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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
正式出版
收录年代

    Experimental study on microscopic mechanisms and displacement efficiency of N2 flooding in deep-buried clastic reservoirs

    Yuliang SuXue ZhangLei Li
    10页
    查看更多>>摘要：Current clastic reservoirs with burial depth of more than 5000 m are important energy sources.And microscopic initiation mechanism of residual oil after water flooding has been regarded as the key to improving oil recovery by gas flooding.In this study,an investigation was conducted in the occurrence states and distribution of residual oil of deep-buried reservoirs from microscopic pore scale.We innovatively designed a microscopic visualization experimental equipment for the first time,which broke through the limitations of visualization accuracy,temperature and pressure of the conventional experimental devices.Microscopic visualization experiments of gas injection after waterflooding at 115 ℃ and 55 MPa were carried out.According to the permeability and pore-throat 0 structure characteristics of deep-buried clastic reservoir,a two-dimensional glass etching micromodel was designed and fabricated.Meanwhile,the occurrence state and formation mechanism of multi-type residual oil were quantitatively characterized by image processing technology.The results showed that there were five kinds of residual oil which were corner,droplet,membranous,columnar and cluster after water flooding.In addition,it was generally concentrated in the fine pore-throats with greater resistance perpendicular to the main stream line.Two mechanisms,immiscible flooding and miscible flooding,were also found in N2 flooding.Moreover,the injected gas carried,squeezed and dispersed the continuous clusters of residual oil,transforming diem into dispersive shapes such as corner and membranous.And a certain amount of microscopic residual oil after water flooding was effectively mobilized by removing the water locking effect.The oil recovery could be improved by 11.49% in low-permeability zone,which was the highest,since the continuous cluster residual oil was decreased significantiy.Membranous,columnar and cluster residual oil were well mobilized in the medium-permeability zone,and oil recovery was increased by 8.31%.In comparison,the oil recovery in high-permeability zone was only increased by 2.53%,and diere was no cluster oil.Our study highlights the migration characteristic and initiation mechanism of residual oil in porous media under N2 injection after water-flooding from the perspective of microscopic visualization,which may help to promote the development of deep-buried clastic reservoirs.
      原文链接:
    • NSTL

    Scheme design and performance analysis of thin-walled pressure-retaining coring tools for seafloor drills in the deep-sea operating environment

    Jialiang WangYang SunDilei Qian
    9页
    查看更多>>摘要：To meet the demand for high-quality pressure-retaining samples for natural gas hydrates research,a pressure-retaining design scheme for a thin-walled coring tool is proposed to suit the characteristics of seafloor drills and meet the requirements of 3000 m water depth.Under the working pressure of 8-30 Mpa,theoretical analysis and a test verification of the pressure-retaining performance of the drilling tool were carried out.Then,the adaptability test,which was between the drilling tool and seafloor drills,and the drilling test were carried out.The results show that the pressure-bearing capacity of the pressure-retaining drilling tool exceeds 30 Mpa;note that this drill is designed based on the direct sealing principle of the core tube.After 12 h,the pressure loss inside the drill tube was not more significant than 10%.In the theoretical calculation of the pressure loss of thin-walled tubes under the pressure of 8-20 Mpa,the calculation accuracy can be improved by considering the influence of the tube outer diameter deformation.The core sample with a diameter of 45 mm can be obtained through a process of 75 mm drilling.The matching performance between the drilling rig and the drilling tool meets the actual requirements of the seafloor drills for small diameter and a large hole depth drilling operation.The related research can enrich the existing technology and theory of natural gas hydrates pressure coring and provide theoretical support for the popularization and application of thin-walled coring tools in the field of seabed pressure exploration.
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    • NSTL

    Restoration of annular zonal isolation using localized casing expansion(LCE)technology:Treatment of near-horizontal test sections containing a ree-water channel

