Evaluation of the Relationship Between Fracture Conductivity, Fracture Fluid Production, and Effective Fracture Length PDF Download

Author: Elyezer P. Lolon
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
Low-permeability gas wells often produce less than predicted after a fracture treatment. One of the reasons for this is that fracture lengths calculated after stimulation are often less than designed lengths. While actual fracture lengths may be shorter due to fracture growth out of zone, improper proppant settling, or proppant flowback, short calculated fracture lengths can also result from incorrect analysis techniques. It is known that fracturing fluid that remains in the fracture and formation after a hydraulic fracture treatment can decrease the productivity of a gas well by reducing the relative permeability to gas in the region invaded by this fluid. However, the relationships between fracture fluid cleanup, effective fracture length, and well productivity are not fully understood. In this work I used reservoir simulation to determine the relationship between fracture conductivity, fracture fluid production, effective fracture length, and well productivity. I simulated water saturation and pressure profiles around a propped fracture, tracked gas production along the length of the propped fracture, and quantified the effective fracture length (i.e., the fracture length under single-phase flow conditions that gives similar performance as for multiphase flow conditions), the "cleanup" fracture length (i.e., the fracture length corresponding to 90% cumulative gas flow rate into the fracture), and the"apparent" fracture length (i.e., the fracture length where the ratio of multiphase to single-phase gas entry rate profiles is unity). This study shows that the proppant pack is generally cleaned up and the cleanup lengths are close to designed lengths in relatively short times. Although gas is entering along entire fracture, fracturing fluid remains in the formation near the fracture. The water saturation distribution affects the gas entry rate profile, which determines the effective fracture length. Subtle changes in the gas rate entry profile can result in significant changes in effective fracture length. The results I derived from this work are consistent with prior work, namely that greater fracture conductivity results in more effective well cleanup and longer effective fracture lengths versus time. This study provides better explanation of mechanisms that affect fracturing fluid cleanup, effective fracture length, and well productivity than previous work.

Author: Juan Correa Castro
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
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: Michael Berry Smith
Publisher: CRC Press
ISBN: 1466566922
Category : Science
Languages : en
Pages : 793

View

Book Description
Hydraulic Fracturing effectively busts the myths associated with hydraulic fracturing. It explains how to properly engineer and optimize a hydraulically fractured well by selecting the right materials, evaluating the economic benefits of the project, and ensuring the safety and success of the people, environment, and equipment. From data estimation

Author: National Research Council
Publisher: National Academies Press
ISBN: 0309049962
Category : Science
Languages : en
Pages : 568

View

Book Description
Scientific understanding of fluid flow in rock fracturesâ€"a process underlying contemporary earth science problems from the search for petroleum to the controversy over nuclear waste storageâ€"has grown significantly in the past 20 years. This volume presents a comprehensive report on the state of the field, with an interdisciplinary viewpoint, case studies of fracture sites, illustrations, conclusions, and research recommendations. The book addresses these questions: How can fractures that are significant hydraulic conductors be identified, located, and characterized? How do flow and transport occur in fracture systems? How can changes in fracture systems be predicted and controlled? Among other topics, the committee provides a geomechanical understanding of fracture formation, reviews methods for detecting subsurface fractures, and looks at the use of hydraulic and tracer tests to investigate fluid flow. The volume examines the state of conceptual and mathematical modeling, and it provides a useful framework for understanding the complexity of fracture changes that occur during fluid pumping and other engineering practices. With a practical and multidisciplinary outlook, this volume will be welcomed by geologists, petroleum geologists, geoengineers, geophysicists, hydrologists, researchers, educators and students in these fields, and public officials involved in geological projects.

Author: Yu-Shu Wu
Publisher: Gulf Professional Publishing
ISBN: 0128129999
Category : Technology & Engineering
Languages : en
Pages : 568

View

Book Description
Hydraulic Fracture Modeling delivers all the pertinent technology and solutions in one product to become the go-to source for petroleum and reservoir engineers. Providing tools and approaches, this multi-contributed reference presents current and upcoming developments for modeling rock fracturing including their limitations and problem-solving applications. Fractures are common in oil and gas reservoir formations, and with the ongoing increase in development of unconventional reservoirs, more petroleum engineers today need to know the latest technology surrounding hydraulic fracturing technology such as fracture rock modeling. There is tremendous research in the area but not all located in one place. Covering two types of modeling technologies, various effective fracturing approaches and model applications for fracturing, the book equips today’s petroleum engineer with an all-inclusive product to characterize and optimize today’s more complex reservoirs. Offers understanding of the details surrounding fracturing and fracture modeling technology, including theories and quantitative methods Provides academic and practical perspective from multiple contributors at the forefront of hydraulic fracturing and rock mechanics Provides today’s petroleum engineer with model validation tools backed by real-world case studies

