Enhanced Oil Recovery (EOR) processes usually involve complex phase behavior between the injected fluid (e.g., steam, hydrocarbon, CO2, sour gas)and the in-situ rock-fluid system. Several fundamental questions remain regarding Equation-of-State (EOS) computations for mixtures that can form three, or more, phases at equilibrium. In addition, numerical and computational issues related to the proper coupling of the thermodynamic phase behavior with multi-component transport must be resolved to accurately and efficiently model the behavior of large-scale EOR processes.
Previous work has shown that the adaptive tabulation of tie-simplexes in the course of a compositional simulation is a reliable alternative to the conventional EOS-based compositional simulation. In this paper, we present the numerical results of reservoir flow simulation with adaptive tie-simplex parameterization of the compositional space. We study the behavior of thermal-compositional reservoir displacement processes across a wide range of fluid mixtures, pressures, and temperatures. We show that our approach rigorously accounts for tie-simplex degeneration across phase boundaries. We also focus on the complex behavior of the tie-triangles and tie-lines associated with three-phase, steam injection problems in heterogeneous formations. Our studies indicate that the tie-simplex-based simulation is a potential approach for fast EOS modeling of complex EOR processes.
Conditional beta distributions are proposed with examples to evaluate the probability of intercepting specific proportions of target rocks in well planning. Geological facies or rock-type proportions are random variables pk(x) at each location, x. This paper recalls and further demonstrates that facies proportions can be modeled by local beta distributions. However, the highly variable shapes of the conditional probability-density functions (PDFs) for the random variables in the field lead to complex nonstationarity and nonlinearity issues. A practical and robust approach is to transform the proportion random variables to Gaussian variables,thus enabling the use of classical geostatistics. Although a direct relationship between Gaussian and beta random variables appears intractable, a suitable transformation that involves second-order expectations of proportions is proposed. The conditional parameters of the beta variables are recovered from kriging estimates after back transformation to proportions through Riemann sums.
RANS computations of a ship with heave and pitch motions in head waves are presented. The added resistance, heave and pitch motions are investigated numerically. The computations are based on volume of fluid (VOF) and dynamic deformation mesh methods, discretized by finite volume method (FVM). A six-degree-of-freedom (6DoF) module is implemented to predict the ship motions. Four wave conditions with a wide range of wave steepness 400025 ≤ .ak ≥ 001005 are onsidered. The wave length for all conditions is one ship length, and the results show strong nonlinear features, especially for .ak D 00100, where the phenomenon of green water on deck is observed. The comparison of added resistance between the presented computational results and measurements shows good agreement. A grid convergence study with three different grids is performed at .ak D 00025 for validation. All computations are performed by our solver, naoe-Foam-SJTU, developed under the framework of the open source code, OpenFOAM.
Salama, Amgad (King Abdullah University of Science and Technology) | Sun, Shuyu (King Abdullah University of Science and Technology) | El-Amin, Mohamed (King Abdullah University of Science and Technology)
The flow of two or more immiscible fluids in porous media is widespread, particularly in the oil industry. This includes secondary and tertiary oil recovery and carbon dioxide (CO2) sequestration. Accurate predictions of the development of these processes are important in estimating the benefits and consequences of the use of certain technologies. However, this accurate prediction depends--to a large extent--on two things. The first is related to our ability to correctly characterize the reservoir with all its complexities; the second depends on our ability to develop robust techniques that solve the governing equations efficiently and accurately. In this work, we introduce a new robust and efficient numerical technique for solving the conservation laws that govern the movement of two immiscible fluids in the subsurface. As an example, this work is applied to the problem of CO2 sequestration in deep saline aquifers; however, it can also be extended to incorporate more scenarios. The traditional solution algorithms to this problem are modeled after discretizing the governing laws on a generic cell and then proceed to the other cells within loops. Therefore, it is expected that calling and iterating these loops multiple times can take a significant amount of computer time. Furthermore, if this process is performed with programming languages that require repeated interpretation each time a loop is called, such as Matlab, Python, and others, much longer time is expected, particularly for larger systems. In this new algorithm, the solution is performed for all the nodes at once and not within loops. The solution methodology involves manipulating all the variables as column vectors. By use of shifting matrices, these vectors are shifted in such a way that subtracting relevant vectors produces the corresponding difference algorithm. It has been found that this technique significantly reduces the amount of central-processing-unit (CPU) time compared with a traditional technique implemented within the framework of Matlab.
The development of compact topside processing plants for floating, production, storage and offloading (FPSO) vessels is a growing industry trend that can reduce operating and capital expenditures over the life of the vessel, a researcher and scientist said recently.
