Density logging is a key technique for calculating reservoir physical parameters, identifying lithology, and evaluating oil and gas reserves. Due to factors such as borehole conditions and poor tool contact, density curves often suffer from local data gaps, distortion, or noise interference. To address these issues, this paper proposes a density logging curve reconstruction method that integrates the K-nearest neighbors algorithm and the Transformer algorithm (KNN-Transformer). The method first employs KNN to retrieve samples with temporal sedimentary characteristics similar to the target segment within a multi-dimensional logging feature space. By calculating the Euclidean distance between the target segment and historical samples across multi-dimensional features such as acoustic travel time, natural gamma ray, and resistivity, the K most similar neighboring samples are selected to construct an enhanced geological prior input set, thereby improving the geological representativeness of the input data. Subsequently, the multi-head self-attention mechanism of the Transformer algorithm is utilized to establish long-range dependencies between arbitrary positions in the depth sequence, effectively integrating local similarity constraints with global sequential patterns. This achieves a synergistic representation of local features and global structures. Experimental results show that the KNN-Transformer algorithm achieves a mean absolute error (MAE) of 0.017 0 and a coefficient of determination (R2) of 0.953 3 for density curve reconstruction. Compared to typical algorithms such as support vector regression (SVR), linear regression, and long short-term memory (LSTM), the value of MAE is reduced by 30% to 60%. The method demonstrates higher reconstruction accuracy for both the overall trend and local details of the density logging curve, along with better stability and correctness at lithological interfaces and in complex intervals. This approach effectively recovers missing sections, corrects distortions, and suppresses noise, significantly improving both the numerical accuracy and geological plausibility of the reconstructed curves. It provides a reliable technical pathway for high-quality logging data reconstruction under complex reservoir conditions.
CHEN Weiming, JIANG Lin, LUO Tongtong, LI Yue, WANG Jianhua
Shale gas reservoirs are characterized by high compactness and significant heterogeneity, with naturally low production that necessitates hydraulic fracturing technology for enhanced productivity to achieve industrial gas flow. The key to evaluating the effectiveness of fracturing operations and optimizing process parameters lies in obtaining accurate fracture network parameters. Traditional fracture monitoring techniques, such as microseismic monitoring, are costly and cannot achieve full coverage monitoring of well areas. Numerical simulation prediction models require a large number of engineering geological parameters, leading to poor prediction effects for geological data that are incomplete or missing well sections. There is an urgent need for a new method that is economically efficient in obtaining fracture network parameters. To address this, a shale gas reservoir fracture network inversion method based on deep learning was proposed. The core of this method is to quantitatively analyze the fracturing curve characteristic parameters based on the site fracturing curve data, using strongly correlated indicators of fracture network parameters as inputs and microseismic monitoring fracture network parameters (including length, width, height, and volume) as target outputs. A back-propagation (BP) neural network inversion model was established to achieve accurate inversion of fracture network parameters. The model was trained and optimized using 450 fracturing curve segments from shale gas wells in western Chongqing, with the average relative error of fracture network parameter inversion results in the test set being below 15%, which verified the feasibility of this new method for inversion of shale gas reservoir fracture networks.
Petroleum refining. Petroleum products, Gas industry
In view of the low recovery of tight low-permeability oil reservoirs by water flooding in a certain block of Changqing Oilfield， a supercritical CO2-nano-polysilicon composite displacement fluid was developed to explore its oil displacement mechanism and the effect of enhanced oil recovery. Poly （2-acrylamido-2-methylpropane sulfonic acid） （PAMPS） was used for in-situ surface modification of SiO2 to prepare nano-polysilicon particles with strong adsorption capacity and interfacial activity. Through core displacement experiments， the oil displacement performance of composite systems of nano-polysilicon with different mass fractions （1%-5%） and supercritical CO2 was compared under miscible and immiscible conditions. The recovery change was monitored in the experiments， and the effects of nano-polysilicon on rock wettability， interfacial tension， and flow characteristics were analyzed. Under miscible conditions， supercritical CO2 dominated the oil displacement process. The recovery of water flooding was only 32.7%， while the composite system increased it to over 70.0%. Among them， low-dose nano-polysilicon （1%-3%） significantly expanded the swept area of the oil phase and improved micro-scale oil displacement efficiency by enhancing the viscoelasticity and interfacial activity of the displacement fluid. However， high-dose nano-polysilicon （4%-5%） was prone to blocking flow channels due to particle accumulation， leading to a sharp increase in displacement pressure and a slowdown in recovery growth. Under immiscible conditions， nano-polysilicon played a more critical role. It reduced the interfacial tension between supercritical CO2 and crude oil， increased fluid viscosity， and synergistically prolonged the shut-in time， promoting more nano-polysilicon to adsorb on the oil-bearing rock surface， transforming the oil-wet surface into a water-wet or neutral-wet state， and stripping residual oil phases. Under these conditions， the recovery increased from 31.6% of water flooding to 50%-60%. The surface modification of nano-polysilicon gave it amphiphilicity， enabling it to form a stable adsorption layer at the rock， oil， and water interface and weaken the adhesion between crude oil and rock. Supercritical CO2 formed miscible displacement by mixing with crude oil. The synergistic effect of the two significantly improved oil washing efficiency. Supercritical CO2 and nano-polysilicon complemented each other in displacement. CO2 dominated macro-scale oil displacement under miscible conditions， while nano-polysilicon strengthens micro-scale oil washing under immiscible conditions， jointly achieving recovery improvement.
