Isolation and algicidal properties study of the strain G1 from reservoir sediments

Microcystis aeruginosa is a globally important cyanobacterial species that poses a threat to human health and development. The use of bacteria to control algal blooms has become an important research topic in recent years. In the present work, the algicidal strain G1 was isolated from sediments of a reservoir in Xi'an, China, identified by 16S ribosomal DNA (rDNA), and its algicidal effects were investigated. The rDNA sequence of G1 (GenBank accession number MW205793) is 99.86% similar to that of Chitinimonas sp., and the strain indirectly solubilised algae. Algae removal by G1 was optimal during the decay phase (algae solubilisation rate = 65.85%). Temperature (5–120 °C) did not significantly affect algae removal, pH 5–9 was tolerated, and pH 7 achieved the highest algae lysis rate (63.56%). Ultrasonic treatment of G1 destroyed the algae-solubilising effect. An injection ratio of 15% achieved the highest algae lysis rate (67.64%) under 12 h:12 h light:dark conditions, and full darkness achieved the highest algae lysis rate (68.21%). Thus, G1 can effectively inhibit the reproduction of M. aeruginosa, making it a promising biological agent for controlling algal growth.

Effect of bentonite slurry on the function of foam for changing the permeability characteristics of sand under high hydraulic gradients

During earth pressure balance (EPB) shield tunnelling in sandy ground, not only foam but also other conditioning agents need to be injected to reduce the permeability of muck and avoid water spewing out of the screw conveyor. Permeability tests were carried out to study the permeability characteristics of conditioned sand under high hydraulic gradients. A low bentonite slurry injection ratio (BIR) enhanced the workability of foam-conditioned sand. As the hydraulic gradient increased, the initial permeability coefficient of conditioned sand increased, and the initial stable period became shorter or disappeared. The BIR had a more significant effect on the permeability of conditioned sand than the foam injection ratio (FIR), and this effect gradually weakened as the hydraulic gradient increased. The initial permeability coefficient of the foam-bentonite slurry-conditioned sand decreased by approximately an order of magnitude compared with that of the foam-conditioned sand. With the addition of bentonite slurry, suitable sand conditioning can accept a higher water content (w) and lower FIR, resulting in suitable ranges of w and FIR that are more flexible. Finally, the mechanism of stabilizing foam under the action of bentonite slurry was discussed by considering the interaction between foam bubbles and fine particles.

Investigation of Hydraulic Performance Based on Response Surface Methodology for an Agricultural Chemigation Proportional Injector

Injectors are key pieces of equipment for chemigation systems, and their hydraulic performance has a significant effect on chemigation systems and crops. In order to investigate the influence of different working parameters on hydraulic performance for a water-powered proportional injector (PI), three key parameters of inlet and injection flow rate were researched using a one-factor experimental design method. The regression equations between different factors and response variables were established through a response surface method based on one-factor experimental results. Lastly, a mathematical model of the actual injection ratio was established. Some experiments under different, randomly selected parameter combinations were carried out to verify the prediction precision of the mathematical mode. The results showed that the injection flow rate increased first within the differential pressure of 0.05 to 0.10 MPa and then tended towards stability with increasing differential pressure. The injection flow rate decreased by increasing the viscosity and the change in the injection flow rate was small enough when the viscosity was greater than 500 mPa·s. The impact factors, in order of significance, for inlet flow rate were differential pressure, viscosity of injection liquid and setting injection ratio. The impact factors, in order of significance, for injection flow rate were viscosity of injection liquid, setting injection ratio and differential pressure. The regressive model for predicting the actual injection ratio was validated using an experiment and the relative deviation between calculated value and tested value was less than 5.98%, which indicated that the mathematical model had high credibility.

Laboratory Investigation on Oil Increment and Water Cut Control of CO2, N2, and Gas Mixture Huff-n-Puff in Edge-Water Fault-Block Reservoirs

Excessive water production is a common matter that seriously affects production efficiency during the development of edge-water fault-block reservoirs. Gas huff-n-puff is an effective water shutoff technology that has the characteristics of small injection volume, no interwell connectivity impact, and minor gas channeling. However, gas injection can destroy the stability of the asphaltene to induce asphaltene deposition. In this article, the laboratory experiment had been conducted to investigate the effect of injection ratio and injection sequence on oil increment and water cut control for gas mixture huff-n-puff. Experimental results indicated that the effect of N2 huff-n-puff on water cut control was the most obvious, while CO2 huff-n-puff had the best performance on oil increment. Oil increment and water cut control of gas mixture huff-n-puff with CO2 injected in advance were obviously better than that of N2 injection preferentially. Subsequently, PVTsim Nova was utilized to investigate whether reducing CO2 injection volume can inhibit asphaltene deposition and predict the possibility of asphaltene deposition at reservoir conditions. Simulation results demonstrated that the asphaltenes were easily deposited with CO2 injection while N2 injection will be unlikely to induce asphaltene deposition. Asphaltene deposition pressure envelope can qualitatively analyze the possibility of asphaltene deposition and provide a reference for screening the appropriate gas injection ratio based on giving full play to the synergistic effect of CO2 and N2. In this study, 7:3 is selected as the optimum injection ratio considering the synergistic effect and the possibility of asphaltene deposition.

Optimization of design and mode parameters of the well ejection system

Insufficient energy performance of ejection equipment and a high probability of non-operating modes of its operation reduce the efficiency of downhole jet pumps. The method of determining the design and operating parameters of the well ejection system, which provide the maximum efficiency of the jet pump, is presented. The proposed algorithm for determining the optimal values of the geometric dimensions of the flowing part of the jet pump involves the construction of a series of pressure characteristics for different values of its geometric parameter, the calculation of the efficiency and the determination of the injection ratio and the relative pressure corresponding to its maximum values. During the studies, the main geometric parameter of the jet pump varied in the range from 2 to 6, given that these geometric dimensions are used in jet devices common in the oil industry. The optimal dimensions of the current part of the jet pump are obtained in the process of studying its pressure characteristics, and the optimal dimensions of the washing system of the bit - in the process of studying the characteristics of the hydraulic system. The design of an at-bit ejection system, which allows to increase the mechanical drilling speed, the passage of the bit, to stabilize the moment on the bit, to reduce its level of vibration and to control the antiaircraft angles of the well is considered. The efficiency of using at-bit jet pumps is in the following: an increase in the mechanical drilling speed up to 18.7%, the passage of the bit up to 50.8%. The research established the optimal diameters of the working nozzle, mixing chamber and bit nozzles, the distance between the working nozzle and the mixing chamber, the injection ratio and the relative pressure of the at-bit jet pump. The obtained values ​​of design and mode parameters exclude the occurrence of cavitation modes of operation of the ejection system and allow the operation of jet pumps with maximum efficiency.