Research into polymer injection timing for Bohai heavy oil reservoirs

Polymer flooding has been proven to effectively improve oil recovery in the Bohai Oil Field. However, due to high oil viscosity and significant formation heterogeneity, it is necessary to further improve the displacement effectiveness of polymer flooding in heavy oil reservoirs in the service life of offshore platforms. In this paper, the effects of the water/oil mobility ratio in heavy oil reservoirs and the dimensionless oil productivity index on polymer flooding effectiveness were studied utilizing rel- ative permeability curves. The results showed that when the water saturation was less than the value, where the water/oil mobility ratio was equal to 1, polymer flooding could effectively control the increase of fractional water flow, which meant that the upper limit of water/oil ratio suitable for polymer flooding should be the value when the water/oil mobility ratio was equal to 1. Mean while, by injecting a certain volume of water to create water channels in the reservoir, the polymer flooding would be the most effective in improving sweep efficiency, and lower the fractional flow of water to the value corresponding to △Jmax. Considering the service life of the platform and the polymer mobility control capacity, the best polymer injection timing for heavy oil reservoirs was optimized. It has been tested for reservoirs with crude oil viscosity of 123 and 70 mPa s, the optimum polymer flooding effec- tiveness could be obtained when the polymer floods were initiated at the time when the fractional flow of water were 10 % and 25 %, respectively. The injection timing range for polymer flooding was also theoretically analyzed for the Bohai Oil Field utilizing which provided methods for effectiveness. relative permeability curves, improving polymer flooding

Optimization of Injection Timing and Injection Duration of a Diesel Engine Running on Pure Biodiesel SME (Soya Methyl Ester)

This study was carried out to predict the impact of injection timing and injection duration on engine brake power and Nitrogen Oxides emissions in a diesel engine using biofuel Soya Methyl Ester (SME). Predictions were accomplished at three different injection timings 10°, 5° Crank Angle (CA) before Top Dead Center (bTDC) and 0° CA at Top Dead Center (TDC) and four injection durations 20°, 25°, 30°, 35° CA. The study was conducted using a simulation software (Diesel-RK). The predicted results showed that the powers produced by all the setups of the different injection timings are almost equal, but they differ in injection durations, e.g. the power at setup (10° CA-bTDC) duration 20° CA and 2500 rpm equal to 52 kW, at setup (5° CA-bTDC) duration 25° CA and same engine speed the power is equal to 51 kW, and at setup (0° CA-TDC) durations 30° the power is equal to 51 kW. The power in all setups are decreased as the injection duration increased, e.g. at setup 0° CA TDC durations 25°, 35°, and 40° CA and at 4000 rpm, the brake powers are equal 71, 65, and 59 kW respectively, thus the reduction percentages are 9% and 17% when compared to the 25° injection duration. The nitrogen oxides emissions decreased as the injection duration is increased, e.g. the emissions at setup (10° CA-bTDC) durations 25°, 30°, and 40° CA and at 2500 rpm are equal 852, 589, 293 ppm respectively, the reduction percentages are 30% and 72%. The variations of injection timing and injection duration have taken a weighty influence on engine performance and emissions. The results are considered as a novelty in the field of using pure biofuel Soya Methyl Ester in diesel engine according to our information.

Optimization of Injection Parameters for Profile Control and Flooding in an Oilfield during High Water Cut Period

In order to improve the effect of water control and oil stabilization during high water cut period, a mathematical model of five point method well group was established with the high water cut well group of an Oilfield as the target area, the variation law of water cut and recovery factor of different injection parameters was analyzed, and the optimization research of injection parameters of polymer enhanced foam flooding was carried out. The results show that the higher the injection rate, the lower the water content curve, and the higher the oil recovery rate. As the foam defoamed when encountering oil, when the injection time was earlier than 80% of water cut, the later the injection time was, the better the oil displacement effect would be. When the injection time was later than 80% of water cut, the later the injection time was, the worse the oil displacement effect would be. The larger the injection volume, the lower the water content curve and the higher the recovery rate. After the injection volume exceeded 0.2 PV, the amplitude of changes in water content and recovery rate slowed down. The optimal injection parameters of profile control agent for high water content well group in Oilfield A were: injection rate of 15 m3/d, injection timing of 80% water content, and injection volume of 0.2 PV.

Effects of injection timing,before and after top dead center on the propulsion and power in a diesel engine

It is well known that injection strategies including the injection timing and pressure play the most important role in determining engine performance,especially in pollutant emissions.However,the injection timing and pressure quantitatively affect the performance of diesel engine with a turbo charger are not well understood.In this paper,the fire computational fluid dynamics(CFD)code with an improved spray model has been used to simulate the spray and combustion processes of diesel with early and late injection timings and six different injection pressure(from 275 bar to 1000 bar).It has been concluded that the use of early injection provides lower soot and higher NOx emissions than the late injection.In this study,it has been tried using the change of fuel injection time at these two next steps:before top dead center(BTDC)and after top dead center(ATDC)in order to achieving optimum emission and power in a specific point.

