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Journal of Petroleum Science & Engineering
Elsevier Science B.V.
Journal of Petroleum Science & Engineering

Elsevier Science B.V.

0920-4105

Journal of Petroleum Science & Engineering/Journal Journal of Petroleum Science & Engineering
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    Oil generation model of the liptinite-rich coals;; Palaeogene in the Xihu Sag, East China Sea Shelf Basin

    Shuxia LiLongyi ShaoJinshui Liu
    16页
    查看更多>>摘要：Hydrocarbon generation from liptinite-rich coal is an important focus in petroleum geology as well as in coal geology. The confined pyrolysis experiment in gold tubes is an effective approach in assessing the hydrocarbon generation potential of coals. Xihu Sag is one of the most hydrocarbon-rich Cenozoic basins in the East China Sea Shelf Basin, and oil and gas are believed to be generated from Paleogene liptinite-rich coals. Coals from the Pinghu and Huagang formations of the Paleogene have a liptinite content mostly higher than 10%, and contain type II-III organic matter. The Hln^ values, H/C, and O/C ratios of these coals are in the range of 200-300 mg/g-TOC, 0.97 to 1.42, and 0.08 to 0.20, respectively. All these characteristics demonstrate good potential for these coals to generate oil. Experimental data show that the maximum cumulative yields of oil produced range from 122.74 to 154.09 mg/g-TOC, and the coals in the sag can also generate oil in their immature stage (Ro = 0.36%-0.5%) due to abundant resinite (mostly higher than 5%). To further assess the characteristics and processes of petroleum generation under geological conditions, we reconstructed the liquid hydrocarbon generation history of the coals in three structural units of Xihu Sag, i.e., the West Slope Belt, West Sub-sag, and Central Anticlinal Belt. For the coals in the Pinghu Formation, the West Slope Belt is a favorable oil-forming area, while the West Sub-sag and the Central Anticlinal Belt are less favorable oil-forming areas. For the coals in the Huagang Formation, the West Slope Belt is a favorable asphaltene (∑C_(14+)-forming area, while the West Sub-sag and Central Anticlinal Belt are favorable light hydrocarbon (∑C_(6-14)-forming areas. Results of this study will contribute to a better understanding of the characteristics and potential of oil generation from the liptinite-rich coals and are of significance for oil exploration in the Xihu Sag.
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    Synthesis, interfacial activity and rheological properties of low interfacial tension viscoelastic Gemini surfactants

    Shuyun FengZhaowen JiangShanfa Tang
    8页
    查看更多>>摘要：In order to develop a special surfactant that is suitable for improving oil recovery in low permeability reservoirs, and simultaneously meet the requirements of effectively improving sweep efficiency, displacement efficiency and good iniectability, a series of new Gemini surfactants (GAC-3m, m = 14,16,18) were synthesized and characterized by FTIR and 1HNMR. The surface activity, interfacial activity, thickening properties and viscoelasticity of GAC-3m solution were systematically studied. The mechanism of viscosity and elasticity enhancement were also discussed. The results showed that with increasing the carbon number of hydrophobic chain, the surface activity and interface activity of GAC-3m surfactant increased first and then decreased, the viscosity and elasticity gradually increased. The micelle microstructures changed from sheet to network-like, and the structural morphology was gradually complete and compact, which made the viscosity and elasticity of the GAC-3m surfactant solution increase. GAC-3m exhibit fascinating surface activity, interfacial activity and low values of CMC (<4.5 x 10"4 mol/L), which is conducive to the formation of micelle structure at low concentration. The 0.5% GAC-316 solution can substantially reduce the oil-water interfacial tension to ultralow values (10~3 mN/m), and also possess attractive viscosity (18.58 mPa s) and viscoelastic properties (tan8 = 0.5 < 1). In accordance with the experimental studies, the novel surfactants (GAC-3m) are a kind of low interfacial tension viscoelastic Gemini surfactant, promising in enhancing the recovery of low permeability reservoirs. The insights gained from this study contribute to enriching the theoretical research of the viscoelastic Gemini surfactant and promote the applications of low interfacial tension viscoelastic Gemini surfactant in the recovery of heterogeneous low permeability reservoirs fields.
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    Pore-fracture network alteration during forced and spontaneous imbibition processes in shale formation

