Continental fine-grained muddy-laminated shale oil is widely developed in eastern China’s faulted lacustrine basins such as the Bohai Bay Basin and Subei Basin. It is characterized by “fine grain size and numerous laminae”, representing a significant new frontier in shale oil exploration and development. However, the complex formation conditions and enrichment patterns of laminated shale oil constrain its effective exploration and development. This study aims to systematically reveal the main controlling factors of the enrichment of this shale oil type, establish corresponding geological theories and reservoir formation models, and develop a supporting key technology system to guide exploration practices and evaluate its resource potential. By comprehensively utilizing core data, well logs, 3D seismic data, geochemical experiments, and production performance data, the geological characteristics, formation conditions, enrichment patterns, and key exploration and development technologies for laminated shale oil were systematically analyzed. The study clarified the advantageous composition of “high brittleness minerals + high-frequency laminae”, the optimal thermal evolution window (maturity between 0.7% and 1.2%), and the enrichment patterns of “medium-to-high matching” (source-to-reservoir lamina thickness ratio of 1∶1.5) that yielded the highest oil content in muddy-laminated shale oil. Two types of micro-migration reservoir formation models were established: felsic + organic matter and calcareous-dolomitic + organic matter. A quantitative standard for identifying Class I enrichment layers was developed, focusing on free hydrocarbon (<italic>S</italic><sub>1</sub>), volume fraction of brittle minerals, resistivity ratio, and natural gamma. A key technology system was developed, centering on geology-logging-seismic integrated “sweet spot” characterization, optimization of horizontal well group parameters, efficient volume fracturing, and controlled pressure production techniques. After the application of this technology system, breakthroughs in high-yield shale oil were achieved in depressions such as Huanghua, Jiyang, Liaohe, Jizhong, and Dongtai. The geological resources of shale oil in eastern faulted basins were estimated to exceed 100×10<sup>8</sup> t, demonstrating promising development prospects. Additionally, the study identified challenges of shale oil from faulted lacustrine basins, including small “sweet spot” scale, great burial depth, inter-well interference, and rapid decline. It proposed research directions such as cost reduction and efficiency improvement, digitalization, and in-situ conversion. By 2030, continental shale oil production in China would account for about 8% of China’s total production.
Petroleum refining. Petroleum products, Gas industry
To improve the accuracy and generalization of well logging curve reconstruction, this paper proposes an artificial intelligence large language model – “Gaia” and conducts model evaluation experiments. By fine-tuning the pre-trained large language model, the Gaia significantly improved its ability in extracting sequential patterns and spatial features from well-log curves. Leveraging the adapter method for fine-tuning, this model required training only about 1/70 of its original parameters, greatly improving training efficiency. Comparative experiments, ablation experiments, and generalization experiments were designed and conducted using well-log data from 250 wells. In the comparative experiment, the Gaia model was benchmarked against cutting-edge small deep learning models and conventional large language models, demonstrating that the Gaia model reduced the mean absolute error (MAE) by at least 20%. In the ablation experiments, the synergistic effect of the Gaia model’s multiple components was validated, with its MAE being at least 30% lower than that of single-component models. In the generalization experiments, the superior performance of the Gaia model in blind-well predictions was further confirmed. Compared to traditional models, the Gaia model is significantly superior in accuracy and generalization for logging curve reconstruction, fully showcasing the potential of large language models in the field of well-logging. This provides a new approach for future intelligent logging data processing.
Pipeline intelligent plugging robot （PIPR） is an indispensable high-end equipment for rapid maintenance and emergency repair operation of pipeline within 12 hours. Achieving efficient and stable deceleration is crucial to the success of plugging operation. A hydraulic control system was designed for a PIPR that uses friction between the slip and the pipe wall to achieve deceleration and positioning. Then， a nonlinear dynamic model of constant deceleration was built for the servo PIPR based on fuzzy PID control. Finally， the numerical simulation method was used to conduct a mechanical-hydraulic co-simulation of the hydraulic control system， and study the influence of important parameters of the control system on the dynamic control stability of the PIPR during the deceleration process. The study results show that as the initial velocity increases， the centroid acceleration of the PIPR gradually increases， with a maximum overshoot of -3.4 m/s2， deceleration process control time within 30 seconds， and positioning accuracy within 5%. Increasing the expected deceleration distance can effectively reduce positioning error； the capacity of the accumulator should be at least greater than 0.25 L. The number of accumulators has a relatively small impact on the system.
