Study and Application of Pulse Hydraulic Fracturing for Tight Oil Reservoir

Pulse hydraulic fracturing is a promising stimulation technology to enhance the effectively permeability of coal seams. The fundamental of pulse hydraulic fracturing is that fracturing fluids with a certain frequency are injected into coal, resulting in the rupture of coal and forming a well-distributed fracture network due to the pulse loading. Better effects of gas extraction using pulse hydraulic fracturing had been gotten compared with that of hydraulic fracturing. Accordingly, how to apply pulse hydraulic fracturing technology to improve the fracturing effect of tight and shale reservoirs is a question worth thinking about, although this is very challenging due to the totally different downhole operating conditions. In this paper, experimental apparatus for fatigue damage of quasi-triaxial rock under alternating loads was established. The maximum injection pressure is 50MPa, while the pulse pressure amplitude is greater than 5MPa, and the pulse frequency is adjustable from 0 to 50Hz. Rock failure experiments under pulsating load were carried out and the effects of different hydraulic pulse parameters and rock properties on rock damage were studied. Experimental results show that hydraulic pulse has different effects on rock compressive strength and fracture pressure of different properties. With the increase of hydraulic pulse frequency, the influence on rock compressive strength increases firstly and then decreases. With the increase of pulse pressure amplitude, the influence on rock strength increases. With the increase of hydraulic pulse processing time, the influence on rock fracture pressure increases firstly and then tends to stabilize. Hydraulic pulse has the greatest influence on the compressive strength and fracture pressure of He 8 reservoir, followed by Chang 8 and Chang 6 reservoir of Changqing Oilfield in China. Based on the experimental results, hydraulic pulse frequency is preferred to be about 18-20Hz, accordingly, a downhole hydraulic pulse generator is designed and manufactured. The indoor test results show that the generator performance meets the design requirements. Field tests of pulse hydraulic fracturing were carried out in 3 wells in Changqing tight oil reservoir. Encouraging results were obtained, the average construction pressure was reduced obviously and average daily production per well increased significantly compared to adjacent wells.

Analysis of structures of flat planting machines

One of the methods of material processing is considered, which allows to obtain high geometric accuracy and low surface roughness of parts, namely their abrasive finishing. The high quality of machining of parts in this way is due to the use of coordinated relative movement of the workpiece and the cutting tool. According to the kinematic features, most lapping machines can be divided into two groups: machines with oscillating working motion and machines with rotating lapping motion. The machines of the first group are more common due to the simplicity of their design and versatility. However, the possibility of their use is limited by the size range of the workpieces and uneven wear of the cutting tool and, as a consequence, the uneven surface treatment of the part. The machines of the second group are considered the most versatile, as they allow processing a wide range of parts, varying in shape and size, but they are also not without such a disadvantage as uneven wear of the cutting tool with all the corresponding consequences. Improving the efficiency of abrasive finishing by complicating the trajectory of the relative movement of the tool and the part, ie the formation of a unique mutual working movement of the lapping and the movement of the workpiece, is one of the most common areas. The main disadvantage of equipment that provides processing of parts on this principle is, in most cases, limited regulation of the operating parameters of the cutting process, so this area remains promising and has broad prospects for development. The constructive scheme of the hydraulic-pulse flat-lapping machine offered in work thanks to a combination of advantages of the hydraulic-pulse drive with use of numerical program control will allow to provide unique mutual multi-movement of preparation and the lapping tool with a possibility of adjustment of its parameters in the course of processing. Purposeful choice of the shape and density of the trajectory of the working movement of the tool will form a micro relief of the treated surface with the necessary statistical parameters and low roughness.

ELABORATION AND RESEARCHES OF HICHLY EFFECTIVE INSTALLATION FOR VIBRO-BLOWING DEHYDRATION OF DISPERSIVE WASTE OF FOOD PRODUCTIONS

There are schemes of equipment for dehydration of damp dispersive waste of food productions (spirit grain, beer pallets, beet pulp, coffee and barley slag) analyzed in this article. These wastes at the majority of food enterprises of Ukraine are poured out onto the ground and that leads to environment pollution. However, in case of dehydration of these wastes to humidity 20 – 25%, they can be used as valuable additions to agricultural forages or as high-energy fuels. Thus, the problems of waste utilization and protection of nature from pollutions are resolved simultaneously. Besides, the enterprise gets a profit from the sales of forage additions or fuel. The known equipment for mechanical dehydration, for example, the screw-presses and the decanter centrifuges, provides the waste final humidity no less 74 – 76%, therefore waste demand of an additional drying after the dehydration at this equipment. That brings to a significant increase of energy expenses. An application of the vibro-blowing dehydration at the installations with the hydraulic pulse drive provides waste final humidity 20 – 25%, but these installations are complex by design, have big dimensions and high cost. A drying in pulverizing or in vacuum dryers is most power-consuming dehydration method (expenses of energy - 740 ÷ 2248 kW h/ ton of dehydrated waste). Equipment for the chemical and biological dehydration is the large multiple-unit complexes with low specific productivity. Therefore, article authors offer a scheme of the installation with the combined unbalanced and hydraulic drive that has a relatively simple design, compact dimensions, high reliability and at the same time, in correspondence with the authors’ estimation, will provide necessary, above indicated humidity. Also equations for determination of the main working parameter – the pressure in the press-form of the proposed installation are presented in the article.

