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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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    Application of machine learning in the identification of fluvial-lacustrine lithofacies from well logs: A case study from Sichuan Basin, China

    Dongyu ZhengMingcai HouAnqing Chen
    14页
    查看更多>>摘要：The lithofacies identification is critical for forecasting sweet spots of hydrocarbon explorations. Well logs are widely used in lithofacies identifications because they are petrophysical measurements of subsurface stratigraphy which reflect lithological successions and depositional processes. The traditional lithofacies identification from well logs is a manual work that is time-consuming and bias-prone. An automated and bias-free method is in demand. To this end, we created a lithofacies dataset of eleven wells with well log records and lithofacies descriptions that were interpreted manually based on facie s analysis of drilling cutting descriptions and well logs. Then we developed machine learning models that were trained using the lithofacies dataset of the fluvial-lacustrine Upper Trias sic Xujiahe and Lower Jurassic Ziliujing formations in Yuanba Area, northern Sichuan Basin of southwestern China. By employing extreme gradient boosting and resampling algorithms, this machine learning model is efficient and outperforms support vector machine and multiple-layer perception, as indicated by its highest accuracy and Fl-score of 0.90, the highest AUC of 0.94, as well as the shortest training time. Moreover, the result suggests that resampling is necessary for lithofacies identification with the unbalanced dataset. A combined method of over sampling and undersampling is better than a single resampling method. This study presents a successful application of machine learning in fluvial-lacustrine lithofacies identification from well logs and suggests the great potentiality of machine learning in subsurface hydrocarbon explorations.
      原文链接:
    • NSTL

    Application of coalbed methane hydraulic j et-increasing permeability-nitrogen injection to increase production in Shanxi mining area

    Hao YangGuichuan LiXiaohui Dong
    12页
    查看更多>>摘要：China is rich in coalbed methane resources, but the geological conditions of coal seams are complex and variable, and gas production is generally low. Simulations are conducted using the #15 coal seam in the Qiyuan mining area as a case study to improve coalbed methane production. The coal seam has low pressure, low permeability, low saturation and strong heterogeneity. Nitrogen injection has been used in this mining area, but the target production capacity has not been reached. This paper proposes a method to increase production using hydraulic jet drilling, controllable shock wave, and nitrogen injection, and field tests are conducted. The gas production increased from 120 m3/d to 600 m3/d-700 m3/d. Numerical simulations were conducted to determine the ability of the three stimulation methods to increase production. It is assumed that a small number of jet holes are used, and the permeability of the coal seam cannot be significantly improved. The results showed that the gas production was 2-8 times higher after using hydraulic jet drilling and a controllable shock wave than without stimulation measures. The combination of hydraulic jet drilling and controllable shock wave plus general nitrogen injection increased the gas production by 13 times compared to no stimulation measures, but the gas production decreased rapidly. The gas production after one year was consistent with that before general nitrogen injection. Gas production increased faster and was maintained longer after segmented nitrogen injection, and the overall gas production increased, but its decreasing trend was consistent with that of general nitrogen injection. This study provides references for conducting production tests in low pressure, low permeability, and low saturation coal seams.
      原文链接:
    • NSTL

    Invasion of CaCO3 particles and polymers into porous formations in presence of fbres

    Karl Ronny KlungtvedtArild Saasen
    9页
    查看更多>>摘要：Formation damage can occur through migration of drilling fuid particles and polymers into porous formations. A methodology for assessing formation damage was applied to measure invasion of CaCO3 and polymers into porous formations, where the CaCO3 particles size had been selected using established particle size selection methods. Tests were conducted with and without the presence of a cellulose-based additive, to study if the fbres could reduce the fuid loss and limit the formation damage. Input factors such as applied differential pressures, ranging from 6.9 to 34.9 MPa (1000-5000psi), and median pore-throat openings of discs were also varied to investigate which parameters affected the signifcance of the formation damage. The results showed invasion of CaCO3/ground marble into the formation and that particle size selection methods used to reduce fuid loss also led to formation damage. Further it was discovered that the presence of fbres limited the invasion of both CaCO3 and polymers into the porous formations when the D90 of the fbres were ≥3/2 times the pore-throat size, and that higher applied pressures led to larger formation damage. The fuid loss tests also showed both lower total fuid losses and lower fuid loss rates over time with the fbres added to the fuids, indicating that the flter-cake permeability was reduced with the addition of the fbre particles.
      原文链接:
    • NSTL