Author: Michael J. Economides
Publisher: Pearson Education
ISBN: 0137031580
Category : Technology & Engineering
Languages : en
Pages : 752

View

Book Description
Written by four leading experts, this edition thoroughly introduces today's modern principles of petroleum production systems development and operation, considering the combined behaviour of reservoirs, surface equipment, pipeline systems, and storage facilities. The authors address key issues including artificial lift, well diagnosis, matrix stimulation, hydraulic fracturing and sand control. They show how to optimise systems for diverse production schedules using queuing theory, as well as linear and dynamic programming. Throughout, they provide both best practices and rationales, fully illuminating the exploitation of unconventional oil and gas reservoirs. Updates include: Extensive new coverage of hydraulic fracturing, including high permeability fracturing New sand and water management techniques * An all-new chapter on Production Analysis New coverage of digital reservoirs and self-learning techniques New skin correlations and HW flow techniques

Author: Murtadha Jawad Al Tammar
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

View

Book Description
Pursuit of unconventional gas and oil has prompted the development and adoption of innovative fracturing solutions. Energized fracturing is one promising technology that can be an effective alternative to mainstream slickwater or hybrid fracturing fluids in many applications. Yet, field use of energized fluids accounted for only 2-3% of 2011-2012 reported fracturing treatments in the U.S. compared to a markedly higher share of 42-46% in Canada. Recently, the superior performance and economics of foams were reported in the Montney Gas Formation in western Canada. In this thesis, we utilized field data and a compositional, 3D fracturing simulator to showcase the production performance of energized fluids in several areas of the Cardium and Bakken Light Oil Formations within the Western Canadian Sedimentary Basin. Average well data in the Cardium revealed better production results for foam compared to nitrified slickwater in the West Willesden Green and Buck Lake-Wilson Creek fields. Foams had a 110% higher initial peak production rate and 51% higher long term cumulative production in the West Willesden Green field with a similar initial production profile and a 16.2% higher long-term production in the Buck Lake-Wilson Creek fields. In contrast, the initial peak production rate of nitrified slickwater was 28% higher with 95% incremental oil production relative to foam in the West Pembina field. This shows that the effectiveness of foam fracturing fluids can vary significantly perhaps because of better fracture containment and lower rock water sensitivity in some fields. Across all the areas studied, foam completions on average were found to have 5-20% lower costs and lower water and proppant requirements by 72-87% and 7-38%, respectively. Fracture modeling, on the other hand, showed 53% higher well productivity increase using nitrified slickwater largely because of better contained fractures in the thin Cardium reservoir interval. Nitrified slickwater had twice the propped fracture length and conductivity of foam. With markedly improved fracture containment in depleted Cardium wells, foam is likely to outperform nitrified slickwater as fracturing fluid recovery is enhanced and permeability/relative permeability damage is reduced in water sensitive areas. In the Bakken Formation, field data showed an average of 15.8% higher long term cumulative production for foam compared to crosslinked gel despite the higher initial rate of crosslinked gel. Foam fractures were predicted to have 44% higher well productivity increase than crosslinked gel fractures based on simulations conducted. Foam had 50% longer propped fracture, 73% higher fracture conductivity, and twice the relative permeability to oil in the invaded zone compared to crosslinked gel. In our simulation, some factors were not accounted for such as formation heterogeneity, the effect of solution gas drive and associated water production, and the interaction between induced and natural fractures. Also, our modeling work was based on generic and synthesized data. For more accurate comparisons, we recommend performing simulation runs with detailed well-specific data.

Author: Mark D. Zoback
Publisher: Cambridge University Press
ISBN: 1107087074
Category : Business & Economics
Languages : en
Pages : 495

View

Book Description
A comprehensive overview of the key geologic, geomechanical and engineering principles that govern the development of unconventional oil and gas reservoirs. Covering hydrocarbon-bearing formations, horizontal drilling, reservoir seismology and environmental impacts, this is an invaluable resource for geologists, geophysicists and reservoir engineers.