Experimental study on pressure pulses in long-distance gas pipeline during the pigging process

Long-distance gas pipelines generally have complex, undulating sections. Trapped air pockets are often present at the high points or ends of pipelines. This article carries out an experimental research to figure out the transient changes. First of all, under the condition of using the pig with 231 g and the injection pressure of 0.3 MPa, the hydraulic pulse increases from 0.31 to 0.54 MPa as the liquid level rises from 1 to 8 m. And at the liquid level of 8 m, the injection pressure grows from 0.3 to 0.75 MPa and the hydraulic pulse from 0.54 to 0.95 MPa. When the interception air mass is located at the blind side of the pipeline’s end, the injection pressure is 0.75 MPa, and the hydraulic pulse decreases from 4.9 to 3.21 MPa with the increase in the void fraction. The maximum hydraulic pressure generates when the air pocket is located at the rear end of the drainage system (4.9 MPa) is far higher than that when the air pocket is located in front of the pig (1.0 MPa). Therefore, it is necessary to minimize the generation of trapped air pockets at the rear end of the pipeline system to ensure safety.

Estimation of the amplitude of dynamic stresses on the contour of the well in the mountain range by the parameters of bench tests of hydraulic oscillators

Presented a method for calculating the dynamic tangential stresses around the wellbore, at the time of its treatment by the hydraulic pulse generator, by the values of its characteristics, obtained at the bench test, and the frequency coefficients of influence. Criteria are formulated for selecting the natural frequencies of the measuring sensors that ensure the coincidence of voltages in the array and on the measuring bench.

Control of Hydraulic Pulse System Based on the PLC and State Machine Programming

In this paper, we deal with a simple embedded electronic system for an industrial pneumatic–hydraulic system, based on a low-cost programmable logic controller (PLC) and industrial electronic parts with 24 V logic. The developed system is a hydraulic pulse system and generates a series of high-pressure hydraulic pulses with up to a max. 200 bar output pressure level and with up to a max. 2 Hz output hydraulic pulses frequency. In this paper we are describing requirements, the concept of the embedded control system in a diagram, security features and its industrial network connectivity (CAN bus, MODBUS). In description of the software solution we describe the implementation of the program threads approach in this low-cost PLC. The PLC programming with threads generate two layers of services—physical and application layer, and as a result, the threads create the main control state machine. In conclusion, we describe the calibration method of the system and the calibration curves. For further study we offer readers the full programming code written in sequential function charts to be used as PLC language. The cost of the described industrial networked control system with industry standard optoelectronic insulated interfaces and certified industrial safety relay does not exceed €1000 Euros.

Control of Hydraulic Pulse System Based on the PLC and State Machine Programming

In the paper is described the control electronics for an industrial pneumatic – hydraulic system based on a low-cost PLC. The developed system is a hydraulic pulse system and it generates series of high pressure hydraulic pulses (max. 200 bar). We describe requirements, an overall concept of the embedded control system, user interface, security features and network connectivity. In the description of the software solution we describe implementation of hierarchical ordered program threads (multithreaded program) and main control state machine. At the conclusion, we describe the calibration method of the system and calibration curves and we present the schematic diagram and a photo of a functional prototype of the system.

Experiment and Dynamic Simulation of PIG Motion during Pigging Operation in a Slope Pipeline

Pigging techniques are widely used in the oil and gas industry. The unsteady motion of the PIG in an undulating pipe section during the pigging process after a water pressure test affects the stable operation of the pipeline and also causes a pipe rupture accident in serious cases. First, an experimental study was conducted to investigate the pigging process of air–water two phase pipe flows, and the PIG reverse movement and hydraulic pulse phenomenon were observed. Subsequently, a hydraulic transient model of the pigging process after a water pressure test was established in a dual-grid system. The model combined mass and motion equations of gas and liquid and PIG dynamic equations, considered three types of PIG motion states, namely positive movement, reverse movement and still, and used the method of characteristics to solve the equations. The model exhibits the ability for PIG tracing and hydraulic pulse prediction. It can be used to obtain the position and speed of the PIG. Finally, the field data and simulation results were compared, and the results indicated that they are essentially identical. This verified the accuracy of the model that is established in this study and the reliability of computed results and provided a reliable and effective theoretical basis for the development of field pigging plans.