    K.Beltran-JimenezH.J.SkadsemJ.K.Sunde
    14页
    查看更多>>摘要：Fluid migration behind casings is a well integrity problem that can result in sustained casing pressure,undetected leaks to the environment,and potentially very difficult remediation attempts.Traditional methods for treating annular fluid migration are perf-and-squeeze cementing or section milling followed by recementing.The main disadvantage of the former is the limited penetrability of cement slurry into narrow cracks and microannuli,while for the latter it is the requirement of a full rig to perform the operation.Casing expansion is a recent alternative remediation technology that involves imposing a permanent radial expansion of the casing and external cement layer,with the purpose of mechanically closing pathways for migrating fluids.A necessary requirement for the treatment to be effective is that the annular cement is confined between casings or between casing and competent rock formations,such that the cement can sustain significant mechanical strains without failure.Recent laboratory experiments and field trials have shown casing expansion to be a promising alternative to traditional treatment mediods.We build on these insights and perform controlled treatment experiments involving a 7-in Local Expander tool and full-scale cemented annulus test assemblies,which contained much larger-scale defects than previously tested.Prior to treatment,the test assemblies had continuous migration channels on the top side of the cement,leading to high effective permeabilities ranging from approximately 80 to hundreds of darcy.The origin of the defects was likely separation of free water from the cement slurry,which is considered a relevant failure mode for primary cementing of inclined wellbores.We study the effect of imposing single and multiple local dents on the annular seepage rates,and probe for potential alteration of the cement and casing properties using Vickers hardness testing.We find that casing expansion can be highly effective in treating relatively major defects in cemented annuli,even when the defect is several millimeters wide and located adjacent to the outer casing.The effectiveness of the treatment is found to be linked to the degree of casing expansion and the initial condition of the annular cement.The deformed cement shows a tendency toward increased Vickers hardness,which is likely linked to densification of the cement microstructure.Vickers hardness testing of casing steel indicated no significant changes in hardness at the dent locations compared to average hardness values away from these points.
      原文链接:
    • NSTL

    MPD choke control considering the thixotropic gelation behavior of drilling fluids

    Oney ErgeQifan GuDongmei Chen
    11页
    查看更多>>摘要：This study evaluates control algorithms that manage choke pressure during managed pressure drilling applications(MPD)while also taking the thixotropic behavior of drilling fluids into account.This evaluation analyzes proportional-integral(PI)feedback control and proposed preview-based feedback control for choke pressure.A pressure spike can be observed in standpipe and bottomhole pressure after making a drillstring connection or experiencing a prolonged break in drilling operations.This is caused by the gelation of drilling fluids.It is vital to be able to predict the magnitude of such pressure spikes when drilling with active annular pressure control,such that the choke can be effectively controlled to mitigate an induced non-productive time event(i.e.,lost circulation events,pump or pipe failures,or well control situations).In this study,a shear-rate and time-dependent thixotropy model is integrated into a rigorously validated transient hydraulics engine with MPD control capabilities.Drilling scenarios are simulated with choke controllers and a case study is presented.When using a preview-based feedback control algorithm,a physics-based model is executed while setpoints are established proactively.The combined capabilities of the physics-based model and the improved MPD controller are demonstrated.Accurately modeling and controlling pressure during drilling operations is essential,especially for wells drilled in narrow-margin environments.The results of our study show that a reactive PI controller is not fast enough to account for transient pressure behavior related to fluid thixotropy.Moreover,the results show that a preview-based feedback controller is more robust and efficient.We demonstrate how a physics-based model can be used in a preview-based control scenario to keep the bottomhole pressure constant with strongly attenuated pressure fluctuations,leading to safer,more optimized operations.
      原文链接:
    • NSTL

    A new set of search criteria for oil deposits in oil-bearing sediments based on geochemical and geophysical information

