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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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    A treatment protocol for controlling gas oil ratio in heterogeneous carbonate reservoirs by foam injection: Case study simulation

    Mohammadali ShojaiepourFariborz RashidiBahram Dabir
    10页
    查看更多>>摘要： In this study, foam is selected to treat production wells of heterogeneous reservoirs that are suffering from high amounts of gas oil ratio (GOR). To this end, a numerical study is carried out by injecting foam through the perforations that produce high amounts of gas to block the gas path and allow much more oil to be Simula neously produced from the remaining perforations by applying a new technology in well completion. For this purpose, three heterogeneous synthetic base sectors are simulated in which large amounts of injected gas are produced from the upper, middle and lower perforations of the producing well, known as gas overriding, gas channeling-midriding and gas channeling-underriding, respectively. Since Kv/Kh is an important, decisive and effective parameter, different values of it have been considered for each of three base sector models including 0.001, 0.01, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0. Then, depending on the magnitude of Kv/Kh, the most optimal treatment method is sensitivity analyzed. In the following, foam injection parameters, e.g. surfactant concentration, depth of packer set, foam injection sequence and foam injection rate are sensitivity analyzed. Also, the phenomenon of gas cross-flow during the treatment process is investigated. The simulation results show that il after some time following well treatment, the GOR level increased, it is suggested to take a production test to determine what length of the production well below the packer produces lots of gas to set the packer at the lower depth and inject a larger volume of foam to block that gas path so that the GOR is reduced. The results also conclude that the magnitude of Kv/Kh on one hand and the location of gas entry to the production well on the other hand play a key role in the selection of the best treatment scenario in heterogeneous reservoirs. This has led to presenting a protocol for treatment of high GOR production wells in a wide range of reservoirs based on anisotropy ratios. Finally, in order to validate the protocol, a real specific sector of a heterogeneous carbonate reservoir located in the Middle East, in which the GOR level has increased, is simulated and treated. The results indicate that the protocol is efficient and causes a reduction in GOR by 60%.
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    Comparative analysis of conventional methods for the evaluation of wettability in shales

    Hamid SharifigaliukSyed Mohammad MahmoodMaqsood Ahmad
    21页
    查看更多>>摘要： Wettability has paramount importance in the characterization of shale reservoirs, yet its determination is quite challenging. The conventional techniques popularly applied for wettability determination of shales include contact angle, spontaneous imbibition, and floatation. However, there is no consensus as to the most appropriate method of assessing shale wettability, and which method is most suitable for a given shale sample. In this study, these techniques were employed to measure the wettability of outcrop Eagle Ford, Mancos, and Marcellus shale samples simultaneously to compare their efficacy. Sessile/Captive contact angles were measured on dry and saturated shale samples. The advancing/receding contact angles were also investigated by the drop-volume inflation/deflation method to understand wettability hysteresis. A better evaluation of shale surfaces' wettability was attained when a water drop was gently placed on the water-saturated chips submerged in the bulk of oil and the contact angle between oil and water was measured. The contact angle and floatation methods showed relatively good agreement, perhaps because both methods relate to shale surficial affinity and mineralogy. However, the wettability of Eagle Ford and Mancos samples derived from contact angle, spontaneous imbibition, and floatation methods were not entirely similar. Only the spontaneous imbibition method was able to evaluate the mixed-wet characteristics of Marcellus shale samples properly because of the overlapped oil and brine saturation due to imbibition. The observed wettabilities are only specified for the studied outcrop samples. A novel approach somewhat like the Amott method is proposed for the quantitative assessment of wettability from spontaneous imbibition datasets, especially for mixed-wet rocks like shales. Overall, the order of reliability of the conventional techniques is spontaneous imbibition > contact angle > floatation.
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    Experimental evaluation of enhanced shale oil recovery in pore scale by CO2 in Jimusar reservoir

