Reservoir Engineering Research Institute

Abstract We investigate the effectiveness of a novel copolymer (copolymer of 1-octene and 1-dodecene with 32 repeating units, C8/C12-32) as a CO2 thickener for enhanced oil recovery (CO2-EOR) at a concentration of 0.3 wt %. The central objective is to evaluate the effectiveness of increased CO2 viscosity and mobility control at low concentration in a live oil. Previous work has focused on a dead oil, demonstrating the C8/C12-32 performance. In this work, we conduct experiments with a live oil. Experiments are conducted using a carbonate core with a 1.5-inch diameter and 10-inch length. CO2 is viscosified by adding 0.3 wt % of the C8/C12-32 at 3500 psi at 120 °C. The viscosity of CO2 is increased by about 2.5 times at 35 °C and 2.1 times at 120 °C. The viscosified CO2 is injected into the live-oil-saturated core in secondary injection, and neat CO2/and brine injection for comparison. In the tertiary process, viscosified CO2 is injected following neat CO2/brine. Under the same conditions, experiments are also conducted using 1.5 wt % C10-20 (an oligomer of 1-decene with 20 repeating units). In the past, we have used the C8/C12-32 oligomer in horizontal dead oil displacement at 3500 psi and 120 °C and 0.3 wt % concentration. In this work, we conduct similar experiments in a live oil. The bubble point pressure is around 2800 psi at 120 °C, and the GOR is about 635 scf/stb. Neat CO2 gives a recovery of about 63 % OOIP. The recovery from the viscosified CO2 injection is about 80 % OOIP. There is about a 27 % additional recovery from viscosified CO2. In the tertiary process, viscosified CO2 is injected following neat CO2 injection (63 % OOIP) and brine injection (57 % OOIP). Injection of viscosified CO2 after neat CO2 increases the recovery to about 72 % OOIP (additional recovery of about 14 %). Injection of viscosified CO2 after brine injection increases the recovery to about 68 % OOIP (additional recovery of about 19 %). Besides 0.3 wt % C8/C12-32 injection, we also conduct experiments using 1.5 wt % oligomer of 1-decne with 20 repeat units. The additional recovery from the viscosified CO2 injection by C10-20 yields about 17 % (secondary) and 18 % (tertiary), which is a substantially lower (secondary, 2-inch), demonstrating the effectiveness of the new thickener. The effectiveness of thickened CO2 is a major step in delaying the breakthrough and adding sustainability by keeping the injected CO2 in the subsurface.

O objetivo deste estudo foi relatar a experiência da operacionalização de grupos focais on-line síncronos como técnica de produção de dados para pesquisas de pós-graduação. Relato de experiência sobre a operacionalização de grupos focais on-line junto a docentes e preceptores de graduação em enfermagem de universidades públicas de Mato Grosso entre os meses de outubro e dezembro de 2021. Foram realizados 11 encontros, com 19 participantes distribuídos em três grupos. A operacionalização foi dividida nas etapas: planejamento, envolvendo preparo do roteiro, teste piloto e escolha da plataforma de reunião virtual; seleção dos participantes; execução; e feedback. Os grupos focais on-line são exequíveis, desde que planejados e adaptados à implementação virtual, como a escolha da plataforma de comunicação, pessoas com experiência em tecnologia da informação, fidelidade ao número e seleção dos participantes, duração dos encontros, roteiros norteadores e feedback. Descritores: Grupos Focais, Metodologia, Pesquisa Qualitativa. Operationalization of synchronous online focus groups: experience report Abstract: The objective of this study was to report the experience of using synchronous online focus groups as a data production technique for graduate research. Experience report on the implementation of online focus groups with undergraduate nursing professors and preceptors at public universities in Mato Grosso between october and december 2021. 11 meetings were held, with 19 participants distributed into three groups. Operationalization was divided into stages: planning, involving preparing the script, pilot testing and choosing the virtual meeting platform; selection of participants; execution; and feedback. Online focus groups are feasible, as long as they are planned and adapted to virtual implementation, such as the choice of communication platform, people with experience in information technology, fidelity to the number and selection of participants, duration of meetings, guiding scripts and feedback. Descriptors: Focus Groups, Methodology, Qualitative Research. Operacionalización de grupos focales en línea sincronicos: reporte de experiencia Resumen: El objetivo de este estudio fue relatar la experiencia del uso de grupos focales en línea sincrónicos como técnica de producción de datos para la investigación de posgrado. Informe de experiencia sobre la implementación de grupos focales en línea con profesores y preceptores de graduación en enfermería en universidades públicas de Mato Grosso entre octubre y diciembre de 2021. Se realizaron 11 reuniones, con 19 participantes distribuidos en tres grupos. La operacionalización se dividió en etapas: planificación, que involucra la preparación del guión, la prueba piloto y la elección de la plataforma de reunión virtual; selección de participantes; ejecución; y retroalimentación. Los grupos focales en línea son factibles, siempre que sean planificados y adaptados a la implementación virtual, como la elección de la plataforma de comunicación, personas con experiencia en tecnologías de la información, fidelidad al número y selección de participantes, duración de las reuniones, guiones orientadores y retroalimentación. Descriptores: Grupos Focales, Metodología, Investigación Cualitativa.