    Andrey A.PonomarevVadim M.AlexandravDanil A.Kobylinskiy
    10页
    查看更多>>摘要：To achieve more effective oil prospecting and exploration,it is important to obtain deeper knowledge of natural petroleum-forming processes that take place within oil-source rocks.The goal of our study is to shed light on the role of geomagnetic fields that can help to accelerate petroleum extraction from oil deposits,an aspect that is still largely unexplored.To fulfill this objective,we conducted the experiment involving heating of oil-source rock(black Bazhenov argillite)pieces within and outside a local magnetic field,where the temperatures were calibrated based on the initial X-ray microtomography study of bitumoid formation and void structures in the heated rock.The heating protocol was followed by the evaluation of the bitumoid coefficient(the measure of carbon content)within the samples,which was determined after chloroform extraction and evaluation of organic carbon in the samples.The results show that the bitumoid content is considerably higher in the samples heated while exposed to a magnetic field than in those heated and unexposed.This difference ranged from 0.4 to 2% and appears to be significant,especially since the samples are taken from the same core.In the second part of our study,we analyzed the distribution of oil reservoirs in the Bazhenov formation(Western Siberia)as a function of total organic matter content,reservoir temperatures,and EMAG2 magnetic anomaly values.This enabled the development of a fundamentally new set of geochemical and geophysical criteria for searching for oil deposits in the Bazhenov formation,which correspond to values of reservoir temperatures>70 ℃,values of total organic carbon>4% and values of magnetic anomalies from-100 to 100 nT.The characterization of oil reservoirs in the oil matrix deposits in otiier regions requires a separate study.
      原文链接:
    • NSTL

    CFD modelling and simulation of drill cuttings transport efficiency in annular bends:Effect of particle size polydispersity

    Emmanuel I.EpelleWinifred ObandeJude A.Okolie
    14页
    查看更多>>摘要：This study analyses the impact of particle polydispersity using the Eulerian-Eulerian(EE)and Lagrangiai Eulerian(LE)modelling approaches in the context of wellbore cleaning operations in the drilling industr Spherical particles of sizes 0.5 mm,0.75 mm and 1 mm are considered,whereas a Power Law rheological mod is used for the fluid phase description.The EE approach implemented herein applies the Kinetic Theory<Granular Flow(KTGF)in ANSYS Fluent~R and accounts for the particle size differences by representing them<different phases within the computational domain.With the LE approach,we employ the Dense Discrete Pha Model(DDPM)and capture this difference with the aid of a size distribution model(the Rosin-Rammler mode The findings of our computational experiments show considerable differences in key variables(the pressure dro and particle deposition tendencies)between monodispersed and polydispersed transport scenarios.
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    • NSTL

    A new comprehensive filtering model for pump shut-in water hammer pressure wave signals during hydraulic fracturing

    Yujiao LiXiaodong HuFujian Zhou
    13页
    查看更多>>摘要：In the process of fracturing,the position of the fractures can be identified by analyzing the spectrum of the water hammer pressure wave signals after pump shut-in.However,the collected water hammer pressure data contain a lot of noises,which brings difficulty to the spectrum analysis and affect the accuracy of the final results.Removing multiple kinds of noises while protecting useful fracture response is the challenge.However,the filtering model for the water hammer pressure wave signals is absent.This paper proposes a new comprehensive filtering model for pump shut-in water hammer pressure wave signals.The filtering model contains three parts.First,we designed a two-step filtering method,including Hampel filter and FIR low-pass filter,to filter signals in the main channel.Second,multi-frequency-adaptive notch and median filter were combined to construct the signals in the reference channel,which can be used to protect the useful frequency of the water hammer wave signals and pressure response of the fractures from being eliminated.Third,the filtered signal is obtained by adaptive cancellation between the signals in the main channel and the reference channel.After that,the filtering effects of signals with and without fractures were studied by constructing simulated signals and collecting the signals in the laboratory experiment.The signal-to-noise ratio(SNR)gain and the mean square error(MSE)reduction were selected as indicators for the model validation,and the cepstrum was also used as the indicator to verify the preservation of fracture response characteristics.Besides,the noise adaptive range of the model was evaluated by increasing the noise intensity to the constructing signal.This research can provide a new and useful filtering method for water hammer pressure wave signals in the field.
      原文链接:
    • NSTL

    Stress and pressure dependent permeability of shale rock:Discrete element method(DEM)simulation on digital core

