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Multistage fracturing in horizontal well has become one of the important techniques for the efficient development of low-permeability sandstone reservoirs. In multistage hydraulic fractured horizontal wells (MHFHWs), the depth of fracturing fluid invasion into the formation is a key parameter evaluating the imbibition enhancement after fracturing. However, few studies have been conducted on the invasion depth of fracturing fluids combining experiments and mathematical models under high-pressure differences in MHFHWs. Therefore, in this work, a mathematical model with experimental validation is proposed for evaluating the fracturing fluids invasion under high pressure. We first conducted a series of displacement experiments under different pressure differences to obtain the breakthrough time and invasion velocity. All core samples are taken from the block X of Xinjiang oilfield. A mathematical model of fracturing fluid injection was then established, considering the two-dimensional filtration of fracturing fluid. Then, the calculated invasion velocity was validated against the experimental data. Afterward, the invasion depth and invasion volume were determined for this typical horizontal well. Results show that at the end of 72 min, the invasion depth reaches 1.516 m when measured by core experiments and 1.434 m when calculated by the proposed model. The total invasion volume of all fracturing stages is estimated as 21,560.05 m3 and the actual total fluid volume injected is 24,019.6 m3. The paper formed a scientific and reasonable evaluation method of fracturing fluid invasion depth during the fracturing of horizontal wells, which provides solid theoretical support for the effective evaluation of fracturing to improve oil recovery. [ABSTRACT FROM AUTHOR]

The objective of this study is to determine the influence of operational parameters of CO2 Huff-n-Puff EOR process in the Eagle Ford shale oil reservoirs using response surface methodology (RSM). Single-factor analysis was first conducted for establishing the Box-Behnken model in RSM. We selected the primary depletion time, gas injection time, cycle number, production time per cycle, and injection rate as the primary input variables using RSM. The cumulative oil production and net present value are optimized as the output factors. After that, Design of Expert 12 software was used to design the experimental table for the above setting factors. Corresponding to the results taken from the optimization, the most significant factor is injection rate, followed by injection time, cycle number, and primary depletion time, and production time per cycle is the least significant. Additionally, the optimum responses were found as primary depletion time of 2.37 years, injection time of 3.4 months, cycle number of 3, production time per cycle of 2.2 years, and injection rate of 5000 MSCF/D. Moreover, correlation coefficient (R2) of the regression model is 0.9977, and adjusted model R2 is 0.8898, which further indicates that the model has good reliability. Results show that RSM is a useful technique for optimization, and it also provides insights into optimizing and designing the CO2 Huff-n-Puff process in the shale oil reservoirs. [ABSTRACT FROM AUTHOR]

High-content H2S gas reservoirs are important for natural gas extraction. However, the precipitation and deposition of elemental sulfur in high-sulfur-content gas reservoirs eventually lead to porosity and permeability damage, resulting in the low well productivity. Therefore, it is worth developing an accurate production prediction model considering sulfur deposition for fractured horizontal wells. In this study, based on the partition model and transient percolation theory, a novel numerical model considering the damage of sulfur deposition with pressure change on reservoir porosity and permeability was first developed to predict the production from fractured horizontal wells in high-sulfur-content gas reservoirs. Then, it was validated by actual field data from a high-sulfur-content gas reservoir. After that, the influence of sulfur deposition on the production of fractured horizontal wells was revealed through theoretical calculations, and the effects of hydraulic fracture parameters on production were analyzed. The results show that elemental sulfur gradually deposits in the reservoir pores as the reservoir pressure decreases and the production time increases, which eventually leads to permeability damage and reduces reservoir productivity; this negative impact gradually increases over time. It is also shown that the production of fractured horizontal wells increases with an increase in the half-length, fracture conductivity, and fracture number. Compared with the fracture half-length, the fracture conductivity and fracture number have a greater influence on the production of a single well. The model can handle the influence of nonlinear parameters caused by sulfur deposition, which allows accurate calculations and provides guidance for the development of fractured horizontal wells in gas reservoirs with high sulfur content. [ABSTRACT FROM AUTHOR]

Stimulated reservoir volume (SRV) which is generated by horizontal drilling with multistage hydraulic fracturing governs the production in the shale gas reservoirs. Although microseismic data has been used to estimate the SRV, it is high-priced and sometimes overestimated. Additionally, the effect of stress sensitivity on SRV is not considered in abnormal overpressure areas. Thus, the objective of this work is to characterize subsurface fracture networks with stress sensitivity of permeability through the shale gas well production data of the early flowback stage. The flowback regions are first identified with the flowback data of two shale gas wells in South China. Then, we measured the permeability stress sensitivity of the core after fracturing, coupled to the dynamic relative permeability (DRP) calculation to obtain an accurate and simple DRP curve. After that, a comprehensive model is built considering dynamic two-phase relative permeability function and stress sensitivity. Finally, we compared the calculated results with the microseismic data. The results show that the proposed model could reasonably predict the SRV using the flowback data after fracturing. Additionally, compared with the microseismic data, the stress sensitivity should be included, especially in the abnormal overpressure block. It is believed that this mathematical model is accurate and useful. The work provides an efficient approach to estimate stimulated reservoir volume in the shale gas reservoirs. [ABSTRACT FROM AUTHOR]

