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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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    Time-series production forecasting method based on the integration of Bidirectional Gated Recurrent Unit (Bi-GRU) network and Sparrow Search Algorithm (SSA)

    Xinfang MaFengchao XiaoXuechen Li
    13页
    查看更多>>摘要：With the go wiling demand of improving quality and benefit of unconventional resources, time-series production prediction plays an increasingly essential role in economic investment, stimulation scale and decision making. However, due to the limitations of traditional model-driven methods and data-driven methods, production forecasting is still challenging. In this paper, we propose a novel framework using Bidirectional Gated Recurrent Unit (Bi-GRU) and Sparrow Search Algorithm (SSA) that improves the accuracy of oil rate forecasting. The Bi-GRU could make full use of both past and future information inside production sequences and related features. SSA is employed for hyperparameter tuning of the Bi-GRU model. To validate the feasibility, robustness and efficiency of the proposed method, three cases are carried out from the perspective of an ideal single well from the simulation model, an actual single well under variable production constraints and actual multiple wells. Model performance is compared with traditional decline curve analysis, conventional time series methods and one-way recurrent neural networks. The observations show that the proposed method performs better than the others in terms of accuracy and robustness.
      原文链接:
    • NSTL

    A workflow of fracture geometry diagnostics of unconventional wells with complex fracture networks coupling fracture mapping and well testing

    Zhiming ChenXinwei Liao
    17页
    查看更多>>摘要：Although many attempts have been made for fracture diagnostics, the complex fracture-network geometries are still ineffectively identified. To improve this situation, this study develops a new workflow to determine the geometries of complex fracture networks of unconventional wells. The theoretical basis of this workflow is containing fracture mapping based on Hough transform and well testing based on semi-analytical model. The flexibility and reliability on identifications of complex-fracture geometries are demonstrated through the case studies. Subsequently, the proposed workflow is applied to perform field application with microseismic data and identify the most likely fracture geometry. Results show that different geometries of fracture networks have different features of flow regimes, which are totally distinct from those of traditional bi-wing fractures. A special "hump" occurs if the fracture geometry is dendritic, and a feature of "fluid feed" from fracture branches to wellbore-connected fracture may occur, and the "pseudo boundary dominated flow" appears for an orthogonal fracture networks. The "fluid feed", "fracture interferences", and "pseudo boundary-dominated flow" are respectively demonstrated by a dual-porosity feature, namely "V-shape", a "hump", and a unit-slope line, which are good tools for fracture-geometry diagnostics. By performing a field application, the estimated fracture-network geometry of well QW1 from the Ordos Basin is obtained using the proposed workflow. The results demonstrate that mutually orthogonal fracture networks may not be generated. This study demonstrates a new way for fracture geometry diagnostics of unconventional wells with complex fracture networks.
      原文链接:
    • NSTL

    Incorporation of geochemical, geometrical and intermolecular interactions into modelling of scale removal in a capillary microchannel

    Amir Hossein NikooM. Reza Malayeri
    14页
    查看更多>>摘要：Along with scale deposition on rock surfaces during brine-rock interactions, it is likely that the formed deposit may be dislodged due to shear stress exerted by flowing brine. This study presents a simplified model for removal of gypsum scale from rock surfaces of anhydrite, calcite, dolomite, and sandstone during the interaction with brines of 3000 mg/L and 6000 mg/L of [Ca~(2+)] within a capillary microchannel. To do so, the intermolecular interaction energies primarily Lewis acid-base adhesion energy for gypsum scale on various rocks were firstly characterized in order to develop the surface energy-based correlation of deposit strength for the formed scale layer. The kinetic and hydrodynamic patterns of scale removal were then attained based on the assumption of asymptotic behaviour for the net mass of scale at the end of the scaling process. The results showed that the removal rate initially increases profoundly followed by a low-sloped increment. Higher flow velocity increases the removal flux of gypsum scale from different rock surfaces as much as 2.4-and 2.2-fold for the brine salinity of 3000 mg/L and 6000 mg/L of [Ca~(2+)], respectively. Furthermore, higher brine salinity in terms of [Ca~(2+)] would lead to more removal of gypsum scale from the rock surfaces of anhydrite followed by carbonate and sandstone reservoir rock surfaces approximately 1.9-fold at the lower flow velocity and 1.8-fold for the higher brine flow velocity, respectively.
      原文链接:
    • NSTL