Chemical technology, Petroleum refining. Petroleum products
In order to solve the problem of high energy consumption during LNG gasification in open rack vaporizer(ORV)at LNG receiving stations,taking into account seasonal differences in export volume,combined with the operational performance of seawater pump,valve characteristics,seawater pump sump level and pipeline resistance loss factors,a pipeline network model from the outlet of seawater pump to the inlet of ORV was built.The seawater supply of the model was optimized by adjusting the valve opening of the seawater pump and the number of seawater pumps in operation,and the accuracy of the model was verified through field test.The research results show that the optimization model provides reliable valve opening and corresponding flow rate prediction for the operation of seawater pumps,which can fully meet the needs of actual flow regulation.The optimization model has a significant effect on energy saving and consumption reduction,reducing the energy consumption of seawater pumps by more than 30% compared to the operating plan before optimization.The conclusions provide technical support for the sustainable operation of LNG receiving stations and the achievement of energy saving and consumption reduction goals.
Chemical engineering, Petroleum refining. Petroleum products
The liquid-gas control valve is used to control the start and stop of the power pump in the blowout preventer control system and stabilize the manifold pressure of the control system.Considering the phenomenon of large pressure fluctuation in manifold on site,numerical modeling was used to identify the open/close characteristics of liquid-gas control valve from three aspects(gas source pressure,oil pressure port area,and spring stiffness),and the test verification was conducted.The results show that the gas source pressure has a relatively small impact on the open/close characteristics of the liquid-gas control valve,the oil pressure port area has a linearly inverse relation with the open/close pressure difference,while the spring stiffness has a conic relation with the open/close pressure difference.It is verified that the spring stiffness should be designed between 94 and 97.3 N/mm,and the oil pressure port area of the liquid-gas control valve should be reasonably increased,in order to achieve stable and precise control.The conclusions provide a theoretical basis for improving the accuracy of liquid-gas control valve,thus ensuring the safety and reliability of the pipe system.
Chemical engineering, Petroleum refining. Petroleum products
The generation and propagation mechanism of sound waves of leakage below fluid level in tubing-casing annulus of gas wells have always been of great concern.In order to study the sound wave source characteristics of leakage below fluid level,a physical model for downhole tubing-casing annulus leakage was built; then,the STAR-CCM+ software was used to conduct simulation analysis of flow field and sound field on gas leakage state below annular fluid level,and obtain the cloud charts for pressure and phase of leak flow field as well as sound pressure frequency curves under different leak apertures,positions and speeds.The study results show that as the leak speed increases,the leak gas flow impacts the pipe wall and the fluid level oscillates violently; the leak sound source below fluid level is dominated by quadrupole sound source; the leak sound source above fluid level is mainly generated by the oscillation rupture of fluid level and the quadrupole sound source below fluid level,and the main distribution frequency of leak sound wave energy is in the range of 0～100 Hz; under single variable conditions,the leak sound pressure level increases with the increase of leak aperture and speed as well as the distance from leak position to bottom.The study results lay a theoretical foundation for the application of acoustic method to detect leakage below fluid level at the wellhead.