Low porosity and permeability in a tight sandstone gas reservoir can cause problems during fracturing. If the fracturing fluid cannot be discharged in a timely fashion after fracturing, the fracturing fluid will move into the deep formation and result in secondary damage. Conversely, if the flowback rate of the fracturing fluid is too high, it will cause the proppant to backflow and reduce the efficiency of fracturing operation. Therefore, it is very important to control the choke sizes and flowback rates for the flowback process of a tight sandstone reservoir. In this study, a model of the time of the closed fracture considering the principle of material balance is built. Subsequently, the relationship between the wellhead pressure and the optimum diameter of the choke at different times is obtained using hydrodynamics and particle dynamics theory. Finally, the proposed optimization method is applied to an actual well from the Xinjiang tight gas reservoirs. Results show that a choke diameter can be reasonably optimized under different wellhead pressures, and that fracturing fluid flows back as much as possible and without proppant backflow. A sound design of a fracturing fluid flowback system is also provided. This study presents the mechanism of post-fracturing management and provides a better understanding of the flowback system in tight gas reservoirs. [ABSTRACT FROM AUTHOR]

Abstract: Sulphur deposition has been the centre of attention in sour gas reservoir development. While Roberts's solubility model is widely used in sour reservoir damage to describe elemental sulphur precipitation and deposition in a near‐wellbore area, this model cannot accurately predict a change in sulphur solubility. A productivity prediction model, with consideration of sulphur deposition, is also not complete, particularly for modelling sulphur deposition and fractured horizontal wells. In this study, based on the unsteady percolation mechanics theory and superposition principle, we develop a new numerical model to quantify fractured horizontal well production by combining various sulphur solubility models. We examine the effects of sulphur deposition on permeability, porosity, and production performance. The results show that sulphur deposition damages reservoirs and thus decreases well production in later stages. These results also show that the permeability and porosity reduction using Roberts's sulphur solubility model is greater than that using Hu et al.'s sulphur solubility model. The damage degree is relatively smaller when using Hu et al.'s sulphur solubility model, and the effect of sulphur deposition on a production performance curve is negligible. Moreover, Hu et al.'s model is closer to actual production data. The results can guide reservoir engineers to optimize development plans in sour gas reservoirs. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) can secrete cytokines stimulated by lipopolysaccharide (LPS), which leads to not just acute inflammatory responses but also Th1 polarization. Furtherly, chronic inflammation or autoimmune diseases could be triggered. As a classic Traditional Chinese Medicine formula, Ephedra Aconite Asarum Decoction with the main ingredients of ephedrine and hypaconitine can show effect on anti-inflammation and immunoregulation. But it remains unclear whether Ephedra Aconite Asarum Decoction controls DCs. In this study, we investigated the effects of Ephedra Aconite Asarum Decoction on LPS-induced bone marrow-derived DCs (BMDCs) in vitro. We found that Ephedra Aconite Asarum Decoction lowered surface costimulators on DCs and reduced the expression of Th1 type cytokines. Yet it is slightly beneficial for shifting to Th2. Our work reveals that the Ephedra Aconite Asarum Decoction can regulate Th1 inflammation through intervening DCs. [ABSTRACT FROM AUTHOR]

ContextIt has been found that hydroxysafflor-yellow A (HSYA) inhibits angiogenesis and the proliferation of abnormal human umbilical vein endothelial cells (HUVECs) in our previous study; however, the mechanism is still unclear. ObjectiveThis study investigates the mechanisms of HSYA inhibiting abnormal proliferation of HUVECs through detecting the expression of vascular endothelial growth factor (VEGF) and its receptor (KDR), and the protein expression in the Ras-Raf-MEK-ERK-signalling pathway. Materials and methodsHepG2 cell cultural supernatant was used to culture HUVECs to make promote abnormal proliferation, and HSYA was added into the medium. The expression of VEGF, KDR, c-myc, N-ras and NF-κB1in abnormal HUVEC was detected by RT-qPCR and ELISA at the mRNA and protein levels. Protein expression of ERK signal pathway was measured by Western blot. ResultsCompared with the abnormal proliferation of HUVECs without any treatment, HSYA inhibited the expression of VEGF and KDRin vitro. Similarly, the protein expression of Ras, p-raf, p-ERK and p-p38MARK in the abnormal HUVECs was reduced when they were treated by HSYA, especially in p-ERK, yet the total raf, ERK, p38MAPK and Akt were not changed whether HSYA existed or not. HSYA could also inhibit the expression of c-myc, N-ras, and NF-κB1. ConclusionWhen the abnormal HUVECs were treated with HSYA, the low expression of VEGF and KDR reduced the expression of oncogene and transcription factor through the Ras-Raf-MEK-ERK1/2 pathway of the MAPK family. This resulted in inhibiting the abnormal proliferation of HUVECs and angiogenesis. [ABSTRACT FROM PUBLISHER]