    Rapid bentonite-cement-oil hydration: Implications to fluid loss control

    Ahmed HafezQi LiuThomas Finkbeiner
    10页
    查看更多>>摘要：Conventional particulate additives fail to control drilling fluid losses into large-aperture fractures. The separate injections of a bentonite-cement-oil suspension and water can cause rapid hydration, swelling and hardening to effectively plug fractures. This experimental study investigates underlying processes and implications in view of optimal fluid flow control in fractures. Results identify several concurrent hydro-chemo-mechanical coupled processes: capillarity-driven water invasion;; cement hydration and the release of Ca + and OH" ions;; bentonite contractive aggregation and increased hydrophilicity: enlarged inter-aggregate pores that facilitate fluid flow;; oil pressurization leading to the formation of oil-filled opening mode discontinuities that facilitate oil escape towards free draining boundaries, and calcium silicate hydrate formation and growth resulting in hardening. The hydration of bentonite-cement-oil suspensions proceeds several times faster than in bentonite-oil suspensions. The optimal mixture should balance competing requirements between flowability, water invasion speed, swelling pressure and plug strength.
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    • NSTL

    Controlled-release chemicals in oilfield application: A review

    Jiang YangYu ChenXiaolong Zhao
    8页
    查看更多>>摘要：Various specialty chemicals are used from exploration and production to transmission in oil and gas industries. However, many of these oilfield chemical treatments are injected into wells that are released in foil at one point upon the addition, and effectiveness lasts for a short time. Controlled-release technology can make the effectiveness of active chemicals last for an extended period in the application. Hence, it also reduces the negative impact of excess chemicals on the environment. Controlled-release technology has begun to play an important role in the oil and gas industries. This paper reviews recent advances and the application of the controlled-release techniques in enhanced oil and gas recovery, flow assurance, asset integrity management, stimulation, and chemical tracer in the oil and gas industry. Novel nanocomposite and encapsulate materials were described. The preparation for the control of released active substances and their released mechanism are also discussed. Applicability in high temperature, pressure, and salinity reservoirs was emphasized. The challenges for the field application of the controlled-release technique in the oil and gas industry are also addressed.
      原文链接:
    • NSTL

    Thermal maturity: The controlling factor of wettability, pore structure, and oil content in the lacustrine Qingshankou shale, Songliao Basin

    Xin WangMin WangJnbu Li
    15页
    查看更多>>摘要：Shale oil resources are abundant in the Qingshankou Formation of the Songliao Basin, but there are significant production differences between wells. Although there are many factors affecting shale oil production capacity, they are all fundamentally reflected in the differences of pore structure and oil-bearing;; however, research on the pore structure and oil-bearing characteristics of naturally mature shale is still rarely reported. Lacustrine shales with low to high maturity developed in the Qingshankou Formation, Songliao Basin;; these shales can be used as good natural mature samples to reveal the wettability, pore structure, oil content, and evolution of shale under the control of thermal maturity. In this study, geochemistry, oil content, and mineral composition information were analyzed using total organic carbon, thermal maturity, Rock-Eval pyrolysis, and X-ray diffraction;; low-temperature nitrogen adsorption-desorption (N2GA), nuclear magnetic resonance (NMR), high-pressure mercury injection, and field emission scanning electron microscopy (FE-SEM) were used to analyze the shale pore structure;; and spontaneous imbibition (SI) combined with NMR and contact angle measurement (CAM) experiments were performed to reveal the shale wettability. The results indicate that with the evolution of maturity from low to high, the cracking degree of organic matter (OM) and the amount of hydrocarbon generation increases, and the scale (number, size) of OM pore development continues to increase. The porosity, pore volume, and Brunauer-Emmet-Teller specific surface area of shale increased continuously due to the increased thermal evolution of OM, and a great many of micropores formed in the shale. Therefore, the average pore size decreased with increased maturity. In addition, shale oil content also improves with the continuous hydrocarbon generation of OM in the process of thermal evolution;; The wettability of the shale interior and surfaces gradually changes from water wetting to oil wetting when vitrinite reflectivity (Ro) > ~1.20% and the degree of oil wetting continues to increase as maturity increases. The crude oil generated by kerogen continues to flow from micropores to macropores, and the pore network continues to develop with increasing oil wetting degree, which is beneficial to crude oil migration and accumulation in the shale reservoir.
      原文链接:
    • NSTL