Chemical engineering, Petroleum refining. Petroleum products
The data of complex well sections are difficult to acquire and the static prediction model is inapplicable to the fluctuating downhole conditions.Considering these challenges, the intelligent method was proposed to predict the fluctuating bottomhole pressure(BHP)in a real-time manner.Based on the generative adversarial network(GAN), which helps to expand the downhole single data measured while drilling and solve the problem of limited effective BHP data, the BHP prediction model with data enhancement was established.In order to effectively improve the adaptability and transfer performance of the model to the variable working conditions, under the condition of incremental update of data, multiple long short-term memory(LSTM)models were trained in a segment-wise manner, and the real-time update of the prediction model was delivered on the basis of transfer and ensemble learning.Finally, the hybrid attention mechanism was used to realize the interpretable analysis of the intelligent prediction model.The results show that the model after data expansion training presents a significant superiority in accuracy and stability, and the incremental update real-time prediction method greatly improves the generalization capacity of the model and the time-effectiveness in field applications.The average relative error of the model is only 0.12%.In addition, the interpretable analysis shows that the BHP has considerable short-term autocorrelation and the wellhead back pressure is characterized by fluctuating transfer.The research findings provide a theoretical guidance for accurate and efficient prediction of BHP and interpretability of intelligent models for drilling deep wells.
Chemical engineering, Petroleum refining. Petroleum products
Ahmed N. Al-Dujaili, Mehdi Shabani, Mohammed S. AL-Jawad
At present, reservoir whether isotropy or anisotropy is taking more attention, particularly the difference in (porosity, permeability, and capillary pressure) associated with pore space. These differences are due to the original sediments and thus diagenetic changes. It has been found that common models are insufficient to predict reservoir performance and field management program design. Recovery factor (RF) is the main factor affecting the optimization process for any reservoir that is very sensitive to reservoir heterogeneity and hence an accurate vertical and horizontal permeability (Kv and Kh) distribution is required. A case study is represented in this paper aimed at vertical permeability estimation from horizontal permeability and porosity for Mishrif reservoir in west Qurna/1 oil field southern Iraq. This study has been accomplished by testing five models, harmonic averaging, Kozeny-Carman equation, Zahaf and Tiab, Iheanacho et al., and Fazelalav to determine vertical permeability and comparing the results with core data values. It is found that the models were used showed an accuracy variation between the units of Mishrif reservoir based on Mishrif full diameter cores from 20 wells. Four new correlations are obtained for mA, CRII, mB1, and mB2 units for Mishrif Reservoir in West Qurna/1 oil field. The correlation shows that the permeability is depending on porosity in the mA unit due to the homogeneity and the Mb1 unit has a higher anisotropy than the other units.
Ryzhkova S.V., Fomin M.A., Zamirailova A.G.
et al.
The article presents the results of revealing the relationship between siliceous, clay, carbonate and organic substances and pyrite from the types of electrical and radioactive logging in Bazhenov Formation. The influence of the content of the listed rock-forming components on the geophysical characteristics is described. The volume lithological model of the Archin-47 well, constructed on the basis of established correlations, is presented.
Evaluation of cement plug integrity is important for successful abandonment operations. Cement plug integrity is influenced by cement filling, but the effect of casing surface roughness on cement plug sealing has not been studied. Norwegian University of Science and Technology and Norwegian Industrial Institute of Science and Technology carried out research on the effect of casing inner surface on cement plugs, which was introduced in this paper. In the research, a cement ring integrity test equipment was applied to test pure cement plugs and silicate cement plugs in three steel pipes with different roughness of inner surfaces, i.e. smooth, medium roughness, high roughness, respectively. Computational fluid dynamics simulation was conducted under test conditions and the simulation results were compared with the test results. The results show that, both pure cement plug and silicate cement plug have poor sealing properties regardless of the inner surface roughness of steel pipe. When the pressure difference is less than 0.001 MPa, the gas leakage rate increases immediately. Rougher inner surface of steel pipes leads to lower gas leakage rate through cement plugs. Pure cement and silicate cement plugs act similarly in decreasing gas leakage rate by 80%～90% in rough steel pipes. The introduction in this paper is helpful to drive the development of abandonment technology in China.
Chemical engineering, Petroleum refining. Petroleum products
In order to improve the safety, reliability and efficiency of composite bridge plug drilling, by taking the carbon fiber composite bridge plug and bit with cylindrical cutters as the researching objects, finite element simulation of composite bride plug drilling process in three dimensional (3D) was made based on the secondary development functions of the ABAQUS software. The influence of bit pressure and drilling speed on bridge plug drill-out rate, axial contact force and torque of the bit was analyzed with the orthogonal experiment. The results show that, the bridge plug drill-out rate, maximum axial contact force and maximum torque of the bit will increase with bit pressure and drilling speed; the sensitive factor for the fluctuation of drill-out rate and torque is the rotational speed, while the sensitive factor for the fluctuation of the axial contact force of the bit is bit pressure; the influence of bit pressure on the axial contact force of the bit is about 2 times that of the rotational speed, but the influence of the bit pressure and rotational speed on torque fluctuation is almost the same. Therefore, during plug drill-through, it may appropriately reduce the bit pressure, increase the rotational speed to decrease the axial force and torque fluctuation, and thus to prolong the bit life. The research results providenew ideas for the research method of composiee bridge plug drilling.
