Research of Mathematical Model and Influencing Factors of Water Invasion Performance for Horizontal Well in Fractured-vuggy Gas Reservoirs with Bottom Water

Abstract

Abstract:

In the development process of gas reservoirs with bottom water, water coning up is easy to happen with the production of gas and well bottom pressure decreasing, which has a strong impact on gas production rate. So if water invasion performance can be predicted in advance, that really has important meaning to develop gas reservoirs with bottom water. Meanwhile, comparing with conventional gas reservoirs with bottom water, fractured-vuggy gas reservoirs with bottom water have the characteristic of triple porosity, fractures and vugs are developed resulting in high heterogeneity and the seepage process of gas is more complex. According to using the permeability variation to deal with the development of fractures and vugs in fractured-vuggy gas reservoirs with bottom water, the absence of fractures and vugs just changes the reservoir’s permeability. What’s more, on the base of the horizontal well bottom water coning performance in the single-porosity reservoir, the critical rate equation and the water breakthrough time equation are established in the use of the permeability variation theory, with their influencing factors analyzed. These equations obtained can be used to calculate the critical rate and the water breakthrough time of the horizontal well and to predict the water breakthrough position of fractured-vuggy gas reservoirs with bottom water, which can guide the development of field fractured-vuggy gas reservoirs with bottom water and determine reasonable gas production rate and prolong the water breakthrough time and then guide the implement of follow-up water shutoff and profile control method. The established numerical simulation model and the actual production data verify that the method is reliable and the numerical simulation result directly shows the right of the water coning up study in fractured-vuggy gas reservoirs with bottom water.

Key words: fractured-vuggy gas reservoir, critical rate, water breakthrough time, permeability variation model, bottom water coning

CLC Number:

TE319

YU Qingyan, LIU Pengcheng, LI Yong, XIA Jing, HAO Mingqiang, LI Baozhu. Research of Mathematical Model and Influencing Factors of Water Invasion Performance for Horizontal Well in Fractured-vuggy Gas Reservoirs with Bottom Water[J]. Geoscience, 2017, 31(03): 614-622.

Figures/Tables 12

Fig.1 Cross-section of horizontal well in gas reservoirs with bottom water

Fig.2 Permeability variation model of horizontal well in fractured-vuggy gas reservoirs with bottom water

Table 1 Reservoir and the fluid characteristic parameters

参数名称	数值	参数名称	数值
气体黏度μ_g/(mPa·s)	0.020	含气层厚度h_g/m	60.0
气体体积系数B_g	0.005	井筒半径r_w/m	0.10
气体密度ρ_g/(kg·m^-3)	0.800	水平井长度L/m	500
地层水密度ρ_w/(kg·m^-3)	1 000	原始地层压力p_e/MPa	57.6

Fig.3 Reservoir carving figure

Fig.4 Influences of the height of water avoidance to the horizontal well critical production rate in fractured-vuggy gas reservoirs with bottom water

Fig.5 Influences of the development of the fractures and vugs to the horizontal well critical production rate in fractured-vuggy gas reservoirs with bottom water

Fig.6 Influences of the size of the fractures and vugs developed to the horizontal well critical production rate in fractured-vuggy gas reservoirs with bottom water

Fig.7 Influences of the height of water avoidance to the horizontal well water breakthrough time in fractured-vuggy gas reservoir with bottom water

Fig.8 Influences of the horizontal well production rate to the horizontal well water breakthrough time in fractured-vuggy gas reservoirs with bottom water

Fig.9 Influences of the horizontal well length to the horizontal well water breakthrough time in fractured-vuggy gas reservoirs with bottom water

Fig.10 Horizontal well water production rate of numerical simulation model

Fig.11 Water crest shape of I-K direction in triple porosity gas reservoirs

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