High-Precision Flow Numerical Simulation and Productivity Evaluation of Shale Oil Considering Stress Sensitivity

Continental shale oil reservoirs,characterized by numerous bedding planes and micro-nano scale pores,feature significantly higher stress sensitivity compared to other types of reservoirs.However,research on suitable stress sensitivity characterization models is still limited.In this study,three commonly used stress sensitivity models for shale oil reservoirs were considered,and experiments on representative core samples were conducted.By fitting and comparing the data,the“exponential model”was identified as a characterization model that accurately represents stress sensitivity in continental shale oil reservoirs.To validate the accuracy of the model,a two-phase seepage mathematical model for shale oil reservoirs coupled with the exponential model was introduced.The model was discretely solved using the finite volume method,and its accuracy was verified through the commercial simulator CMG.The study evaluated the productivity of a typical horizontal well under different engineering,geological,and fracture conditions.The results indicate that considering stress sensitivity leads to a 13.57%reduction in production for the same matrix permeability.Additionally,as the fracture half-length and the number of fractures increase,and the bottomhole flowing pressure decreases,the reservoir stress sensitivity becomes higher.

Production Capacity Prediction Method of Shale Oil Based on Machine Learning Combination Model

The production capacity of shale oil reservoirs after hydraulic fracturing is influenced by a complex interplay involving geological characteristics,engineering quality,and well conditions.These relationships,nonlinear in nature,pose challenges for accurate description through physical models.While field data provides insights into real-world effects,its limited volume and quality restrict its utility.Complementing this,numerical simulation models offer effective support.To harness the strengths of both data-driven and model-driven approaches,this study established a shale oil production capacity prediction model based on a machine learning combination model.Leveraging fracturing development data from 236 wells in the field,a data-driven method employing the random forest algorithm is implemented to identify the main controlling factors for different types of shale oil reservoirs.Through the combination model integrating support vector machine(SVM)algorithm and back propagation neural network(BPNN),a model-driven shale oil production capacity prediction model is developed,capable of swiftly responding to shale oil development performance under varying geological,fluid,and well conditions.The results of numerical experiments show that the proposed method demonstrates a notable enhancement in R2 by 22.5%and 5.8%compared to singular machine learning models like SVM and BPNN,showcasing its superior precision in predicting shale oil production capacity across diverse datasets.

Research on U-steel yieldable support with backfill technology in rock roadway

The loading on U-steel yieldable support cannot be organically combined withthe law of strata behaviors from the surrounding rocks of roadway. In order to effectivelysolve the problem, U-steel yieldable support with backfill material and the performancerequirements of backfill material were analyzed on the basis of structural mechanics. Themechanical properties of backfill material selected were tested in the laboratory, and thetest results show that the ratio of the backfill material complies with the requirements ofbackfill technology; it can effectively optimize the relationship between the support and thesurrounding rock, and the filling layer can avoid the partial stress concentration and fullyimprove the support performance. Compared with U-steel yieldable support with ganguefilling, the filed application shows that the supporting result of U-steel yieldable supportwith backfill technology is satisfactory, the stress on U-steel yieldable support with backfilltechnology decreases greatly and distributes uniformly, convergence of the surroundingrock of roadway is decreased by more than 50%, and the surrounding rocks of roadwayare controlled effectively.

Simulation of Gas-Water Two-Phase Flow in Tight Gas Reservoirs Considering the Gas Slip Effect

A mathematical model for the gas-water two-phase flow in tight gas reservoirs is elaborated.The model can account for the gas slip effect,stress sensitivity,and high-speed non-Darcy factors.The related equations are solved in the framework of a finite element method.The results are validated against those obtained by using the commercial software CMG(Computer Modeling Group software for advanced recovery process simulation).It is shown that the proposed method is reliable.It can capture the fracture rejection characteristics of tight gas reservoirs better than the CMG.A sensitivity analysis of various control factors(initial water saturation,reservoir parameters,and fracturing parameters)affecting the production in tight gas wells is conducted accordingly.Finally,a series of theoretical arguments are provided for a rational and effective development/exploitation of tight sandstone gas reservoirs.