Chemical engineering, Petroleum refining. Petroleum products
To address the interferes of the flowback drilling fluid from the pilot bit of the dual-stage PDC bit with the flow field of the reaming bit, a new dual-stage bit hydraulic structure is formed by adding the inter-stage nozzle on the flow distribution assembly. Based on the DPM (Discrete Phase Model) model in FLUENT, the bottomhole drilling fluid flow rate, bottomhole pressure drop and bottomhole cuttings concentration distribution are simulated. The effectiveness of the inter-stage nozzle for flow field improvement is verified. Based on this, the inter-stage structure influence on the bottom flow field of the dual-stage PDC bit is analyzed. The simulation results show that the drilling fluid cleaning performance is great when the inter-stage nozzle angle is 75°. The positions of the blade of the pilot bit and the reaming bit should be inline as much as possible, thus forming a bottom-up flow passage that facilitates the rapid return of the cuttings. When the length between the pilot bit and the reaming bit increases to 40 mm, the suction of the inter-stage nozzle is most pronounced and then gradually weakened. The increase of the flow ratio of the pilot bit and the reaming bit nozzle improves the cleaning efficiency of the pilot bit bottomhole flow field and reduces the cleaning efficiency of the reaming bit bottomhole flow field. The optimal flow distribution ratio between the pilot and the reaming bit nozzle is 5:5.
Chemical engineering, Petroleum refining. Petroleum products
Abstract Geological investigation have led to discovery of huge tar sand deposits within Afowo Formation of the Turonian–Maastrichtianage (95.9–66.0 Ma) in the Nigerian sector of the Eastern Dahomey Basin. This study aims at determining the feasibility of exploiting the major hydrocarbon resource steam assisted gravity drainage enhanced recovery technique. Samples from three core holes were dry sievied to determine the particle size distribution and their sections studied using a petrographic microscope. Clay mineral content was determined using X-ray diffraction scanning electron microscopy. The granulometric analysis shows the bituminous sediments to be generally fine grained and moderate to well sorted, and the grains are angular to subangular. Porosity ranges from 15.5 to 33.6 ɸ with average value of 26.4 ɸ, while permeability ranges from 270 to 4800 mD, with an average value of 4800 mD (very high) recorded for the sandstones. Petrographic study, scanning electron microscopy and X-ray diffractometry showed quartz as the dominant mineral component, with subordinate feldspar and other accessory minerals. The predominance of quartz is probably due to its mechanical stability. The low frequency of feldspar is attributable to its susceptibility to chemical breakdown and alteration, respectively, during transport and after deposition, with latter accounting for the observed secondary porosity. Kaolinite is the common clay mineral present in the oil sands and may not have sufficiently reduced the reservoir quality to negatively impacting enhanced recovery operation by steam assisted gravity drainage.
The water-powder mixing by Venturi jet and mixing tank mixing are important processes in the injection stage of polymer flooding. In order to study the mixing and dispersing effect of the Venturi jet and the mixing tank, the computational fluid dynamics software FLUENT was used to simulate and analyze the multiphase flow field of the disperse and dissolution system. The mixing performance of water and powder by the Venturi jet under different working conditions was analyzed. The multiphase flow field in the mixing tank was numerically simulated to obtain the distribution of velocity, volume fraction, pressure and turbulent kinetic energy of each phase. Then, the mass fraction of the polymer powder and the dispersion and dissolution effect of the polymer under corresponding conditions was analyzed. The results showed that, with the combination of Venturi jet and the mixing tank, the polymer powder could be uniformly and fully dispersed into the water, which is theoretically superior to the air-mixing. The study results could provide references for the on-site polymer injection process.