    Synergetic effects of PVP/HEC polymers on rheology and stability of polymeric solutions for enhanced oil recovery at harsh reservoirs

    Akbar Sabzian melleiAli MadadizadehSiavash Riahi
    11页
    查看更多>>摘要：Polymer solutions reduce the water-oil mobility ratio and improve sweep efficiency and are used for enhanced oil recovery (EOR) in petroleum reservoirs. However, they have some limitations, especially in harsh reservoir conditions. At high temperatures and high salinities (HTHS), the polymers' efficiency decreases because of their viscosity reduction. Using a mixture of polymers that are stable in harsh conditions could solve this challenge. In this study, the synergetic effect of hydroxyethyl celluloses' (HECs) resistance to salinity, and the polyvinyl pyrrolidones' (PVP) resistance to elevated temperatures are studied for their mixtures in different situations. The effects of temperature, salinity, and shear rate on the viscosity of PVP and HEC mixtures were investigated. Measuring the viscosity of PVP and HEC at various concentrations showed that a maximum viscosity could be achieved at a composition ratio of 40:60 for HEC/PVP which is considered an optimum composition. While results indicated that increasing shear rate reduces viscosity, the optimum concentration has the greatest reduction that could make the flooding operation more efficient. Studies on temperature and salinities showed that mixtures of PVP and HEC have good stability in the HTHS conditions. The optimum solution had the lowest independence to temperature compared to other concentrations of HEC and PVP. As lower interfacial tension (IFT) assists in more efficient flooding, the interfacial tension between oil and polymer solutions was measured. It was observed that the suggested polymeric solution has desirable IFT (less than 8 mN/m) with oil in the presence of different salts.
      原文链接:
    • NSTL

    Heat pulse testing at monitoring wells to estimate subsurface fluid velocities in geological CO2 storage

    Refaat G. HashishMehdi Zeidouni
    12页
    查看更多>>摘要：Monitoring the injected CO2 during geological CO2 storage (GCS) is essential to assure containment and identify CO2 leakage. In this work, a new approach is introduced to estimate the evolution of the downhole fluid velocity at a monitoring well and identify CO2 arrival time using in-well heat pulse/tracer test. The proposed technique involves using a downhole heater to generate a series of heat pulses and measuring their corresponding temperature response. The surface temperature of the downhole heater is controlled by the supplied electrical power and the heat loss by convection to the surroundings. Convective heat transfer is well described using Newton's law of cooling in which the temperature difference between the heater and the surrounding fluids drives the heat transfer, for which the convection heat transfer coefficient (h) controls the magnitude of heat loss. Among various factors that control h, it depends on the type of the flowing fluid and its velocity. Through analyzing the measured temperature at different heat pulses, the changes in h-due to mobilization of the in-situ brine or CO2 arrival-can be estimated. Consequently, the velocity of the flowing fluid across the heater can be obtained. Since heat transfer by convection is sensitive to the type of the surrounding fluid, intrusion of CO2 can be detected from the relatively higher surface temperature obtained at CO2 arrival. Churchill and Bernstein (1977)'s correlation is adopted to estimate the change of fluid velocity in terms of the change in h. To demonstrate the validity of the proposed technique, the results are applied and validated against those of COMSOL Multiphysics simulation tool for single-phase brine (before CO2 arrival) and single-phase CO2 (after CO2 arrival). The observed temperature heating is sensitive to the flowing fluid velocity and fluid type. The temperature signal observed at CO2 arrival is large and easily detectable using temperature monitoring tool which provides reliable indication for tracking CO2 arrival at monitoring wells compared with passive temperature monitoring. The results obtained using the proposed technique agree very well with the numerical results obtained from the simulation tool with a maximum estimation error of 7 percent.
      原文链接:
    • NSTL