Chemical engineering, Petroleum refining. Petroleum products
Shahejie Formation of Boxing Subsag in Dongying Sag is rich in hydrocarbon resources and holds significant exploration potential. However， the complex geological structure， rapid lateral lithological changes in lacustrine shales， strong reservoir heterogeneity， and significant burial depth pose substantial challenges. Multiple fault zones significantly affect the spatial distribution of the in-situ stress field， leading to frequent drilling issues such as collapse and fluid invasion. Additionally， during reservoir fracturing operations， the interference between wellbore fracture networks and difficulties in fracturing key intervals directly hinder hydrocarbon exploration and development of Boxing Subsag. The Upper Submember of the 4th Member of the Eocene Shahejie Formation （Es4U） to the Lower Submember of the 3rd Member of the Eocene Shahejie Formation（Es3L） （Es4U-Es3L） were taken as research objects， and mechanical experiments， logging interpretation， and seismic attribute analysis were integrated to construct a heterogeneous rock mechanics parameter model and determine the in-situ stress state of individual wells. Based on the finite element geomechanical model， the study employed elastoplastic finite element numerical simulations to characterize the in-situ stress field spatially and analyze the controlling factors and mechanisms of in-situ stress field distribution differences. Results indicate that the central-western part of Boxing Subsag has experienced prolonged structural activity， with major faults exhibiting extension and strike-slip characteristics. The overall trend of structural activity is from the south to the north and from the subsag center towards major faults. The overall in-situ stress state of the Es4U-Es3L falls into Class I but varies with depth in some areas. The maximum horizontal principal stress shows an NE-WN extension of high， low， and high-value variation. High in-situ stress zones are mainly concentrated near the Gaoqing-Pingnan fault corner， dominated by nearly EW-trending horizontal compression. The main controlling factors for in-situ stress field distribution include reservoir lithology， structural morphology， and faults. Reservoir lithology results in uneven distribution of in-situ stress due to different mechanical properties of rock， and structural morphology influences in-situ stress properties. Faults lead to chaotic in-situ stress directions， with stress concentrations at fault tips and bends.
Chemical technology, Petroleum refining. Petroleum products
YAO Hongsheng,YUN Lu,ZAN Ling,ZHANG Longsheng,QIU Weisheng
In order to explore the beneficial development path of fault-block shale oil in Qintong Sag, a development mode for the fracturing of directional wells combined with pseudo-horizontal wells has been proposed based on the study on the geological characteristics of shale oil in the second member of Funing Formation, and two wells are successfully implemented. The results show that the east and west wings of the deep sag belt of Qitong Sag in Subei Basin are structural complex areas with fault-block shale reservoirs, which are with large thick, developed natural fracture network, high pressure coefficient, and good mobility and transformability. The geological conditions here is not suitable for the development of long horizontal wells but for the directional wells. For the multi-layer development of thick shale oil, the rectangular directional well pattern is conducive to the CO2 huff and puff, while the diamond reverse nine-spot well pattern is reasonable for the CO2 flooding. Therefore, with the fracturing technology system based on “large-scale liquid injection energy storage & flow limiting perforation promotion and equalization & flow adjustment and fracture-stabilizing network & three-stage support and maintenance filling & continuous construction with all electric pumps”, the fracturing of the directional wells took as the “pseudo-horizontal well” can achieve the transformation effect of the horizontal wells, and the transformation volume of the single stage is 28.6 % larger than that of horizontal wells. This new develop mode of shale oil has high initial productivity, early oil breakthrough time, low flowback rate, fast water cut decline, and long stable production time. The single stage has high elastic productivity, high recovery degree, and good economic benefits, realizing beneficial development of shale oil in advance. The beneficial development shows a good prospect for the evaluation of shale oil in complex structural areas by the directional wells.
Petroleum refining. Petroleum products, Gas industry
The article is devoted to clarifying the structural zoning of the onshore part of the Kaliningrad region. Based on a comprehensive analysis of a significant amount of new research data carried out in the period from 2003 to 2019, the pattern of structural zoning has been refined. It is based on the structural construction between of the basement surface and the top of Ordovician level. The generalization of new and reprocessed materials was carried out as part of the research activity carried out by VNIGRI, VNIGNI, VSEGEI and JSC RosGeo.