Chemical engineering, Petroleum refining. Petroleum products
The reservoir characteristics of the Upper Ordovician Wufeng-Lower Silurian Longmaxi Formations in southern Sichuan Basin were preliminarily revealed in this study by identifying and quantitatively evaluating the fracture pores of five appraisal wells in the central and northern parts of the southern Sichuan Depression by several methods. Four conclusions were reached as follows: (1) In the central zone of the Depression, the deep reservoir space of the Wufeng-Longmaxi producing pay is composed mainly of matrix pores and the microcracks are not common, whether on the local structural highs, flanks or lows. The physical properties are similar to that of the matrix pores in Changning, Weiyuan and Fuling gas fields. (2) In the northern zone of the Depression, the deep reservoir space of the Wufeng-Longmaxi black shale is composed mainly of matrix pores, and fracture pores mainly occur in local discrete intervals, with a total porosity range from 3.5% to 6.7%, on average 5.3%, and fracture porosity of 0-2.1%, on average 0.3%. (3) In the central and northern parts of the southern Sichuan Depression, the Wufeng-Longmaxi producing pays have undeveloped fracture pores and chiefly extensively distributed matrix pores, indirectly indicating relatively stable tectonic activities and corresponding weaker reservoir reworking there than Fuling field located in eastern Sichuan Basin. (4) The size and distribution of the gypsum-salt layer in the Cambrian are the key controlling factors of fracture pore development in the Wufeng-Longmaxi Formations. Therefore, the areas including Wellblocks L7, GS1, eastern Sichuan Basin and western Hubei province, where gypsum-salt layer in the Cambrian is thick and stable, and fracture intervals are likely to occur in the Wufeng-Longmaxi producing pay controlled by decollement structure above salt structure since the Yanshan Movement, are the potential favorable areas for fracture pore development. Key words: Sichuan Basin, southern Sichuan Depression, shale gas, Upper Ordovician Wufeng Formation, Lower Silurian Longmaxi Formation, matrix pore, fracture pore, gypsum-salt layer, decollement
Abstract: The "experience curve" used to be treated as a rule of thumb in strategic management theory. However, it would be hasty to conclude that an approximately 80% log-linear experience curve is a rule of thumb regardless of the industry, company, or product. According to the fundamental research on learning curves, generally, the new model of a product is partly composed of old model parts and we cannot observe the progress of these parts from the beginning of the processes. Therefore, in the first product of the new model, the learning rates of old model parts cannot be identical logically, even if the parts' learning rates are identical at the beginning. In fact, empirical data repeatedly deny identical learning rates for all products. Applying search theory, we obtain an approximate log-linear learning curve and show the curve's initial concavity, that is, if we started observing the progress midstream, and not from the beginning of the process. Thus, both varied learning rate proper to each product and initial concavity of the learning curve are phenomena induced by observing the progress midstream.Keywords: learning curve, experience curve, search theory, initial concavity, progress function(ProQuest: ... denotes formulae omitted.)IntroductionThe continuing production of multiple units of the same product often shows the phenomenon of decreasing production cost per unit. The pattern in which the production cost per unit (or the direct labor hours per unit) decreases at a given reduction rate is known and researched as the "progress function" or "learning curved An early observation of this pattern emerged in aircraft manufacturing (Dutton & Thomas, 1984; Dutton, Thomas, & Butler, 1984). In 1936, T. P. Wright, aeronautical engineer for Curtiss-Wright Corporation, published a widely referenced paper (Wright, 1936) on the learning curve.The learning curve is generally expressed by the progress function f: the production cost2 of the nth unit of the product is formulated as...where the n of the nth unit of the product is the cumulative number of units produced, and a and b are constants (a > 0, -1With respect to the progress function for the log-linear model, when the cumulative unit number doubles, the production cost per unit declines 2b times:...where p = 2b is the learning rate, and 1 - p = 1 - 2b is the progress ratio.3 For example, when b = -0.322, the progress ratio (1 - p) is 20% and the learning rate (p) is 80%, which means an 80% learning curve. Following the progress function, the production cost per unit declines to 100 p % with each doubling of cumulative volume. During World War II, progress functions were applied not only to the aircraft industry but also to the shipbuilding industry in an attempt to use the data created by government shipbuilding contractors (Searle, 1945; Yelle, 1979).From Learning Curve to Experience CurveAfter World War II, Andress (1954) advocated that the application of learning curves developed in the aircraft industry during World War II would result in more accurate and easier forecasting of production costs. Thus, he insisted that their application is valid in industries other than aircraft, namely, electronics, home appliances, residential home construction, shipbuilding, and machine shops. Further, Hirschmann (1964), whose basic argument relies on Andress (1954), advocates that the learning curve is applicable in petroleum refining, to which Andress disagreed. He insisted on the application of the learning curve at the industry level in the petroleum, electric power, and steel industries.The progress of assembly work is much faster than that of machine work, and approximately 75% of the total direct labor input in the aircraft industry is assembly work. …