Optimization of the Plugging Agent Dosage for High Temperature Salt Profile Control in Heavy Oil Reservoirs

After steam discharge in heavy oil reservoirs,the distribution of temperature,pressure,and permeability in different wells becomes irregular.Flow channels can easily be produced,which affect the sweep efficiency of the oil displacement.Previous studies have shown that the salting-out plugging method can effectively block these channels in high-temperature reservoirs,improve the suction profile,and increase oil production.In the present study,the optimal dosage of the plugging agent is determined taking into account connection transmissibility and inter-well volumes.Together with the connectivity model,a water flooding simulation model is introduced.Moreover,a non-gradient stochastic disturbance algorithm is used to obtain the optimal plugging agent dosage,which provides the basis for the high-temperature salting-out plugging agent adjustment in the field.

Application of brassinolide alleviates cold stress at the booting stage of rice

The objective of the study was to determine the physiological mechanisms of plants in response to brassinolide(BR) alleviating cold water stress on rice. In this study, physiological responses of rice to exogenous BR and cold water submergence were investigated using the chilling-tolerant cultivar Kongyu 131(KY131) and the chilling-sensitive cultivar Kenjiandao 6(KJD6). A total of 2 mg L^-1 BR increased activities of superoxide dismutase(SOD) and peroxidase(POD) and the contents of soluble sugar, soluble protein, and chlorophyll, but decreased the malondialdehyde(MDA) content in KY131 and KJD6 under cold water stress. The observed decreases in SOD and POD activities and MDA content recovered quickly after plants were returned to irrigation with water at temperatures of about 23.0°C in 2014. Additionally, the contents of nitrogen(N), phosphorous(P), and potassium(K) were increased by BR treatment under cold water stress. Exposure to BR also raised the percentage of high effective leaf area and leaf area index at the heading stage. Furthermore, it promoted soluble sugar synthesis, increased the rate of dry matter accumulation, and enhanced the export and translocation rates of the stem-sheath. The yield in KJD6 was significantly(P≤0.01 and P≤0.05) higher than that of the control in 2013 and 2014, respectively. The effect of BR treatment on rice leaf SOD and POD activities, MDA, chlorophyll, P, and stem-sheath K contents were more significant in KJD6 than in KY131. In conclusion, exogenous BR effectively reduced the physiological and metabolic damage in rice due to cold stress at the booting stage, promoted functional recovery in plants that received irrigation with water at a normal temperature following cold stress, and mitigated the effects of cold water stress on yield.The two varieties exhibited differential responses to BR;the weaker cold-resistant variety was more sensitive to BR and displayed stronger responses to exogenous BR.

Energy-Efficient User Association in Heterogeneous Networks with M2M/H2H Coexistence under QoS Guarantees

In this paper, we propose an energy efficient user association scheme for uplink heterogeneous networks with machine-to-machine(M2M) and human-to-human(H2H) coexistence. A group based random access protocol is designed for massive number of machine-typecommunications(MTC) user equipments'(UEs) transmissions. A user association problem for UEs' energy efficiency maximization is formulated considering the HTC UEs' quality of service(QoS) guarantees and load balance among multiple BSs, simultaneously. A distributed iterative algorithm is developed to solve the optimization problem. In addition, the convergence of the proposed algorithm is proved. Simulation results show that our proposed scheme outperforms other schemes in terms of energy efficiency and QoS guarantees.

