فهرست مطالب ahmed zoeir

Oil extraction from weak sandstone formations that fails under changing in situ stresses leads to fine migration in near wellbore regions. Companies use selective completion practices or downhole filters to control particle production in oil wells. However, fines with various size dispersions will always remain that cause erosion damage in crude oil pipelines. Particles influence oil viscosity as well as density therefore impact flow regime rather than pressure drop in various depths. In this work, we employ Fluent software to simulate particle transport with the multiphase flow in the annulus that models cutting extraction during drilling rather than pipes which simulates the production process. We further estimate damage due to erosive flow under different flow regimes via adjusting various dissimilar particle dispersion functions. Results show erosion damage is at its highest value since a thin film of liquid slurry with high particle concentration forms near the inner wall pipe in the annular flow regime. Outcomes also illustrate that at high drill pipe rotation rates, flow conflicts therefore erosion damage in the annulus increases significantly.

Fractured carbonate reservoirs account for 25% of world’s total oil resources and for 90% of Iranian oil reserves. Since calcite and dolomite minerals are oil wet, gas oil gravity drainage (GOGD) is known as the most influencing production mechanism. The most important issue within gas injection into fractured media is the channeling problem which makes the efficiency of gas injection process extremely low. As a solution, foam is used to change the mobility ratio, to increase volumetric sweep efficiency, and to overcome the fingering problem. In this work, we inspected three main influencing mechanisms that affect oil extraction from matrix, namely foam/oil gravity drainage, viscous pressure drop  due to foam flow in fractures, and foaming agent diffusion from fractures into the matrixes. Foam injection simulations were performed using CMG STARS 2015, on a single matrix unit model and on some vertical cross section models. A number of sensitivity analyses were performed on foam strength, injection rate, fracture and matrix properties, matrix heights, and the initial oil saturation within matrixes. The results show that the roles of the mass transfer of the foaming agent and viscous pressure drop  are significant, especially when matrix average heights are small. Moreover, the mechanism for viscous pressure drop  remains unchanged, which continues to aid oil extraction from matrixes while the other two mechanisms weaken with time.

Future exploitation scheme of an oil reservoir in each cycle within its production life depends on the profitability of the current extraction scenario compared with predicted recoveries that acquire with applying other available methods. In fractured reservoirs appropriate time to pass from the gas injection process into chemical enhanced oil recovery (EOR) firmly depends on the oil extraction efficiency within the gas invaded zone. Several variables including fluid characteristic, fracture network and matrix units properties, etc., impact gas-oil gravity drainage (GOGD) performance within the gas invaded zone. In this work, CMG GEM and ECLIPSE 300 were used to simulate GOGD mechanism in several 2D cross-sectional models to investigate effects of the matrix height, matrix rock type, fracture network transmissibility, and miscibility conditions on the oil extraction rate, change of average pressure and producing gas-oil ratio (GOR). Results showed that in small heights of the matrix units especially at compacted rock types, GOGD was weak that caused a rapid decrease in oil production rates and early increase in producing GOR. Results also showed that wherever the matrix porosity and permeability values were high, recovery was accelerated and GOR remained constant for longer exploitation times. Furthermore, using high-pressure lean gas injection for miscible GOGD gives higher extraction efficiencies rather than applying rich or enriched gas.

With significant increase of tomographic equipment power, demand for Prediction relative permeability prediction Predicting in porous media from digital image data. In this work, it is predicted three -phase relative permeabilities with co-applying Darcy’s and Stokes equations in two case studies, namely Bentheimer sandstone and Estaillades limestone which their micro-CT data files were downloaded from Imperial College website. In order to perform calculations firstly we extracted pore connected network from the micro-CT data and it is estimated fluids distribution within pore channels during two-phase flow. Then we calculated pressure distribution of each phase solving its continuity and momentum equations within the obtained connected phase network. Pressure distribution and fixed volumetric flow rate ( that flows through all cross-sections perpendicular to the supposed flow direction), then were applied to solve for effective permeabilities. Effective permeabilities were then related to the relevant saturation and curves of two -phase relative permeabilities were derived in this manner. Stone’s equation was finally applied to estimate three phase permeability ternary curves. Results showed that application of correlations for determining fluid distributions is accurate enough for multiphase relative permeability estimation in real case studies. This paper also shows that performing calculations on the segmented REVs is more accurate than work on simplified pore network models extracted from micro-CT data. 

