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Formation damage caused by drilling-fluid invasion, production, or injection can lead to positive skin factors and affect fluid flow by reducing permeability. When mud filtrate invades the formation surrounding a borehole, it will generally remain in the formation even after the well is cased and perforated. This mud filtrate in the formation reduces the effective permeability to hydrocarbons near the wellbore. It may also cause clays in the formation to swell, reducing the absolute permeability of the formation. In addition, solid particles from the mud may enter the formation and reduce permeability at the formation face.
High-fidelity 3D engineering simulations can be valuable for operators looking to predict the behaviors of various components in their operations, but the computational requirements of these simulations can make them cost-prohibitive. To help alleviate the cost pressures, companies are examining the potential of integrating deep-learning neural networks (DNN) with computational fluid dynamics (CFD) to accelerate the simulation process. Speaking at an SPE Gulf Coast Section CFD Study Group symposium on digital solutions for fluid flow problems, Kuochen Tsai, a staff engineer/researcher in CFD modeling at Shell, outlined the development of a DNN model trained by CFD simulations that would be capable of predicting oil/water separation in horizontal oil pipelines. The goal of the model was to provide useful information for operators to effectively determine the use of corrosion inhibitors, which could have significant financial and environmental impacts if used improperly. Tsai said that multiphase flow simulations in CFD require expertise to set up, and their computational requirements can be expensive both in time (where they can possibly take months to complete) and in money.
Gels are a fluid-based system to which some solid-like structural properties have been imparted. In other words, gels are a fluid-based system within which the base fluid has acquired at least some 3D solid-like structural properties. These structural properties are often elastic in nature. All of the conformance improvement gels discussed are aqueous-based materials. The term "gel" as used in this page (unless specifically noted otherwise) refers to classical, continuous, bulk, and "relatively strong" gel material and does not refer to discontinuous, dispersed, "relatively weak," microgel particles in an aqueous solution. Gels discussed in this page, when formed in a beaker for example, constitute a single and continuous gel mass throughout its entire volume within the beaker.
Many wells, particularly gas wells in low-permeability formations require hydraulic fracturing to be commercially viable. Interpretation of pressure-transient data in hydraulically fractured wells is important for evaluating the success of fracture treatments and predicting the future performance of fractured wells. This page includes graphical techniques for analyzing post-fracture pressure transient tests after identifying several flow patterns that are characteristic of hydraulically fractured wells. Often, identification of specific flow patterns can aid in well test analysis. Five distinct flow patterns (Figure 1) occur in the fracture and formation around a hydraulically fractured well.
This article discusses the basic concepts of single-component or constant-composition, single phase fluid flow in homogeneous petroleum reservoirs, which include flow equations for unsteady-state, pseudosteady-state, and steady-state flow of fluids. Various flow geometries are treated, including radial, linear, and spherical flow. Virtually no important applications of fluid flow in permeable media involve single component, single phase 1D, radial or spherical flow in homogeneous systems (multiple phases are almost always involved, which also leads to multidimensional requirements). The applications given in this Chapter are based on a model that includes many simplifying assumptions about the well and reservoir, and are interesting mainly only from a historical perspective See "Reservoir Simulation" for proper treatment of multi-component, multiphase, multidimensional flow in heterogeneous porous media. The simplifying assumptions are introduced here as needed to combine the law of conservation of mass, Darcy's law, and equations of state to obtain closed-form solutions for simple cases. Consider radial flow toward a well in a circular reservoir. Combining the law of conservation of mass and Darcy's law for the isothermal flow of fluids of small and constant compressibility yields the radial diffusivity equation,  In the derivation of this equation, it is assumed that compressibility of the total system, ct, is small and independent of pressure; permeability, k, is constant and isotropic; viscosity, μ, is independent of pressure; porosity, ϕ, is constant; and that certain terms in the basic differential equation (involving pressure gradients squared) are negligible.
To efficiently develop and operate a petroleum reservoir, it is important to have a model. Currently, numerical reservoir simulation is the accepted and widely used technology for this purpose. Data-driven reservoir modeling (also known as top-down modeling or TDM) is an alternative or a complement to numerical simulation. TDM uses the "big data" solutions of machine learning and data mining to develop--train, calibrate, and validate--full-field reservoir models based on measurements rather than mathematical formulation of our current understanding of the physics of fluid flow through porous media. Unlike other empirical technologies that forecast production such as decline curve analysis, or only use production/injection data for analysis (capacitance resistance model), TDM integrates all available field measurements such as well locations and trajectories, completions and stimulations, well logs, core data, well tests, seismic, as well as production/injection history, including wellhead pressure and choke setting.
Add a new possible use for downhole casing: It can serve as broadcast antennae. Saudi Aramco recently reported that it has successfully tested a method for mapping oil and water underground using electromagnetic waves generated by running an electrical current through the steel casing in a well (IPTC 17845). The method could represent a cost-saving step forward for the Saudi Arabian national oil company's long-term effort to monitor changing fluid flows in its reservoirs with electromagnetic energy to study how water injected into its fields is sweeping out the remaining oil, and see what it is missing. Previously, Saudi Aramco created the electromagnetic field needed for this imaging method by using electrodes deep in the well to send an electrical current to electrodes on the surface. Arrays of up to 1,000 field sensors as far as 4 km away from the well gather data on how fluids in the reservoir respond to the energy field.
Editor's Note: This is another in a series of in which SPE's technical directors comment on the state of their industry sector heading into 2019. The shale revolution was a call to action for SPE Reservoir Technical Director Erdal Ozkan. He had expected to spend the latter years of his career tinkering at the edges of conventional reservoir engineering. That plan was demolished a decade ago when the decline curves collided with production data from unconventional plays that did not fit the curves. Since then, he has built an unconven tional reservoir research lab with a pitch he described as: "Do not expect a tool you can use tomorrow. We have to scratch below the surface to see what we are not doing right."
This paper presents a coupled 3D fluid-flow and geomechanics simulator developed to model induced seismicity resulting from wastewater injection. The simulator modeled several cases of induced earthquakes with the hope of providing a better understanding of such earthquakes and their dominant causal factors, along with primary mitigation controls. Implementation of rate-and-state friction to model friction weakening and strengthening during fault slip to accurately model earthquake occurrence, and an embedded discrete fracture model to efficiently model fluid flow inside the fault, are among the essential features of the simulator. The complete paper presents results from a combined model that brings together injection physics, reservoir dynamics, and fault physics to explain better the primary controls on induced seismicity. Since 2009, a substantial increase in the number of earthquakes in the central and eastern United States has occurred.
With the objective of increasing its production to 4.0 million BOPD, the Kuwait Oil Company (KOC) is developing its fields with optimum technology solutions. One of these promising technologies is that of advanced completions--specifically, inflow-control devices (ICDs) and interval-control valves (ICVs). Application of this technology led to multifold increases in sustained production in horizontal wells in all reservoirs and a simultaneous reduction in water cut. The main reservoir objectives for applying advanced completions include decreasing the influence of heel-to-toe effects, controlling influx from high-permeability zones, delaying water/gas fronting, depleting the reservoir uniformly, and improving well cleanup and sweep efficiency. Advanced completions are applicable in both sandstone and carbonate reservoirs.