The utilization of a horizontal well has a great significance in the development of sour gas reservoir. The accurate prediction of the productivity of horizontal well will become more and more important in developing sour gas reservoir. In this paper, the effect of sulfur deposition on permeability is considered and a productivity prediction formula of the horizontal well is established. The effects of the length of horizontal well, the effective thickness of the reservoir, elemental sulfur deposition, and reservoir heterogeneity on productivity are analyzed and calculated. The theoretical results show that elemental sulfur disposition and the heterogeneity are the most important factors. According to the field case, the calculating results of improved Joshi’s equation approaches the real productivity, which means that it could be used to predict the productivity of horizontal well at initial stage during sour gas reservoir development. The results can be used as a reference for the development of similar sour gas reservoir. [ABSTRACT FROM PUBLISHER]

Matrix permeability is an important parameter in shale gas productivity prediction. However, the permeability affected by multi-scale seepage is difficult to calculate accurately. The object of this study is to develop an integrated apparent permeability model for multi-scale seepage mechanisms. The apparent permeability model considered shale gas flow from shrinkable matrix to fracture system with slip flow, Knudsen diffusion, and surface diffusion. The transport capacity change with different seepage mechanisms under different conditions was specifically analyzed. The importance of each parameter in the apparent permeability model was qualified using Grey correlation method. In addition, a semi-analytical model for horizontal-well productivity was developed to describe shale gas transport in reservoir. The semi-analytical model was solved using Laplace integral transformation and point source method. According to the results based on Grey correlation method, the effects of pore radius and Langmuir volume on dimensionless-type curves were discussed. Compared with the pore radius, the Langmuir volume had more influences on the shape of typical curve. The slip flow played the most important role in gas transport in mesopores and macropores when the pressure was more than 2 MPa and the surface diffusion was the primary transporting mechanism at any pressure in micropores but it can be negligible in macropores. The research result presented that the multi-scale seepage mechanisms would be considered in well tests and shale gas production. • Slip flow should be considered in macropores when pressure is more than 2 MPa. • The apparent permeability increases with increasing Langmuir volume and decreases with increasing Langmuir pressure. • The biggest influence on the permeability model is the pore radius. • Compared with the pore radius, the influence of Langmuir volume is more obvious on the shape of typical curve. [ABSTRACT FROM AUTHOR]

Combining horizontal drilling with hydraulic fracturing has become a well-established technique to improve well productivity in tight oil reservoirs. The existence of micro-fractures in these reservoirs affects the fluid flow process as well as the productivity. However, current models for evaluating the well performance of fractured horizontal wells containing micro-fractures lack accuracy. Hence, the objective of this study is to build an efficient model to analyze well productivity, considering the effects of micro-fractures. A novel flow model for multi-fractured horizontal wells was established, considering the effect of micro-fractures on the fluid flow. Subsequently, we built a reservoir model based on the typical fracture and fluid properties of a tight oil block in the Daqing oil field, China. Good agreement between the prediction results and field data was obtained, indicating that the effect of micro-fractures on well productivity cannot be neglected. Further study reveals that micro-fractures essentially function as a joint connecting reservoir matrix and have a persistent impact on well productivity. Micro-fractures can promote well productivity; however, if the value of micro-fracture permeability increases, this promotional effect will slow down. Well productivity can be considerably improved as an increase in micro-fracture percentage. Finally, a series of sensitivity studies were conducted to identify the effects of critical parameters on well productivity. Results show that reservoir permeability significantly influences well productivity, followed by reservoir effective thickness, micro-fracture percentage, fracture number, hydraulic fracture half-length. Pressure sensitivity coefficient, threshold pressure gradient and micro-fracture permeability have the least effect on well productivity. This work provides a sophisticated and efficient tool to evaluate the productivity of multi-fractured horizontal wells in tight oil reservoirs with micro-fractures. • A comprehensive productivity prediction model considering micro-fracture is proposed in tight oil reservoirs. • Validation study illustrates that this proposed model can accurately and efficiently evaluate well productivity. • Sensitivity studies show that micro-fracture is a critical parameter of well performance. [ABSTRACT FROM AUTHOR]

