Gas injection is a critical technique to replenish formation pressure for enhancing oil recovery in low-permeability oilfields. At present， the single-string separate-layer gas injection with throwing and fishing gas nozzles is adopted in the Bohai Oilfield， but it cannot read downhole data in a real-time manner while regulation and thus fails to accurately adjust the injection volume. This paper presents the concentric fine separate-layer gas injection process for offshore oilfields and develops associated tools and techniques. Among these tools， the gas injection measurement and adjustment working cylinder with maximum temperature and pressure resistance up to 150 ℃ and 60 MPa， respectively， can realize a stepless regulation of gas injection rate， and the gas flow tester relying on flow-concentrating test process can achieve test of individual intervals and also two-way communication with downhole equipment. Field applications have demonstrated successful measurement and adjustment of the concentric fine separate-layer gas injection process. The proposed process was verified to be applicable to wellbores with diameter of 98.55 mm and inclination not greater than 60°， and could effectively address the issues of gas sealing， gas corrosion， gas erosion， and gas injection safety. Moreover， it yielded a qualified injection rate reaching 95% and reduced the overall injection adjustment duration from 48 h to 12 h. This study provides a new technical option for efficient gas flooding in offshore low-permeability oilfields.
Chemical engineering, Petroleum refining. Petroleum products
杨思婕1,2，方学智2，杜孟浩2，吴苏喜1，罗凡2 YANG Sijie1,2, FANG Xuezhi2, DU Menghao2, WU Suxi1, LUO Fan2
为优选出功能营养与氧化稳定性兼顾的油茶籽油制备工艺，以油茶籽仁为原料，采用超临界CO2萃取法、湿法和热榨法制备油茶籽油，并测定其基本理化指标、活性成分含量、脂肪酸组成和氧化稳定性，以评价3种制油工艺对油茶籽油品质的影响。结果表明：湿法制备的油茶籽油的酸值（KOH）和过氧化值较超临界CO2萃取法和热榨法低，分别为0.63 mg/g和0.14 g/100 g；湿法制备的油茶籽油的生育酚含量最高；超临界CO2萃取法制备的油茶籽油的角鲨烯、β-谷甾醇、类胡萝卜素和多酚含量均最高，其中角鲨烯、β-谷甾醇、类胡萝卜素含量分别为热榨法的1.36、1.74倍和1.38倍；热榨法制备的油茶籽油中饱和脂肪酸含量低于湿法与超临界CO2萃取法，但脂肪酸组成无显著差异；湿法制备的油茶籽油的氧化诱导时间最长，运用外推法计算出25 ℃下其氧化诱导时间为1 037 h。综上，湿法制备的油茶籽油氧化稳定性最佳，超临界CO2萃取法制备的油茶籽油活性成分保留率总体最高，适合功能性油脂生产，热榨法满足油茶籽油传统风味需求，可根据产品需求选择合适的制油工艺。
To select an optimal preparation process of camellia seed oils that balances functional nutrients and oxidative stability, with camellia seed kernel as the material, camellia seed oils were extracted by supercritical CO2 extraction, wet extraction, and hot pressing. Their basic physicochemical indicators, active component content, fatty acid composition, and oxidative stability were determined to evaluate the effects of the three oil production processes on the quality of camellia seed oils. The results showed that the acid value and peroxide value of camellia seed oil prepared by wet extraction were lower than those obtained by supercritical CO2 extraction and hot pressing, at 0.63 mgKOH/g and 0.14 g/100 g, respectively. The camellia seed oil prepared by wet extraction had the highest tocopherol content. The camellia seed oil prepared by supercritical CO2 extraction had the highest contents of squalene, β-sitosterol, carotenoids, and polyphenols. Specifically, the contents of squalene, β-sitosterol, and carotenoids in the oil obtained by supercritical CO2 extraction were 1.36, 1.74 times, and 1.38 times those in the oil obtained by hot pressing, respectively. The saturated fatty acid content in camellia seed oil prepared by hot pressing was lower than that in the oils obtained by wet extraction and supercritical CO2 extraction, but there was no significant difference in fatty acid composition. The camellia seed oil prepared by wet extraction had the longest oxidation induction time. Using the extrapolation method, its oxidation induction time at 25 ℃ was calculated to be 1 037 h. In conclusion, camellia seed oil prepared by wet extraction exhibits the best stability, camellia seed oil prepared by supercritical CO2 extraction generally has the highest retention rate of active components, and the oil prepared by hot pressing meets the demand for traditional flavor of camellia seed oil. The appropriate oil production process can be selected according to product requirements.
