Remaining Oil In Place Research Articles

Material Balance Applied to Dynamic Reservoir-Surveillance Patterns

Summary Determining the remaining spatial oil-saturation distribution or current reservoir-pressure distribution for a mature (water, solvent, CO2) flood is a cornerstone of reservoir management for improving sweep and selecting infill-well locations. Decisions of these types are typically supported by reservoir flow simulation models that have been calibrated to historical injection/production data. In this paper, we present a novel-pattern material-balance (PatMB) approach to estimating remaining fluids in place as an alternative to flow simulation. First, we use the historical injection/production volumes to solve for streamlines and streamline-derived pattern metrics such as well-allocation factors and injector/producer-pair reservoir pore volumes (PVs). Then, we apply material balance on these volumes over time to estimate the remaining oil in place (ROIP) and pressures at the end of history. Resembling reservoir simulation, the method considers changing well patterns through time, requires a 3D static geological model, and yields 3D saturation distributions of oil, water, and gas. However, unlike reservoir simulation, because historical injected and produced voidage terms are honored, calibration is only possible through the 3D distribution of PV and fluids initially in place. We present results for the Berrymoor-pattern waterflood and show that the ROIP distribution is a strong function of the original-oil-in-place (OOIP) distribution, well locations, and historical oil, gas, and water production/injection volumes. For this case, the ROIP distribution is almost insensitive to interwell permeability distributions, suggesting that the primary focus when estimating ROIP with the PatMB approach is to ensure a good estimate of OOIP, major flow units, and the correct injection/production data. We also compare our method to reservoir flow simulation for a large water/hydrocarbon miscible flood (HCMF), and we observed that the ROIP maps compare well, with both methods highlighting similar areas for potential infill locations. However, the remaining-gas-in-place maps differed with PatMB, showing a more diffused distribution than flow simulation of the gas. We attribute the difference to the fact that PatMB does not account for transport effects such as separation of the phases caused by density differences.

Synthesis and Characterization of Yttrium Iron Garnet (YIG) Nanoparticles Activated by Electromagnetic Wave in Enhanced Oil Recovery

Due to the geographical location and technological limitation, various novel enhanced oil recovery (EOR) methods has been proposed to recover the remaining oil from a depleted oil reservoir. Research on application of nanoparticles either on its own or coupled with other stimulating agents has been growing enormously and some of them have shown a promising future. In high temperature and high pressure reservoirs, thermal degradation will cause failure to the conventional chemicals. In this work, temperature-stable YIG magnetic nanoparticles with an electromagnetic wave has been proposed as a new candidate for reservoir stimulating agent. The purpose of nanoparticle injection is to increase the sweep efficiency in the reservoir by increasing the viscosity of displacing fluid. In this research, Yttrium iron garnet (YIG) nanoparticles have been injected into a waterflooded oil saturated porous medium to recover the remaining oil in the presence of an electromagnetic wave. At the sintering temperature 1200°C, a mixture of hematite and YIG was obtained, suggesting a higher temperature for single phase YIG. From VSM analysis, the average magnetic saturation, coercivity and remanence are 18.17 emu/g, 21.73 Oe and 2.38 emu/g, respectively. 1.0 wt% of YIG nanofluid was prepared and subsequently injected into the pre-saturated porous medium in the presence of square electromagnetic wave of 13.6 MHz. As much as 43.64% of the remaining oil in place (ROIP) was recovered following the injection of 2 pore volume of YIG nanofluid.

Influence of wettability and permeability heterogeneity on miscible CO2 flooding efficiency

CO2 flooding is a proven enhanced oil recovery (EOR) technique and is also considered as a potential method for CO2 sequestration. Despite having successful field trials on CO2 EOR, the effects of reservoir wettability and permeability heterogeneity on the efficiency of miscible CO2 flooding are not well understood. In this work, laboratory investigations have been carried out to evaluate the influence of these properties on the miscible CO2 EOR performance. The wettability of hydrophilic Berea core samples was altered to be oil-wet by vacuum saturation of the clean and dry core samples with n-hexadecane. The permeability heterogeneity was obtained by combining two half pieces of axially split water-wet core samples of different permeabilities. Core flooding experiments were conducted for n-hexadecane – synthetic brine – CO2 systems at 1400psig backpressure to achieve minimum miscibility pressure (MMP) of CO2 in n-hexadecane at the test temperature (24±1°C). It was found that wettability strongly influences CO2 EOR. For the alternate cases of previously brine flooded (to remaining oil saturation) oil-wet and water-wet core samples, five pore volumes (PVs) of CO2 recovered 100% and only 43% of remaining oil in place (ROIP) respectively. Three PVs of CO2 could recover only about 0–5% ROIP from the split core samples. The mechanisms underlying these results are discussed. This study sheds light on the significant influence of reservoir wettability and permeability heterogeneity on the performance of miscible CO2 EOR.

Understanding Volumetric Sweep Efficiency in SAGD Projects

Abstract An understanding of volumetric sweep and capture efficiency are critical to optimizing SAGD projects. Capture efficiency refers to how much mobilized and heated oil is actually produced. Volumetric sweep efficiency can be estimated reasonably well for SAGD pilots having an abundance of information. A rich data set may include geological, petrophysical, production, injection, pressure, temperature observation and 4D seismic data. With this information, excellent insight into steam chamber development can be assessed. However, determining volumetric sweep and op­timal strategies is a problem where data are sparse. This paper summarizes analytical SAGD surveillance methods that estimate volumetric sweep and presents a work flow that can help optimize SAGD processes with limited data. Although the methods each have their assumptions and are not perfect, there is general agreement. The various techniques are corroborated using public core, injection/production, temperature observation and 4D seismic for the Surmont and Christina Lake pilot projects. Introduction Evaluating reservoir performance through the surveillance of production data is an excellent reservoir management tool. For waterflooding, this can be achieved through a conformance plot(1) that indicates how efficiently net water throughput affects recovery. Associating a water balance with an oil balance enhances the understanding of the influx/efflux of fluids and outer boundary losses out of zones. The plot works well for waterfloods because of the low compressibility of the fluids. For SAGD, a similar surveillance principle using abundant data is applied. However, a material balance alone is not definitive because SAGD is an energy-intensive process where steam is required to reduce the oil viscosity to a point where it will flow. Therefore, accounting for the energy within the SAGD process provides a different perspective for multiple geologies and heterogeneities. Typical objectives of SAGD surveillance using production and monitoring data are to determine: Original oil in place (OOIP) Remaining oil in place (ROIP) Mobile ROIP distribution and current condition (saturation, temperature and pressure) Limiting factors in recovery Potential improvements to economic oil recovery Recovery profile and optimizing recovery factor Operating strategies to achieve better volumetric sweep