    Tao WanJing ZhangZiyan Jing
    11页
    查看更多>>摘要： With the domestic energy supply increase, exploitation of unconventional shale oil resources has drawn great attention from the industry. In this paper, laboratory studies were conducted to investigate the potential of cyclic CO2 injection process to enhanced oil recovery after primary production in shale oil reservoirs. Experimental results indicated that incremental oil production from CO2 huff-n-puff was obtained. The available literature provides limited information on examination of what pore size recovers the most incremental oil recovery by the applicability of CO2 huff-n-puff in shale formations. In this paper, the cyclic CO2 injection performance on three different reservoir rocks was investigated. The enhanced oil recovery by CO2 huff and puff is not limited to macropores, but the remaining oil in the 0.1-pm pore scale is recovered as well. The moveable oil in the large pores (1 μm < D < 10 μm) is mostly recovered at the first CO2 puff cycle. After the second cycle of CO2 huff-n-puff, oil recovery percentage from the large pores decreases significantly. The formation rocks were divided into 3 types based on the geological condition and petrophysical characteristics: type I, II and III. The incremental oil recovery from the type I rock is higher than type II and III. The oil recovery yields mostly from the pore size 0.1 urn <D < 1 μm.
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    Experimental and theoretical evaluation of interlayer interference in multi-layer commingled gas production of tight gas reservoirs

    Guandong SuXiujuan TaoChinedu J. Okere
    12页
    查看更多>>摘要： Tight gas reservoirs are characterized by multiple thin and vertically distributed development layers with similar or different lithology and varying geological conditions. To increase the production per well and reduce development costs, field experts have widely adopted the commingled production of tight gas in multi-layer reservoirs. However, differences in reservoir properties and pressure might lead to interlayer interference which could influence the overall wellhead output. In this study, we propose a mathematical model for predicting the overall wellhead output of single and multi-layer tight gas reservoirs after interlayer interference. A reservoir(a) and process factor(b) were deduced to quantitatively analyze the difference in interlayer interference. The range and accuracy of the model were analyzed through a goodness-of-fit test. The results showed that the interlayer interference in multi-layer commingled production systems with three or more layers was decreasing, and the interlayer interference in multi-layer commingled production systems with three or more layers was not significantly affected by the increment of layers, the accuracy of the model was greater than 80% and closer to the lower limit of the process and reservoir factors. The model will provide a quantitative method for predicting interlayer interference in multi-layer commingled production, a reliable basis for understanding the mechanism of interlayer interference, and a theoretical framework for evaluating the feasibility of commingled production in multi-layer tight gas reservoirs.
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    Simulation of hybrid nanofluid flow within a microchannel heat sink considering porous media analyzing CPU stability

    Raed QahitiJinyuan WangYi-Peng Xu
    10页
    查看更多>>摘要： Current article aims to numerically scrutinize and compare the forced convection in three different configurations of a 3D heat sink. Two models of porous were designed aiming to evaluate the effects of nanomaterial and metallic foam to the conventional solid heat sink on thermal performance. In these two models, porous material with the same volume fraction was located in two different positions to have different contact areas with the solid. MWCNT-Fe3O4 hybrid nanofluid has been utilized as coolant working fluid. Validations were carried out in the critical case of 47 W for pure water through comparison with previous experimental work in which the whole surface of the CPU is covered with porous media. According to the results, at the constant Reynolds number, the heat sinks, which are consist of metallic foam, have better cooling performance and are able to decrease the surface temperature of heat sink more.
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    Accelerating gas production of the depressurization-induced natural gas hydrate by electrical heating

    Shuyang LiuHangyu LiBin Wang
    16页
    查看更多>>摘要： Natural gas hydrate (NGH) will be one of the major future energy sources due to its properties of clean energy and large reserves. Depressurization is proposed as an effective method to extract natural gas from hydrate, however, the gas production from hydrate dissociation may be interrupted by ice generation and hydrate reformation due to insufficient heat supply in the single depressurization process. To solve this issue, this work conducted simulation on accelerating gas production from the depressurization-induced methane hydrate by electrical heating. The continuous heating and intermittent heating modes were employed and then the electrical heating scheme was optimized for the comprehensive effect of high energy efficiency and high gas production rate. The results show that electrical heating is conducive to gas production from hydrate dissociation at a rapid rate. In the continuous heating, a high initial hydration saturation, low initial water saturation, low specific heat capacity, and high thermal conductivity result in the high gas generation rate and efficient electrical energy utilization (a large energy efficiency ratio). The intermittent heating has a higher efficient utilization of electrical energy than continuous heating. The optimal scheme is determined as the first-half heating type with the optimized electrical heating power of 25.6 W and the heating time of 12.5 min by the gradient descent method of AdaGrad. Compared to the baseline continuous heating case, the energy efficiency ratio (10.70) of the optimal scheme is enhanced by 24.7% with the average gas production rate (2.55 SmL/s) enhanced by 18.2%. It's hoped that the findings of this work can provide some insights into extracting natural gas from gas hydrate deposits.
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    Dynamic analysis of oil-water interface, taking Shunbei oilfield as an example