Author: Songyang Tong
Publisher:
ISBN:
Category :
Languages : en
Pages : 360

View

Book Description
During hydraulic fracturing treatments, proppants – usually sand – are placed inside fractures to improve fracture conductivity. However, a large portion of the generated hydraulic fractures often remain unpropped after fracturing treatments. There are two primary reasons for this poor proppant placement. First, proppants settle quickly in common fracturing fluids (e.g., slickwater), which results in unpropped sections at the tip or top of the fracture. Second, a large number of the microfractures are too narrow to accommodate any common commercial proppant. Such unpropped fractures hold a large potential flow capacity as they exhibit a large contact area with the reservoir. However, their potential flow capacity is diminished during production due to closing of unpropped fractures because of closure stress. In this study, fractures are categorized as wider fractures, which are accessible to proppant, and narrower fractures, which are inaccessible to proppant. For wider fractures, proppant transport is important as proppant is needed for keeping them open. For narrower fractures, a chemical formulation is proposed as there is less physical restriction for fluids to flow inside across them. The chemical formulation is expected to improve fracture conductivity by generating roughness on fracture surfaces. This dissertation uses experiments and simulations to investigate proppant transport in a complex fracture network with laboratory-scale transparent fracture slots. Proppant size, injection flow rate and bypass fracture angle are varied and their effects are systematically evaluated. Based on experimental results, a straight-line relationship can be used to quantify the fraction of proppant that flows into bypass fractures with the total amount of proppant injected. A Computational Fluid Dynamics (CFD) model is developed to simulate the experiments; both qualitative and quantitative matches are achieved with this model. It is concluded that the fraction of proppant which flows into bypass fractures could be small unless a significant amount of proppant is injected, which indicates the inefficiency of slickwater in transporting proppant. An alternative fracturing fluid – foam – has been proposed to improve proppant placement because of its proppant carrying capacity. Foam is not a single-phase fluid, and it suffers liquid drainage with time due to gravity. Additionally, the existence of foam bubbles and lamellae could alter the movement of proppants. Experiments and simulations are performed to evaluate proppant placement in field-scale foam fracturing application. A liquid drainage model and a proppant settling correlation are developed and incorporated into an in-housing fracturing simulator. Results indicate that liquid drainage could negatively affect proppant placement, while dry foams could lead to negligible proppant settling and consequently uniform proppant placement. For narrower fractures, two chemical stimulation techniques are proposed to improve fracture conductivity by increasing fracture surface roughness. The first is a nanoparticle-microencapsulated acid (MEA) system for shale acidizing applications, and the second is a new technology which can generate mineral crystals on the shale surface to act as in-situ proppants. The MEA could be released as the fracture closes and the released acid could etch the surface of the rock locally, in a non-uniform way, to improve fracture conductivity (up to 40 times). Furthermore, the in-situ proppant generation technology can lead to crystal growth in both fracking water and formation brine conditions, and it also improves fracture conductivity (up to 10 times) based on core flooding experiments

Author: Mark John McGinley
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
Production of hydrocarbons from low-permeability shale reservoirs has become economically feasible thanks in part to advances in horizontal drilling and hydraulic fracturing. Together, these two techniques help to create a network of highly-permeable fractures, which act as fluid conduits from the reservoir to the wellbore. The efficacy of a fracturing treatment can best be determined through fracture conductivity analysis. Fracture conductivity is defined as the product of fracture permeability and fracture width, and describes both how much and how easily fluid can flow through fractures. It is therefore directly related to well performance. The goal of this work is to explore fracture conductivity of Marcellus shale samples fractured in both horizontal and vertical orientations. The Marcellus shale, located primarily in Pennsylvania, Ohio, West Virginia, New York, and Maryland, is the largest gas-bearing shale formation in North America, and its development has significant implications on regional economies, the northeast United States' energy infrastructure, and the availability of petrochemical plant feedstock. In this work, a series of experiments was conducted to determine the propped fracture conductivity of 23 different samples from Elimsport and Allenwood, Pennsylvania. Before conductivity measurements were taken, the pedigree of samples was verified through XRD analysis, elastic rock properties were measured and compared against literature values, and fracture surface contours were mapped and measured. Fracture conductivity of both horizontally and vertically-fracture samples was determined by measuring the pressure drop of nitrogen gas through a modified API conductivity cell. Results show that fracture conductivity varies as a function of fracture orientation only when anisotropy of the rock's mechanical properties is pronounced. It is hypothesized that the anisotropy of Young's Modulus and Poisson's Ratio play a significant role in fracture mechanics, and therefore in the width of hydraulically-induced fractures. Ultimately, the experiments conducted as part of this work show that fracture conductivity trends are strongly tied to both proppant concentration and the rock's mechanical properties. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155300