To explore the influence of differential diagenesis on the oil bearing properties of tight sandstone reservoirs， Chang 8 reservoirs with ultra-low porosity and ultra-low permeability in the Qingcheng area were used as an example. Based on the statistical cast thin section data of 337 samples and the scanning electron microscope （SEM） and high-pressure mercury injection data of 10 samples， the porosity evolution characteristics of different types of reservoirs were calculated， and the influence of differential diagenesis on the oil bearing properties of the reservoirs was analyzed. The research results show that the Chang 8 tight sandstone reservoirs in the Qingcheng area are mainly composed of lithic feldspar sandstone and feldspathic litharenite， with dissolution pores and residual intergranular pores developed. According to the characteristics of brittle mineral content， soft particle content， porosity， and calcareous cement content， the Chang 8 reservoirs can be divided into three types： high-porosity sandstone （Type Ⅰ）， high-porosity calcareous sandstone （Type Ⅱ）， and rich soft particle sandstone （Type Ⅲ）. Type Ⅰ reservoirs are mostly underwater distributary channel sand bodies and have the strongest compaction effect in the early diagenesis stage， with an average compaction porosity reduction rate of 60.0%， but they have a strong dissolution effect in the later stage， with an average dissolution porosity increase rate of 11.8%， weak cementation effect， and an average cementation porosity reduction rate of 27%. The average remaining porosity value is 9.5%. Type Ⅱ reservoirs are mostly underwater distributary channel sand bodies， and their estuarine bar sand body is slightly developed compared with Type Ⅰ reservoirs. The early calcium cementation of Type Ⅱ reservoirs is strong， and the compaction is relatively weak. The average compaction porosity reduction rate is 56.8%， and the average cementation porosity reduction rate is 34.1%； the average dissolution porosity increase rate is 11.5%， and the average remaining porosity is 7.9%. Type III reservoirs are more likely to develop in sand bodies along the side of underwater distributary channels. The early compaction of Type II reservoirs is not strong， with an average compaction porosity reduction rate of 49.3%， but the later dissolution is weak， with an average dissolution porosity increase rate of 10.5%. The late cementation is strong， with an average cementation porosity reduction rate of 43.2%. The final porosity is the lowest， with an average value of 6.9%. The pore throat radius of Type Ⅰ and Type Ⅱ reservoirs is concentrated in 0.1-1 μm， and the pore throat connectivity is good. The pore throat heterogeneity is weak， and the oil bearing property is good. The distribution of pore throat in Type III reservoirs is not concentrated， and the connectivity is poor； the pore throat heterogeneity is strong， and the oil bearing property is poor. In the Late Early Cretaceous， oil and gas migrated and accumulated on a large scale， and the three types of reservoirs were not densified. With the further densification of reservoirs in the middle diagenesis A stage， the differences in physical properties and pore throat structure of the three types of reservoirs are enhanced， affecting the adjustment distribution of oil and gas in the later stage. The oil bearing property of Chang 82 is poorer than that of Chang 81 because the Type II reservoirs in Chang 82 are more developed， and strong carbonate cementation reduces the connectivity of pore throats， which is not conducive to oil and gas charging.
Chemical technology, Petroleum refining. Petroleum products
HU Junjie, LU Cong, GUO Jianchun, ZENG Bo, GUO Xingwu, MA Li, SUN Yuduo
With technological advancements, fibers now serve roles beyond proppant backflow prevention, including proppant transport, plugging, fracture morphology optimization, and other aspects, namely, fiber-network proppant fracturing technology. The fiber-based proppant transport and fiber temporary plugging technologies can effectively address issues currently faced by deep shale gas, such as proppant near-wellbore accumulation and insufficient temporary plugging effectiveness, thereby improving the effectiveness of volumetric fracturing stimulation. To this end, the study was conducted in a deep shale gas block in the southern Sichuan Basin, investigating fiber-based proppant transport and fiber temporary plugging mechanisms, as well as laboratory physical simulations to optimize and evaluate the performance of fiber materials. Based on the regional geological and engineering characteristics of the study area, fracturing software simulations were carried out to determine the hydraulic fracture width for deep shale gas. A field test plan was then developed, and the fracturing construction, flowback, plugging, and fracturing effectiveness of the test wells were monitored and evaluated. The research results indicated that fibers had strong proppant transport assistance and flexible bridging capabilities. By modifying the molecular structure of fiber materials and adding a certain amount of structural stabilizers, discontinuous cluster-like support structures can be formed, significantly enhancing the placement effect and conductivity of proppants. Based on fracture width simulation calculations, the hydraulic fracture width for deep shale gas is between 2 to 5 mm. By optimizing fiber types based on fracture width, proppant grain size, and concentration, full support of fractures can be achieved. Compared to conventional fracturing wells, the test wells with modified fiber + structural stabilizer for sand-carrying fracturing exhibited better production increase and proppant flowback prevention. Fibers can be used for temporary in-fracture plugging. During the construction process, the pressure response is evident, which may lead to excessively high pressure during subsequent operations, making proppant addition difficult. Optimizing the timing of fiber injection is beneficial for the subsequent overall sand addition process. Additionally, fibers can also be used to address the inter-well gas migration issue in deep shale gas wells by strengthening the temporary plugging of fracture openings and sealing natural fractures, thereby preventing further communication between hydraulic fractures and distant natural fractures. The study, based on the characteristics of deep shale reservoirs in the southern Sichuan Basin, has developed a set of performance indicators for fiber materials suitable for deep shale gas, including fiber length, stability, compatibility, and degradation rate. It also proposes a four-in-one fiber injection process and design method, focusing on “entry, distance, height, and prevention”. It provides strong support for the future economic development, technology optimization, and fracturing process adjustments of shale gas.
