Category Archives: New publication

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PPG modeling and simulation in JPSE

Category : New publication

Dr. Amir Farasat (alumni PhD. student at TMU) and Mr. Hossein Younesian-Farid (alumni Msc. student) from PermLab could publish their fundings on PPG flooding into mature waterflooded reservoirs in JPSE. Congrats to both of them for their great effort in finalizing this paper.

Conformance control study of preformed particle gels (PPGs) in mature waterflooded reservoirs: numerical and experimental investigations

In this study, a new mathematical transport model of PPG injection in mature waterflooded reservoirs is developed. The model is based on the experimental results of PPG swelling ratio and entrapment analyses in a carbonate rock sample. The entrapment is considered a function of the PPG-to-pore size ratio, fluid velocity, temperature, salinity, PPG concentration, and swelling ratio. The formulations of the resistance factor (RF) and residual resistance factor (RRF) are obtained from the injection experiment results at various fluid velocity and PPG concentrations. The entrapment model is coupled with the transport equations of the MATLAB Reservoir Simulation Toolbox (MRST). The model is validated by predicting the pressure drop changes during the 1D PPG injection experiments at three different flow rates. The validated model is then used to predict PPG transport behavior in several 3D field-scale scenarios.

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Abolfazl did a great job in Adv. Water Resour.

Category : New publication

Abolfazl Moslemipour could publish his findings from the MSc. thesis in Advance in Water Resources Journal. Many congrats to Abolfazl for this great achievement. The title of this paper is “Dual-Scale Pore Network Reconstruction of Vugular Carbonates using Multi-Scale Imaging Techniques“.

In this study, a dual-scale PNM was implemented to reconstruct the behavior of a vuggy carbonate sample. The rock sample was CT scanned at two different scales. At the macro-scale (i.e., vugular-network), a medical-CT scanner was used to image the rock sample at the resolution of 100 μm. The rock was also imaged by a micro-CT scanner at the resolution of 0.75 μm to extract the micro-scale properties (i.e., micro-network).

The vuggy carbonate rock. (a) A 1.5 inches plug sample was used for porosity and permeability measurement. (b) The end face of the plug sample. (c) The upper trim used for medical-CT imaging (d) A mini plug of the rock was used for micro-CT scanning. e) The bottom trim of the sample was used for MICP analysis.

A stochastically equivalent network based on the extracted micro-network properties was generated with a larger field of view (FOV). Then, vugs were randomly added to the reconstructed micro-network based on the properties of the macro-scale CT images. The result was a dual-scale unstructured irregular PNM. The results show that the reconstructed dual-scale PNM has very close properties to the laboratory measurement data of the real rock sample.

The boxplot diagram of the percolated and non-percolated systems of vugs in this study compared with that of the previous study.

Congrats Nader for his first publication

Nader Faramarzi could defend his MSc thesis with a successful grade. Also, he could recently publish his findings in the “Journal of Natural gas Science & Engineering“. Congrats Nader for his achievements and wish him the best.

The response of gas condensate reservoirs is directly influenced by heterogeneity. In such reservoirs, condensate is created around wellbore areas, when the reservoir pressure falls below the dew point pressure. Consequently, the distribution of this condensate bank makes fluid flow in the reservoir even more complicated by changing rock-fluid properties (e.g., relative permeability). This alteration can be assumed as a new heterogeneity, called fluid heterogeneity.

Fig. 1: Schematic of the condensate bank around a wellbore with three regions. In Region 3, there is only single-phase gas. In Region 2, gas and immobile condensate coexists. Region 1 contains both mobile condensate and gas phases.

The separation of fluid heterogeneity from rock heterogeneity is a challenging task. The main idea of this study was to investigate the transient pressure responses of a gas condensate reservoir to separate rock and fluid heterogeneities. Different homogeneous and heterogeneous reservoir models of a reservoir were constructed by the geostatistical approach. A commercial reservoir simulator was used to simulate the behavior of different drawdown and buildup scenarios. The fluid was a lean gas condensate selected from one of the Middle East formations. The wavelet transform (WT) approach was implemented to characterize the behavior of condensate banks for both homogeneous and heterogeneous models.

