Author: Suzie Jia
Publisher:
ISBN:
Category : Engineering geology
Languages : en
Pages : 148
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Book Description
With the increasing exploitation of unconventional reservoirs, the demands of implementing geomechanics to improve the exploration and development process have been greater than before. Knowledge of in-situ stresses and rock failure mechanisms is key for building a comprehensive geomechanical model. Consequently, it is necessary to evaluate the state of stress in the Earth in order to design and efficiently operate engineered geothermal systems. The goal of this study is to investigate the variations of near-wellbore stress concentrations as a function of formation anisotropy, stress regimes and borehole relative orientations with respect to the in-situ stress, and then further examine the mechanical behavior of drilling induced tensile fractures. This is done by developing various MATLAB based analytical programs, creating numerical models and conducting lab simulations. Results from analytical models demonstrate that effects of formation anisotropy on borehole stress rise with increasing degree of anisotropy and the drilling-induced tensile fractures are not symmetrical when the borehole axis is not aligned with any of the in-situ stresses. Those models can also be integrated with different industry data sets to estimate the stress states in the formation of interest and enable us have better insights for drilling optimization, hydraulic fracturing design, completion planning and production maximization. Moreover, in the lab, both axial and en echelon drilling-induced tensile fractures were generated and their failure mechanisms agree with the general theory. Numerical models are not fully completed as the final goal is to develop a dynamic 3-D model based upon the current static model to simulate the lab processes in real-time.
Author: K. W. MacGregor
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Author: Jon Jincai Zhang
Publisher: Gulf Professional Publishing
ISBN: 0128148152
Category : Science
Languages : en
Pages : 534
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Book Description
Applied Petroleum Geomechanics provides a bridge between theory and practice as a daily use reference that contains direct industry applications. Going beyond the basic fundamentals of rock properties, this guide covers critical field and lab tests, along with interpretations from actual drilling operations and worldwide case studies, including abnormal formation pressures from many major petroleum basins. Rounding out with borehole stability solutions and the geomechanics surrounding hydraulic fracturing and unconventional reservoirs, this comprehensive resource gives petroleum engineers a much-needed guide on how to tackle today’s advanced oil and gas operations. Presents methods in formation evaluation and the most recent advancements in the area, including tools, techniques and success stories Bridges the gap between theory of rock mechanics and practical oil and gas applications Helps readers understand pore pressure calculations and predictions that are critical to shale and hydraulic activity
Author: Xinding Fang (Ph. D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 271
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Book Description
We study the effect of fractures on reservoir characterization and subsurface rock property measurements using seismic data. Based on the scale of a fracture relative to seismic wavelength, we divide the dissertation into two parts: larger scale fractures and microcracks. In the first part, we study the sensitivity of seismic waves and their time-lapse changes in hydraulic fracturing to the geometrical and mechanical properties of fractures that have dimensions comparable to the seismic wavelength. Through our analysis, we give the general seismic response of a fracture with a linear slip boundary and introduce the fracture sensitivity wave equation for optimal time-lapse survey design. Based on the characteristics of scattering from fractures, we develop an approach to determine the fracture properties using scattered seismic waves. The applicability and accuracy of our method is validated through both numerical simulations and laboratory experiments. Application of our approach to the Emilio Field shows that two orthogonal fracture systems exist and the field data results are consistent with well data. In the second part, we study the effects of microcracks and in situ stress on the formation properties measured from borehole sonic logging. Formation property measurements in a borehole could be biased by the borehole stress concentration, which alters the near wellbore formation properties from their original state. To study this problem, we first develop an iterative approach, which combines a rock physics model and a finite-element method, to calculate the stress-dependent elastic properties of the rock around a borehole when it is subjected to an anisotropic stress loading. The validity of this approach is demonstrated through a laboratory experiment on a Berea sandstone sample. We then use the model obtained from the first step and a finite-difference method to simulate the acoustic response in a borehole. We compare our numerical results with published laboratory acoustic wave measurements of the azimuthal velocity variations along a borehole under uniaxial loading and find very good agreement. Our results show that the variation of P-wave velocity versus azimuth is different from the presumed cosine behavior due to the preference of the wavefield to propagate through a higher velocity region.
Author: F. L. Paillet
Publisher:
ISBN:
Category : Aquifers
Languages : en
Pages : 46
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Book Description
Author:
Publisher:
ISBN:
Category : Petroleum
Languages : en
Pages : 1608
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Book Description
Author: Hans-Joachim Kümpel
Publisher: Springer Science & Business Media
ISBN: 9783764302535
Category : Nature
Languages : en
Pages : 364
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Book Description
The supply and protection of groundwater, the production of hydrocarbon reservoirs, land subsidence in coastal areas, exploitation of geothermal energy, the long-term disposal of critical wastes ... What do these issues have in common besides their high socio-economic impact? They are all closely related to fluid flow in porous and/or fractured rock. As the conditions of fluid flow in many cases depend on the mechanical behavior of rocks, coupling between the liquid phase and the rock matrix can generally not be neglected. For the past five years or so, studies of rock physics and rock mechanics linked to coupling phenomena have received increased attention. In recognition of this, a Euroconference on thermo-hydro-mechanical coupling in fractured rock was held at Bad Honnef, Germany, in November 2000. Most of the twenty papers collected in this volume were presented at this meeting. The contributions lead to deeper insight in processes where such coupling is relevant.