Petroleum refining. Petroleum products, Gas industry
To increase the penetration performance of perforating bullet, the powder particle grade technique is studied by increasing the density of tungsten powder liner. By using the method of geometric configuration analysis and the effect of cramming and cladding between the big and small particles, an idealized particle grading model considering the morphology of tungsten powder particles is constructed. The compact density formula of the packing system formed by the interaction of large and small tungsten powder particles and the relation formula of each parameter are obtained. Tungsten powder particle grading technology is applied to make the tungsten powder liner of perforating, and the bulk density of tungsten powder and density of the liner are tested. The result shows that the the bulk density of tungsten powder is increased from 7.96 g/cm3 to 9.65 g/cm3 with a growth rate of 21.2%. The density of perforating liner is increased from 14.70 g/cm3 to 15.69 g/cm3 with a growth rate of 7.6%. This has fully proved that the particle grade model is right and the tungsten powder partical grade has prominent effect on density increasment of the liner of perforating. The tungsten powder partical grade has been proved an effective method to increase the performance of perorating bult.
周沁颖，金俊，王颖琪，王雨昕，金青哲，王兴国ZHOU Qinying, JIN Jun, WANG Yingqi, WANG Yuxin, JIN Qingzhe, WANG Xingguo
烛果油富含1，3-硬脂酸-2-油酸甘油三酯（StOSt），是可可脂的理想改良剂。为探究烛果油在巧克力中的应用效果，以市售烛果油为研究对象，分析其组成特征，并研究其与可可脂复配的相行为及复配体系在经典黑巧克力中的抗霜性能。结果显示：烛果油中的StOSt（57.1%）和甘油二酯（6.65%）含量显著高于可可脂的（23.8%、4.48%），且烛果油中低熔点甘油三酯含量也高于可可脂的；烛果油在室温下的固体脂肪含量比可可脂低10~20百分点；当烛果油与可可脂按质量比9∶ 1复配时，其相应的巧克力抗霜性显著强于可可脂基巧克力，其中，合适的StOSt、POSt、POP三者比例（10∶ 3∶ 1）提高了油基的相容性，而适当的甘油二酯含量有助于保持相的均一性。综上，烛果油可应用于巧克力中以延缓巧克力起抗霜。Kokum fat is rich in StOSt and is an ideal modifier for cocoa butter. In order to explore the effect of its application in chocolate, commercial kokum fat was taken as the research object, its composition characteristics were analyzed, and the phase behavior of the compound with cocoa butter and the bloom resistance abilities of the compound system in classic dark chocolate were studied. The results showed that the contents of StOSt (57.1%) and diglycerol (6.65%) in kokum fat were significantly higher than that in cocoa butter (23.8%, 4.48%), and the content of low-melting triglyceride in kokum fat was also higher than that in cocoa butter. The solid fat content of kokum fat at room temperature was 10 to 20 percentage point lower than that of cocoa butter. Chocolate formulated with the binary fat containing 90%of kokum fat and 10% of cocoa butter exhibited desirable bloom resistance compared with cocoa butter based-chocolate. It was suggested that when the ratio of StOSt/POSt/POP was 10∶ 3∶ 1, the compatibility of fat phase could be improved, and desirable levels of diglycerides contributed to maintain phase homogeneity. In conclusion, kokum fat can be applied in the production of chocolate to delay the bloom of chocolate.
Gravé Gwendoline, Mouloungui Zephirin, Cerny Muriel
et al.