The critical energy release rate (Gc) is a key parameter in numerical simulations of hydraulic fracturing, which may be affected by a fluid. Molecular dynamics (MD) simulations of minerals' tensile failure can be performed to gain insights into the mechanisms relevant to the critical energy release rate at the microscale. The methodology of calculating the critical energy release rate for solid-fluid systems is challenging. In this study, we conduct extensive MD simulations for solid-vacuum and solid-fluid systems. Typical components in shale and andesite, including quartz, muscovite, and kerogen, are selected in our investigation. The effect of H2O and CO2 on the critical energy release rate is analyzed. Fracture propagation and fluid invasion in fractures are also monitored. The results show that quartz and muscovite are brittle in H2O and CO2 and kerogen has very pronounced ductile behavior. H2O can reduce the critical energy release rate of quartz and muscovite slightly, but may increase that of kerogen. The effect of CO2 on quartz and muscovite is mild, while it reduces Gc of kerogen significantly. The implication is the creation of a much higher surface area in kerogen by CO2 than by H2O, which is in line with large-scale observations.

Abstract Accurate numerical modeling of fracture propagation and deflection in porous media is important in the development of georesources. To this end, we propose a novel modeling framework to simulate nonplanar three‐dimensional fracture growth within poroelastic media, using an iteratively coupled approach based on time‐/scale‐dependent fracture stiffness. In this approach, the propagating fractures are explicitly tracked and fitted at each growth step using triangular elements that are independent of the matrix discretized by hexahedral grids. The finite volume/finite element method is employed to solve the hydromechanical system, based on the embedded discrete fracture model. The calculated pressure in fractures and the stress state of the host grid of the embedded fractures constitute the boundary conditions for the boundary element method. The boundary element method module, in turn, renders the evolving fracture stiffness and aperture for the finite volume/finite element method module. Finally, the total stresses and the fracture tip displacements are computed at the end of each time step to estimate the velocity and direction of newly created fractures ahead of the fracture tip. The proposed model is first validated against analytical solutions. Then, in three different examples, results are shown from the fracture's footprint under layered stress conditions, simultaneous propagation of two nonplanar three‐dimensional fractures, and the mechanical interaction of en échelon arrays. This work presents an efficient framework to simulate propagation of nonplanar fractures and establishes the foundation to build an integrated simulator for fracture propagation, proppant transport, and production forecasting in unconventional formations.

Shale gas has redefined the energy landscape in the world. The scientific community makes efforts to exploit shale gas resources with minimum environmental impact. Shale gas is mainly located in mi...

Summary Petroleum fluids from shale light-oil and gas/condensate reservoirs generally have a high content of normal paraffins. Paraffin-wax deposition is among the challenges in shale gas and oil production and in offshore flow assurance. Low-dosage chemical additives can be effective in paraffin-wax mitigation because of their high efficiency and economics. These additives are divided into broad categories of crystal modifiers and dispersants with vastly different molecular structures and mechanisms in wax-crystal-particle stabilization and wetting. This investigation focuses on the understanding of the differences in the aggregate size and morphology of chemical additives, and it centers on (1) wax-particle sedimentation from diluted petroleum fluids in vial tests, (2) wax-crystal-particle-size distributions and morphology by dynamic light scattering (DLS) and polarized-light microscopy, and (3) the wetting state from the effect of water. In two of the three petroleum-fluid samples used in this work, there is no visible precipitation at the bottom of the vials at temperatures below the wax-appearance temperature (WAT). The microscopic image of fluids along the length of the tube shows that the wax-particle size and intensity increase from top to bottom. To observe precipitation, we dilute the crude with a hydrocarbon such as n-heptane. The sedimentation of wax is then observed. The petroleum fluids used in this work have very low asphaltene content, and there is no complication from asphaltene precipitation. Our study shows that a small amount of crystal modifier and dispersant can reduce crystal-particle size to the submicron scale, and change the crystal morphology. We investigate the differences in the mechanisms of dispersants and crystal modifiers in bulk. Water, which is often coproduced with petroleum fluids, can increase the effectiveness of dispersants significantly by altering the wetting state of the wax-particle surface. Such enhancement is not found in crystal modifiers. Both additives affect the rheology of petroleum fluids.

In oil–water–mineral\nsubstrate systems, we show that the contact angle can be tuned by\nionic structures in the water layer confined between an oil droplet\nand the substrate. We perform molecular dynamics simulations of a\ncomplex oil droplet in a NaCl aqueous solution on a mica surface;\nthe oil is a mixture of <i>n</i>-decane and surfactant molecules.\nThe surfactant head contains an OH group and an aromatic ring. A thin\nwater layer between the oil droplet and the substrate and ionic stratification\nregulate the wetting behavior. The concentration of salt ions in the\nthin film is nonmonotonic; it first increases, then decreases, and\nstarts increasing again as the salt concentration in the bulk increases.\nOn the other hand, the surfactant head adsorption in the thin film\nfirst increases as the bulk salt concentration increases. Then, it\ndecreases with further increase in the bulk salt concentration. The\nchange of contact angle with salt concentration also shows a nonmonotonic\nbehavior; the contact angle is first nearly constant to a low salt\nconcentration of 0.1 wt % NaCl. Then, it decreases sharply as the\nsalt concentration increases from 0.1 to 1.1 wt % NaCl. A reverse\ntrend in contact angle follows with further salt concentration increase.\nThe nonmonotonic trend unlike the monotonic trend of interfacial tension\nwith salt concentration is in line with recent measurements of contact\nangle of oil–brine–substrate systems. A sharp increase\nof surfactant head adsorption in the thin film, the decrease of ion\nadsorption, and the minimum of contact angle are all related. This\nis the first report of such correlations with change of wetting in\nthe brine–complex oil–mineral substrate predicted from\nmolecular simulations.