Marcelo Lopes, Joao von Hohendorff Filho, Denis Schiozer
Simulation models of integrated reservoir and production systems are required for a robust production forecast. Traditionally, reservoir and production system models are calibrated against dynamic data to establish future boundary conditions. Herein, we propose probabilistic data assimilation for production system models to improve the quality of production forecasts. We used a benchmark case through a reference model, which represents the real field, and a simulation model for (1) sensitivity analysis of production system parameters; (2) adjustment of production system parameters, based on dynamic production history data, to minimize the gap between data and model using an optimization method; and (3) comparison of production forecast in the simulation model, coupled to history-matched and non-matched production systems, and a reference model. Sensitivity analysis of production system parameters indicated a significant impact of the pressure gradient adjustment parameter. But we verified that there were no unique correlations (multiphase flow and fluid) and absolute roughness in the production tubing that fit overall production history, affecting production forecast. Comparing production curves of simulations, coupled with history-matched and non-matched production system models to the reference model, we show that adequately adjusted models are closer to the real model. It is mainly the case for systems with higher capacity, where production is more dependent on the responses of the production system. The probabilistic calibration approach of production systems before integrating reservoir models to adjust production systems simulation models is simple to perform. It can improve the quality of the forecast of the field.
An orthogonal 2D training image is constructed from the geological analysis results of well logs and sedimentary facies; the 2D probabilities in three directions are obtained through linear pooling method and then aggregated by the logarithmic linear pooling to determine the 3D multi-point pattern probabilities at the unknown points, to realize the reconstruction of a 3D model from 2D cross-section. To solve the problems of reducing pattern variability in the 2D training image and increasing sampling uncertainty, an adaptive spatial sampling method is introduced, and an iterative simulation strategy is adopted, in which sample points from the region with higher reliability of the previous simulation results are extracted to be additional condition points in the following simulation to improve the pattern probability sampling stability. The comparison of lateral accretion layer conceptual models shows that the reconstructing algorithm using self-adaptive spatial sampling can improve the accuracy of pattern sampling and rationality of spatial structure characteristics, and accurately reflect the morphology and distribution pattern of the lateral accretion layer. Application of the method in reconstructing the meandering river reservoir of the Cretaceous McMurray Formation in Canada shows that the new method can accurately reproduce the shape, spatial distribution pattern and development features of complex lateral accretion layers in the meandering river reservoir under tide effect. The test by sparse wells shows that the simulation accuracy is above 85%, and the coincidence rate of interpretation and prediction results of newly drilled horizontal wells is up to 80%.
Hery Tristijanto, Mochammad Noer Ilman, Priyo Tri Iswanto
The demand for improved reliability and prolong the lifetime of piping and pipelines has led to the development of various methods to protect piping and pipelines from corrosion attack, one of which is the use of inhibitors such as molybdate. Molybdate is a corrosion inhibitor that is non-toxic and environmentally friendly. The present paper aims to study effect of molybdate on corrosion behaviors of various regions in submerged arc API 5L X-52 steel welded joints including weld metal (WM), heat affected zone (HAZ) and base metal (BM) in a 3.5% NaCl solution. In this study, corrosion characteristics of welded API 5L X-52 steel pipelines were studied using Tafel polarization method by immersing the specimens in 3.5% NaCl solution with different percentages of Na2MoO4 inhibitors, namely 0.1, 0.2, 0.3, and 0.4% combined with SEM microanalysis of corrosion products. Results show that HAZ seems to be the most susceptible region for corrosion attack, and this undesirable effect is associated with bainitic microstructure present in the region. The additions of molybdate have two effects. First, the corrosion rate decreases with increasing inhibitor concentration and secondly; the corrosion potential is shifted to the positive direction in the polarization curve. The molybdate inhibition of corrosion could be related to its ability to form passive film, and it is discussed in the present study.
Abo Taleb T. Al-Hameedi, Husam H. Alkinani, Mohammed M. Alkhamis
et al.