    EOR Perspective of microemulsions;; A review

    Ahmad MahboobShams KalamMuhammad Shahzad Kamal
    20页
    查看更多>>摘要：Since conventional oil recovery techniques only produce a limited fraction of the original oil in place (OOIP), the need for Enhanced Oil Recovery (EOR) methods has become imperative. Chemical enhanced oil recovery (cEOR) techniques have been widely studied for decades. Surfactants are frequently employed in cEOR processes. Micelles are formed when the amount of surfactant exceeds the critical micelle concentration (CMC) by aggregation of monomers;; this can potentially result in the formation of microemulsions when the surfactant solution comes in contact with reservoir fluids. These microemulsions are homogenous and thermodynamically stable. This review focuses on factors affecting the formation of microemulsions such as pressure, temperature, salinity, nature of cosurfactants, cosolvent type and concentration, water-oil-ratio, pH, and oil properties. This review also covers the characterization of microemulsions, such as via;; phase behavior and rheological properties, visual inspections, polarized light microscopy studies, their interfacial, surface tension, and zeta potential measurement plus investigations of the particle size distributions. Finally, a comprehensive review of surfactant systems that have been used to generate microemulsions at different reservoir conditions is presented. This review reveals that anionic surfactants are capable of generating a Winsor III type microemulsion-which is optimal in EOR processes. On the other hand, cationic surfactants usually do not exhibit Winsor III type behavior, and nonionic surfactants are normally only applicable as cosurfactants in EOR contexts.
      原文链接:
    • NSTL

    Pore structure heterogeneity of Wufeng-Longmaxi shale, Sichuan Basin, China;; Evidence from gas physisorption and multifractal geometries

    Yang WangHongfei ChengQinhong Hu
    13页
    查看更多>>摘要：Understanding the heterogeneity of the nano scale pore structure is critical for assessment of hydrocarbon flow and storage in porous reservoirs. Multifractal theory is a powerful method to acquire the detailed heterogeneity information of the multiple pore system. The generalized dimension spectrum and singularity spectrum are two forms to depict the multifractal feature. Hurst exponent (H) and the width of singularity spectrum (Aa) are two parameters to effectively assess the pore connectivity and heterogeneity, respectively. In this study, multifractal analysis was performed on over-mature Wufeng-Longmaxi shales and their corresponding isolated organic matter (OM) via gas physisorption (CO2 and N2) test to ascertain the pore heterogeneity and its governing factors. Micropore (diameter<2 nm) structure in bulk shale contains stronger pore heterogeneity but weaker connectivity than meso-macropore (diameter = 2~(-1)00 nm) structure. The comparison of heterogeneity features of shale versus its isolated OM reveals that micropore associated with minerals could enhance the micropore heterogeneity in bulk shale, while meso-macropore existing in minerals could reduce the meso-macropore heterogeneity in bulk shale. Besides, the total organic carbon content has a positive effect on the micropore heterogeneity. The micropore and meso-macropore volume have a certain impact on the pore heterogeneity in the corresponding pore size ranges. Compared with the low-mature Bakken shale, the over-mature Wufeng-Longmaxi shale contains the stronger micropore heterogeneity but weaker meso-macropore heterogeneity, where less difference between the micropore and meso-macropore heterogeneities was also observed. We deduced that the whole shale pore spectrum likely tends to be homogeneous along with the OM thermal maturation.
      原文链接:
    • NSTL

    A calibrated surface complexation model for carbonate-oil-brine interactions coupled with reservoir simulation-Application to controlled salinity water flooding