    Yijin ZengYu PangShidong Ding
    10页
    查看更多>>摘要：Imbibition controls mass transfer in the complex pore-fracture network in shale, which may change the pore-fracture network and lead to a low efficient flowback of fracturing fluid. Thus, it is necessary to accurately characterize the pore-fracture network alteration during the imbibition process. In this study, forced and spontaneous imbibition tests were conducted under the confining pressure on selected shale core samples with induced fractures, collected from Longmaxi Formation, Sichuan Basin, China. The low-field nuclear magnetic resonance (NMR) spectrometer was employed to monitor the variation of pores and microfractures in the shale core samples during the dynamic imbibition process. In addition, optimal surface relaxivities, ranging from 0.019 to 0.033 [im/ms, were determined by comparing the NMR T2 distributions with the pore size distributions (PSDs) measured via high-pressure mercury intrusion (HPMI) tests. Then, the measured dynamic T2 spectra with three distinct peaks were converted into the corresponding PSDs to quantitatively analyze the number, size, and connectivity changes of small pores, large pores, and micro-fractures in shale. Results show that the total porosities of the four shale core samples are increased by 3.5%, 10.2%, 32.9%, and 36.3% after the imbibition tests. The forced imbibition leads to more remarkable improvements in the pore volume of large pores with radius between 0.2 and 3.6 jim. In contrast, the spontaneous imbibition results in more significant increases in the number and size of small pores with radius between 0.0004 and 0.36 μm. It is also found that the total porosity increment is primarily an outcome of small pore alteration during the imbibition. Moreover, the enlarged pores and micro-fractures are mainly categorized as the capillary bounded fluid pores and movable fluid pores, which significantly affect the efficiency of oil and gas transfer in shale. The findings of our study demonstrate the comprehensive effects of capillary force, clay hydration, osmotic potential, confining and pore pressures, and creep deformation and failure on the pore-fracture network alteration in shale and advance the understanding of the mechanisms behind the forced and spontaneous imbibition processes.
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    Optimization of injection water composition during low salinity water flooding in carbonate rocks;; A numerical simulation study

    Zahra NegahdariSabber KhandooziMojtaba Ghaedi
    12页
    查看更多>>摘要：Low salinity water flooding as a novel enhanced oil recovery method has gained increased attention especially during the past decade. Akin to other methods, low salinity water flooding carries some risks, being able to lead to failure in the target reservoir. To reduce the potential risk of incompatibility between injection water and initial crude-oil/brine/rock system, the composition of injection water needs to be optimized to prevent formation damage due to incompatibility problem. Moreover, careful selection of injection water composition would profoundly influence the performance of low salinity water flooding. In this study, a detailed workflow is presented to resolve problems in terms of maximizing wettability alteration and minimizing compatibility in a core model of carbonate rock. The proposed framework can be utilized to plan an effective low salinity water flooding injection. For simulation of low salinity water flooding, the method proposed in our previous work considering time-dependent wettability alteration was applied. Furthermore, genetic algorithm (GA) was utilized to optimize injection water composition. In the proposed method, a geochemical software (PHREEQC) was coupled with GA optimizer and a commercial numerical simulator. Prior to any numerical simulation, for each suggested scenario by GA, compatibility between injection and formation water was examined via mixing in this geochemical software and evaluation of saturation index. Results demonstrated that no unique optimized water composition can be advised for an efficient low salinity water flooding process. Furthermore, some suggestions are put forward for optimization of low salinity water flooding.
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    • NSTL

    Water-in-oil emulsion stability and demulsification via surface-active compounds;; A review

    Murtada Mohammed AbdulredhaSiti Aslina HussainLuqman Chuah Abdullah
    15页
    查看更多>>摘要：This paper aimed to review the research on emulsion formation, stability, chemical demulsification, and hydrophilic-lipophilic balance in chemical studies and other aspects related to emulsion thermodynamics. The global increase in energy demand pressures oil and gas producers to develop and explore a new source of energy. Crude oil is one of the indispensable sources produced from unconventional and conventional resources. It is accompanied by high water content during production activities, and this water is complex and has a high content of contaminants. This water is also produced in the form of foam or emulsion. Water-in-oil emulsion is considered as a common type in petroleum industry. Oil emulsion is very harmful due to the associated difficulties during the refining and transportation of crude oil and the limitation in the produced water discharge. The emulsion in petroleum industry is stable due to the natural surface-active compounds in crude oil. Thus, oilfield researchers need to study different utilization methods to demulsify emulsion. Chemical method is considered as an essential method in treating petroleum emulsion by using demulsifiers, such as non-ionic surfactant.
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    • NSTL