Chia (Salvia hispanica L.) is a candidate to be included in European diet due to its seed oil content and composition. Its cultivation in Europe has been assessed in several European countries by introducing genotypes from Latin America. The cultivar Oruro (released by Panam Company, France) was used in this study and cultivated at two locations of southern West of France (Lavaur and Samatan). The aims of this study were to investigate the oil content and composition of chia seeds cultivated in two locations under organic conditions in southern West of France. As expected, location factor affected oil content. Moreover, this factor affected also fatty acid, sterols and tocopherols content and composition. Lavaur presented higher oil content than Samatan. This later location presented higher temperature during grain filling period. Polyunsaturated fatty acids were more represented at Lavaur than at Samatan. Saturated and monounsaturated fatty acids showed the opposite trends. Sterols and tocopherols were more accumulated in chia seeds at Lavaur. These results showed that all quality traits of chia seed cultivated in France were affected by climatic conditions prevailing in location of cultivation.
To investigate the 4D stress change during injection and production in tight sandstone reservoirs, a multi-physical fields modeling method is proposed considering the reservoir heterogeneity, hydraulic fracture and complex injection-production system. The 4D stress evolution of tight sandstone reservoir in Yuan 284 block of Huaqing oilfield, Ordos Basin, during injection-production in horizontal well network is investigated by modeling coupled flow and geomechanics. Results show: (1) Induced by injection and production, the 3D stress increases near the injectors but decreases near the producers, and the horizontal stresses are distributed in obvious strips along their respective stress directions. (2) The horizontal stress difference is the highest at the horizontal wellbore beside injectors during injection and production, while it is the lowest in undeveloped zone between the injectors, and the orientation of maximum horizontal principal stress changes the most near the injectors, which is distributed radially. (3) The hydraulic fracture in re-fracturing well was observed to be asymmetrical in geometry and deflected as the stress changed. The results provide theoretical guidance for horizantal well network modification and re-fracturing optimization design in tight sandstone reservoir.
The health benefits of a diet rich in omega-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA) no longer need to be proven. However, while health authorities attempt to increase the consumption of the n-3 LC-PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), data from the latest intake surveys demonstrate that EPA and DHA consumption is still too low. A push towards greater sustainability, and a rise in vegetarianism are pushing manufacturers to move from traditional fish oils towards alternative sources. Microalgae oils provide a source of n-3 LC-PUFA with a lower environmental impact and are produced using processes that limit damage to the oils. This review aims to report on oleaginous microalgae strains available for n-3 LC-PUFA production, the processes used for their growth and the extraction and refining processes for their oils. It also addresses the challenges inherent in these products and their fabrication, and some of the novel characteristics of microalgal oils, including their very high n-3 LC-PUFA content and the chemical structure of their triglycerides, that lead to exciting opportunities in their use as functional food ingredients.
A forecasting method of oil well production based on multivariate time series (MTS) and vector autoregressive (VAR) machine learning model for waterflooding reservoir is proposed, and an example application is carried out. This method first uses MTS analysis to optimize injection and production data on the basis of well pattern analysis. The oil production of different production wells and water injection of injection wells in the well group are regarded as mutually related time series. Then a VAR model is established to mine the linear relationship from MTS data and forecast the oil well production by model fitting. The analysis of history production data of waterflooding reservoirs shows that, compared with history matching results of numerical reservoir simulation, the production forecasting results from the machine learning model are more accurate, and uncertainty analysis can improve the safety of forecasting results. Furthermore, impulse response analysis can evaluate the oil production contribution of the injection well, which can provide theoretical guidance for adjustment of waterflooding development plan.
In-situ polymerization gel system is one of the important measures to alleviate reservoir heterogeneity. In order to solve the problem that the gelation time of in-situ polymerization gel system is too fast, taking polyvinyl butyral（PVB） as the wall material and the mixture of ethanol and water as solvent, the delayed gelation microcapsule initiator with ammonium persulfate as the active core has been prepared by interfacial precipitation method. Meanwhile, the performance of microcapsule regulating gelation time of in-situ polymerization gel system has been studied. By mixing 0.05 % ethanol solution of PVB with aqueous solution containing ammonium persulfate and 0.6 % compound stabilizer（OP-10 and Tween 80） at a volume ratio of 7:3, microcapsule initiator with an average particle size of 0.7~1.5 μm have been prepared, and the optimal concentration of ammonium persulfate is 0.2 % ~ 0.4 %. At 40 ~ 90 ℃, the gelation time can be longer than 30 h by adjusting the concentration of microcapsule initiator. Core test result shows that the microcapsule initiator can be successfully injected into the core with an average permeability of 50×10<sup>-3</sup> μm<sup>2</sup>, and initiate the polymerization of in-situ polymerized gel system to produce effective plugging. The in-situ polymerization systems with initiator microcapsules can be injected into reservoirs with an average permeability of 50×10<sup>-3</sup> μm<sup>2</sup>, and initiate the polymerization of in-situ polymerization gel system to produce effective plugging. The enhanced oil recovery（EOR） result indicates that the oil recovery increases by 20.24 % after the gelation of the in-situ polymerization gel system.
Petroleum refining. Petroleum products, Gas industry