Advanced Materials Research Vols. 734-737

Abstract: Hydraulic fracturing is the main method to increase the output of coal-bed methane wells, however, the hydraulic fracturing result of coal-bed methane well is usually affected by large number of factors such as the conditions of coal-bed, the conditions of coal-bed methane well, fracturing operation parameters and so on. As a result, the fracturing operation result is difficult to predict. This paper assumed coal seam thickness, the depth of coal seam, coal seam gas content and other six main factors which affect hydraulic fracturing results by analysis various factors. Membership function of the expert system was established to divide the level of each factor. The established method which applies the expert system to predict the hydraulic fracturing results of coal-bed methane wells was based on expert database. Using the established expert system to calculate 200 groups of test data and the prediction error rate is only 3.5%. The prediction results are accurate and reliable, and can provide guidance for coal-bed methane wells fracturing optimization.

Abstract: The wide use of oil drilling rig brings nominated economic profits for oil drilling industry. However, it will bring about great quantities of harmonic current to the grid, lowering the power quality and reliability of the power grid. Meanwhile, harmonic currents will have a deteriorated influence to surrounding electrical equipment and grid. This paper studies the distribution characteristics of the harmonic current in the oil industry and puts forward a control strategy aiming for improving stability and reliability of the power supply system. This paper also proposes an algorithm for detecting harmonic current based on time domain transformation and control strategy based on two cascade (voltage and current) control loop. Experiment and simulation results validate the proposed control strategy.

Abstract: According to the 2012s workover treatment statistic in the Hancheng block, the eastern Ordos gas field, the workover caused by pulverized coal accounts for 41.8% of the total, which has seriously affected the continuous and stable drainage. This is one of the main factors which constraint coalbed methane production yield. In this paper, geological factors including the composition of coal petrography, the mechanical strength of coal petrography and coalbody structure destruction and engineering factors including drilling, fracturing and drainage were analyzed to study on the controlling factors on the output of pulverized coal. We conclude that the determinant on output of pulverized coal is the nature of coal seam, however engineering factors cause the output of pulverized coal directly. The root-mean-square amplitude attribute analysis was first used to display the mechanical strength of coal seam. Based on the result, we made the prediction about the possibility of the output of pulverized coal and divided the studying area into four grades. The research on the controlling factors and the prediction of the output of pulverized coal could provide the basis for the prevention and comprehensive treatment of pulverized coal.

Abstract: Gao 89 Block is a low permeability oil reservoir. These reservoirs have difficulty in water injection, poor well condition, and low original production. Gas injection can solve this problem. It is the most efficient recovery method for low-permeability reservoirs at home and abroad. In accordance with the geological features and development actuality of Gao89 Block, the feasibility and optimization of gas injection are studied, the effect of gas injection on the development index and development results are demonstrated. The results indicate that the gas injection can dramatically enhance oil recovery and increase the oil production.

Abstract: In order to visually reflect the characteristics of flowing tracks of horizontal linear well pattern in anisotropic reservoirs, By means of the source-sink theory, Newmans product method and potential superposition principle, the transient flow pressure distribution equation of horizontal well pattern is obtained, the calculation method of seepage field streamline is presented, and the distribution law for streamline is studied. It is shown that the streamline of horizontal linear well pattern is sensitive to the reservoir anisotropic and horizontal well length. In the pattern of well, there is a reasonable well spacing and row spacing under a given degree of anisotropy, which can maximize the effect of displacement and the productivity of horizontal well. The drainage area of production well will increase with the increasing of horizontal well length, which can improve the productivity of horizontal well. The streamline plots generated by this method can provide a scientific basis for the design of horizontal development well pattern, analysis of remain oil and optimization of injection strategy in anisotropic reservoirs.

Abstract: Non-acid plug removal technology is new ways of plug removal technology which applies to unconsolidated sandstone reservoir. An effective plug removal agent will be chose through detailed study of the blockage features in block G104-5 of JD oil field. The production history curves show that the non-acid plug removal jobs with 5 well times in block G104-5 are all successful.

Abstract: Pu I formation in Gaotaizi oilfield mainly developed delta distributary channels. The sand body is narrow and has a complex superimposition in vertical, which caused the sand body hard to forecast. To solve this problem the method of seismic sedimentology was applied to building high frequency stratigraphic framework and extracting high-precision stratal slice. The technique of 90-degree phasing conversion and multi-attribute comprehensive analysis to the channel sand was also performed. At last Pu I formation in Gaotaizi Oilfield is divided into fifteen fifth-order sequences. The attributes of Rms amplitude and Arc length are considered as the best attribute to reflect the characteristics of the channel sand in study area. By a multiple linear regression to the attributes, the prediction accuracy between wells is improved from 61% to 78%.

Abstract: When horizontal wells are used to exploit reservoir with bottom water, oil wells water breakthrough prematurely due to water coning, water-free oil recovery is reduced. The reason of the formation of horizontal well water cone is analyzed. Then analysis of the mechanism using balanced screen pipe to inhibit bottom water coning in horizontal well is completed. According to the existing screen pipe size, screen configuration is optimized. Horizontal section pressure distribution is controlled by the balanced screen pipe, and then flow of horizontal well sections is adjusted. Bottom water coning speed of all well sections is controlled. An example is calculated by the software which established and the result shows that optimization method can improve water-free oil recovery.

Abstract: With the oil field developing, the water cut increased, gradually and the efficiency of injection-production reduced year by year. Since the water flooding of Lamadian Oilfield entered extra high water cut period, the distribution of flow flied become more and more complex. The distribution of remaining oil and ineffective circulation is complex. The existing of ineffective circulation led to the flooding efficiency reducing sharply and cost of crude oil per ton by water flooding increased. In order to control production energy consumption in the extra high water cut, the method of improving the efficiency of Injection-production is studied in the Lamadian oilfield. Through the analysis of injection-production status, the factors that influence the injection efficiency is studied. The distribution of ineffective circulation which seriously affects the efficiency of Injection-production is made clearly. According to the factors that influence the efficiency of injection-production, based on flow field characteristics of water flooding, the countermeasure to enhance efficiency of injection-production is put forward in order to reduce the energy consumption and cost of producing crude oil.

Abstract: The fractures after artificial steering fracturing appear in shades of curved surface. Aiming at the problem of steering fracture, in the paper, numerical simulation method under the condition of three-dimensional two-phase flow is presented based on finite element method. In this method, of steering fracture was achieved by adopting surface elements fractures and tetrahedron elements to describe formation. By numerical simulation, the change rule of oil and water production performance of steering fractures can be calculated, and then the steering fracture parameters can be optimized before fracturing. A new method was supplied for the numerical simulation of artificial fractured well.