Author: Peidong Zhao
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Drilling in complex geological settings often possesses significant risk for unplanned events that potentially intensify the economic problem of cost-demanding operations. Lost circulation, a major challenge in well construction operations, refers to the loss of drilling fluid into formation during drilling operations. Over years of research effort and field practices, wellbore strengthening techniques have been successfully applied in the field to mitigate lost circulation and have proved effective in extending the drilling mud weight margin to access undrillable formations. In fact, wellbore strengthening contributes additional resistance to fractures so that an equivalent circulating density higher than the conventionally estimated fracture gradient can be exerted on the wellbore. Therefore, wellbore strengthening techniques artificially elevate the upper limit of the mud weight window. Wellbore strengthening techniques have seen profound advancement in the last 20 years. Several proposed wellbore strengthening models have contributed considerable knowledge for the drilling community to mitigate lost circulation. However, in each of these models, wellbore strengthening is uniquely explained as a different concept, with supporting mathematical models, experimental validation, and field best practices. Due to simplifications of the mathematical models, the limited scale of experiments, and insufficient validation of field observations, investigating the fundamental mechanisms of wellbore strengthening has been an active and controversial topic within the industry. Nevertheless, lost circulation is undoubtedly induced by tensile failure or reopening of natural fractures when excessive wellbore pressure appears. In this thesis, a fully coupled hydraulic fracturing model is developed using Abaqus Standard. By implementing this numerical model, an extensive parametric study on lost circulation is performed to investigate mechanical behaviors of the wellbore and the induced fracture under various rock properties and bottomhole conditions. Based on the fracture analysis, a novel approach to simulate the fracture sealing effect of wellbore strengthening is developed, along with a workflow quantifying fracture gradient extension for drilling operations. A case study on fracture sealing is performed to investigate the role of sealing permeability and sealing length. The results described in this thesis indicate the feasibility of hoop stress enhancement, detail the mechanism of fracture resistance enhancement, and provide insights for lost circulation mitigation and wellbore strengthening treatment.
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309049962
Category : Science
Languages : en
Pages : 568
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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: Seyed Omid Razavi
Publisher:
ISBN:
Category :
Languages : en
Pages : 280
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Book Description
An experimental approach was employed to study the Wellbore Strengthening (WBS) phenomenon. A state-of-the-art experimental set-up was designed to carry out high-pressure borehole fracturing tests on cylindrical rock samples. The experimental set-up offers full control over borehole, confining, and pore pressures. Fracturing experiments were conducted on three different rock types, namely Berea sandstone, Castlegate sandstone, and Mancos shale. Several injections were performed on each sample to characterize the values of the fracture initiation pressure (FIP) and the fracture propagation pressure (FPP) and thereby characterize the WBS phenomenon. Typical experimental variables include the applied confining pressure, type of base fluid (water-based or synthetic-based), and concentration, type, and particle size distribution (PSD) of the lost circulation material (LCM) used to achieve WBS benefits. Post-fracturing analysis was conducted by using techniques such as computerized axial tomography (CAT) scan and petrographic imaging to investigate the geometry of induced fractures and formed seals. The experimental results show that the FIP is mainly a function of the rock fracture toughness and stress concentration around the borehole, and independent of the drilling fluid used. The FPP, however, is mainly affected by the formulation of the drilling fluid and can be significantly enhanced by adding LCM. The obtained FPP values are compared with the large-scale fracturing experiments conducted at the Drilling Engineering Association (DEA) 13 investigations. Excellent agreement was observed between the DEA 13 and UT MudFrac experimental results. Furthermore, it is shown that FPP changes linearly with the minimum horizontal stress (Shmin), and the results of fracturing experiments using a relatively small borehole size at low confining pressures can be extrapolated to predict the FPP of large-scale fracturing experiments, and possibly field applications. The effect of LCM concentration on strengthening effects is investigated. It was found that although a minimum concentration of LCMs is required for effective WBS, FPP does not increase significantly for concentrations above a certain upper threshold value. Moreover, for any rock with a given set of rock strength and failure parameters, there exists an optimum PSD to maximize WBS benefits. Optimum PSD appears to be of primary importance for WBS, almost independent of LCM type. The experimental results presented in this dissertation are in clear disagreement with wellbore stress augmentation (WSA) mechanisms such as stress caging (SC) and fracture closure stress (FCS) which were previously proposed to explain the WBS phenomenon. Furthermore, they clearly favor the fracture propagation resistance (FPR) explanation to WBS. Existing guidelines to design WBS treatments such as the one-third rule, the Vickers criteria, and the ideal packing theory are evaluated. It is shown that none of these theories properly represents the physics of fracture sealing. To remedy this situation, a new family of design curves is introduced to determine the optimum PSD for WBS applications.