Abstract The cost of the drilling operation is very high. Drilling fluid presents 15 to 30% of the entire expense of the drilling process. Ordinarily, the major drilling fluids additives are viscosity modifiers, filtration control agents, and partial loss treatments. In this experimental work, full-set measurements under fresh and aged conditions, as well as high-temperature and high-pressure (HTHP) API filtration, were conducted to study the impacts of adding 0.5%, 1.5%, 2.5%, and 3.5% of black sunflower seeds’ shell powder (BSSSP) to spud mud. BSSSP of various grain sizes showed their ability to be invested for viscosity modifying, seepage loss controlling, and partial loss remediation. In addition to BSSSP eminent efficiency to be used as a multifunctional additive, the BSSSP is cheap, locally obtainable in commercial quantities, environmentally friendly additive and easy to grind into various desired grain sizes. Besides its outstanding strength to behave under conditions up to 30 h aged time and under 50 °C (122 °F) temperature, the utilization of powdered waste black sunflower shells in the drilling process and other industrial applications can reduce the effects of food waste on the environment and the personnel safety. To sum it up, experimental findings revealed that BSSSP can be used for multiple applications as a novel fibrous and particulate additive. The results elucidated BSSSP suitability in substituting or at least minimizing some of the traditional chemical materials utilized in the petroleum industry such as salt clay, polymers, and lost circulation materials (LCM).
To address the partial failure problem of hydraulic slip of snubbing unit under high load, the three structural parameters of slot width, slot position and tooth crest width of slip were studied by the method of test and simulation. The hydraulic slip structure design method of combining the finite element analysis method, orthogonal test method, linear weighting method and Matlabs optimization toolbox was proposed. The results show that the weak parts of hydraulic slip are slip teeth, which have uneven distribution of stress in the circumferential direction and the axial direction. Mises stress in the circumferential direction of slip basically shows a symmetrical trend. Mises stress in the axial direction presents a saddle shape that larger values are at both ends and smaller value is in the middle. The analysis shows that the optimized slip structure has the slot width of 5 mm, the tooth crest width of 0.23 mm, and the angle between the slot plane and the left and right end faces of 21.67°. The study results are of great significance to the improvement of the stress distribution of hydraulic slips and the improvement of clamping capacity.
Chemical engineering, Petroleum refining. Petroleum products
As a new parameter of the rock mechanics evaluation, the brittleness index （BI） has an important influence on the later fracturing and reconstruction of the reservoirs. The traditional calculation methods of the BI applied to the geosteering drilling of the shale gas horizontal wells have many limitations. Aiming at the calculation of the BI in real time by the LWD curves, we started with the experimental study on the BI and porosity to provide an experimental basis for calculating the BI by the porosity log information. Then, we used the regression method to analyze the relevance of the AC, DEN, CNL, GR logging values and BI, calculated the BI by using single LWD curves, and through the contribution of different logging curves to the BI, established a BI calculation method by logging while drilling of the shale reservoirs. Finally, we analyzed the feasibility of the model by the examples. The research result shows that the model is effective and adaptable, which provides a reliable basis for the geosteering drilling of the horizontal wells of the shale gas by the BI.
Petroleum refining. Petroleum products, Gas industry
Microbial surfactants are widely used for industrial, agricultural, food, cosmetics, pharmaceutical, and medical applications. In this study, two bacterial strains namely, Ochrobactrum anthropi HM-1 and Citrobacter freundii HM-2, previously isolated from used engine oil contaminated soil, and capable of producing biosurfactants, were used. Their cell-free culture broth showed positive results toward five screening tests (hemolysis in blood agar, drop collapse, oil displacement, emulsification activity (E24), and surface tension (ST) reduction). They reduced the ST of growth medium (70 ± 0.9) to 30.8 ± 0.6 and 32.5 ± 1.3 mN/m, respectively. The biosurfactants were classified as anionic biomolecules. Based on TLC pattern and FT-IR analysis, they were designated as glycolipids (rhamnolipid). Waste frying oil was feasibly used as a cheap and dominant carbon source for biosurfactants production; 4.9 and 4.1 g/l were obtained after 96 h of incubation, respectively. Compared with non-irradiated cells, gamma-irradiated cells (1.5 kGy) revealed enhanced biosurfactant production by 56 and 49% for HM-1 and HM-2, respectively. The biosurfactants showed good stability after exposure to extreme conditions [temperatures (50–100 °C for 30 min), pH (2–12) and salinity (2–10% NaCl)], they retained 83 and 79.3% of their E24, respectively, after incubation for a month, under extreme conditions. Biosurfactants effectively recovered up to 70 and 67% of the residual oil, respectively, from oil-saturated sand pack columns. These biosurfactants are an interesting biotechnological product for many environmental and industrial applications. Keywords: Ochrobactrum anthropi, Citrobacter freundii, Biosurfactant, Characterization, Stability
Failure of cement sheath seal will lead to underground fluid channeling and annulus pressuring, which will affect the productivity of oil and gas wells and the safety of production operation. The optical fiber sensing system can identify whether the cement sheath seal fails by detecting unnecessary oil and gas in the cement sheath. To promote the development of optical fiber sensing technology for detecting the cement sheath seal, the working principle of DTSS data acquisition device was introduced. The optical fiber calibration test device was designed. The strain values of cable submerged in different test liquids were tested. The sensitivities of cable on different liquid were analyzed. The results show that, by means of the distributed temperature and strain sensing data acquisition device and the newly designed optical fiber sensing cable, the optical fiber sensing technology could achieve real-time, in-situ, continuous and non-destructive monitoring of cement sheath sealing, contributing to saving cost. The results obtained laid the foundation for further research and field application of optical fiber sensing system.
