Barnea (1986) is modified by using the proposed HLST correlations, instead of using a constant value. The modification results in a significant improvement in the prediction of SL/CH and SL/PS transitions and fixes the incorrect decrease of superficial gas velocity (VSG) with increasing VSL. The modified model follows the expected increase of VSG for high VSL, shown by the published observations. The proposed combinations are compared with the existing transition models and show superior performance among all models when tested against 357 measured data from independent studies.
US Secretary of the Interior Deb Haaland joined the secretaries of Energy, Commerce, and Transportation in a White House forum on 29 March to meet with representatives from states, the offshore wind industry, and members of the labor community to identify solutions to the greatest challenges facing the development of the new industry. The event included a commitment by Interior, Energy, and Commerce to establish a target to deploy 30 gigawatts of offshore wind by 2030, which they say will create nearly 80,000 jobs. "For generations, we've put off the transition to clean energy, and now we're facing a climate crisis. It's a crisis that doesn't discriminate; every community is facing more extreme weather and the costs associated with that," Secretary of the Interior Deb Haaland said. "But not every community has the resources to rebuild, or even get up and relocate when a climate event happens in their backyards. As our country faces the interlocking challenges of a global pandemic, economic downturn, racial injustice, and the climate crisis, we must transition to a brighter future for everyone."
A complete approach for wall-modeled large-eddy simulation (WMLES) is demonstrated for the simulation of the flow around a bulk carrier in the model scale. Essential components of the method are an a-priori estimate of the thickness of the turbulent boundary layer (TBL) over the hull and to use an unstructured grid with the appropriate resolution relative to this thickness. Expressions from the literature for the scaling of the computational cost, in terms of the grid size, with Reynolds number, are adapted in this application. It is shown that WMLES is possible for model scale ship hydrodynamics, with ∼10 grid cells, which is a gain of at least one order of magnitude as compared with wall-resolving LES. For the canonical case of a flat-plate TBL, the effects of wall model parameters and grid cell topology on the predictive accuracy of the method are investigated. For the flat-plate case, WMLES results are compared with results from direct numerical simulation, RANS (Reynolds-averaged Navier-Stokes), and semi-empirical formulas. For the bulk carrier flow, WMLES and RANS are compared, but further validation is needed to assess the predictive accuracy of the approach.
Abstract Unexpected situations and system failures during well construction operations are always possible. In the context of drilling automation, or even autonomous drilling, proper automatic management of these situations is of critical importance as the situation awareness of the human operator is very much reduced. The proper management of the transition between automatic and manual modes is necessary to improve the safety of automation solutions. An important characteristic of drilling automation solutions is their ability to cope with unexpected situations. This also encompasses, placing the drilling system in a state that is easy and intuitive for the human operator when manual control is required. Our approach to safe mode management is dependent on a good state estimation of the current conditions of the process. If for any reason, manual control must be regained, then the automated function itself triggers the necessary actions that will ensure a stable current state. In case of a drilling problem or a system failure, the human operator may have to regain control when the context might be totally different from the one left when the automation or autonomous function was enabled. It may even be a different human operator that has to take control, if a crew change has taken place. To make the transition from the automated/autonomous context to manual control, the automation/autonomous system sets the drilling machines in a so-called safe transition state. A safe transition state is one for which leaving the current setpoints of drilling machines untouched for a reasonable amount of time, will not immediately jeopardize the safety of the drilling operation. A safe transition state is contextual as it is not necessarily the same sequence of actions that must be performed to reach the safe transition state every time. The novel safe modes management method is integrated into existing drilling automation solutions. In a drilling automation context, the situation awareness of the human operator is considerably reduced as the automated functions control the process and the human operator is not actively driving the drilling machines. Without active safe mode management, there is a risk that drilling automation solutions may lead to serious situations as the driller may be totally unprepared to regain control in the middle of a critical situation. When it is needed to return to manual mode in the middle of the execution of an automatic procedure, an adequate procedure is executed. The choice of the procedure and its parameters depend on the current state of the process and system.
Resistivity is the one of the most difficult formation parameters to measure accurately because of the complex changes that occur during and after drilling a well and that may still be occurring during logging. The various components of the downhole environment may have strongly contrasting resistivities, some of which cannot be measured directly, and their physical dimensions may not be readily available. Figure 1 shows an idealized relationship of the main environmental components. There is no direct measurement of Rt. It must be inferred from the multiple-depth resistivity measurements.
Launched on 27 January at the Davos Agenda 2021, the Mission Possible Partnership (MPP) aims to accelerate the decarbonization of seven global industries representing 30% of global emissions, which include shipping, aviation, steel, trucking, chemicals, cement, and aluminum. Among the members are Shell, Trafigura Group, A.P. Møller-Maersk, BASF, and Lloyd's Register. MPP is centered on the idea that, while the Paris Agreement lays the groundwork for global cooperation, its focus on national targets will not generate the plans and solutions necessary to achieve efficient and effective transition strategies for global industries on its own. An important missing piece of the global climate action architecture is an effort by sectors, complementing country-centric strategies with action from global industries to unlock technology and energy transformation. This is particularly important for heavy-emitting industries.