    Lawrence Opoku BoampongRoozbeh RafatiAmin Sharifi Haddad
    22页
    查看更多>>摘要：Vast majority of past studies that have been conducted on controlled salinity water flooding (CSWF) use diffuse layer model (DLM) that calculates only the surface potential, which can be significantly different from the ^-potential of the interface. Importantly, stability of the water-film (between the oil and the rock surface) which dictates ultimate oil recovery is related to ^-potential. As such, using DLM calculated surface potential (directly) for CSWF can be misleading. Additionally, most of the existing DLMs use integer charges instead of fractional charges to model carbonate-brine interactions, which may not represent the actual carbonate crystallographic. We present a triple layer surface complexation model (TLM) which offers the option to locate and distribute charge of the adsorbing ion(s) at three locations. TLM can therefore calculate potentials at three different locations within the Stem layer. To the best of our knowledge, only few authors have used TLM to simulate CSWF. However, some surface reactions were ignored in these models. For instance, adsorption of monovalent ions such as Na+ and Cl" ions was ignored in some of the few available TLMs. Also, the effect of basic-oil components was not considered in some TLMs, and lastly, some TLMs used integer charges for the carbonate surface group. This study introduced a comprehensive TLM that includes all these complexities. Moreover, we introduced a new wettability indicator (WI) that is related to the electrostatic forces between the oil-brine and the rock-brine interfaces. That is, WI was calculated from ζ-potentials at the oil-brine and rock-brine interfaces. The TLM, built in a geochemical simulator, PHREEQC, was then coupled with UTCHEM, a multiphase reservoir simulator. The developed simulator based on the TLM-CSWF model was tested against several experimentally measured oil recovery data sets. Results of the model suggest that Oil basic component significantly impacts oil-brine interface ζ-potential irrespective of temperature, brine composition, and ionic strength. On the otherhand, Na+ ions in brine may influence oil-brine ζ-potential, and this relates to temperature, brine composition, and ionic strength. The results further suggest that injection of (sulfate-free) diluted brine in chalk resulted to increased oil adhesion, shifting the reservoir to oil-wet condition. Hence, no additional oil is recovered with this brine injected at tertiary oil recovery stage. Finally, the results showed that wettability is related to ζ-potentials at the oil-brine and rock-brine interfaces, and the carbonate rock would be strongly oil-wet or water-wet only at significantly large magnitude of ζ-potentials at the interfaces.
      原文链接:
    • NSTL

    Predicting formation damage of oil fields due to mineral scaling during water-flooding operations;; Gradient boosting decision tree and cascade-forward back-propagation network

    Seyed Pezhman MousaviAydin LarestarriFahimeh Hadavimoghaddam
    13页
    查看更多>>摘要：Water-flooding is one of the main options employed by the oil industry to meet the world's ever-increasing demand for oil, as the primary source of energy. This approach is highly prone to cause formation damage if the injected water is not compatible with the formation brine. In this study, decision tree optimized with gradient boosting (GBDT), cascade-forward back-propagation network (CFBPN), and generalized regression neural networks (GRNN) were employed, as relatively novel intelligent models, for the first time to develop accurate models to estimate the formation damage during a waterflooding operation in terms of damaged permeability. To compare the performance of these models, radial basis function (RBF) and multilayer perceptron (MLP) neural networks were also developed. The Levenberg-Marquardt algorithm (LMA), scaled conjugate gradient (SCG), and Bayesian regularization (BR) were used for training the MLP and CFBPN models. The results of this study showed the outperformance of the proposed GBDT model compared to the other developed models as well as previously proposed ones with an average absolute percent relative error (AAPRE) of 0.1465 % and correlation coefficient (R2) of 0.9991 for the whole dataset. According to the results, the accuracy of the developed models could be ranked as follows;; GBDT > CFBPN-LM > CFBPN-BR > RBF > MLP-LM > GRNN > MLP-BR > CFBPN-SCG > MLP-SCG. Moreover, it was shown that the GBDT mode could estimate more than 90 % of points with an absolute relative error of lower than 0.5 %. The trend analysis showed the high capability of the developed models in detecting the physical trend of the formation damage with variation of inputs. Then, the variable impact analysis was performed for this model, and the results reflect the high dependency of the model's predictions on the volume of injected water (Vinj), initial permeability (Ki), and ionic concentration of sulfate. Lastly, the Leverage approach was employed to determine suspected points as well as the applicability realm of the GBDT model. The results of the outlier detection indicated that only 4 points (0.93 % of the dataset) were detected as outliers, and the applicability realm of the proposed GBDT was verified. The findings of this communication shed light on the application of intelligent models and their power in predicting the formation damage caused during water-flooding operations before their occurrence.
      原文链接:
    • NSTL