    Ran LinLan RenJinzhou Zhao
    12页
    查看更多>>摘要：Shale permeability will change with the variation of reservoir pressure and formation stress,especially when natural fractures occur failure due to pressure and stress perturbation during hydraulic fracturing,the permeability will change dramatically.So far,however,there is no comprehensive theoretical method could estimate the rock permeability change with natural fractures failure under true-triaxial stress condition.This paper aims to propose a numerical method to investigate the influence of pore pressure,triaxial stress,and natural fractures failure on the shale rock permeability.Firstly,this paper built a digital shale core cylinder by combining the discrete element method(DEM)and fluid-solid coupling model.Then,all the micro parameters of the digital rock were delicately calibrated according to the quasi-triaxial compression tests data of real rock core collected from Bakken shale formation,making the macro-mechanical property and seepage characteristic of digital rock are consistent with real shale rock.Then,based on the calibrated micro-parameters,we constructed a digital core cube to simulate the permeability test under true triaxial conditions.Finally,some natural fractures,as the weak planes,were preset in digital core,and the shale rock permeability change was analyzed with natural fractures failure.It shows that the intact shale permeability will decrease with triaxial stress increasing or pore pressure decreasing.Besides,the permeability of shale will be affected by the natural fractures'property and failure states.In general,as the triaxial stress increases,the natural fractures in shale rock cube will occur failure gradually,meanwhile,its permeability will rise remarkably in the beginning.However,after most of the natural fractures have occurred failure under high-stress or high-pressure,shale permeability will turn to decrease as the stress continues to increase.This paper explores the inner mechanism and exterior behavior of shale permeability dependence on triaxial stress,pore pressure,and natural fractures failure.
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    • NSTL

    Laboratory study of fracture permeability of mineral-filled coal from Fanzhuang Block,southern Qinshui Basin,China

    Bo WangYanting WuGuofu Li
    5页
    查看更多>>摘要：Coalbed methane(CBM)has achieved commercial production in China over the past decade.However,its single well production rate is relatively low.This is mainly due to the low coal permeability,which is a critical property for gas production.Fanzhuang block,southern Qinshui Basin,is a main CBM production area in China.The coals have mineral fillings in the cleat system and the mineral fillings have significant impact on coal permeability,thus the production rate.In this work,methane permeabilities on two selected samples from the Fanzhuang block were measured from high gas pressure to low gas pressure,simulating the gas production process.CT scans were performed on the two samples and two sets of fracture systems were observed.One set of fractures was filled with minerals,while another set of fractures was open.Therefore,the impact of minerals filling on permeability and fracture compressibility is complex.Moreover,the strong swelling strain anisotropy and low Poisson's ratio are also speculated to be closely related to the mineral fillings in the fracture system.
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    • NSTL

    An improved empirical model for rapid and accurate production prediction of shale gas wells

    Wente NiuJialiang LuYuping Sun
    9页
    查看更多>>摘要：The estimated ultimate recovery(EUR)of a single shale gas well is one of the important evaluation indicators for the scale and benefit development of shale gas.Nevertheless,due to the lack of engineering and geologic data,as well as the limitations of the existing empirical methods,the current production forecasting methods cannot make reasonable predictions for EUR.Therefore,Duong method is used as the prototype in this paper,a rapid and accurate empirical model for improved production prediction is proposed based on the historical production profile analysis of mass producing wells in Sichuan Basin.The accuracy and universality of the new model are verified by production examples in the Weiyuan,Changning,Luzhou and Yuxi blocks of the Sichuan Basin.The examples illustrate that the new model can be applied well in typical wells,and has no limitation of flow regimes for the production prediction of gas wells.In order to solve the problem of production data fluctuation and decline curve deviation caused by stimulation measures in the production process,a multi-segment production prediction model analysis method is proposed based on the improved model in this study and has been well applied in the field.Most importantly,the new model has clear physical parameters and is easy to operate.Performance of the new model based on production data is as reasonable as the modern production decline methods(including analytical model),which is better than existing empirical methods.
      原文链接:
    • NSTL