Numerical simulation of heat extraction performance in enhanced geothermal system with multilateral wells

This paper reviews basic results and recent developments in the field of small-scale gaseous hydrodynamics which has received significant attention in connection with small-scale science and technology. We focus on the modeling challenges arising from the breakdown of the Navier-Stokes description, observed when characteristic lengthscales become of the order of, or smaller than, the molecular mean free path. We discuss both theoretical results and numerical methods development. Examples of the former include the limit of applicability of the Navier-Stokes constitutive laws, the concept of second-order slip and the appropriate form of such a model, and how to reconcile experimental measurements of slipping flows with theory. We also review a number of recently developed theoretical descriptions of canonical nanoscale flows of engineering interest. On the simulation front, we review recent progress in characterizing the accuracy of the prevalent Boltzmann simulation method known as direct simulation Monte Carlo. We also present recent variance reduction ideas which address the prohibitive cost associated with the statistical sampling of macroscopic properties in low-speed flows.

http://absimage.aps.org/image/DFD05/MWS_DFD05-2005-020061.pdf

The limits of Navier-Stokes theory and kinetic extensions for describing small-scale gaseous hydrodynamics

Alkaline–surfactant–polymer (ASP) flooding is a combination process in which alkali, surfactant, and polymer are injected in the same slug. Because of the synergy of these three components, ASP is the current worldwide focus of research and field trial in chemical enhanced oil recovery (EOR).

This paper is to provide a comprehensive review of the ASP process. The reviewed topics include the following: 

ASP synergy and its EOR mechanisms
Screening criteria
Laboratory work
Numerical simulation work
Summary of pilots and large-scale applications
Project economics
Chemicals used
Water quality
Mobility control requirement
Problems associated with ASP flooding and possible solutions


In addition to the comprehensive review, future developments are also discussed. Data and analyzed results presented in this review will provide the reader with the updated information about ASP and a guide to read relevant papers for those who are new to chemical EOR. The survey data also provide operators with some reference data for their project design and optimization. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

A comprehensive review of alkaline–surfactant–polymer (ASP) flooding

The adsorption behavior and underlying mechanism of CO2 and CH4 binary mixture in shale kerogen significantly affect the CO2 sequestration with enhanced gas recovery project (CS-EGR). In this study, we investigated the competitive adsorption behaviors of CO2 and CH4 in shale kerogen nanopores using grand canonical Monte Carlo (GCMC) method. Kerogen model takes into effect of matrix and slit nanopores and moisture content based on Ungerer’s molecular model and scanning electron microscope (SEM) analysis, and is successfully validated against experimental data. The effects of temperature, CO2 and CH4 distribution, moisture content, adsorption selectivity, and optimal formation for injection were discussed. The results show that adsorption amount of CH4 on the kerogen increases with increasing pressure and decreases with increasing temperature. The adsorption selectivity of CO2 over CH4 is 2.53–7.25, which indicates that CO2 is preferentially adsorbed over CH4 under different temperatures. H2O prefers to ads...

Molecular Simulation of CO2/CH4 Competitive Adsorption on Shale Kerogen for CO2 Sequestration and Enhanced Gas Recovery