XRCC1 Arg399Gln and Arg194Trp polymorphisms regulate XRCC1 expression and chemoresistance of non-small cell lung cancer cells

X-ray repair cross-complementing protein 1(XRCC1)could repair cisplatin-induced DNA damage.XRCC1 Arg399Gln and Arg194Trp variants alter XRCC1 expression and function,leading to changes in cancer sensitivity to cisplatin treatment.This study aimed to investigate the effects of XRCC1 Arg399Gln and Arg194Trp polymorphisms on cell viability,apoptosis and XRCC1 expression in cisplatin-sensitive A549 and cisplatin-resistant A549/DDP non-small cell lung cancer(NSCLC)cells.Plasmids carrying XRCC1 Arg399Gln and Arg194Trp were constructed and transfected into A549 and A549/DDP cells.RT-PCR,Western blot,MTT assay,and flow cytometry analysis were performed to assess cell viability,apoptosis,and XRCC1 expression.Compared to control cells,the viability of A549 and A549/DDP cells transfected with XRCC1 Arg399Gln and Arg194Trp was higher and the apoptosis rate was lower,and XRCC1 mRNA and protein expression levels were significantly higher.In conclusion,our results suggest that XRCC1 Arg399Gln and Arg194Trp polymorphisms change XRCC1 expression in NSCLC cells and alter the sensitivity of NSCLC to cisplatin-based chemotherapy.

Counterparty risk valuation on credit-linked notes under a Markov Chain framework

A credit-linked note(CLN)is a note paying an enhanced coupon to investors for bearing the credit risk of a reference entity.In this paper,we study the counterparty risk on CLNs under a Markov chain framework,and introduce a Markov copula model to describe joint defaults between the reference entity underlying the CLN and CLN issuer.Assuming that the respective default intensities are directly and inversely proportional to the interest rate,which follows a CIR process,we obtain the explicit formulae for CLN values through a PDE approach.Finally,credit valuation adjustment(CVA)formula is derived to price counterparty credit risk.

Effects of Pretreatment Conditions on Redox Property over Au/Co_3O_4/CeO_2 Material

Au/Co3O4/CeO2 materials are prepared using conventional deposition-precipitation method. The effects of calcination temperatures and pretreatment conditions on the catalytic performance of Au/Co3O4/CeO2 for CO low-temperature oxidation in humid circumstance are investigated. The sample calcines at 443 K in flowing air exhibited good activity and stability for CO oxidation. 80% CO conversion rate can be achieved after 3 000 min with a feed gas contained 3.1%(φw) of water vapor. The physical and chemical properties of the Au/Co3O4/CeO2 samples are characterized by X-ray diffraction (XRD),temperature-programmed reduction (H2-TPR),and transmission electron microscopy (TEM) techniques. The characterized results show that the prepared material calcined at 443 K has a weak diffraction peak of gold species observed by XRD,the grain diameter of 3 nm by TEM and best redox property and the highest activity for CO oxidation by H2-TPR at prope calcined temperature.

Simulation of Oil-Water Flow in Shale Oil Reservoirs Based on Smooth Particle Hydrodynamics

A Smooth Particle Hydrodynamics(SPH)method is employed to simulate the two-phase flow of oil and water in a reservoir.It is shown that,in comparison to the classical finite difference approach,this method is more stable and effective at capturing the complex evolution of this category of two-phase flows.The influence of several smooth functions is explored and it is concluded that the Gaussian function is the best one.After 200 days,the block water cutoff for the Gaussian function is 0.3,whereas the other functions have a block water cutoff of 0.8.The effect of various injection ratios on real reservoir production is explored.When 14 and 8 m^(3)/day is employed,the water breakthrough time is 130 and 170 days,respectively,and the block produces 9246 m^(3) and 6338 m^(3) of oil cumulatively over 400 days.

Simulation of Oil-Water Flow in a Shale Reservoir Using a Radial Basis Function

Due to the difficulties associated with preprocessing activities and poor grid convergence when simulating shale reservoirs in the context of traditional grid methods,in this study an innovative two-phase oil-water seepage model is elaborated.The modes is based on the radial basis meshless approach and is used to determine the pressure and water saturation in a sample reservoir.Two-dimensional examples demonstrate that,when compared to the finite difference method,the radial basis function method produces less errors and is more accurate in predicting daily oil production.The radial basis function and finite difference methods provide errors of 5.78 percent and 7.5 percent,respectively,when estimating the daily oil production data for a sample well.A sensitivity analysis of the key parameters that affect the radial basis function’s computation outcomes is also presented.