    Computing wave velocity of rock sample using rock chips and cuttings

    Parisa KhodaeiSadegh KarimpouliMartin Balcewicz
    11页
    查看更多>>摘要：Rock cuttings and chips, usually from boreholes, are considered as direct samples from the subsurface layers containing valuable information. They are rarely used in routine studies because of their imprecise depth, induced cracks during transfer, and saturation by mud fluid, however, mainly due to their small sizes. To investigate the latter, we computed P-and S-wave velocity of Ruhr and Bentheimer sandstones from 2D images using a 2D-to-3D procedure in Digital Rock Physics (DRP). We found that cuttings are problematic when;; a. the size of their images is smaller than Representative Elementary Volume (REV) and b. their porosity is medium to high. To overcome these problems, we introduce two methods based on Differential Effective Medium equations (equation-based method) and Cross-Correlation Simulation (CCSIM) (simulation-based method). From both sample preparation and computational perspectives, these methods are easy to apply, inexpensive and fast relative to standard 3D DRP. Results on Bentheimer and Berea sandstone and Grosmont carbonate showed that both methods are valid and reliable. In the best cases, they could compute wave velocity of rock with a root mean square error (RMSE) less than 100 m/s, which are comparable or, in some cases, even better than 3D DRP. The size of cuttings images could also be up to 5 and 3 times smaller than REV for the equation-and simulation-based methods, respectively, which is promising for practical purposes in the petroleum industry.
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    • NSTL

    Enhanced oil recovery by foam flooding using foam stabilized with modified Fe3O4 nanoparticles

    Qi LiuYusong ZhangXuesong Zhao
    11页
    查看更多>>摘要：Nanoparticles (NPs) could enhance the stability of foam to allow recovery of greater amounts of residual oil during foam flooding. However, conventional nanoparticles are non-recyclable and affect the quality of the produced oil. Magnetic nanoparticles could respond to magnetic field and be recycled for reuse, thus reducing the cost for enhanced oil recovery (EOR) process and improving the quality of the produced oil. In this study, Fe3O4 nanoparticles were used as foam stabilizer. The Fe3O4 nanoparticles were modified with tetraethyl orthosilicate (TEOS) and n-dodecyltrimethoxysilane (WD~(-1)0) to make them hydrophobic. The optimal nanoparticles were Fe3O4@SiO2-700 with a contact angle of 68.5°. Foam was generated by sodium dodecyl sulphate (SDS) surfactant and the longest drainage half-life time was 746 s in the 1 wt% NPs+0.23 wt% SDS+3 wt% NaCl foam system. After evaluating foam stability, the nanoparticles were recycled and reused to stabilize foam again, and the results indicated that recycling nanoparticles three times was optimal. Finally, the core flooding experiments showed that the nanoparticles stabilized foam EOR rate was 17.4% and the system obtained a greater pressure drop to improved sweep area. These results indicated that the magnetic nanoparticles could stabilize foam effectively and could be recycled by magnetic field to reuse in stabilizing foam. This study suggested directions for further studies concerned with the application of magnetic nanoparticles for enhanced oil recovery.
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    • NSTL

    Data assimilation for uncertainty reduction using different fidelity numerical models

