Fracturing Fluid Cleanup by Controlled Release of Enzymes from Polyelectrolyte Complex Nanoparticles

Guar-based polymer gels are used in the oil and gas industry to viscosify fluids used in hydraulic fracturing of production wells, in order to reduce leak-off of fluids and pressure, and improve the transport of proppants. After fracturing, the gel and associated filter cake must be degraded to very low viscosities using breakers to recover the hydraulic conductivity of the well. Enzymes are widely used to achieve this but injecting high concentrations of enzyme may result in premature degradation, or failure to gel; denaturation of enzymes at alkaline pH and high temperature conditions can also limit their applicability. In this study, application of polyelectrolyte nanoparticles for entrapping, carrying, releasing and protecting enzymes for fracturing fluids was examined. The objective of this research is to develop nano-sized carriers capable of carrying the enzymes to the filter cake, delaying the release of enzyme and protecting the enzyme against pH and temperature conditions inhospitable to native enzyme. Polyethylenimine-dextran sulfate (PEI-DS) polyelectrolyte complexes (PECs) were used to entrap two enzymes commonly used in the oil industry in order to obtain delayed release and to protect the enzyme from conditions inhospitable to native enzyme. Stability and reproducibility of PEC nanoparticles was assured over time. An activity measurement method was used to measure the entrapment efficiency of enzyme using PEC nanoparticles. This method was confirmed using a concentration measurement method (SDS-PAGE). Entrapment efficiencies of pectinase and a commercial high-temperature enzyme mixture in polyelectrolyte complex nanoparticles were maximized. Degradation, as revealed by reduction in viscoelastic moduli of borate-crosslinked hydroxypropyl guar (HPG) gel by commercial enzyme loaded in polyelectrolyte nanoparticles, was delayed, compared to equivalent systems where the enzyme mixture was not entrapped. This indicates that PEC nanoparticles delay the activity of enzymes by entrapping them. It was also observed that control PEC nanoparticles decreased both viscoelastic moduli, but with a slower rate compared to the PEC nanoparticles loaded with enzyme. Preparation shear and applied shear showed no significant effect on activity of enzyme-loaded PEC nanoparticles mixed with HPG solutions. However, fast addition of chemicals during the preparations showed smaller particle size compared to the drop-wise method. PEC nanoparticles (PECNPs) also protected both enzymes from denaturation at elevated temperature and pH. Following preparation, enzyme-loaded PEC nanoparticles were mixed with borate crosslinked HPG and the mixture was injected through a shear loop. Pectinase-loaded nanoparticles mixed with gelled HPG showed no sensitivity to shear applied along the shear loop at 25 °C. However, EL2X-loaded PEC nanoparticles showed sensitivity to shear applied along the shear loop at 40 °C. Filter cake was formed and degraded in a fluid loss cell for borate crosslinked HPG solutions mixed with either enzymes or enzyme-loaded PEC nanoparticles. Cleanup slopes of filter cake degraded using enzyme-loaded PEC nanoparticles and systems with enzymes mixed with HPG gel were significantly higher than for the filter cake formed with HPG gel mixed with no enzyme. In a different application, enzyme-loaded PEC nanoparticles showed significantly slower reduction in viscosity of HPG solution over time compared to the HPG systems mixed with enzyme. Increasing the viscosity of low concentration HPG, used as slick-water, decreases the proppant settling velocity. This is of specific interest in fracturing fluids used for unconventional reservoirs

Carbon Dioxide Utilization and Sequestration in Kerogen Nanopores

Carbon dioxide (CO2) has been injected into oil reservoirs to maximize production for decades. On the other hand, emitted CO2 from industrial processes is captured and stored in geological formations to mitigate greenhouse gas effects. As such, greater attention is drawn to the potential of utilizing the captured CO2 in EOR processes. A significant portion of the injected CO2 remains trapped due to capillary forces and through dissolution in residual liquids. In organic-rich shales, the presence of isolated kerogen nanopores add to the sequestration process due to the adsorptive nature of the surface and its preference to CO2 over methane (CH4), in addition to the sealing capacities of these formations. This work summarizes the latest findings of the literature with the purpose of defining further areas of investigation to fully capitalize on the potential of CO2 sequestration and utilization in kerogen nanopores

