Three-Dimensional Visualization of Oil Displacement by Foam in Porous Media

Foam Enhanced Oil Recovery (EOR) has been employed as an improved recovery method due to its best sweep efficiency and best mobility control over the other injection method such as gas flooding, water flooding and other EOR methods. Foam which has high viscosity illustrates great potential for displacing liquid. The relative immobility of foam in porous media seems to be able to suppress the formation of fingers during oil displacement leading a more stable displacement. However, there are still various parameters that may influence the efficiency of foam assisted oil displacement such as oil properties, permeability of reservoir rock, physical and chemical properties of foam, and other parameters. Also, the interaction and displacement patterns of foam inside the porous media are remained unknown. Thus, in this study, we investigated the three-dimensional (3D) characteristics of oil recovery with gases, water, surfactant, and foam injection in a porous media set-up. By using CT scanning machine, the fluid displacement patterns were captured and analyzed. Moreover, the effect of oil viscosity on foam displacement patterns is studied. The study provides a qualitative and quantitative experimental visualization of 3D displacement structure, oil recovery with gases, liquid and foam injection. As a result, the comparison of fluid displacement patterns between gases, water, surfactant and foam injection show that foam has the good ability in sweeping and forms stable displacement front. The combination of surfactant, liquid and gas, which makes up foam resulted in a synergistic effect in oil displacement. On the other hand, viscous fingering, gravity segregation, trapped oil phenomena are shown in gas flooding and liquid flooding experiments. Thus, foam which displaced stably across the permeable bed resulted in the highest oil recovery factor. The mechanism of foam flow in porous media was understood in this study. Foam, as a series of bubble, burst and become free moving liquid and gas particles when in contact with oil and porous media. Therefore, two displacement fronts could be found from the foam injection experiment, in which the front layer moving ahead in contacting with oil bank is the discontinuous gas/liquid layer and followed by stably foam bank at the back. Due to the stable displacement of foam bank, the effect of oil viscosity on foam displacement is suppressed and showed no distinction in terms of displacement patterns. The flow regimes are found to be the same despite different viscosity of displaced oil. There has been no linear correlation proved between the oil viscosity and oil recovery factor.

NEURAL NETWORK-BASED APPROACH TO RESISTIVITY LOGS EXPRESS SIMULATION IN REALISTIC MODELS OF COMPLEX TERRIGENOUS SEDIMENTS

The article proposes a new algorithmic approach to resistivity logs simulation based on convolutional neural networks wich allows constructing algorithms for solving forward problems for specific logging tools in detailed models of near-wellbore space with thin layers, accounting for radial resistivity changes, borehole wall irregularities and drilling fluid displacement by the logging tool. Experimental algorithms for expressmodeling for three common Russian galvanic and induсtion logging methods in two-dimensional models of the near-wellbore space have been implemented based on the proposed approach. Logs simulation using the developed neural network algorithms is multi pletimes faster than using numerical solvers. The proposed solutions open up possibilities to use more sophisticated basic geoelectric models of the near-wellbore space. The use of models adequate in complexity to the actual target geological objects will increase the reliability of interpretation results of resistivity logs measured in complex geological conditions.

Pulsed Second Order Magnetic Field Nuclear Magnetic Resonance for Real-Time Fluid Transport Measurements

<p>Nuclear magnetic resonance (NMR) measurement techniques are able to characterise a large array of physical properties and systems, both transparent and opaque, in a nondestructive, non-invasive manner. This allows systems to be probed with minimal disturbance, and in most cases, information can be obtained with little to no experimental bias. For these reasons NMR lends itself well to many fields of research. Of particular importance to this research is NMR measurement of the characteristic function which defines fluid transport known as the average propagator. This quantity provides the probability distribution for fluid displacement, and all mobility information of the fluid matter under measurement. The average propagator is normally measured by NMR with a series of experiments which require an extended period of time. When systems are evolving on a time scale which is shorter than the total experimental time required to measure the average propagator, the measurement cannot be performed as different experiments in the series relate to different states of the system. In this thesis a method for transforming the slow, serial process of measuring the average propagator into an instantaneous, parallel process has been developed. This allows real-time characterisation of flows, diffusion, and the properties of the pore spaces in porous media containing fluid. The details of the newly developed technique are provided along with new hardware designed and built to perform the new parallel method, allowing instantaneous measurement of the average propagator. Experimental results are presented for well known model systems. These systems are used because their properties and models describing their behaviour are well understood. The experimental measurements for these model systems were compared to theoretical predictions to verify the effectiveness of the new average propagator measurement technique, providing a proof of concept, and proving the validity of this new average propagator measurement for real-time characterisation of fluid transport and porous media.</p>