    Celio MaschioGuilherme Daniel AvansiFelipe Bruno Mesquita da Silva
    18页
    查看更多>>摘要：Data assimilation (DA) for uncertainty reduction based on reservoir simulation models is generally an intense and high time-consuming process due to the number of uncertain parameters involved and the computational time required to run the flow simulation models. Depending on the degree of model description (fidelity), DA can take days or even weeks to be executed because it can take several hundred (or thousands) of reservoir simulations, even applying efficient DA methods. Since quick decisions on reservoir development and management phases have to be made, the process must be carried out in a suitable and affordable computational time. There are two complimentary ways of dealing with this problem;; the first is reducing the model simulation time (trying to maintain the quality of results), and the second is the application of efficient and effective DA methods. In this work, we propose a methodology that consists of generating and using efficient and effective lower-fidelity models (LFM), combined with the application of the Ensemble Smoother with Multiple Data Assimilation (ES-MDA) method which is the state-of-art on data assimilation combining efficiency and efficacy. The focus is to present a comprehensive and robust analysis of the DA process by assessing different model fidelities to achieve the best trade-oft between computational time and quality of results. We applied the methodology in a real field using six different fidelities;; an initial (fit-for-purpose) model named the medium-fidelity model (MFM) and five LFM. Their performances are benchmarked against the MFM results. For each fidelity model, we ran a DA process and compared the results, including (1) quality of data match and computational time, (2) prior and posterior attribute distributions, and (3) predictive capacity of the models. To conclude, we showed that the DA process using LFM reduced the computational time from days to hours, being up to about 11 times faster than the process using the original model with similar or even better results, making it clear the advantage of building, evaluating and selecting a lower-fidelity model based on the purpose of the study. This is important because, after the data assimilation, high number of reservoir simulations (typically thousands) is necessary for reliable decisions in the context of reservoir development and management.
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    • NSTL

    Transient behavior modeling of a multi-well horizontal pad in a reservoir with irregular boundary using boundary element method

    Hongyang ChuZhiming ChenXinwei Liao
    20页
    查看更多>>摘要：The probability of well interference in reservoirs has greatly increased due to the introduction of offsetting wells. At the early stage of production, the well connectivity is mainly through the connected fractures, but the well interference is time-dependent. The connected fractures may not remain open during the whole period of production. Therefore, it becomes essential to identify different types of interference. In this study, a new transient model based on the boundary element method (BEM) is presented to efficiently evaluate the targeted well's behaviors with the offsetting well production interference in 2D and 3D bounded formations. The findings have shed light on the flow regions and factors that substantially influence the transient behaviors. We observed that the flow regions of the targeted well, a multiple fractured horizontal well (MFHW), have two prominent linear flows. The first linear flow presents the flow from the formation into the hydraulic fracture, while the second linear flow is dominated by the flow from the offsetting well into the targeted well. The well spacing is closely related to the behaviors during the second linear flow period, which offers the probability to evaluate the well spacing on the basis of transient behaviors. Properties and geometries of offsetting well have important impacts on the second linear flow and pseudo-radial flow with interference, which yields a mathematical formula for the relationship between the second pseudo-radial flow and 0.5 line. Sensitivity analysis also indicates that the first pseudo-radial flow could be replaced by the spherical or hemispherical flow in 3D domain. The introduction of offsetting wells will cause an increase of the pressure behaviors of the targeted well, as caused by formation heterogeneity. Results from the application indicate the existing depleted pressure areas could be the most likely cause for the well interference.
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    • NSTL

    Comparison of machine learning techniques for predicting porosity of chalk

    Meysam NouraniNajeh MaliSaeed Samadianfard
    9页
    查看更多>>摘要：Precise and fast estimation of porosity is a vital element of reservoir characterization. A new technology for fast and reliable porosity prediction of chalk samples is presented by applying machine learning methods and X-ray fluorescence (XRF) elemental analysis. Input parameters of prediction models are based on rapid and accurate elemental analysis of chalk samples obtained from Hand-held X-ray fluorescence (HH-XRF) measurements. The intelligent models, including Random Forest (RF), Multilayer perceptron (MLP), Random Forest integrated by Genetic Algorithm (GA-RF) and Multilayer Perceptron integrated by Genetic Algorithm (GA-MLP), are trained and tested based on samples consisting of outcrop chalk samples from Rordal and Stevns Klint (ST) and core samples from Ekofisk Formation in the North Sea. Results are evaluated by sustainability index (SI), determination coefficient (R2), correlation coefficient (CC), and Willmott's Index of agreement (WI). Results indicate that the combination of GA-RF intelligent method with XRF elemental analysis successfully provides an accurate model by 0.99, 0.02, 0.995 and 0.99 respectively for CC, SI, WI and R2, respectively.
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    • NSTL