Reservoir structural strategies on the integrity of gas mobility ratio.

In this study, four commonly injected EOR gases, CH4, N2, Air, and CO2, have been simultaneously investigated through an experimental method to determine the effect and correlational relevance of 28 structural and 22 fluid quantities to mobility ratio integrity. An experimental method involving five analogous structural strategies has been conducted. A total of 1,920 experimental runs were executed, and 15,360 data points were generated. The results revealed that the mobility ratio is significantly affected by the structural and fluid realities of the EOR process. The mobility integrity for the four gases were correlated to Reservoir Quality and Transmissibility variations the most. Overall the mobilities of the four gases experienced correlational variations for 12 structural parameters. Fourteen of the fluid properties have correlational relevance to CH4 mobility. N2 and CO2 have 11, and Air has 10. The findings from this study can be directly applied in selecting suitable injection gas and screening reservoirs so that the correlational dynamics are favourable to mobility objective and integrity, thereby optimising oil recovery in hetrogeneous reservoirs

Experimental determination of carbon capture and sequestration response to reservoir quantities.

Reservoir entities can be classified into geological, geometrical and fluidic. To complicate matters, reservoirs are usually set in geological layers, such that each layer interacts with injected and resident fluids differently. Carbon dioxide (CO2) is one of the fluids injected in reservoirs. This injection process achieves both economic and environmental benefits. On the one hand, the CO2 injection increases oil production in a process called CO2 Enhanced Oil Recovery (CO2 EOR). On the other hand, it engenders the storage of CO2 in subsurface geological sites to reduce greenhouse gas and mitigate global warming in a process called Carbon Capture and Sequestration (CCS). Consequently, CO2 injection has to effectively couple with these reservoirs entities individually and collectively to achieve CO2 EOR and sequestration optimisations. Other investigators have not properly documented the CO2 sequestration optimisation subject area in light of its response to reservoirs entities. Hence the purpose of this study is to offer information on this area. Rigorous data mining and experimental methods have been applied to characterise and determine CCS response to the petrophysical quantities of reservoirs. The data mining analysis phase indicate that reservoirs’ suitability to CO2 EOR application can be characterised by reservoir petrophysical quantities, such as permeability, porosity, oil viscosity and API gravity. In the experimental phase, five analogous core samples with varying structural quantities were used. The empirical analysis investigated the response of CCS to 20 reservoir quantities. Reservoirs are natural replicas of industrial materials such as nano, ceramics and silicate materials. Although reservoirs are made of sedimentations of sandstones, shale and carbonate, they however, significantly share similar physical property characteristics with the aforementioned industry material. The characterisation of reservoir rock pores size includes nanopores in shale and microspores in sandstone rocks. Similarly, authors characterisation of permeability in reservoir rocks is similar to that of industrial materials such as ceramic membranes. Consequently, these materials can be aptly used to study the carbon capture and sequestration CCS in reservoir rock to a significant degree of accuracy. The series of graphs generated in the course of the investigation show that the relationship between CCS and the petrophysical quantities ranges from linear to higher-order polynomial. The results demonstrated that CCS directly responds to pore size and gas density. CSS inversely responds to the aspect ratio, pore density, specific surface area, and displacement pressure. Furthermore, CCS is found to be responsive to porosity, tortuosity and permeability in the third-order polynomial. The research outcome provides a deeper understanding of CCS optimisation in structurally complicated multilayer reservoirs. The result also provides utility in investigating CCS response to the variability encountered in reservoir systems

Gas injection power requirements in gas enhanced oil recovery (EOR).

The purpose of this study is to investigate the geological and engineering factors that affect the compressor power requirement of the gases (CH4, N2, Air, and CO2) injected into reservoirs pores to displace trapped oil. This gas -oil displacement process is called Gas Enhanced Oil Recovery (GEOR) and it is a well developed research area. However, little is known about the power requirement and competitiveness of the respective gases. Power requirement in reservoir management has economic and technical implications, and gas compression/injection cost is a significant unit in the power cost centre , hence low compression power demand is desired in GEOR processes. Granted the gases have different fluid properties such as viscosity, density, specific heat capacity. It is hypothesised that the gases distinctive characteristics might couple with the reservoirs geological settings differently, such that the power required to achieve certain compression and displacement magnitude would differ from gas to gas and from one reservoir layer to another. This study aims to identify the gas and geological settings that enable compression power optimisation in the gas EOR process. The study used two empirical methods, that is, data mining and experimental. Data mining of field data from over 450 oilfields were analysed to qualitatively discover patterns for power characterisation of Gas EOR processes. Subsequently, an experimental method was conducted to quantitatively evaluate the respective gases competitiveness. The minimum power required for a steady-state permeation is estimated from the respective threshold displacement pressures (TDP), which were calculated from Darcy flow rates for several analogous core samples with varying structural parameters such as porosity, permeability, number of pores and thickness . The experimental results implicated reservoir structural parameters as the major determining factors for the power requirement of GEOR processes. A scatter plot of gas TDP for the respective EOR gases as a function of their injection power requirements or ratings was presented in the study. The mean values of the gas TDP suggest N2 requires a relatively high compressor rating, while CO2 requires the least ratings. Therefore, CO2 is the most competitive gas. The coefficient of variation (CV) analysis shows N2 gas injection power rating is the most affected by structural variability or reservoir heterogeneity. The competitive ranking for power requirement is experimentally determined as CO2, >Air, > CH4, > N2. The information from this study can be directly applied in selecting gas and screening reservoirs for GROR processes. It can also find application in gas separation processes such as the separation between CO2 and CH4 in biogas production