It has been just over 20 years since the last review paper on core analysis appeared in Petrophysics (Skopec, 1992). Comparing the topics covered in that review with the topics of interest to industry today, one is immediately struck by the recent rise and focus in two new areas: digital rock physics and the petrophysical characterization of unconventional source-rock reservoirs, i.e., ‘shale’. This review, which consists of contributions from nine specialists in their respective fields, covers (a) wellsite coring and coring handling, (b) conventional and unconventional core analysis, (c) rock mechanics in support of reservoir engineering, and (d) digital core analysis.
The goals of core analysis today remain the same as those identified 21 years ago: to "reduce uncertainty in reservoir evaluation" and finding ways to obtain this information faster. In the past, the focus was on developing experimental protocols that could shorten the experimental time, such as the continuous-injection-resistivity protocol. Today, the focus has changed to simulating rock properties from micro- and nano-CT images. In the past, we had to be concerned about how to scale up results on a 4×7 cm core plug to reservoir scale. With today’s use of micro-CT imaging, which uses millimeter-size samples, the upscaling to reservoir scale has increased by an additional three orders of magnitude.
With the huge success and rapid development of ‘shale’ resources, the United States is fast becoming the world’s leading producer of hydrocarbons. Underpinning and supporting this effort has been the enormous interest and increase in studying the petrophysics of these reservoirs. In particular, developing shale core-analysis experimental protocols for these challenging ultralow-permeability resesrvoirs and developing characterization methods and techniques that often involve digital rock physics.
Liu, Yuetian (China University of Petroleum) | Ding, Zupeng (China University of Petroleum) | Ao, Kun (China University of Petroleum) | Zhang, Yong (China University of Petroleum) | Wei, Jun (China University of Petroleum)
A new manufacturing method for a fractured porous model for macroscopic experimental simulation of an oil reservoir is presented to reduce significantly the uncertainty of reservoir numerical simulation. Large numbers of small-cube rocks with the same size made from natural rocks of selected outcrops are bonded in specific ways to form a big rock. The bonded faces among the small rocks compose a 3D fracture system in the big rock. The big rock is the fractured porous medium of the models for experimental reservoir simulation. Every small rock exists as a particle of the fractured medium.Because the number, size, and positions of small rocks can be adjusted optionally, the size and shape of the fractured media can also be adjusted optionally. With the selection of suitable rocks, adhesives, and bonding patterns, the distributions of physical properties in fractured media (e.g.,fracture density, permeability, porosity, imbibition) are quantitatively controlled, and they can be heterogeneous and anisotropic in accordance with objective reservoirs. Experimental models made of the fractured media can fully satisfy similarity criteria. The application example in this paper showed that experimental models can be used not only to simulate and forecast directly the exploitation processes of the fractured porous media reservoirs but also to verify and/or modify numerical reservoir simulation.
Bailey, Jeffrey R (ExxonMobil Development Company) | Elsborg, Carsten C (ExxonMobil Exploration & Production Norway) | James, Richard W (ExxonMobil Development Company) | Pastusek, Paul (ExxonMobil Development) | Prim, Matthew T (ExxonMobil Development Company) | Watson, William W (ExxonMobil Development Company)
The development of modeling methods to characterize the relative vibration tendency of alternative bottomhole assemblies (BHAs) has enabled deliberate tool redesign to reduce vibrations. To achieve the greatest benefit, tool redesign is most effective if applied early in the tool-design cycle in which important configuration parameters are most easily adjusted. This paper outlines several design issues to resolve so that future generations of tools have inherently lower vibration levels. The use of multiple special-purpose tools [such as logging tools, rotary-steerable assemblies, and ream-while-drilling (RWD) tools] generates significant constraints onBHA-configuration options. A redesign methodology to achieve lower vibration indices can be used to investigate modified components, dimensions, and configurations to select the best BHA configuration for specific drilling-operating conditions. Case studies are used to investigate BHA designs with flex stabilizers above rotary-steerable tools. The flex stabilizer is composed of a stabilizer with a smaller-diameter connecting flex sub to facilitate rotary-steerable directional objectives. It is typically wired for tool signals and is frequently run by vendors. In one case study, the spacing below a reamer is evaluated, and drilling data are compared with other assemblies in the same formation. In this example, the spacer provides an increase in the distance between contact points, to allow both the stabilizer and the reamer to seek the centerline with less interference. Another case study evaluates changing contact locations in the BHA by swapping the order of logging tools, resulting in different borehole-contact positions. Finally, a theoretical modeling study illustrates how changing BHA components and dimensions affects the vibration indices. The operator has field experience with BHA redesign that has directly led to significant improvement in drilling performance. The benefits include a higher rate of penetration (ROP), a longer time on the bottom, less wear of drilling-tool components, and a reduced frequency of trips.