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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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    Investigations of CO2 storage capacity and flow behavior in shale formation

    Bao JiaZeliang ChenChenggang Xian
    12页
    查看更多>>摘要： CO2 storage, CO2 stimulation, CO2-enhanced oil recovery (EOR), and CO2-enhanced gas recovery (EGR) in shale reservoirs have recently attracted attention. Thorough investigations mimicking high pressure and high-temperature subsurface conditions are necessary to understand the interaction between CO2 and organic-rich shales, advance the fundamental understating of flow mechanisms in unconventional reservoirs, and successfully implement a field project. Most of the previous work focused on one aspect of adsorption, flow behavior, and reservoir numerical simulation. We suggest that a single approach investigation may lead to incomplete conclusions of CO2 injection in shales. This work comprehensively evaluates CO2 storage potential and injectivity in the Bakken Formation through various approaches. Samples are tested from the Lower Bakken Shale (LBS), the Middle Bakken (MB), and the Upper Bakken Shale (UBS). In terms of absolute and Gibbs/excess, adsorption isotherms of these two types are both measured, and the adsorbate density is estimated. We differentiate two adsorption isotherms and emphasize the correct use of the isotherm in the current commercial reservoir simulator, which is relatively obscure in the existing literature body. Nuclear magnetic resonance (NMR) confirms a portion of bitumen/absorption mobilization because of CO2 exposure. In the compositional simulations of CO2 injection in shales, several novel conclusions are obtained regarding analyzing main control factors; the most important one is that adsorption outweighs molecular diffusion in determining CO2 injection rate.
      原文链接:
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    A constrained version for the stereology inverse problem: Honoring power law and persistences of the fracture traces exposed on arbitrary surfaces

    Renato R.S. DantasWalter E. MedeirosJoao V.F. Pereira
    15页
    查看更多>>摘要： We present a stereological study in a cave setting that is part of a karstic carbonate system located in the Sao Francisco Craton, Brazil. Using a Lagrangian approach, a constrained version of the nonlinear inverse problem of stereology is solved. Besides the classical demand of fitting the histogram of fracture traces measured on arbitrary exposed surface, it is imposed that the solution honors also measures of surface intensity (P~(21)) and power law exponent obtained from fracture traces on the same exposed surfaces. Estimates of volumetric intensities (P~(32)) of conjugate fracture pairs might be also imposed to be close values. The resulting cost functional is minimized using the Particle Swarm Optimization (PSO) method. The implemented version of PSO furnishes the best solution and a set of suboptimal quasisolutions, from which the solution uncertainty is evaluated. A key aspect of the implemented approach is that all terms composing the cost functional are normalized, obtaining as a result, robustness for the weighting parameters to changes in the input data. The resulting stochastically simulated discrete fracture networks honor all statistical observations but, in general, do not reproduce the positions of the observed fracture traces. The methodology is applied to synthetic and field data examples. All obtained solutions are stable and geologically reliable.
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    • NSTL

    Evolution of static and kinetic friction in a horizontal well using an adaptive model-based observer: Field validation

    Shanti Swaroop KandalaRoman Shor
    10页
    查看更多>>摘要： Evolution of static and kinetic friction coefficients across the depth of a horizontal wellbore and field validation against the downhole parameters is presented in this paper. It has been observed in the literature that stick-slip oscillations exist in drill strings even with bit off-bottom and persist with the bit on bottom. In the past, various lumped mass models have failed to explain this phenomenon, as they have only considered bit-rock interaction to be the main reason for the stick-slip oscillations. The model considered in this study was used previously to estimate the friction factors at particular connections with bit off-bottom. For effective estimation of the downhole parameters, the model employs an adaptive soft sensor, robust to capture the disturbances occurring at the downhole. Using only the topside measurements (i.e., surface measurements), downhole RPM is estimated along with the evolution of friction coefficients (static (μ_s) and kinetic (μ_k) using the soft sensor. For obtaining the friction factors profile, those values of μ_s and μ_k that converge and remain stable for a specified time are considered. The model is first validated against the downhole RPM data obtained for a well in North America. It was observed that the estimates of the downhole RPM obtained using the model are in close agreement with that of the actual data. Next, the model was employed to obtain reasonable downhole RPM estimates for another well in North America where the downhole data is unavailable.
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    • NSTL

    Novel laboratory setup for realistic wellbore cement and formation integrity studies