    Liu HailongLai Fengpeng
    10页
    查看更多>>摘要： The oil-water interface changes dynamically as oil is produced. The dynamic analysis of oil-water interface is the key to oil stabilization and water control in Shunbei oilfield. This paper presents a way to investigate oil-water interface behavior by using dynamic data. In this paper, we validated this method available with the actual data. Sensitivity analyses about the effects of the main parameters are also presented in detail. The water breaking time of oil wells is fully investigated. The oil-water interface movement chart under different development conditions is established to predict the oil-water interface in the late stage of oil well production and extend the waterless developing period. Being based on this chart, a water breakthrough warning can be realized, and oil recovery can be improved. The findings of the research have led to the conclusion that the rising speed of oil-water interface is proportional to the production rate, on the contrary, it is inversely proportional to cave volume and initial oil-water volume ratio. This method is not only suitable for any well type; but also has the function of calculating the real-time oil-water interface of multi-wells. This method can be further developed as its great applicability in fracture-cavity reservoir.
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    Numerical and experimental investigation on a downhole gas-liquid separator for natural gas hydrate exploitation

    Wenjian LanHanxiang WangYuquan Li
    17页
    查看更多>>摘要： Natural gas hydrate (NGH) is widely considered as an alternative energy source due to its tremendous reserves cleanness and high energy density. During the exploitation process, discharging the gas-liquid phase to the surface for separation not only affects the pump performance but also increases the space requirements of the offshore platform. Taking NGH production test data in South China Sea for example, a downhole spiral gas-liquid separator is designed for high gas-liquid ratio (liquid content is less than 10%) in this paper. The forces of droplets in the separator are analyzed and the CFD model for gas-liquid two phase flow is established. The RNG k-e turbulence model is used for analyzing the velocity field distribution and the pressure field distribution in the separator. The influence of structure parameters (pitch, cycle number of spiral piece, and the outer diameter of spiral pipe) and scale on the separation performance is investigated. The energy loss increases sharply after scaling in the separator and some necessary measures should be taken to avoid the generation of the sale and the secondary hydrate. Based on steepest ascent design, response surface methodology and particle swarm optimization, the optimal structure of the separator with high separation efficiency 87.26% and low pressure drop 2614.19Pa is obtained. The experimental platform is built for testing the gas-liquid separator. The comparison of numerical simulations and experiments show that the calculation model for the hydrate gas-liquid separation is correct and feasible. The separation device with the optimal structural parameters has good separation performance.
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    Characteristics of hydrocarbon migration and accumulation in the Lower Jurassic reservoirs in the Tugerming area of the eastern Kuqa Depression, Tarim Basin