Non-overshooting PD and PID controllers design

This paper involves the design of non-overshooting PD and PID controllers for some special plants. The PID controller parameters are determined to reach a stable closed-loop system with monotonically decreasing frequency response. Thus specific regions in the controller parameters space are obtained. Gain crossover frequency and phase isodamping property are employed to choose an appropriate solution among the obtained solutions. The performance of the proposed PD and PID controllers in position and velocity control of a laboratory DC servomechanism system is investigated through experimental tests

Improvement of Hydraulic Fracture Conductivity Using Nanoparticles

Hydraulic fracturing is a commonly used practice in the oil industry for well stimulation and production enhancement. With the general theme of the oil and gas industry moving toward systems with nano-sized pores, nanoparticles have gained a significant amount of attention especially in the field of hydraulic fracturing. Several groups have developed different nanoparticle systems that improve hydraulic fracture conductivity. This paper is a review of the highlighted work published in the area of application of nanoparticles to improve fracture conductivity. Nanotechnology can be used to improve the efficiency of hydraulic fracturing process. Four major production challenges faced by the oil and gas industry including incomplete filter cake cleanup, proppant pack damage, formation damage, and having micro-fractures that are not packed with proppants and will close under closure stress are introduced in this work. Solutions have also been reported using the advances in nanotechnology to address some of these challenges

Enhancing Planning and Scheduling Program by Using Benefits of BIM-Based Applications

2D drawings are commonly being used to present the work process of 3D objects in the construction industry. The engineers require having sufficient knowledge to interpret these drawings for use in various areas of the work especially for providing planning and scheduling programs. In the construction projects, construction managers face many problems such as over budget projects, schedule errors, omission of some activities like safety tasks that originate from poor planning methods. Therefore, the study is going to examine alternative tools for better understanding of real project tasks sequences and procedures. One of the most reliable applications is introduced by the Building Information Modeling approach (BIM) that develops four-dimension model based on a combination of three dimension models with time. The benefits of BIM-based on 4D modeling not only improving the perception of planners and construction teams but also facilitate the procedure of planning and scheduling like automatically clash detection, introduce parallel activity and etc. .This study discusses the development and implementation of this innovative approach in construction planning. The research was carried out based on questionnaire survey within construction companies in Singapore. The data was analyzed using descriptive statistical analysis and been ranked with Average Index method. Keywords: Planning, scheduling, BIM-Based Application

Enhancing Planning and Scheduling Program by Using Benefits of BIM-Based Applications

2D drawings are commonly being used to present the work process of 3D objects in the construction industry. The engineers require having sufficient knowledge to interpret these drawings for use in various areas of the work especially for providing planning and scheduling programs. In the construction projects, construction managers face many problems such as over budget projects, schedule errors, omission of some activities like safety tasks that originate from poor planning methods. Therefore, the study is going to examine alternative tools for better understanding of real project tasks sequences and procedures. One of the most reliable applications is introduced by the Building Information Modeling approach (BIM) that develops four-dimension model based on a combination of three dimension models with time. The benefits of BIM-based on 4D modeling not only improving the perception of planners and construction teams but also facilitate the procedure of planning and scheduling like automatically clash detection, introduce parallel activity and etc. .This study discusses the development and implementation of this innovative approach in construction planning. The research was carried out based on questionnaire survey within construction companies in Singapore. The data was analyzed using descriptive statistical analysis and been ranked with Average Index method. Keywords: Planning, scheduling, BIM-Based Application

Coupled Lattice Boltzmann Modeling Framework for Pore-Scale Fluid Flow and Reactive Transport

