Study On Production Prediction For Ladder_like And Branched Horizontal Wells

In a complex of low-permeability reservoirs, the traditional vertical well production capacity has reached less than expected results. In order to enhance oil recovery, We will try our best to exploit the remaining oil, In recent years, We generally used the horizontal wells, branch wells and the other Complex drilling technology. Zhaozhou Putaohua oil is low abundance of reservoir, We used the exploitation of conventional vertical wells, Economic benefits was poor. In order to explore this part of the effective use of reserves means ,enhance the use of unused reserves and ultimate recovery, Daqing oil field development of horizontal wells tests and We have successfully finished drilling and putting in production more than a dozen Horizontal wells in Zhaozhou Putaohua oilfield.The Production capacity of horizontal wells and branch horizontal wells reflects that they provide the ability of the size of fluid flow. The production capacity prediction of horizontal well is the important parameters of the design of horizontal wells, horizontal wells with production allocation, establishing a reasonable system. It is very important to improve the effectiveness of the development of oil fields and give full play to the potential of the horizontal wells and branch horizontal wells that we Study on the production capacity of them.In this paper, We deeply studied of wells Percolation mechanism of different boundary conditions for horizontal wells and analyzed the influencing factors of the production capacity of horizontal wells. According to the results of research and analysis, We use the combination of analytical methods and numerical simulation to establish capacity theoretical model and calculation method under various boundary conditions. We prepared a set of "horizontal well production capacity prediction software" system that focused on low-yield Daqing Putaohua permeability characteristics of horizontal wells. In a given reservoir parameters and reservoir parameters, the software can be used in the design and calculation of horizontal wells. The project was divided into five parts:First, Percolation mechanism analysis of horizontal wellsWhen the Horizontal wells and Branch horizontal wells produced, the flow to the wellbore fluid was three-dimensional form. When the wellbore flow of horizontal wells and horizontal branch well fluid to flow with the client.There is still pressure drop. These show that the Production capacity of horizontal wells, We should be targeted at the nature of three-dimensional flow to research. When the Horizontal wells and Branch horizontal wells produced, Flow can be divided into five stages: Wellbore storage phase,the early phase of radial flow,the second phase of the radial flow,the mid and late stages of linear flow to radial flow stage.Second, the stability production capacity of horizontal well prediction methodUnder the conditions of stable flow,Evaluation of horizontal well productivity is a horizontal well reservoir engineering one of the fundamental issues. However, due to the complexity of the horizontal well, In the derivation process of the current popular production capacity of horizontal wells in the stability of flow , The majority of researchers, including Giger and Joshi will be actual production capacity of the horizontal well , Three-dimensional seepage problem in oil production capacity Simplified horizontal and vertical movement of the two two-dimensional problem to study. Then we use the equivalent flow resistance law to be superimposed solution to the original question. This simplification does not fully reflect the actual production capacity level of oil wells within the characteristics of three-dimensional flow. The project will be horizontal well as three-dimensional sinks, We derived a variety of boundary conditions of horizontal well production prediction formula.The impact of its production capacity of the main factors: length of horizontal wells, horizontal well location, anisotropy, shaft number of branch horizontal wells, the number of cracks. When the increase in the length of horizontal well is conducive to the improvement of production capacity; Horizontal wells farther from the oil-water boundary, the smaller the output of horizontal wells; With anisotropic permeability ratio (Kh / Kv) of the increase in the production capacity of horizontal wells to reduce; Shaft to increase the number of branching levels can increase oil production capacity, Shaft should be a reasonable number of generally 2 to 4; Article cracks increase in the number can increase production capacity of fractured horizontal wells, 3 ~ 5 best.Third, instability in horizontal wells percolation theoryThe percolation mechanism of horizontal wells is complicated, The flow lines of the near wellbore show characteristics of three-dimensional space, and the flow lines of far zone wells are degradation for characteristics of two-dimensional space. In order to accurately describe the level of the three-dimensional flow characteristics well, we based on Gringartan and Ramey 1973 years of Green's function and source function, We have to use for point-source technology and the principle of superposition to obtain a three-dimensional percolation model of a variety of boundary conditions, horizontal wells. The basic idea is: First of all, we solve the free three-dimensional space in response to the point source;Second, Through the superposition mirror, We built the point source response based on typical outside the boundary conditions. Finally, through point source points, We built the line source,Non-point source,the pressure respond within the borders(various different types of well ).After we got the bottom-hole pressure response, we used Duhamel principle to get the relationship between yield of horizontal wells and time in all cases.Fourth, prediction about instability production capacity of Horizontal well and impact factor analysis.The combined effect of epidermal and wells Reserve, We have reached the bottom of the actual total dimensionless pressure drop, Through Laplace transform, we transformed the pressure drop into pressure as function, then we used Duhamel principle and got dimensionless yield formula in Laplace space. The use of numerical inversion methods, we got the all cases output of horizontal wells.The impact factor of instability production capacity of Horizontal well: horizontal well length,border distance,boundary type,effective thickness,penetration,location of horizontal wells,Skin effect,wellbore storage effect,border nature and so on. After horizontal wells put into production, these situation such as fracture,acidification,water can affect the larger on the latter stability production capacity of horizontal wells, in general, these are conducive to production capacity. By increasing the wellbore numbers of branch horizontal wells, it can increase oil productivity. Reasonable Wellbore number is generally 2 to 4. It is different of the productivity in each cracks of fractured horizontal wells .The crack is the highest output, the crack in the middle is the lowest productivity. It is the best that the number of cracks is 3 to 5 ; Cracks is greater conductivity, production capacity is the higher, but the growth of time, Conductivity of the cracks in the impact of production capacity decreases, even disappear.Fifth, the preparation of a set of "production capacity of horizontal well prediction software"We programmed a set of "production capacity of horizontal well prediction software" system that based on Daqing Putaohua low permeability characteristics of horizontal wells. In a given reservoir parameters and storage layer parameters, the software can be used in the design and calculation production capacity of horizontal wells. In the case that we knew part of the production capacity data, we can use the software to carry out on horizontal well production capacity prediction by fitting analysis.We use this software calculated and analyzed the 5 production capacity for horizontal wells, we compared the actual production data, results was in line with actual data. The average relative error was in the range of 2.59-6.78.Thanks to our team efforts, We have established production capacity forecast theory for ladder like and branched horizontal wells. We forecast 5 production capacity of horizontal wells. In line with the rate of 85%.This is expected to reach our goal. The project in Daqing Oilfield have applied.