The Optimization Design Of Horizontal Well With Multiple Hydraulic Fractures

Since1990s, with the development of technology and the more need of application, horizontal well has develop a lot and widely applied. Horizontal well can increase the contact area between production wells and the formation, decreasing the producing pressure drop, improve the single well production, and lower the well count. Finally, horizontal well should improve the development effect and benefit. The technology of horizontal well has been one of important methods to enhance oil recovery. As the oil exploration and development time extension, the high permeability reservoir has been tapering off, the low permeability reservoir is important more and more. The horizontal well with multiple hydraulic fractures is become a important orientation and approach to develop low permeability reservoir, especially tight reservoir. It is the key technology to realize develop tight reservoir economically and effectively, and it has a broad prospect. At present, the calculation of the production for the multiple hydraulic fractured horizontal well is immature. The research on the optimization of the horizontal well with multiple hydraulic fractures is very few. So the study of this paper is of great importance.A comprehensive review on the horizontal well fracturing techniques, fracturing horizontal wells productivity calculation formula and optimizing the design of horizontal well fracturing is made. This paper study the seepage flow characteristic of horizontal well fracturing, and made contrastive analysis on the fracturing horizontal well productivity calculation formula, On the basis of the above, horizontal well productivity calculation formula—Ning Zhengfu method is improved. Then, the analysis of influencing factors for fracture production is researched. Finally, based on the analysis of the fracturing horizontal well productivity calculation formula, the improved fracturing horizontal well productivity calculation formula and the influencing factors for fracture production, this paper optimizes the design of fracture parameters.At present, some better fracturing horizontal well formula basically has Lang Zhaoxin method, Li Hujun method and Ning Zhengfu method. The Lang Zhaoxin method ignore more factors, the calculation results bigger, Li Hujun method consider of fracture interference is not enough, Ning Zhengfu method is improve Lang Zhaoxin method, and considering the seepage resistance in the fractures, but still ignore more factors, the calculation results is also bigger.According to the actual situation start-up pressure gradient and horizontal well bore pressure drop is analyzed. Usually when start-up pressure gradient is greater than0.001MPa/m, it will need to consider start-up pressure gradient in production calculation, when start-up pressure gradient more than0.01MPa/m, it must be considered. If there is not a huge influence on production, horizontal well bore pressure drop can be ignored.Horizontal well productivity calculation formula—Ning Zhengfu method is improved, new method modify the flow model as plane radial flow, and consider the pressure drop be a cause for concourse effect. And by programming the numerical algorithm of matrix equation, the calculated result is more accurate.The fracture interference is analyzed. The analysis shows that the distance of fracture interference increase over time and pressure transmitting coefficient. Instead, the fracture interference time is along with the pressure coefficient increases to shorten. Fracturing horizontal well production influence factors were also analyzed.Comprehensive analysis, the fracture parameters are optimized:the more number fractures the more production, and the increase of production is smaller. But the decrease of low permeability reservoirs is not obvious, fracture interference is small. The same as the increase of fracture distance, it has not big effect to the increase of production. For in this paper fracturing wells parameters, the number of fracture is8～10, the fracture spacing for75～125meter is better. The longer the fractures length, the greater the production, but the increase is not obvious. For the low permeability reservoir, the increase of fracture length to get higher production is more effectively than higher permeability reservoir. In the case of this paper, fracture length is250～350meter for good. For a certain fracture length and oil reservoir conditions, there exists optimal flow conductivity. Reservoir thickness is bigger, the flow conductivity is smaller. This paper example fracture diverting capacity for30to50um2·cm is better. In the case of this paper, flow conductivity is30～50um·cm...