Oyinkepreye D. Orodu

Influence and Sensitivity Study of Matrix Shrinkage and Swelling on Enhanced Coalbed Methane Production and CO2 Sequestration with Mixed Gas Injection

Matrix compressibility, shrinkage and swelling can cause profound changes in porosity and permeability of coalbed during gas sorption and desorption. These factors affect the distribution of pressure, methane production and CO2 sequestration. This paper compares the effects of cleat compression and matrix shrinkage and swelling models with the injection of different compositional gas mixtures (CO2 and N2). It shows that well performance, pressure distribution and properties of the seam are strongly affected by matrix shrinkage and swelling. Matrix shrinkage and swelling also affects net present value of the enhanced coalbed methane recovery scheme. In order to select the best enhanced coalbed methane recovery schemes, economic evaluation and sensitivity studies are necessary.

Optimizing the rheological properties of silica nano-modified bentonite mud using overlaid contour plot and estimation of maximum or upper shear stress limit

Abstract An optimization based statistical (response surface) approach was used to evaluate the rheological properties of bentonite mud treated with silica nanoparticles. The overlaid contour plot established the feasible region for the various factor settings from multiple regression equations. The steepest method was used to further determine the optimal factor settings for minimum rheological properties and this was established at 6.3 wt.% bentonite content and 0.94 wt.% silica nanoparticles. The rheological properties of the bentonite mud containing and without silica nanoparticles was evaluated using a Hyperbolic (new) model and related with other oil industry based models: Herschel Bulkley, Sisko, Casson. The hyperbolic rheological model estimated the rheological behaviour of the nano-modified mud satisfactorily while also predicting a shear stress limit for the nano-modified mud. The maximum shear stress limit values for 6.3, 13 and 15 wt.% mud were 14.59, 61.74 and 107.4 Pa respectively. Upper shear stress values obtained from a 1.5 wt.% silica nanoparticle modified 6.3, 13 and 15 wt.% bentonite mud were 22.27, 72.62 and 171.3 Pa respectively, which represents an increment of 34.5 to 37.4% in the upper limit of shear stress. The effect of silica nanoparticles on the upper shear stress limit was quantified using a response surface design.

The Performance of a High Paraffin Reservoir Under Non-isothermal Waterflooding

This study analyzes the performance of a high paraffin reservoir under cold waterflooding for 17 years using a 3-D finite difference simulator and analytical solution of injection wellbore temperature profile to upgrade reservoir management strategies. The reservoir has been marked by injectivity issues, early injection rate decline by half initial values and low incremental recovery, hence subject to alternate developmental schemes. The influence of cold waterflooding is assessed from simulated temperature maps due to nonisothermal injection and solution of injection well temperature profile.

SIMULATION STUDY ON WATERFLOOD FRONT: BLOCK HADE OF TARIM OILFIELD IN NORTHWEST CHINA

Block Hade consist of a deep thin sandstone reservoir of two sub-layer reservoirs. The thickness is about 1.5 m for each layer. The two-layer “staircase” horizontal well is used for recovery. In order to determine water displacement front and edge water movement, tracer test is conducted in the reservoir. But the cycle of field tracer monitoring is about 150-360 days. This prevented the efficient monitoring of waterflood swept area and waterflood advance direction and velocity, after the cycle of tracer monitoring. Conservation of mass with respect to tracer flow and history performance matching of tracer enabled the study of water-flood front and edge-water advance. The simulation result is basically consistent with the monitored field tracer results. Therefore, numerical model can be used to conduct a longer monitoring period. It can make up for the disadvantage of the complexity of the tracer monitoring setup, its implementation, and time-consuming monitoring cycle. The water-flood front, water-flood swept area, advancing velocity and the predominant water injection direction can be obtained. Furthermore, it is possible to evaluate and predict the injection-production well interaction and can also provide a reliable basis to deploy reasonable flood patterns to enhance oil recovery. Keyword: waterflood front; tracer monitoring; simulation; Hade reservoir.

Case Study of the Impact of Cold and Hot Waterflooding Performance by Simulation and Experiment of High Pour Point Oil Reservoir,, Liaohe Oilfield, North-East China

Block Shen-95 has been under cold waterflooding for 17 years. Of particular interest is the low recovery of 11.27% for the North Block due to crude oil cloud point being very close to the reservoir temperature. Formation damage near the wellbore region is controlled at production wells by hot-oiling and low injection rates of non-isothermal waterflooding. Optimizing production necessitated looking at core-scale experiment and reservoir-scale simulation waterflooding performance at different temperatures. The intent also, is basically to condition core-scale flooding observations to properly initialize the numerical model. Based on experiment carried out on core samples, sharp decline in oil displacement efficiency occurred, increase in residual oil saturation and increase in the intensity of formation damage below the cloud point. Reservoir simulation depicted decline in production with decreasing flooding temperature captured specifically by change in viscosity around the wellbore region. Change in flow dynamics due to change in relative permeability was not efficiently captured and formation damage impact on porosity and permeability. Reservoir-scale performance for high pour point oil reservoir can better be understood by considering the effects of formation damage on storativity and transmissibility, and fluid rheology. The irreversible process of wax precipitation may cause permanent damage if further from the wellbore region

Descriptive statistics and probability distributions of volumetric parameters of a Nigerian heavy oil and bitumen deposit