Experimental study of the development mode of gas-cap edge-water reservoir:A case study of Khasib reservoir of Halfaya oilfield in Iraq

Based on the oil,gas and water distribution characteristics of Khasib reservoir in Halfaya oilfield,Iraq,a core displacement experiment is designed to evaluate the influence of different displacement methods and displacement parameters on oil displacement efficiency.The research shows that,in the displacement method with water injected from the edge of the reservoir,early depletion production is conducive to the elastic expansion of the gas cap,forming the three-dimensional displacement of"upper pressure and lower pushing",and the oil displacement effect is good.When gas injection at the top and water injection at the edge are used for synergistic displacement,the injection timing has different influences on the oil displacement effects of high and low parts.Considering the overall oil displacement efficiency,the injection pressure should be greater than the bubble point pressure of crude oil.Two displacement methods are recommended with the reasonable injection time at 20–25 MPa.The injection speed has the same influence on different injection media.Appropriately reducing the injection speed is conducive to the stability of the displacement front,delaying the breakthrough of injection media and improving the oil displacement effect.The reasonable injection rate of water flooding is 0.075 mL/min,the reasonable injection rates of water and gas are 0.15 mL/min and 0.10 mL/min,respectively in gas-water synergistic displacement.Gas-water synergistic displacement is conducive to the production of crude oil at high position,and has crude oil recovery 5.0%–14.8%higher than water flooding from the edge,so it is recommended as the development mode of Khasib reservoir at the middle and late stages.

Location of Sentinel Lymph Node in Gastric Cancer:A Modified,Painless And Noninvasive Approach

Objective： The presence of lymph node metastases is an important factor in the prognosis of gastric cancer patient. Therefore, the precise identification of sentinel lymph nodes （SLN） in these patients is critical. In this work, we investigated the feasibility and preciseness by injection of 99mTc-sulfur colloid （SC） 2 hours before operation after general anesthesia, instead of one day before surgery. Methods： Thirty-one patients of gastric cancer diagnosed as T1-T3 were enrolled in this study. During operation, a SLN was defined as those containing 10 times more radioactivity than surrounding tissue with a hand-held gamma probe and removed. All the patients underwent radical gastrectomy with extended lymphadenectomy. All resected nodes were examined postoperatively by routine H＆E stain and those negative SLNs were examined with further cytokeratin immunohistochemistical staining. Results： The incidence of metastasis was significantly higher in SLNs than in non-SLNs （x2=67.48, P〈0.001）. The overall sensitivity, specificity and accuracy of the SLN status in the diagnosis of the lymph node status of the patient were 86.36%, 100% and 96.77%, respectively. The positive predictive value and negative predictive value of SLN biopsy were 100%, and 75.0%, respectively. SLNs were used to diagnose the lymph node status with 100% accuracy in the T1 group. In the T2 and T3 groups, the sensitivity, specificity, and diagnostic accuracy were 92.3%, 100%, and 94.44%, 60.0%, 100%, and 66.66%, respectively. Most of the SLNs were located in the #1, #2, #3, #4, #5, and #6, except in 3 patients （9.68%）.With cytokeratin immunohistochemical staining, lymphatic pathologic staging in 1 patient was upstaged. Conclusion： SLN biopsy with the above approach is a feasible and accurate diagnostic procedure for detecting lymph node metastasis in patients with gastric cancer, which is painless, noninvasive, easily accepted by patients and suitable for extensive clinical applications.

Reasonable start time of carbon dioxide injection in enhanced coalbed methane recovery involving thermal-hydraulic-mechanical couplings

Injection of gas (CO_(2)) into coal seams is an effective method to benefit from both CO_(2) geological storage and coalbed methane recovery. Based on the dual pore structure of coal mass, and the Weibull distribution of fracture permeability, a menmal-hydraulic-mechanical (THM) coupling mathematical model is proposed involving the non-isothermal adsorption of binary gases, dynamic gas diffusion between matrix and fractures, multiphase seepage, coal deformation, heat conduction and heat convection. This mathematical model is applied to study the process of CO_(2)-enhanced coalbed methane recovery (CO_(2)-ECBM). Results show that the CH4 content of CO_(2)-ECBM in coal seam decreases significantly when compared with that of regular drainage, and decreases rapidly in the early stage but slowly in the later stage. Coal seam permeability evolution is triggered by changes in gas adsorption/desorption, temperature and effective stress. For regular drainage, the early permeability shows a decreasing trend dominated by the increase of effective stress, while the later permeability shows an increasing trend dominated by the CH4 desorption caused shrinkage of coal matrix. For CO_(2)-ECBM, the permeability in coal seam generally shows a downward trend due to both matrix swelling induced by gas adsorption and thermal expansion, particularly near injection well. There appears an increased and delayed peak production rate of CH4. The CH4 production rate of CO_(2)-ECBM is always higher than that of regular drainage. The CH4 cumulative production and CO_(2) cumulative storage linearly increase with time, and the CH4 cumulative production of CO_(2)-ECBM increased by 39.2% in the duration of 5000 d compared with regular drainage. Reasonable CO_(2) injection starting time can overcome the issue of early CO_(2) breakthrough and ineffective increase of CH4 production. In the studied case, the optimal injection starting time is 2500 d. Compared with the simultaneous CH4 extraction and CO_(2) injection, the CH4 cumulative production of optimal time has increased by 30.1%. The research provides a reference for determining the reasonable CO_(2) injection time under similar conditions.