Chemical engineering, Petroleum refining. Petroleum products
There had been a long history of the buried-hill hydrocarbon reservoirs exploration operation in Bohai Sea. Between 1970s and 1990s, based on the onshore exploration experiences in eastern China, many boreholes were drilled in order to detect large-scale carbonate buried-hill hydrocarbon reservoirs in Bohai Sea, but no prominent discoveries was achieved. In-depth re-evaluation and examination were conducted upon these exploration failures, a new understanding that Bohai Sea had unique geological characteristics of buried hills was concluded. Bedrocks on the uplifts of Bohai oil province were mainly granites and migmatitic granites of Archean, Proterozoic and Mesozoic, as well as minor Lower Paleozoic carbonates. Proterozoic algae dolomite was most favorable for buried-hill hydrocarbon reservoirs however which were not developed in Bohai Sea. A large number of faults in Bohai oil province were developed and faults activities were intense in the late period. Thus, conventionally, reservoirs and preservation conditions of the buried hills were believed to be poor in Bohai Sea, and were not favourable for formation of large-scale buried-hill hydrocarbon reservoirs. Through the long-term practices and deep analyses, the coupling between granites, migmatitic granites and intense bedrock faults was favorable for buried-hill reservoirs with high test production and relatively low core recovery rate. Geophysical data could be used for accurate predictions of bedrock lithology and faults. The monadnock buried hills on the low uplifts adjacent to hydrocarbon-rich sags were covered by shallow to semi-deep lacustrine shale, which was favorable for buried-hill hydrocarbon reservoirs. Under the guidance of a series of innovative understandings, the re-exploration of buried hills in Bohai Sea achieved two largest granite buried-hill oil and gas fields with 100 million tons of reserves. The understanding and practice processes might also inspire exploration of other areas. Keywords: The buried-hill hydrocarbon reservoir, Bedrock, Granite, Carbonate rocks, Coupling between lithology and fault, Bohai Sea
Oils, fats, and waxes, Petroleum refining. Petroleum products
Nermen H. Mohamed, Reem K. Farag, Shimaa M. Elsaeed
et al.
Porous membranes are prepared through micro phase separation of immiscible polymers consisting of hydrophobic polymer (polystyrene) and hydrophilic polymer (poly(2-vinylpyridine)). The greatest difficulties during petrolatum deoiling are related to the filtration stage for obtaining microcrystalline wax. The present study deals with the addition of porous membrane as modifier for the crystal structure of solid hydrocarbons, which will be the cornerstone in rearrangement and reformulation of new hard crystals in deoiling process. XRD and SEM photographs were used to evaluate the crystallinity and crystal sizes of the separated hard waxes.
Aiming to optimize the truss leg structure of self-elevating unit, the sensitivity of leg strength to different chord space was analyzed, and the optimal value of chord space for legs was presented. The wind load under storm condition was obtained by wind tunnel test, and the wave and current loads were calculated based on theoretical and numerical methods. The natural vibration period and first order offset value were obtained by eigenvalue analysis, thus the inertial load considering the dynamic amplification factor and the inertial moment considering the geometric nonlinearity were obtained. It is found out through analysis that: the inertial load considering the dynamic amplification factor is more sensitive to chord space under a certain wave and current angle, and decreases with the increase of chord space in general; the inertial moment considering the geometric nonlinearity also decreases with the increase of chord space. According to the environment load, the strength of leg structures at different chord spaces were checked and the sensitivity of the structure strength to chord space was compared. Based on this, the optimal values of chord space for legs at three water depths were presented. Key words: self-elevating unit, environment load, leg strength, chord space