The absence of geostatistical modeling of volumetric parameters of the long-discovered Nigerian heavy oil and bitumen deposits is responsible for the inconsistencies surrounding estimates of hydrocarbon-in-place contained therein. An exploratory data analysis (EDA) is a pre-cursor to such modeling. As part of EDA, this work presents the descriptive statistics and probability distributions of the volumetric parameters of a Nigerian heavy oil and bitumen deposit. Raw data from the existing works have been assembled into a database. Using basic principles, porosity have been computed, from the raw data, for several core samples retrieved from the two bituminous horizons in the deposit. The computed database has been partitioned into the two horizons, using depth-to-top and thickness data. Furthermore, this work has conducted detailed analyses and offers robust discussions on the descriptive statistics and probability distributions of the porosity, depth-to-top, and thickness databases. The statistics and distribution curves obtained are observed to exhibit good correlations with existing geologic, stratigraphic, and textural data. An hypothesis suggesting the two horizons belong to same geological population has been formulated and tested at field and well levels; with results affirming the hypothesis. The descriptive statistics and probability distributions obtained offer a significant understanding of the characteristics and features of the available data. In addition, the distributions now become prior information to which reservoir descriptions would be constrained, in the future conditional simulation stage of this work. The correlation of core data obtained here with the existing geologic, stratigraphic, and textural data would promote data integration in the characterization of this deposit.

Rheology of Gum Arabic Polymer and Gum Arabic Coated Nanoparticle for enhanced recovery of Nigerian medium crude oil under varying temperatures

The dataset in this article are related to the rheology of dispersions containing Gum Arabic coated Alumina Nanoparticles (GCNPs) and Gum Arabic (GA) polymer for Enhanced Oil Recovery (EOR) of Nigerian medium crude oil under varying temperatures. The data included the viscosity of the dispersion containing GCNPs compared to GA at different shear rates. In addition, data on the rheological properties (plastic viscosity, yield point, and apparent viscosity) of the dispersions under varying temperatures was also presented.

Dataset on experimental investigation of gum arabic coated alumina nanoparticles for enhanced recovery of nigerian medium crude oil

The dataset in this article are related to an experimental Enhanced Oil Recovery (EOR) scheme involving the use of dispersions containing Gum Arabic coated Alumina Nanoparticles (GCNPs) for Nigerian medium crude oil. The result contained in the dataset showed a 7.18% (5 wt% GCNPs), 7.81% (5 wt% GCNPs), and 5.61% (3 wt% GCNPs) improvement in the recovery oil beyond the water flooding stage for core samples A, B, and C respectively. Also, the improvement in recovery of the medium crude oil by the GCNPs dispersions when compared to Gum Arabic polymer flooding was evident in the dataset.

Uncertainty assessment of onset sand prediction model for reservoir applications

Abstract Modeling physical systems in engineering always comes with uncertainties in terms of the model’s input parameters. These uncertainties are also present in modeling the onset of sand production, even though considerable effort may be required in incorporating uncertainties into the process of modeling, because getting it right will definitely provide important knowledge about the input parameters for predicting the onset of sanding which provides useful hints that inform apt decision-making for sand control. In this study, a Monte Carlo simulation of some parametric input variables alongside the incorporation of the Hoek–Brown material constants was investigated using a predictive model for sand production anchored on Hoek–Brown failure criterion, so as to rank some key input uncertainties in order of the effect their magnitudinal disparities on the model output. The key inputs in the model are reservoir pressure, rock strength (uniaxial compressive strength, UCS), minimum horizontal stress, Poisson’s ratio and Hoek–Brown material constants M and S. Different diagnostic Tornado and spider plots were generated and interpreted for two wells and it was observed that the predicted well pressure is most sensitive to rock strength and generally has an inverse relationship with the rock strength. The parametric study on Hoek–Brown material constants shows that higher values of M and S correspond to lower minimum well pressure at which sanding is expected. The model is a useful tool for a quick assessment of the onset of sanding in reservoir rocks and can also be used to evaluate the effect of different rock mechanical properties.

Modelling the Effect of Composition Change During Condensate Dropout in a Horizontal Gas Well

This paper presents a mathematical model describing the behavior analysis for a two-phased gas-condensate system narrowing down on the three zone method. The three zone method accounts for the composition change in the reservoir and is based on modeling the depletion by three main flow regions: • A near wellbore region (Region 1) where the oil saturation is important allowing both phase, vapor and liquid to be mobile. • Region 2 where condensate and gas are present but only the gas is mobile. • An outer Region 3 exists when the reservoir pressure is greater than the initial gas dew point and contains only gas. This research proposed a fourth region (Region I) which is the immediate vicinity of the well where accumulation of liquid buildup at high rates which yielded from an increase of liquid saturation and a probable decrease in gas relative permeability. The existence of the fourth region or flushed zone is particularly important as it represent the total skin effect: mechanical skin, rate dependent two-phase skin and skin due to gas condensate blockage. The calculated well deliverability rate using the modeled equation for gas condensate reservoir showed a relatively high difference when compared to other known equations. This significant difference is as a result of the effects of the proposed Region I. The developed correlation confirms that as the pressure drops below dew point there occurs condensate banking which when the critical saturation is reached becomes mobile and leads to a reduction in gas flow rate in the reservoir.