    Jialin WanYanjie GongWenhui Huang
    15页
    查看更多>>摘要： The hydrocarbon migration and accumulation process in the Kuqa Depression are complex. In recent years, the Jurassic strata have recorded hydrocarbon discoveries in the Tugerming area of the eastern Kuqa Depression However, it is a new exploration area, and the characteristics of hydrocarbon accumulation are unclear restricting oil and gas exploration and development. In our study, the deeply-buried and shallow-buried Jurassic strata in the Tugerming area are the research objects. Quantitative fluorescence technique and the observation of fluid inclusions are implemented on the selected samples of Jurassic reservoirs to determine the stages and times of hydrocarbon charging. Gas chromatography-mass spectrometry analysis for saturated hydrocarbons is used to identify the origin of organic matter in oils. Combined analytical data with the reconstructed histories of burial, thermal evolution and tectonic evolution, allow simulating the hydrocarbon migration and accumulation process in the Tugerming area. The results show that two categories of hydrocarbon accumulation mechanisms (Burn-ham and Sweeney, 1989). The first type is acted as the type of 'self-generation and self-storage and late accumulation'. Three stages of hydrocarbon charging have occurred in the deeply-buried Lower Jurassic reservoirs, represented by two wells (Tudong 2 and Tuge 4). The charging time is the early-middle stage of Miocene Kangcun Formation (18-9 Ma), forming the yellow or yellow-green fluorescent oil inclusions and paleo-oil reservoir. During the sedimentary period of the late Kangcun Formation to the early Kuqa Formation (9-5 Ma), the reservoir experienced massive condensate oil migration, corresponding to blue-white fluorescent oil inclusions. Large-scale natural gas was expelled into the reservoirs since the deposition stage of Kuqa Formation (5-0 Ma), and then accumulated in the trap controlled by the late Himalayan movement, forming the current gas reservoir. Moreover, the hydrocarbons are generated from Jurassic coal measure source rocks in the Well Tudong 2 based on the characteristics of biomarkers (Burruss et al., 1991). The second type is characterized by 'lower source rock and upper reservoir and accumulation in the late or recent period', developed in the shallow-buried Lower Jurassic reservoirs containing two wells (Tuxi 1 and Mingnan 1). In this case, there are two stages of crude oil charging: mature oil charging in the early-medium Miocene (18-12 Ma) and condensate oil migration in the late Miocene (8-5 Ma). The strata suffered denudation due to the stratigraphic uplifting in the orogemc movement, resulting in the leakage of the early oil reservoir. In both categories, it suggests that the Lower Jurassic reservoirs in the Tugerming area have the favorable potential for oil and gas exploration. The understanding of hydrocarbon migration and accumulation in the Lower Jurassic reservoirs in the Kuqa Depression of Tarim Basin can contribute to the knowledge of the potential to form large oil and gas reservoirs Tugerming Area, and reservoirs of basins with a similar tectonic settings, such as the Jungar Basin.
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    Multiscale pore structure characterization of an ultra-deep carbonate gas reservoir

    Yuxiarig ZhangShenglai YangZheng Zhang
    18页
    查看更多>>摘要： The pore structures of shallow and mid-deep carbonate gas reservoirs have been well explored. Totally different from these reservoirs, however, the pore structure of a target ultra-deep carbonate gas reservoir, the Qixia Reservoir in the Shuangyushi play is still unknown. Affected by tectonic movement and deep hydrothermal transformation, the lithology of this target reservoir has significantly changed and it has developed different scales of pores and fractures. Thus, a multiscale micro-CT (computed tomography) method is needed to combine different scales of its pore space to evaluate carbonate samples more realistically. In this study, the multiscale micro-CT method and other traditional methods including X-ray diffraction (XRD), casting thin section, scanning electron microscope (SEM), routine petrophysical measurements (RPM), and high-pressure mercury intrusion (HPMI) are first combined to quantitatively describe a distribution of multi-scale pores, throats, and fractures in the target ultra-deep carbonate gas reservoir. The results showed that micro pores (70%-90%), micro throats (>90%), and micro fractures (>90%) dominated in this reservoir. Dolomite accounted for more than 90% of the rock mineral composition in the Qixia reservoir with few clay minerals. Intercrystalline pores and micro fractures were the main pore types and the mean reservoir porosity was less than 2%. Micro fractures play a great role in improving reservoir permeability. The HPMI method presented with errors in the classification of ultra-deep carbonate reservoir types owing to the development of vugs, large pores, and fractures. In this study, a new classification method was proposed to classify this type of reservoirs based on porosity, permeability, and the studied parameters from the multiscale micro-CT method such as throat number and connected porosity proportion. The target reservoir was divided into the following four categories according to the new classification method: fracture macropore type (FMA), macropore type (MA), fracture micropore type (FMI), and micropore type (MI). According to the results of multiscale CT scanning, a strong linear relationship was observed between the number of throats, the connected porosity, and the permeability of the ultra-deep carbonate rock samples studied. Fractures improved the permeability of rock samples by aiding the connection of isolated pores and the expansion of the number of throats. Therefore, the MA and MI types of reservoirs should be properly fractured to increase their productivity.
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