Fig. 2: Schematic of the DWT (i.e., applying high- and low-pass filters) on the pressure-transient data. Approximates and details are created at each level of WT as the outputs.

Analyzing the wavelet approximate and detail coefficients of the pressure-transient responses enabled us to distinguish the rock and fluid heterogeneities. The results showed that the wavelet detail coefficient could be a good indicator of reservoir heterogeneity. Moreover, the WT could be successfully used to distinguish different regions of a condensate bank inside the reservoir under study.

Fig. 3: Detail WTC of pressure-transient responses for a) scenario 1 (Pres>Pdew) and b) scenario 2 (Pres=Pdew). Peaks I and II are related to shutting in and opening the well, respectively. Peaks A and B are because of condensate bank creation during the buildup test. Peaks A’ and B’ appear as a result of the condensate bank during the drawdown test

Designing transparent rock micromodel in Permlab for reaction flow studies

Alireza Teimory during his MSc. thesis could design and manufacture a transparent micro model to study reactive flow in porous media. Congrats Alireza for his success. The cell of this study has two characteristics. First, it enables us to work on a real rock sample to investigate geochemical reactions by incorporating actual rocks. Second, it provides a visual observation capability to monitor the behavior of fluid injection into rocks. The transparent cell consists of two transparent Plexiglass plates. A square pocket was precisely machined at the center of the bottom plate to provide a holder for a slabbed rock to be installed in the cell. Bolts and nuts were used to stitch both plates together. An opaque silicon rubber O-ring was used between the plates to prevent any fluid leakage during the experiments. The designed cell was hydraulically tested up to 120 psi before the main experiments.

In the first application, we implemented the manufactured setup to investigate weak acid injection on fracture opening in calcite and dolomite reservoirs. The results were published in the “Petroleum Research” Journal.

In the second study, we investigated acid pre-flushing and pH-sensitive microgel injection in fractured carbonate rocks for conformance control purposes. First, the dependency of fracture aperture changes to the acid pre-flush flow rate was examined. Then, we investigated the effect of pH-sensitive microgel concentration on its resistance to block fractures during post-water flooding by studying the gel failure mechanisms (e.g., adhesive separation, cohesive failure). Finally, the effect of an initial aperture of fracture was examined on microgel washout when water injection is resumed. The results showed that both decreasing the acid flow rate and lowering the initial aperture could increase the rate of aperture changes. Moreover, the microgel solution with a concentration of 1 wt.% showed the highest resistance (98.2 psi/ft) against post-water injection. Additionally, this microgel concentration had the highest permeability reduction factor. Meanwhile, the smaller initial aperture of fracture contributed to a higher microgel resistance. The results were published in “Oil & Gas Science and Technology – Rev. IFP Energies Nouvelles“.

Permlab wishes Alireza the best in the next phase of his life.

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Matrix acidizing of sandstones

Hossein Younesian-Farid published his 2nd paper in the JPSE.  In this study, the interaction of citric acid, as a weak acid, with a sandstone core containing ankerite cement was investigated during matrix acidizing. The model, developed in Python, implemented a global implicit numerical approach to consider acid-rock geochemical interactions. The effect of multi-step dissociation of citric acid on lowering rock pH was investigated. The sugar-lump approach was used to estimate the behavior of the ions concentration originated from the variation of the reactive surface area (RSA). Moreover, the model outputs were validated against matrix sandstone acidizing experiments from the literature.

The concentration of non-ionized acetic acid across the core during the injection of citric acid.

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Speed-up of Soxhlet Core Cleaning in RCAL

Pouya Soltani has published his first paper at PermLab in the SPE Reservoir Evaluation & Engineering Journal. The main idea of this paper is to introduce a methodology of measuring the cleaning time that can be implemented as a routine screening tool in RCAL projects to nominate the proper solvent, which can reduce the Soxhlet cleaning time.