A Comprehensive Review of Alkaline-Surfactant-Polymer (ASP) Flooding

Waterless fracturing techniques have been recognized as a sustainable solution to minimize the environmental footprint and efficiently develop unconventional natural gas resources. Supercritical CO2 (SC-CO2) and liquid nitrogen are two practical fluids to conduct waterless fracturing. The fracturing mechanics imposed by SC-CO2 and liquid nitrogen are fundamental to understanding their impacts on fracture propagation behaviors. This chapter reviews a series of fracturing mechanics tests and triaxial fracturing system from microscale to macroscale. Grid nanoindentation and Atomic Force Microscopy combined with SEM and EDS were used to characterize the impacts of SC-CO2 and liquid nitrogen on mechanical properties in microscale. The macro mechanical properties of unconventional rock imposed by SC-CO2 and liquid nitrogen were evaluated through in-situ compression and shearing tests. The triaxial fracturing system with capacity to pump SC-CO2 and liquid nitrogen was developed. Acoustic emission and CT images were used to detect the fracture profiles and real time fracture propagation. The experimental setup, procedures, and the requirements of rock specimens are comprehensively described. Banner headline Waterless fracturing techniques have been recognized as a potential sustainable solution to minimize the environmental footprint and efficiently develop unconventional natural gas resources. Hydraulic fracturing related rock mechanics and fractures initiation and propagation behaviors are fundamentals to optimize the waterless fracturing design. This chapter focuses on advances of the fracturing mechanics tests and triaxial fracturing system from microscale to macroscale. The microscale mechanics, triaxial fracturing tests, and monitoring approaches were present. In addition, the experimental setup, procedures, and the requirements of rock specimens were comprehensively described.

Experimental methods in fracturing mechanics focused on minimizing their environmental footprint

Laboratory Experiment of Using Liquid Nitrogen as a Temporary Blocking Agent for Coalbed Methane Fractured Wells

Experimental study on replacing ceramsite with quartz sand in hydraulic fracturing


 Hydraulic fracturing is one of the important stimulation methods to enhance the productivity of coalbed methane (CBM) wells. However, the commonly used water-based fracturing fluids can bring some bottlenecks such as large amount of water consumption, clay-mineral swelling, and poor fracturing performance on ductile coals. Cyclic liquid nitrogen (LN2) fracturing, as a novel nonaqueous stimulation method, has the potential to solve the above problems. In cyclic LN2 fracturing, supercooling LN2 is injected in a cyclic manner [i.e., alternating high injection rate (or pressure) and low injection rate (or pressure)]. Coals will be subjected to cyclic freeze-thaw, stress oscillation, and fatigue damage, which is expected to improve the stimulated reservoir volume. First, laboratory cyclic LN2 fracturing tests were conducted on coal samples with various coal ranks to investigate the fracture initiation/propagation behavior and fracture network patterns. Cyclic water fracturing tests were also conducted as comparisons. Then, computed tomography (CT) scanning and geomechanical/petrophysical properties tests before and after LN2 fracturing were performed to assist in understanding the cyclic LN2 fracturing mechanisms and implications. Finally, to solve the field application concerns, we investigated the possible fracture geometries at the field scale, temperature distribution of LN2 along the wellbore during injection, and the economic feasibility. The key factors affecting the temperature distribution during LN2 transportation along the wellbore were clarified for the first time. The results indicate that cyclic LN2 fracturing shows the potential to decrease the breakdown pressure and produce complex fracture networks. Different coal ranks have different responses to cyclic LN2 fracturing attributed to the variances in natural fracture development and geomechanical/petrophysical properties. Besides, increasing the cycle number is effective in enhancing the cyclic LN2 fracturing performance on coals with relatively higher geomechanical strengths and tighter rock mass. The suggested cycle numbers from low to high for different coal ranks are listed here: low-rank coal < high-rank coal < middle-rank coal. In field applications, gaseous nitrogen (N2) can be used as the annulus fluid to provide an effective insulation for heat transfer between the low-temperature LN2 and the surrounding environment. In addition, the net present value (NPV) analysis indicates that LN2 fracturing is an economically feasible stimulation method, which can exceed slickwater fracturing in some cases. The key findings are expected to provide preliminary insights into the potential field applications of cyclic LN2 fracturing in CBM or other unconventional oil/gas exploitation.

Ruiyue Yang

Papers

Experimental methods in fracturing mechanics focused on minimizing their environmental footprint

Laboratory Experiment of Using Liquid Nitrogen as a Temporary Blocking Agent for Coalbed Methane Fractured Wells

Experimental study on replacing ceramsite with quartz sand in hydraulic fracturing

Cyclic Liquid Nitrogen Fracturing Performance on Coal with Various Coal Ranks: Laboratory Investigation and Mechanism Analysis

Geomechanical Properties of Thinly Interbedded Rocks Based on Micro- and Macro-Scale Measurements