In this study, we have extended and applied the diffuse source upscaling methodology to sandstone and carbonate pore network models in order to evaluate their effective transmissibility and permeability. The proposed method allows us to find transmissibility values for sub-volumes of the pore network during the transition from transient to pseudo steady state flow. The pore network models utilize a lattice grid construction, consisting of nodes and bonds that connect the nodes. The Eikonal equation is solved on the lattice using Dijkstra's method to obtain the diffusive time of flight, which is then used to model the transition from transient to pseudo steady state flow. The solution uses the concept of a transient drainage volume, which increases with time as pressure propagates into the nodes of the pore network. The diffuse source upscaling approach allows us to calculate the transmissibility of the drainage volume as it increases with time. The calculated results can be compared to the analytical results, where the sample is assumed to be internally homogeneous. A synthetic model was created to illustrate how the calculated lattice model and the analytic reference results compare for a homogeneous model. The comparison of the carbonate analytical and calculated results showed that there exists a high degree of internal heterogeneity while the more homogeneous sandstone model showed a close agreement with the synthetic model. For both samples, the late time pseudo steady state permeability showed a good correspondence with other permeability evaluations. The diffuse source method has more directional information available than the steady state method. Hence, the new method of analysis can be viewed as an extension of pseudo steady state concepts of permeability to transient flow, with increased spatial resolution corresponding to the transient drainage volume. Instead of obtaining only the steady state transmissibility from a pore network model, the diffuse source approach provides us with the ability to better characterize the internal heterogeneity of a model and to explain the wide range of permeability values obtained by other approaches.
Acid fracture operations in carbonate formations are used to create highly conductive channels from the reservoir to the wellbore. Conductivity in calcite formations is expected to be highest near the wellbore, where most of the etching occurs. The near wellbore fracture etched-width profile can be estimated from the measured temperature distribution. Temperature data can be obtained from fiber optic distributed temperature sensing (DTS) installed behind casings to monitor fracturing operations.
Heat transfer is commonly coupled in acid fracture models to account for temperature's effects on acid reactivity with carbonate minerals. Temperature profiles are usually evaluated during simulations of fracture fluid injection, but seldom during fracture closure. Since most of the acid is spent during injection, many models have assumed that the remaining acid reacts proportionally along the fracture length. Because of this assumption, neither acid spending nor temperature is usually simulated during fracture closure.
In this study, a fully integrated temperature model was developed wherein both the acid reaction and heat transfer were simulated while the fracture was closing. At each time step, transient heat convection, conduction, and generation were calculated along the wellbore, reservoir, and fracture dimensions. Modeling temperature during this transient period provides a significant understanding of the fracture etched-width distribution. During shut-in, cold fracture fluids are heated, mainly because of heat flow from the formation to the fracture. The amount of fluid stored in the fracture determines how fast the fluid is heated. Wider fracture segments contain larger amounts of cold fracture fluids, resulting in it taking longer to reach the reservoir temperature. Because of this phenomenon, near a wellbore, the vertical fracture etched-width profile can be determined from the temperature distribution. Also, minerals' spatial distributions along the wellbore's lateral can be estimated in multistage acid fracturing. This is done by minimizing the difference between the observed and modeled temperatures.
This evaluation of etched width profiles at the fracture entrance provides an estimation of fracture-conductive channel locations. Moreover, it has significantly improved the understanding of mineralogy distribution in multi-layer formations. This information will be particularly useful when designing acid fracturing jobs in nearby wells or revisiting the same wellbore for further stimulation.
New long-term contracts between offshore drillers and equipment makers reduce downtime and risks associated with key components, from blowout preventers to risers. This paper evaluates the feasibility of a number of production- and export-riser configurations for ultradeepwater applications. This paper presents results from full-scale testing of a flexible riser equipped with embedded sensors for distributed-temperature sensing (DTS).
With multistage operations becoming the industry norm, operators need easily deployable diversion technologies that will protect previously stimulated perforations and enable addition of new ones. This paper reviews several aspects of the use of in-stage diversion. Significant production gains are being made with hydraulicly fractured wells using diversion to stimulate a higher percentage of the perforations.
In a collaborative project, the possibility of measuring fluid levels in a wellbore by use of distributed optical pressure gauges was conceived, prototyped, field-trialed, and further developed to a point of widespread commercialization. The treatment in a deepwater, frac-packed well with fiber-optic-equipped coiled tubing (CT) and a rotating, hydraulic high-pressure jetting tool achieved successful stimulation of a 500-ft-long frac-packed zone after several previous failures using different techniques. In the past decade, fiber-optic -based sensing has opened up opportunities for in-well reservoir surveillance in the oil and gas industry. In this paper, the authors present a recent example of single-phase-flow profiling with distributed acoustic sensing.
As natural gas pipeline systems have grown larger and more complex, the importance of optimization of design and operation of pipelines has increased. This paper examines the optimization issue for the Egyptian gas transmission pipeline network. Paradoxical effects can exist when expanding the capacity of natural-gas-transportation networks. This paper derives conditions where it can be expected, how the effect can be masked, and provide analysis to support identification in larger-scale networks. The present work describes the development of a 1D steady-state isothermal reservoir/surface gas-pipeline-network model.
A company is selling a new well testing tool designed to be a cheaper, simpler way to do fiber optic sensing, and then it fades away. With the availability of more-complex smart-well instrumentation, immediate evaluation of the well response is possible as changes in the reservoir or well occur. Mechanical-diversion techniques can ensure acid injection into the various intervals of naturally fractured reservoirs. This paper presents results from full-scale testing of a flexible riser equipped with embedded sensors for distributed-temperature sensing (DTS).
A company is selling a new well testing tool designed to be a cheaper, simpler way to do fiber optic sensing, and then it fades away. This paper shows results from use of a new technology that uses in-well-conveyed fiber-optic distributed acoustic sensing (DAS) for the detection of sand-ingress zones across the reservoir section throughout the production period in real time. With the availability of more-complex smart-well instrumentation, immediate evaluation of the well response is possible as changes in the reservoir or well occur.
In this paper, the authors describe a project to design, field trial, and qualify an alternative solution for real-time monitoring of the oil rim in carbonate reservoirs that overcomes these disadvantages. This paper shows results from use of a new technology that uses in-well-conveyed fiber-optic distributed acoustic sensing (DAS) for the detection of sand-ingress zones across the reservoir section throughout the production period in real time. This paper discusses the objectives of the Fiber-Optic Leak-Detection (FOLD) project, carried out in Verneuil-en-Halatte, France.