    Amir GhaderiPierre CerasiAli Taghipour
    7页
    查看更多>>摘要： Oilfield wellbore integrity relies on a good well cement formulation, placement, and resistance to solicitations when aging, either due to chemical or stress changes. Requirements are that the cement sheath and plugs remain as proper hydraulic barriers for all foreseeable future. Thus, to qualify the cement formulations with respect to various types of stress changes, it is important to carry out these tests in the field relevant conditions in the laboratory. These tests will contribute to improved understanding of the limiting factors influencing the well integrity and assist in design of remediation strategies. Hence, a new experimental setup designed for studying near wellbore systems in field conditions is introduced. The setup comprises of an advanced X-ray cell with the possibility of three independent pressure controls of casing, pore and formation pressures. The experiments are carried out under simultaneous X-ray Micro-CT imaging allowing to monitor the in-situ mechanical changes. Numerical calculations in the finite element domain are carried out for the same test conditions with first results showing the evolution of radial cracks in the cement sheath and the formation rock submitted to excessive well pressures. The test results confirm with the numerical simulation. These results may provide valuable input for near-wellbore integrity assessments.
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    • NSTL

    A review of the frictional contact in rock cutting with a PDC bit

    Iman RostamsowlatBrian EvansHyock Ju Kwon
    17页
    查看更多>>摘要： Drilling is one of the most expensive processes in the oil and gas exploration and exploitation processes which is commonly performed with polycrystalline diamond compact (PDC) fixed-cutter bits (or PDC bits as they are often referred to) due to their good stability and high flexibility in design. The PDC bit longevity strongly depends on the wear flat surface that changes during progression through rock materials. The wear flat size increases with time and can greatly influences the bit performance and efficiency. The increase in wear causes increasing weight-on-bit (WOB) on the PDC bit to keep the rate of penetration (ROP) constant. Over the past decades, contrary to the pure cutting process, not many investigations have been devoted to studying the friction mechanism at the wear flat-rock interface, resulting in poor understanding of the friction mechanism. The objective of this paper is to provide a detailed review of the state-of-the-art in rock cutting with particular focus on the frictional mechanism of the blunt PDC cutters and issues associated with the contact stress and the friction coefficient at the wear flat-rock interface. Moreover, the contact forces at the wear flat are governed by the wear flat inclination angle. Gaining a better understanding of the frictional contact process can eventually play a significant role in addressing practical issues such as drilling efficiency, optimization, and susceptibility to vibrations. Further, in spite of some obvious differences between the indentation and rock cutting processes, the main similarities between these two processes are also discussed which can provide new insights for the further studies.
      原文链接:
    • NSTL

    3-D numerical simulation of sandstone matrix acidizing by non-Newtonian fluid

    Hooman AfsarFereshteh SamadiFeridun Esmaeilzadeh
    12页
    查看更多>>摘要： Matrix acidizing is a common technique to increase oil recovery in sandstone oil reservoirs. In the matrix acidizing process, reactive fluids are injected into the reservoir with the scope of dissolving and dispersing the rocks near the wellbore.In this study, the matrix acidizing of sandstone wells by a hydrochloric acid/hydrofluoric acid/additives mixture is described through mathematical modeling using the two-scale continuum model.The model developed in this study indicates the reactions and transport phenomena at pore and Darcy scales in 3-D radial flow. Due to using several additives during the acid injection process, the fluid phase has non-Newtonian behavior (shear-thinning). The effect of non-Newtonian fluid in porous media was investigated using a modified continuum model due to importance calculations in field scale. The Carreau-Yasuda constitutive equation has been used to modify the continuum model to consider the non-Newtonian fluid effects. In the proposed model, partial differential equations of reaction and diffusion at pore-scale, and simultaneously convection and dispersion phenomena at Darcy scale are solved using numerical methods. The finite volume and tri-diagonal matrix algorithm (TDMA) techniques were employed to gain a precise solution for the model and observe the dissolution pattern in different acidizing regimes and rheological properties. The effect of acid injection rate, dissolution rate constant and different reservoir properties, including permeability, porosity and heterogeneity on dissolution patterns, was investigated by considering non-Newtonian fluid effects, and concluded that acid having high shear-thinning behaviour (i. e., acid having low power-law index) seemed more promising for field operations because of deep penetration. The reservoir heterogeneity was defined by selecting a random local porosity distribution. It should be noted that the presented model can reproduce different types of acid/rock system (carbonate or sandstone reservoirs). Finally, the skin factor would be calculated to study the acidizing performance in the damaged zone. To solve the porosity evolution equation, couple pore and Darcy scales, and update the pore-scale parameters at each time step, the program was developed in FORTRAN by Parallel Processing and consisting of functions and routines.
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    • NSTL

