Development, Setup and Testing of a Dynamic Hydraulic Fracture Conductivity Apparatus PDF Download

Author: Potcharaporn Pongthunya
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Languages : en
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One of the most critical parameters in the success of a hydraulic fracturing treatment is to have sufficiently high fracture conductivity. Unbroken polymers can cause permeability impairment in the proppant pack and/or in the matrix along the fracture face. The objectives of this research project were to design and set up an experimental apparatus for dynamic fracture conductivity testing and to create a fracture conductivity test workflow standard. This entirely new dynamic fracture conductivity measurement will be used to perform extensive experiments to study fracturing fluid cleanup characteristics and investigate damage resulting from unbroken polymer gel in the proppant pack. The dynamic fracture conductivity experiment comprises two parts: pumping fracturing fluid into the cell and measuring proppant pack conductivity. I carefully designed the hydraulic fracturing laboratory to provide appropriate scaling of the field conditions experimentally. The specifications for each apparatus were carefully considered with flexibility for further studies and the capability of each apparatus was defined. I generated comprehensive experimental procedures for each experiment stage. By following the procedure, the experiment can run smoothly. Most of dry runs and experiments performed with sandstone were successful.

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Languages : en
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The objectives of this project are to develop and test new techniques for creating extensive, conductive hydraulic fractures in unconventional tight gas reservoirs by statistically assessing the productivity achieved in hundreds of field treatments with a variety of current fracturing practices ranging from 'water fracs' to conventional gel fracture treatments; by laboratory measurements of the conductivity created with high rate proppant fracturing using an entirely new conductivity test - the 'dynamic fracture conductivity test'; and by developing design models to implement the optimal fracture treatments determined from the field assessment and the laboratory measurements. One of the tasks of this project is to create an 'advisor' or expert system for completion, production and stimulation of tight gas reservoirs. A central part of this study is an extensive survey of the productivity of hundreds of tight gas wells that have been hydraulically fractured. We have been doing an extensive literature search of the SPE eLibrary, DOE, Gas Technology Institute (GTI), Bureau of Economic Geology and IHS Energy, for publicly available technical reports about procedures of drilling, completion and production of the tight gas wells. We have downloaded numerous papers and read and summarized the information to build a database that will contain field treatment data, organized by geographic location, and hydraulic fracture treatment design data, organized by the treatment type. We have conducted experimental study on 'dynamic fracture conductivity' created when proppant slurries are pumped into hydraulic fractures in tight gas sands. Unlike conventional fracture conductivity tests in which proppant is loaded into the fracture artificially; we pump proppant/frac fluid slurries into a fracture cell, dynamically placing the proppant just as it occurs in the field. From such tests, we expect to gain new insights into some of the critical issues in tight gas fracturing, in particular the roles of gel damage, polymer loading (water-frac versus gel frac), and proppant concentration on the created fracture conductivity. To achieve this objective, we have designed the experimental apparatus to conduct the dynamic fracture conductivity tests. The experimental apparatus has been built and some preliminary tests have been conducted to test the apparatus.

Author: Fivman Marpaung
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Languages : en
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The key to producing gas from tight gas reservoirs is to create a long, highly conductive flow path, via the placement of a hydraulic fracture, to stimulate flow from the reservoir to the wellbore. Viscous fluid is used to transport proppant into the fracture. However, these same viscous fluids need to break to a thin fluid after the treatment is over so that the fracture fluid can be cleaned up. In shallower, lower temperature (less than 250°F) reservoirs, the choice of a fracture fluid is very critical to the success of the treatment. Current hydraulic fracturing methods in unconventional tight gas reservoirs have been developed largely through ad-hoc application of low-cost water fracs, with little optimization of the process. It seems clear that some of the standard tests and models are missing some of the physics of the fracturing process in low-permeability environments. A series of the extensive laboratory "dynamic fracture conductivity" tests have been conducted. Dynamic fracture conductivity is created when proppant slurry is pumped into a hydraulic fracture in low permeability rock. Unlike conventional fracture conductivity tests in which proppant is loaded into the fracture artificially, we pump proppant/ fracturing fluid slurries into a fracture cell, dynamically placing the proppant just as it occurs in the field. Test results indicate that increasing gel concentration decreases retained fracture conductivity for a constant gas flow rate and decreasing gas flow rate decreases retained fracture conductivity. Without breaker, the damaging effect of viscous hydraulic fracturing fluids on the conductivity of proppant packs is significant at temperature of 150°F. Static conductivity testing results in higher retained fracture conductivity when compared to dynamic conductivity testing.