    Combination of seismic attributes using graph-based methods to identify the salt dome boundary

    Amin Roshandel-KahooMehrdad Soleimani-MonfaredKeyvan Khayer
    12页
    查看更多>>摘要：Geological structural and target stratigraphic units can be well distinguished and clearly presented in seismic data based on their physical characteristics. However, due to the inherent band limited and noise contaminated and sometime distorted image on seismic data, it is not straight forward to identify, delineate and image those targets in seismic data. In this regard, the seismic attributes are used as a tool for extracting valuable information and characteristics from the seismic data for further appropriate geological interpretation of the target. In large size 3D seismic data, extreme interaction time with costly labor force is required for the manual interpretation of the seismic images. Automation of this procedure besides intelligent analysis of large number of various combination of attributes with different computational algorithms provides a reliable, fast and high productive alternative path. In this study, an automatic object delineation method based on combination of seismic attributes is developed based on the graph theory, mainly to identify the salt dome boundary in seismic data. Results are compared with the MLP and weight of evidence methods. For this purpose, initially a set of attributes with different window lengths are extracted from the data and then by using the principal component analysis method, the most appropriate set of attributes for combining are determined. Then a corresponding graph is derived for each attribute and the distance matrix of each graph is calculated and finally the similarity matrix is defined. Subsequently, the graphs are combined using the distance method. The binary model then is obtained by applying a threshold and image segmentation technique. To evaluate the results, they are compared with the interpreted models from the leading-edge methods, and for quantitative comparison, the accuracy value of the method then is calculated pixel by pixel. Based on the quantitative comparison of results, the accuracy obtained by the proposed method here is acceptable and is higher than the well-known MLP and weight of evidence methods, which shows the efficient application of the graph-based combination method in combining seismic attributes and delineation the salt dome boundary.
      原文链接:
    • NSTL

    Geochemical investigation of electrical conductivity and electrical double layer based wettability alteration during engineered water injection in carbonates

    llyas KhurshidImran Afgan
    22页
    查看更多>>摘要：The injection of engineered water to increase the oil recovery from carbonates is increasingly becoming popular due to its reduced environmental impact and low cost of operation. However, the related variation in electric properties of rock and fluid with this technique is still ambiguous and needs thorough investigation. This study explores the variation in electrical conductivity, ion mobility, electrical double layer thickness, and the related oil recovery with the change in water composition from a geochemical perspective. In this study, we implemented an improved wettability alteration model based on the variation in electrical conductivity with a Matlab-IPhreeqc coupled simulator, to model the electrical conductivity, ion mobility, and electrical double layer (EDL) thickness. The variation in concentration of the ionic species obtained from the geochemical model is used to determine the electrical conductivity. This electrical conductivity-based wettability modification is dynamically simulated in the transport model. The model is validated with experimental coreflood data conducted on carbonates by simulating the electrical conductivity measurements reported in the literature. From the findings, it is evident that the formation temperature, sulfate concentration, and dilution of injected seawater has a noticeable effect on electrical conductivity during engineered water injection. It is important to mention that the EDL thickness is the main parameter affected by the change in electrical conductivity. In consequence, it is suggested to inject high-temperature water in carbonate reservoirs because it will increase ion mobility. This increase in ion mobility will enhance the EDL thickness and water film will become stabilized. Moreover, seawater dilution decreases electrical conductivity while spiking of sulfate concentration increases the activity of sulfate ions. However, the concentration of sulfate ions must be controlled as a wettability alteration agent, as it can cause the formation and precipitation of calcium sulfate. Furthermore, the variation in electrical conductivity and EDL thickness caused by the injection of seawater and diluted seawater increased the recovery of oil by approximately 16-21% in the selected case study.
      原文链接:
    • NSTL