    Petroleum resource potential evaluation using insights based on hydrocarbon generation, expulsion, and retention capabilities-A case study targeting the Paleogene Es1 formation, Qikou Sag

    Zhuoya WuXianzheng ZhaoXiugang Pu
    15页
    查看更多>>摘要： The Shahejie Formation of the Bohai Bay Basin has been set as a favorable shale oil area for exploration in currently practice. However, the process was impeded by the obscurity of favorable exploration area in the shale play and resource evaluation targeted at the main research area, the Qikou Sag. In particular, there is a need for a systematic assessment of the various types of resources present. The study presented herein emphasizes on quantifying source rock generation, expulsion, and retention hydrocarbon characteristics using the advanced hydrocarbon-generation potential model (HGPM) in the first member of the Paleogene Shahejie Formation (Es1) of the Qikou Sag. Geological and geochemical features reveal that the Es1 source rocks are of relatively high quality with a 1200-m maximum thickness and abundant organic matter (total organic carbon (TOC) content of 2.27% on average; type I kerogen dominated; mature stage). The type of organic matter was reassessed using the progressive and reasonable dimensionless TOC and S2 variables. The HGPM demonstrated that the expulsion threshold was R_o = 0.50% and the maximum generation hydrocarbon potential (Q_g), expulsion hydrocarbon potential (Q_e), and retention potential (Q_r) were 746.99, 231.57, and 515.42 mg HC/g TOC, respectively. The hydrocarbon generation (I_g), expulsion (I_e), retention (I_r), and effective retention intensity (I_(re)) all centered in the Qikou main depression at 450 x 10~4, 200 x 10~4, 300 x 10~4, and 230 x 10~4 t/km~2, respectively. The predicted resource potential can be finally queued as follows; retention shale resources with 22.90 x 10~8 t oil equivalent, including movable shale oil and gas of 12.21 x 10~8 t, and conventional and tight oil or gas resources with 9.62 x 10~8 t oil equivalent. The most favorable exploration areas are mainly distributed in the Qikou main depression and Qibei Subsag. Quantitative and detailed evaluation provides a reasonable prediction of exploration targets and prospects and further mitigates risks and losses incurred during shale-exploration successions.
      原文链接:
    • NSTL

    Application of factor analysis to investigating molecular geochemical characteristics of organic matter and oil sources: An exploratory study of the Yanchang Formation in the Ordos Basin, China

    Shijia ChenYuting HouKaiming Su
    15页
    查看更多>>摘要： Due to the similarity of the biomarker characteristics of the source rocks of different layers, the progress of the oil source research of the Yanchang Formation in die Ordos Basin is difficult and slow, which highlights the shortcomings of traditional research methods. Given this, this paper uses the gas chromatography-mass spectrometry analysis results of a large volume of samples of the Yanchang Formation in the basin as the dataset, and performs an exploratory application of the factor analysis (FA, a multivariate statistical method) to analyze the molecular geochemical characteristics of organic matter, with an aim to find features that have not been noticed in the past, and give a reasonable explanation for the oil source. The findings are summarized as below: with the help of multivariate (31 molecular geochemical parameters are introduced), FA can quantify many geochemical properties of samples well, which brings convenience to research. Based on the results, it was found that parameters such as C_(26)TT/C_(25)TT, sterane/hopane, and ∑C_(19-26)TT/C_(30)αβ can effectively distinguish the samples of different areas and layers, and it is further believed that the Chang 9 source rock has higher contributions to adjacent layers (mainly the Chang 8-Chang 10 oil groups) in areas where it is abundant (mainly the Wuqi-Zhidan area), while in the other areas and layers, oil is mostly attributed to the Chang 7 source rock.
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    • NSTL

    Diagenetic controls on porosity evolution and reservoir quality of an outcrop analogue of the Jurassic carbonate reservoirs in the Arabian Plate: An example from the Middle Jurassic Tuwaiq Mountain Formation, Central Saudi Arabia