Author: Jose Domingo Romero Lugo
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Languages : en
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Hydraulic Fracturing stimulation technology is used to increase the amount of oil and gas produced from low permeability reservoirs. The primary objective of the process is to increase the conductivity of the reservoir by the creation of fractures deep into the formation, changing the flow pattern from radial to linear flow. The dynamic conductivity test was used for this research to evaluate the effect of closure stress, temperature, proppant concentration, and flow back rates on fracture conductivity. The objective of performing a dynamic conductivity test is to be able to mimic actual field conditions by pumping fracturing fluid/proppant slurry fluid into a conductivity cell, and applying closure stress afterwards. In addition, a factorial design was implemented in order to determine the main effect of each of the investigated factors and to minimize the number of experimental runs. Due to the stochastic nature of the dynamic conductivity test, each experiment was repeated several times to evaluate the consistency of the results. Experimental results indicate that the increase in closure stress has a detrimental effect on fracture conductivity. This effect can be attributed to the reduction in fracture width as closure stress was increased. Moreover, the formation of channels at low proppant concentration plays a significant role in determining the final conductivity of a fracture. The presence of these channels created an additional flow path for nitrogen, resulting in a significant increase in the conductivity of the fracture. In addition, experiments performed at high temperatures and stresses exhibited a reduction in fracture conductivity. The formation of a polymer cake due to unbroken gel dried up at high temperatures further impeded the propped conductivity. The effect of nitrogen rate was observed to be inversely proportional to fracture conductivity. The significant reduction in fracture conductivity could possibly be due to the effect of polymer dehydration at higher flow rates and temperatures. However, there is no certainty from experimental results that this conductivity reduction is an effect that occurs in real fractures or whether it is an effect that is only significant in laboratory conditions. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/148364

Author: Mark W. McClure
Publisher: Springer Science & Business Media
ISBN: 3319003836
Category : Technology & Engineering
Languages : en
Pages : 96

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Discrete Fracture Network Modeling of Hydraulic Stimulation describes the development and testing of a model that couples fluid-flow, deformation, friction weakening, and permeability evolution in large, complex two-dimensional discrete fracture networks. The model can be used to explore the behavior of hydraulic stimulation in settings where matrix permeability is low and preexisting fractures play an important role, such as Enhanced Geothermal Systems and gas shale. Used also to describe pure shear stimulation, mixed-mechanism stimulation, or pure opening-mode stimulation. A variety of novel techniques to ensure efficiency and realistic model behavior are implemented, and tested. The simulation methodology can also be used as an efficient method for directly solving quasistatic fracture contact problems. Results show how stresses induced by fracture deformation during stimulation directly impact the mechanism of propagation and the resulting fracture network.

Author: Mengting Li
Publisher: Cuvillier Verlag
ISBN: 3736989342
Category : Technology & Engineering
Languages : en
Pages : 208

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Hydraulic fracturing is essential technology for the development of unconventional resources such as tight gas. So far, there are no numerical tools which can optimize the whole process from geological modeling, hydraulic fracturing until production simulation with the same 3D model with consideration of the thermo-hydro-mechanical coupling. In this dissertation, a workflow and a numerical tool chain were developed for design and optimization of multistage hydraulic fracturing in horizontal well regarding a maximum productivity of the tight gas wellbore. After the verification a full 3D reservoir model is generated based on a real tight gas field in the North German Basin. Through analysis of simulation results, a new calculation formula of FCD was proposed, which takes the proppant position and concentration into account and can predict the gas production rate more accurately. However, not only FCD but also proppant distribution and hydraulic connection of stimulated fractures to the well, geological structure and the interaction between fractures are determinant for the gas production volume. Through analysis the numerical results of sensitivity analysis and optimization variations, there is no unique criterion to determine the optimal number and spacing of the fractures, it should be analyzed firstly in detail to the actual situation and decided then from case to case.

Author: Juan Correa Castro
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Languages : en
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Unconventional gas has become an important resource to help meet our future energy demands. Although plentiful, it is difficult to produce this resource, when locked in a massive sedimentary formation. Among all unconventional gas resources, tight gas sands represent a big fraction and are often characterized by very low porosity and permeability associated with their producing formations, resulting in extremely low production rate. The low flow properties and the recovery factors of these sands make necessary continuous efforts to reduce costs and improve efficiency in all aspects of drilling, completion and production techniques. Many of the recent improvements have been in well completions and hydraulic fracturing. Thus, the main goal of a hydraulic fracture is to create a long, highly conductive fracture to facilitate the gas flow from the reservoir to the wellbore to obtain commercial production rates. Fracture conductivity depends on several factors, such as like the damage created by the gel during the treatment and the gel clean-up after the treatment. This research is focused on predicting more accurately the fracture conductivity, the gel damage created in fractures, and the fracture cleanup after a hydraulic fracture treatment under certain pressure and temperature conditions. Parameters that alter fracture conductivity, such as polymer concentration, breaker concentration and gas flow rate, are also examined in this study. A series of experiments, using a procedure of "dynamical fracture conductivity test," were carried out. This procedure simulates the proppant/frac fluid slurries flow into the fractures in a low-permeability rock, as it occurs in the field, using different combinations of polymer and breaker concentrations under reservoirs conditions. The result of this study provides the basis to optimize the fracturing fluids and the polymer loading at different reservoir conditions, which may result in a clean and conductive fracture. Success in improving this process will help to decrease capital expenditures and increase the production in unconventional tight gas reservoirs.