Comparative Assessment of Low-Concentration Ethanol and Waste Fish Oil Biodiesel Blends on Emission Reduction and Performance Improvement in Variable Compression Ratio Engine

The costs of conventional fuels are rising on a daily basis as a result of technical limits,a misallocation of resources between demand and supply,and a shortage of conventional fuel.The use of crude oil contributes to increased environmental contamination,and as a result,there is a pressing need to investigate alternate fuel sources for car applications.Biodiesel is a renewable fuel that is derived chemically by reacting with the sources of biodiesel.The present research is based on analyzing the effect of fish oil biodiesel-ethanol blend in variable compression engine for variable compression ratio(VCR).The processed fish oil was procured and subjected to a transesterification process to convert fatty acids into methyl esters.The obtained methyl esters(biodiesel)were blended with ethanol and diesel to obtain a ternary blend.The ternary blend was tested for its stability,and a stable blend was obtained and tested in VCR engines for its performance,combustion,and emission characteristics.In the second phase,experiments are conducted in the diesel engine by fueling the fish oil methyl ester and ethanol blended with diesel fuel in the concentration of 92.5 vol%of Diesel+7.5 vol%of Fish oil+1.25vol%ethanol,92.5 vol%of Diesel+7.5 vol%of Fish oil+5 vol%ethanol,87.5 vol%of Diesel+12.5 vol%of Fish oil+1.25 vol%ethanol,87.5 vol%of Diesel+12.5 vol%of Fish oil+5 vol%ethanol,82.5 vol%of Diesel+17.5vol%of Fish oil+1.25 vol%ethanol,82.5 vol%of Diesel+17.5 vol%of Fish oil+5 vol%ethanol to find out the performance parameters and emissions.Because the alternative fuel performs better in terms of engine performance and pollution management,the percentage chosen is considered the best mix.The results showed that the use of a lower concentration of ethanol in the fish oil biodiesel blend improved the engine thermal efficiency by 5.23%at a higher compression ratio.Similarly,the engine operated with a higher compression ratio reduced the formation of HC and CO emissions,whereas the NOxand CO_(2)emissions increased with an increased proportion of biodiesel in diesel and ethanol blends.

Experimental study on combustion pressure oscillation of soybean bio diesel oil

The principal objectives of this study were to examine in-cylinder combustion pressure oscillation characteristics of soybean biodiesel in time domain and time-frequency domain,and their influences on the control and operational parameters,such as injection timing,exhaust gas recirculation(EGR)ratio,engine load and engine speed.In this study,the combustion pressure oscillation characteristics of biodiesel engine for various injection timing,EGR ratio and engine speed were investigated.The corresponding relation of pressure characteristics in the time domain and frequency domain were obtained.The results showed that the pressure oscillation and peak pressure rise acceleration occurred mainly in the diffusion combustion,and the peak pressure rise rate located in the premixed combustion.The in-cylinder pressure level curve can be divided into three stages.The pressure levels of stage 1,stage 2 and stage 3 represent the peak in-cylinder pressure,the maximum amplitude of pressure rise rate and pressure rise acceleration,respectively.As the injection timing retards,the pressure levels of stage 1 and stage 3 decrease gradually.The pressure level curve of stage 3 with 25°before top dead center(BTDC)is the highest and the oscillation is the most significant.It is worth noting that the location of each stage with various operate conditions is not fixed.At 0.41 MPa indicated mean effective pressure(IMEP),with the increase of EGR rate,the pressure levels of stage 1 and stage 2 decrease gradually.The pressure level curve of stage 3 and the maximum amplitude of pressure rise acceleration with 0%EGR rate are the highest.The oscillation with 0%EGR rate is the most significant at 0.41 MPa IMEP.Compared to 0.41 MPa IMEP,the frequency bands of stage 1 and stage 2 at 1.1 MPa IMEP are relatively low due to the soft combustion in the cylinder.As EGR rate increases,the pressure level of stage 1 decreases,and those of stage 2 and stage 3 increase gradually.The oscillation with 30%EGR rate is the most significant.With the increase of engine speed,the pressure levels of stage 1 and stage 2 decrease,and move to the low frequency.The pressure level in the high frequency domain at 1600 r/min is less than that at 1100 r/min,and the combustion process is smooth.