Pulsed Second Order Magnetic Field Nuclear Magnetic Resonance for Real-Time Fluid Transport Measurements

<p>Nuclear magnetic resonance (NMR) measurement techniques are able to characterise a large array of physical properties and systems, both transparent and opaque, in a nondestructive, non-invasive manner. This allows systems to be probed with minimal disturbance, and in most cases, information can be obtained with little to no experimental bias. For these reasons NMR lends itself well to many fields of research. Of particular importance to this research is NMR measurement of the characteristic function which defines fluid transport known as the average propagator. This quantity provides the probability distribution for fluid displacement, and all mobility information of the fluid matter under measurement. The average propagator is normally measured by NMR with a series of experiments which require an extended period of time. When systems are evolving on a time scale which is shorter than the total experimental time required to measure the average propagator, the measurement cannot be performed as different experiments in the series relate to different states of the system. In this thesis a method for transforming the slow, serial process of measuring the average propagator into an instantaneous, parallel process has been developed. This allows real-time characterisation of flows, diffusion, and the properties of the pore spaces in porous media containing fluid. The details of the newly developed technique are provided along with new hardware designed and built to perform the new parallel method, allowing instantaneous measurement of the average propagator. Experimental results are presented for well known model systems. These systems are used because their properties and models describing their behaviour are well understood. The experimental measurements for these model systems were compared to theoretical predictions to verify the effectiveness of the new average propagator measurement technique, providing a proof of concept, and proving the validity of this new average propagator measurement for real-time characterisation of fluid transport and porous media.</p>

Combined Control Mechanism of Weight on Bit and Rate of Penetration with a Downhole Robot in the Coiled-Tubing Drilling Process

Summary Downhole robots were used to solve the problem of downhole tool transportation in an oil/gas horizontal well. However, current downhole robots do not control the weight on bit (WOB) and rate of penetration (ROP). This paper proposes the combined control method of WOB and ROP using an electric proportional overflow valve (EPOV) and an electric proportional throttle valve (EPTV). First, the mathematical model of the electrohydraulic control of the downhole robot is established. It is found that when the maximum pressure of the EPOV is greater than the differential pressure between the inner and outer of the downhole robot, the control parameters are drilling-fluid displacement and circulation area of the EPTV. When the maximum pressure of the EPOV is less than the differential pressure between the inner and outer of the downhole robot, the control parameters are drilling-fluid displacement, circulation area of the EPTV, and pressure of the EPOV. Moreover, it is found that the relationship of WOB and ROP in the combined control method is a surface rather than a line in a 2D coordinate. Therefore, the downhole robot can be adjusted while drilling at a stable ROP or a stable WOB. Finally, the combined control method of WOB and ROP with the downhole robot proposed in this paper was verified with an experiment. According to the experimental data, it is further found that an EPOV cannot only control WOB and ROP, but also can control the upper limit of WOB fluctuation. Thus, the control of WOB fluctuation can protect the bit from damage and prolong the life of the bit. This paper presents a foundation for the control of WOB and ROP with downhole robots. It has scientific and engineering significance for promoting downhole robots in drilling engineering.

Growing Interface with Phase Separation and Spontaneous Convection during Hydrodynamically Stable Displacement

The displacement of one fluid by another is an important process, not only in industrial and environmental fields, such as chromatography, enhanced oil recovery, and CO2 sequestration, but also material processing, such as Lost Foam Casting. Even during hydrodynamically stable fluid displacement where a more viscous fluid displaces a less viscous fluid in porous media or in Hele-Shaw cells, the growing interface fluctuates slightly. This fluctuation is attributed to thermodynamic conditions, which can be categorized as the following systems: fully miscible, partially miscible, and immiscible. The dynamics of these three systems differ significantly. Here, we analyze interfacial fluctuations under the three systems using Family–Vicsek scaling and calculate the scaling indexes. We discovered that the roughness exponent, , and growth exponent, , of the partially miscible case are larger than those of the immiscible and fully miscible cases due to the effects of the Korteweg convection as induced during phase separation. Moreover, it is confirmed that fluctuations in all systems with steady values of and are represented as a single curve, which implies that accurate predictions for the growing interface with fluctuations in Hele-Shaw flows can be accomplished at any scale and time, regardless of the miscibility conditions.