Author: Janice Helene Merl
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Languages : en
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Author: Richard Thomas Mastanduno
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Category :
Languages : en
Pages : 122

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Author: Matin Parchei Esfahani
Publisher:
ISBN:
Category : Finite element method
Languages : en
Pages : 170

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Hydraulic fracturing (HF) is an effective technique for permeability enhancement of conventional and unconventional reservoirs. HF is performed by injecting a fluid (usually water-based), sand, and chemicals into a formation under high pressure in order to induce damage and improve the interconnectivity of the fracture network through reopening of natural fractures and generation of new fractures. Hydraulic fracturing is a complex multi-physics process that involves the coupling of several physical phenomena, such as rock deformation, fluid flow, fracture propagation, etc. The simulation of HF is complex due to its coupled multi-physics nature. Despite recent advancements in HF simulations, relatively little attention has been given to improving the coupling algorithms used in these simulations. In many cases, sequential coupling algorithms are preferred over the monolithic approach due to the availability of independent solvers for each subproblem (e.g., independent deformable solid and fluid flow models), and the costliness of the monolithic approach. However, the available sequential algorithms widely used in the simulation of hydraulic fractures are known to lack robustness and encounter stability and/or convergence issues. The unavailability of efficient and effective sequential algorithms for the simulation of hydraulic fractures is currently one of the major gaps in the literature. The majority of hydraulic fracture models use quasi-static analysis, which neglects the inertial effects that are important when injection rates are very high or vary quickly in time, as during stimulation by pressure pulsing. The application of the dynamic models currently available in the literature is mainly limited to the dynamic simulations of acoustic wave emissions in porous media. Very few studies, until now, have considered dynamic simulation of fluid driven fractures. Hence, the unavailability of reliable dynamic hydraulic fracture models is another major gap in the hydraulic fracture literature. This thesis has three objectives. The first objective is to develop a stable sequential coupling algorithm for enforcing the hydro-mechanical coupling in the simulation of hydraulic fractures. The focus of the first objective is on the sequential algorithms that solve the mechanics subproblem first, in each iteration. This objective is realized in Chapter 2 of the thesis. The split is derived using the analogy of the undrained split in poromechanics; hence the new algorithm is named the \emph{undrained HF split}. The undrained HF split converges to the solution of the fully coupled (monolithic) approach. It's also shown to be stable and convergent in applications in which the conventional coupling strategies fail to converge due to oscillations. The convergence of the undrained HF split is generally slower than the fully coupled model. The second objective of the thesis is to develop a stable sequential coupling algorithm that solves the fluid flow subproblem first, in each iteration. This objective is addressed in Chapter 3 of the thesis. This algorithm is derived using the analogy of the fixed stress split in poromechanics and, therefore, named the \emph{fixed stress HF split}. The fixed stress HF split is stable and shown to converge to the solution of the fully coupled model. The algorithm is shown to successfully simulate nonplanar hydraulic fracture trajectories in flow rate controlled hydraulic fracture simulations. The third objective of the thesis is to develop a dynamic hydraulic fracture model for investigating the effect of rapidly changing loads, such as those caused by pressure pulses, on the dynamic propagation of hydraulic fractures. Chapter 4 of the thesis addresses this objective. A dynamic HF model with leak-off is developed in Chapter 4. The dynamic HF model is used to study wellbore stimulation by high rate and high amplitude pressure pulses and investigate the effect of formation porosity and permeability on the dynamic response of the system. It is observed that generally, formations with higher porosity and permeability generate shorter and wider hydraulic fractures. The dynamic response of hydraulic fractures is found to contain a phase lag with respect to the applied pressure pulse, which slightly increases with an increase in the porosity and permeability of the formation. Fracture closure mechanism is directly affected by the rate of fluid leak-off from hydraulic fractures, which also depends on the porosity and permeability of the formation. Unique acoustic wave emission patterns are observed from the response of hydraulic fracture and wellbore system to the pressure pulse at each stage of the stimulation.