Acoustic localization scheme and accuracy analysis for underwater vertical moving target using seabed stations

To measure the trajectory of an underwater vertical moving target(UVMT) in transient motion with high accuracy and high frame rate,an acoustic localization model using seabed stations with an acoustic beacon was presented.A solution algorithm based on the Gauss-Newton method was derived,which was shown to satisfy the local linear convergence.Accuracy analysis of the numerical simulation indicated that the station location,sound velocity,and signal time delay estimation errors were propagated to location parameters through measurement ranges,and the main affecting factors included the station geometry,target relative location,and acoustic conditions.Vertical accuracy was improved using a supplemental surface station coupled with the seabed stations.Detailed characteristics were indicated by accuracy distribution from the full test sea area.A 14-station array composed of 13 seabed stations and 1 surface station in a test sea of 1 km x 1 km and 60 m in depth demonstrated that the average root mean square errors(RMSEs) in the x,y,and z directions were 0.30,1.47,and0.34 m,respectively,in the vertical range of 35-60 m.This work provided a technical approach for UVMT localization,which would be useful for designing related measurement systems.

A feedback-retransmission based asynchronous frequency hopping MAC protocol for military aeronautical ad hoc networks

Attacking time-sensitive targets has rigid demands for the timeliness and reliability of information transmission, while typical Media Access Control（MAC） designed for this application works well only in very light-load scenarios; as a consequence, the performances of system throughput and channel utilization are degraded. For this problem, a feedback-retransmission based asynchronous FRequency hopping Media Access（FRMA） control protocol is proposed. Burst communication, asynchronous Frequency Hopping（FH）, channel coding, and feedback retransmission are utilized in FRMA. With the mechanism of asynchronous FH, immediate packet transmission and multi-packet reception can be realized, and thus the timeliness is improved.Furthermore, reliability can be achieved via channel coding and feedback retransmission. With theories of queuing theory, Markov model, packets collision model, and discrete Laplace transformation, the formulas of packet success probability, system throughput, average packet end-to-end delay, and delay distribution are obtained. The approximation accuracy of theoretical derivation is verified by experimental results. Within a light-load network, the proposed FRMA has the ability of millisecond delay and 99% reliability as well as outperforms the non-feedback-retransmission based asynchronous frequency hopping media access control protocol.

Shale pore characteristics of Shahejie Formation: Implication for pore evolution of shale oil reservoirs in Dongying sag, north China

The pore characteristics of shale reservoirs in the lower submember of Member 3 to upper submember of Member 4 of Shahejie Formation in Dongying sag are analyzed,influences of mineral content and organic matter content on porosity and pore size are also investigated,and through the diagenetic thermal simulation experiment,the main pore evolution is further discussed.The results show that the pore structure of shale reservoirs is complex,the micron-nanometer pores can storage liquid hydrocarbons,and the free-phase crude oil is mainly distributed in intergranular dissolution pores of calcite,recrystallized intergranular pores,intergranular shrinkage fractures of clay mineral which have large pore size.Framework minerals and organic matter content directly influence porosity and pore size of shale reservoirs,relationship between porosity and content of felsic mineral as well as content of organic matter content is linear and positive,while relationship between content of carbonated mineral is negative.At the buried depth from 2500 to 3500 m,concentration of organic acid from hydrocarbon generation and expulsion of organic matter,increasing range of pressure coefficient,are well corresponding to highporosity intervals;pore formation in shale oil reservoirs are almost controlled by diagenetic evolution of clay minerals;framework storage spaces formed by carbonate grain crystals as well as intergranular and intergranular dissolution pores of carbonate increases porosity of shale oil reservoirs;local increase of porosity at the depth of 3500e3800 m is mainly caused by coupling of hydrocarbon-generating overpressure and dissolution,and size,distribution and connectivity of pores are enhanced obviously.