CO2 injection has great potentials to improve the oil production for the fractured tight oil reservoirs. However, Current works mainly focus on its operation processes; full examination of CO2 molecular diffusion and adsorption was still limited in the petroleum industry. To fill this gap, we proposed an efficient method to accurately and comprehensively evaluate the efficiency of CO2-EOR process. We first calculated the confined fluid properties with the nanopore effects. Subsequently, a reservoir simulation model was built based on the experiment test of the Eagle Ford core sample. History matching was performed for the model validation. After that, we examined the effects of adsorption and molecular diffusion on the multi-well production with CO2 injection. Results illustrate that in the CO2-EOR process, the molecular diffusion has a positive impact on the oil production, while adsorption negatively impacts the well production, indicating that the mechanisms should be reasonably incorporated in the simulation analysis. Additionally, simulation results show that the mechanisms of molecular diffusion and adsorption make great contributions to the capacity of CO2 storage in tight formations. This study provides a strong basis to reasonably forecast the long-term production during CO2 Huff-n-Puff process. [ABSTRACT FROM AUTHOR]

Gas injection is one of the most effective enhanced oil recovery methods for the unconventional reservoirs. Recently, CH4 has been widely used; however, few studies exist to accurately evaluate the cyclic CH4 injection considering molecular diffusion and nanopore effects. Additionally, the effects of operation parameters are still not systematically understood. Therefore, the objective of this work is to build an efficient numerical model to investigate the impacts of molecular diffusion, capillary pressure, and operation parameters. The confined phase behavior was incorporated in the model considering the critical property shifts and capillary pressure. Subsequently, we built a field-scale simulation model of the Eagle Ford shale reservoir. The fluid properties under different pore sizes were evaluated. Finally, a series of studies were conducted to examine the contributions of each key parameter on the well production. Results of sensitivity analysis indicate that the effect of confinement and molecular diffusion significantly influence CH4 injection effectiveness, followed by matrix permeability, injection rate, injection time, and number of cycles. Primary depletion period and soaking time are less noticeable for the well performance in the selected case. Considering the effect of confinement and molecular diffusion leads to the increase in the well performance during the CH4 injection process. This work, for the first time, evaluates the nanopore effects and molecular diffusion on the CH4 injection. It provides an efficient numerical method to predict the well production in the EOR process. Additionally, it presents useful insights into the prediction of cyclic CH4 injection effectiveness and helps operators to optimize the EOR process in the shale reservoirs. [ABSTRACT FROM AUTHOR]

Abstract: Ethnopharmacological relevance: Tong Luo Jiu Nao injection (TLJN), a Chinese medicine preparation, was extracted from the Chinese herbs Panax notoginseng and Gardenia jasminoides. Its pharmacological effect on cerebral ischemia was observed in the study. We previously reported that paracrine signaling of brain microvascular endothelial cells (BMECs) had a direct impact on the survival of neurons in mimicked cerebral ischemia in vitro. The current study was designed to investigate whether paracrine signaling of BMECs could be regulated by drug to achieve neuroprotection. Materials and methods: First, an in vitro model of cerebral ischemia in BMECs or neurons was established by oxygen–glucose-deprivation (OGD). TLJN was used as a medicine of intervention. Injured neurons were cultured in the conditioned media from normal and injured BMECs treated with TLJN. The changes in neurons, including the expression of N-methyl-D-aspartate receptor 1(NMDAR1), Ca2+ concentration, cytochrome c release, the mitochondrial membrane potential, were determined by the immunofluorescence staining and molecular Probes. The content of Vascular endothelial growth factor (VEGF) and platelet activating factor (PAF) in various BMECs were also examined by Western blotting and Elisa. Results: The results showed the activity of injured neurons was significantly increased when they were grown in conditioned media of normal or injured BMECs treated with TLJN, compared with that of normal or injured BMECs. These changes include a decrease of Ca2+ concentration, of NMDAR1 expression, and of cytochrome c release, also an increase of the mitochondrial membrane potential. Moreover, the VEGF expression was up-regulated and the PAF expression was down-regulated by TLJN in BMECs. Conclusion: The results suggest that a neuroprotective effect of TLJN could be achieved by regulating paracrine signaling of BMECs, which could in part be explained by a TLJN-induced up-regulation of VEGF and a down-regulation of PAF in BMECs. Therefore, regulating the paracrine of BMECs could be the important target of the drug action on injured-neurons, which may be a novel path for therapeutic intervention in ischemic injury. [ABSTRACT FROM AUTHOR]