In this paper, we propose a modeling framework for pore-scale fluid flow and reactive transport based on a coupled lattice Boltzmann model (LBM). We develop a modeling interface to integrate the LBM modeling code parallel lattice Boltzmann solver and the PHREEQC reaction solver using multiple flow and reaction cell mapping schemes. The major advantage of the proposed workflow is the high modeling flexibility obtained by coupling the geochemical model with the LBM fluid flow model. Consequently, the model is capable of executing one or more complex reactions within desired cells while preserving the high data communication efficiency between the two codes. Meanwhile, the developed mapping mechanism enables the flow, diffusion, and reactions in complex pore-scale geometries. We validate the coupled code in a series of benchmark numerical experiments, including 2D single-phase Poiseuille flow and diffusion, 2D reactive transport with calcite dissolution, as well as surface complexation reactions. The simulation results show good agreement with analytical solutions, experimental data, and multiple other simulation codes. In addition, we design an AI-based optimization workflow and implement it on the surface complexation model to enable increased capacity of the coupled modeling framework. Compared to the manual tuning results proposed in the literature, our workflow demonstrates fast and reliable model optimization results without incorporating pre-existing domain knowledge

A Review of Brittleness Index Correlations for Unconventional Tight and Ultra-Tight Reservoirs

Brittleness is a key parameter in the development of the unconventional shale and tight carbonate reservoirs as it plays a role in the design of the hydraulic fractures as well as the selection of the sweet-spot locations for perforation and fracture initiation. The brittleness index (BI) is utilized to indicate if the formation rocks are brittle, which are preferable to form a complex network of fractures, or ductile, which are occasionally desirable to seal the fractures from growing. However, there is a wide variety of BI methods in the literature that lead to inconclusive BI values. The Mineral-based brittleness index (MBI), which is a method based on the mineral composition of the formation, can be derived from mineral well logging data or laboratory core testing. Another approach in describing the brittleness is the Fracability Index (FI), which is a combination of Young’s modulus and Poisson’s ratio. Differentiation is also made between the dynamic FI, which is calculated from well logging data, and the static FI, which is derived from laboratory core testing such as uniaxial compressive strength, Brazilian tensile strength and triaxial testing. Hence, to understand the complexity of the brittleness, it is crucial to consider all dependencies such as the lithology, mineral composition, TOC, porosity, temperature and pressure amongst others. In this work, a comprehensive review and analysis of the existing equations and correlations for the calculation of the MBI and FI was conducted. These methods were applied on different low porosity and low permeability rocks. A thorough comparison has also been conducted between the MBI and FI correlations as well as between the dynamic FI and the static FI to ultimately clarify and improve the definition of brittleness as a function of lithology. High content of quartz and carbonates result in high values of MBI, and high Young’s modulus values yield high FI values. On the other hand, high clay content and high porosity lead to low MBI values

Impact of Heterogeneity on the Transient Gas Flow Process in Tight Rock

This work is licensed under a Creative Commons Attribution 4.0 International License.There exits a great challenge to evaluate the flow properties of tight porous media even at the core scale. A pulse-decay experiment is routinely used to measure the petrophysical properties of tight cores including permeability and porosity. In this study, 5 sets of pulse-decay experiments are performed on a tight heterogeneous core by flowing nitrogen in the forward and backward directions under different pressures under pore pressures approximately from 100 psi to 300 psi. Permeability values from history matching are from about 300 nD to 600 nD which shows a good linear relationship with the inverse of pore pressure. A preferential flow path is found even when the microcrack is absent. The preferential path causes different porosity values using differential initial upstream and downstream pressure. In addition, the porosity values calculated based on the forward and backward flow directions are also different, and the values are about 1.0% and 2.3%, respectively, which is the primary novelty of this study. The core heterogeneity effect significantly affects the very early stage of pressure responses in both the upstream and downstream but the permeability values are very close in the late-stage experiment. We proposed that that there are two reasons for the preferential flow path: the Joule–Thomson effect for non-ideal gas and the core heterogeneity effect. Based on the finding of this study, we suggest that very early pressure response in a pulse-decay experiment should be closely examined to identify the preferential flow path, and failure to identify the preferential flow path leads to significant porosity and permeability underestimation