The routine measurement of direction-dependent reservoir rock properties like permeability often takes place along the axial direction of core samples. As permeability is a tensor property of porous materials, it should be fully described by a tensor matrix or by three main permeabilities in principal directions. Due to compaction, cementation, and other lithification processes, which take place after sedimentation, or later distortion and fractionation of the regional earth’s crust, the axial direction of core samples, may not be always one of the main permeability directions. In this paper, a computational technique to find principal permeability directions from micro-CT images of core samples was developed by us. Moreover, an assumed cube inside the core sample data with dimensions small enough to be able to imaginarily rotate inside the core limits has been chosen by us. Also, connected pore network was extracted from micro-CT data, and permeability was calculated in all space directions. In addition, stepwise rotation process continued until all possible space directions were covered. Then calculated permeabilities from all directions have been compared with each other by us. Afterwards, maximum and minimum values have been found by us. In this paper, two micro-CT datasets, which were taken from the Imperial College website, are used. Finally, the obtained results showed that the direction of maximum permeability within the carbonate core sample is about 30° deviation from the axial core direction. In addition to the main direction, the proposed computational technique can be effectively used to describe the permeability tensor of the reservoir rocks.

In sour gas flares,  content like any other components in inlet gas influences adiabatic flame temperature, which, in turn, impacts on the pollutant emission. Wherever flame temperature increases, the endothermic reaction between  and  is accelerated, which means higher  emission to the atmosphere. In this work, we developed an in-house MATLAB code to provide an environment for combustion calculations. Then, this written code was used to perform sensitivity analyses on  content, air temperature, and excess air ratio in sour gas flares. We used Environmental Protection Agency (EPA) reports to assign weighting indexes to each air contaminant according to its harmfulness to environment; thereafter, sour gas flaring conditions were optimized for two real field case studies, namely Ahwaz (AMAK) and South Pars, to reach the minimum integrated pollutant concentrations. The results show that each 2% increase in the  content of the entrance feed may produce 0.3% additional  in the exhaust. The results also confirm that decreases of 20 °F and 50 °F in the oxidant temperature cause  emission to reduce by 0.5% to 1% respectively. Finally, to verify and validate our results acquired from the written MATLAB code, FRNC 2012 industrial software was used to duplicate the oxidation results for the two sour flare case studies.

Application of foam in EOR, increases macroscopic sweep efficiency via awesome increscent of mobility control. Macroscopic manifestation of foam application performance in porous media is complex process that involves several interacting microscopic foam events. Stability as an important factor in foam injection within large reservoirs, depends on several variables including oil saturation, connate water salinity and the foam texture. In addition to mentioned parameters, internal structure is known to affect the foam’s stability and performance via influencing foam formation and destruction mechanisms within the porous media. In this paper we mathematically expressed main mechanism of snap-off for foam generation, mechanisms of capillary suction and diffusion coarsening for foam coalescences in some simplified models. Then we extended the calculations to more realistic 2D spherical models of porous media which were manufactured applying some morphological parameters. Simulation results show that in topologies in which the structure represents high difference in pore and throat average diameters, foam formation mechanisms are dominant making foam flow more stable while conversely when the path tortuosity is high, foam destruction mechanisms overcome and the stability decreases.

Despite advancements in specifying 3D internal microstructure of reservoir rocks, identifying some sensitive phenomenons are still problematic particularly due to image resolution limitation. Discretization study on such CT-scan data always has encountered with such conflicts that the original data do not fully describe the real porous media. As an alternative attractive approach, one can reconstruct porous media to generate pore space representations. The reconstructed structures are then used for simulations using some sort of discretization. In this paper, It is examined the effect of discretization on porosity and saturation calculations in porous media models. Some 3D Boolean models of random overlapping spheres of fixed and variable diameters in three dimensions are used. The generated models are then discretized over 3D grids with different number of voxels. The porosity can be calculated and saturation of the discretized models are then compared with the analytical solutions. The results show that when meshgrid sizes are 8% of smallest grains, porosity is calculated with 95% precision. In addition to that, meshgrid sizes of 5% and 3% of average grain diameter are adequate to calculate non-wetting and wetting phase saturations with at least 95% precision. This helps in choosing the optimum voxel size required in imaging for efficiently use of available computational facility