    Performance prediction and multi-objective optimization of metal seals in roller cone bits

    Yi MaZiyang YuanYang Ni
    13页
    查看更多>>摘要：Metal seals are the critical component of roller cone bits in oil and gas drilling. The performance of metal seals directly impacts the service life and efficiency of the entire drilling system. How to accurately predict the sealing performance of metal seals with multi-field coupling and optimize the overall sealing performance under the influence of various factors are the main difficulties of this study. A novel thermal-fluid-solid coupling numerical model was established and verified for the new-generation single energizer metal seals (SEMS2). The fluid film characteristics, interface temperatures, and sealing performance of SEMS2 were investigated under different operating conditions, structural parameters, and material parameters by the co-simulation of MATLAB and ANSYS. Based on the coupling analysis results, the significance analysis of the parameters was performed by using the orthogonal test. Furthermore, the multi-objective optimization of SEMS2 was carried out using the Back Propagation Neural Network (BP NN) and three typical multi-objective evolutionary algorithms (MOEAs). By comparison, the elitist non-dominated sorting genetic algorithm (NSGA-II) performed better than the strength Pareto evolutionary algorithm (SPEA2) and region-based Pareto Envelope based Selection Algorithm (PESA-II). The leakage rate and factional force of SEMS2 were reduced by 52.3 % and 11.0 %, respectively, after multi-objective optimization. The results could provide theoretical support for designing a high-efficiency and long-life sealing system for onshore and offshore drill bits.
      原文链接:
    • NSTL

    Determining whether the swirling jet is applicable in bottom-hole cleaning;; A CFD study

    Dongyu WuHuaidong ZhangShaohe Zhang
    11页
    查看更多>>摘要：Borehole cleaning is a major concern in well drilling which significantly relevant to the drilling cost and safety. In this work, the bottom-hole cleaning performance of swirling jet induced by a drill bit nozzle was discussed. Computational fluid dynamics (CFD) simulations of cuttings transport have been conducted in a full three-dimensional, unsteady multiple-Euler framework by means of the commercial software ANSYS-FLUENT. A detailed comparison, including velocity and pressure fields, Reynolds numbers, cuttings trajectory and volume fraction variation has been made based on the simulation results. The results indicate that swirling jet showed bad bottom-hole cleaning performance compared with straight jet with conventional drilling control parameters. That is, the peculiar properties of swirling jet such as higher turbulent level and entrainment did not cause more efficient removal of drilled cuttings. Relevant conclusions are helpful to promote thorough understanding of the use of swirling jets.
      原文链接:
    • NSTL

    An experimental and field case study to evaluate the effects of shut-in on well performance

    Taregh Soleiman AslAli HabibiMahmood Reza Yassin
    19页
    查看更多>>摘要：There is still debate on how shutting fractured wells for a period of time can affect the well performance. In this study, we combined two approaches to better understand the effects of shut-in time on well performance. First, we analyzed flowback and post-flowback production data from a horizontal well drilled in the Montney Formation, which was fractured with water containing a microemulsion (ME) additive. After the shut-in time for 7 months, the oil and solution gas rates significantly increased by 750% and 671%, respectively. However, the free gas rate decreased by 95% in 65 days, before it started to build up again to exceed the values at the start of the production. Second, we performed a series of imbibition oil-recovery, dynamic liquid-liquid contact angle, and interfacial tension measurements to investigate how the interplay of (i) capillary suction and (ii) osmotic pressure affects oil production from core plugs during the counter-current imbibition tests. Combined analyses of field and laboratory results suggest that the increase in oil production rate after the shut-in period is due to combined effects of (i) free-gas dissolution into the oil (ii) capillary imbibition of fracturing water containing ME solution into the rock matrix driven by wettability alteration and osmotic pressure, and (hi) reduction in phase trapping near fracture face due to interfacial tension reduction.
      原文链接:
    • NSTL