The process of running core analysis experiments (in both RCAL and SCAL) is very time-consuming. As all plug samples should be cleaned during the RCAL phase; therefore, finding of a solvent that can speed-up this process is necessary. The cleanliness of a core sample during Soxhlet extraction is usually determined by monitoring the color of solvents, qualitatively. The main contribution of this study was to propose a methodology during RCAL to nominate the best solvent during the Soxhlet cleaning experiments. By introducing a state-of-the-art quantitative method, the cleaning time of different solvents (i.e., tetrachloroethene, acetone, toluene, chloroform, xylene, and n-hexane) was investigated. This quantitative method is based on turbidity measurement of the solvent that siphons periodically from the Soxhlet extractor. Moreover, the wettability alteration of the implemented solvents was monitored by contact angle measurements.

Designed Soxhlet setup. a) Heater, b) Round-bottom flask, c) Two-neck extractor, d) Condenser, e) Sampling Syringe. The solvent samples are taken from part e by a needle syringe.

Farhoodi did great in JNGSE

Shahab Farhoodi, did great and published a very good paper (here) in Journal of Natural Gas Science & Engineering (JNGSE). We in this study payed attention to the analysis of the combined effect of geological heterogeneity and condensate drop out in condensate reservcoirs. A geostatistical approach was used to build reservoir models with different amount of heterogeneity. These models were simulated by a compositional reservoir simulator to generate pseudo-pressure data versus time of these heterogeneous models.

Condensate saturation, Scond, and pressure profile versus the radius from the wellbore, r, for a gas condensate reservoir. Different flow regimes are depicted during the production.

It was revealed that the intensity of the condensate formation around the wellbore is a strong function of the reservoir heterogeneity. The results showed that increasing of the model heterogeneity can entirely complicate the well-test responses when condensate drops near the wellbore region.

Bottomhole pressure and rate history of 10 days. The flowing and shut-in period is one day each.

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Geological Boundary Detection in JPSE

Category : New publication

Congratulations to Mohammad Amin Partovi, Msc student of petroleum engineering, for his recently published work about geological boundary detection from well-logs using pattern recognition techniques in Petroleum Science & Engineering.

In this study, we implemented an automatic well-to-well correlation approach based on pattern extraction from well-logs. The well-log patterns were recognized by calculating several statistical and fractal parameters. As a fractal parameter, we selected the wavelet standard deviation exponent, calculated by the discrete wavelet transform. Furthermore, to select the proper wavelet function, the energy to Shannon entropy ratio criterion was implemented. The statistical pattern recognition parameters of this study include average value, maximum to minimum ratio, coefficient of variation, and the trend angle of well-log data (i.e., Gamma ray log) in a window around the geological boundary. Moreover, the analysis of variance (ANOVA) tool and the Tukey multiple comparison method were implemented to evaluate the effectiveness of each parameter (i.e., fractal or statistical parameters) during the determination of boundary depths. The gamma ray logs from three wells of an oil field were used as a dataset for the evaluation of our algorithm. The outputs of our methodology were also compared with the new detrended fluctuation analysis (DFA) method, which show promising outcomes over it. The results show that the average value of the signal, among the analyzed parameters, is the most effective parameter; however, implementing the combination of all fractal and statistical parameters can improve the accuracy of the geological boundary detection.


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PermLab in IAMG2018

Category : New publication

Permlab has participated in IAMG2018, Olomouc, Czech Republic with two papers,

1-“Reconstruction of vugular carbonate rocks by pore network modeling and image-based network technique”, which was a collaboration between PermLab at TMU and PMEAL research group at Waterloo University.

2-“Modeling and simulation of geochemical reactions during acid pre-flush to improve conformance control of pH-sensitive polymer flooding” written by Hossein Younesian-Farid from PermLab.

Ali published his first paper

Category : New publication

Congrats to Ali Soltani for his publication in PhysicaA. This work models scaling & critical properties of percolation-like porous media. Both site & continuum systems with different well configurations were analyzed.