    Mahmoud Samir El-YamaniKhalid Al-RamadanDave Cantrell
    21页
    查看更多>>摘要： The Middle Jurassic Tuwaiq Mountain Formation (TMF; formed of three members, from bottom to top T1, T2, and T3) represents one of the primary conventional and unconventional reservoirs to be assessed in Saudi Arabia. It is considered as a tight carbonate reservoir in the Jafurah Basin and conventional reservoir in the Arabian Basin. Here, we investigate the depositional, diagenetic, and stratigraphic impact on reservoir quality and porosity evolution of the TMF through an integrated petrographical, geochemical and petrophysical analyses on outcrop samples. The TMF has a complex diagenetic history including micritization, dissolution, recrystallization and neo-morphism, meteoric cementation, evaporite precipitation, dolomitization, silicification, dolomite dissolution and calcitization. Dolomitization occurred via a hypersaline fluid mechanism, based on texture, association with evaporites, and Sr concentration. X-ray diffraction results support chert replacing evaporite as the mechanism of the two chert beds in the T3 member due to the presence of anhydrite relics in their samples. This replacement formed the necessary Ca~(2+) rich fluid for dolomite dissolution and calcitization. Therefore, dolomite calcitization occurs locally and is stratigraphically controlled based on its position relative to chert beds in T3. T3 and the upper part of the T2 member contain calcitized dolomites, while the lower part of T2 and T1 contain only dissolved dolomite. As the fluid went deeper in the TMF, it became weaker. Therefore, the fluid was too weak to develop dolomite calcitization process and instead only affected T1 and the lower part of T2 by dolomite dissolution. Overall, dolomite dissolution and dolomite calcitization didn't have a high impact on porosity evolution as the TMF isn't a highly dolomitized formation. The distribution of porosity (φ), permeability (K), and reservoir-quality-index (RQI) of the TMF are stratigraphically controlled. The TMF represents the regressive system tract of a 3rd order depositional sequence, which is composed of seven 4th order cycles (i.e. deep lagoon cycles (DLC) and shallow lagoon cycles (SLC)). RQI, φ, and K plots showed great fitting with the 4th order depositional-cycles as DLC has very poor reservoir properties (average φ = 7.7%, average K = 0.17 mD, average RQI = 0.03), while SLC has fair reservoir properties (average φ = 15.4%, average K = 2.64 mD, average RQI = 0.11). Reservoir quality contrast is controlled by two factors: (1) the reduced mud-content and increased grain-content in SLC compared with DLC resulted in increased primary interparticle porosity, and is governed by depositional energy; and (2) the higher primary interparticle porosity in SLCs compared with DLCs preferentially facilitated more infiltration of undersaturated meteoric fluids, resulting in enhanced grain dissolution. This is reflected on the higher proportion of moldic and vuggy porosity in SLCs compared with DLCs. The accurate assessment of the TMF micro-scale attributes and controls on reservoir quality in an outcrop analogue that occurs in close proximity to subsurface hydrocarbon producing intervals can provide important input for oilfield appraisal and enhanced oil recovery performance.
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    Source rock with high abundance of C_(28) regular sterane in typical brackish-saline lacustrine sediments: Biogenic source, depositional environment and hydrocarbon generation potential in Junggar Basin, China

    Shiju LiuGang GaoJun Jin
    14页
    查看更多>>摘要： In the brackish water sedimentary environment of the Junggar Basin in Xinjiang, the organic-rich shale and shale oil formation with relatively low maturity, is characterized by relatively high abundance of C_(28) regular steranes. However, the biogenic source of organic matter and favorable sedimentary environment for the type of source rock has been thoroughly classified. In this paper, organic geochemical and penological, analyses of the Lucaogou Formation shale in the Jimusaer Sag, Junggar Basin in the north of Xinjiang Uygur Autonomy Region were carried out. The source rocks in the Lucaogou Formation are mainly composed of two types of maceral including lamalginite (cyanobacteria) and telalginite (green algae), with the former predominantiy fueling the high C_(28) regular sterane content. Penological, organic and inorganic geochemical analyses suggest that the lamalginite was developed in low-salinity water while the telalginite was developed in high-salinity water. Based on geochemical and organic penological characteristics, both the lamalginite and telalginite have good hydrocarbon-generating potential, but in the lower thermal evolution stage of the Lucaogou Formation source rock, telalginite have higher hydrocarbon-generating rate.
      原文链接:
    • NSTL