Journal of Petroleum Science Research (JPSR) Volume 2 Issue 2, April 2013
were probably caused by lithological change or oil water interface around injection front. Based on dynamic response, there were injection wells with no-mobile boundaries. The first time analysis result of injection well Lu 39-18 showed the existence of 2 no-mobile boundaries and the Lu 39-17 well on the west did not show effectual response. The second time analysis result still showed the existence of 2 nomobile boundaries. Although the Lu 39-17 well on the west showed effectual response because fluid production, oil production and working fluid level all increased and water cut decreased. This effect should be caused by Lu 39-16 because the injection rate of Lu 39-18 decreased from 35m3/d to 20m3/d while the injection rate of Lu 39-16 stayed in 40m3/d. Lu 39-19 on the east did not show any effectual response.
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equation proposed in the paper: Oil and Gas Well Test Data Interpretation write by Ding Gui-ming[3,6], the equation for calculating radial flow is:
t Dbs = 5exp[ −0.5( k fd ⋅ Wfd ) −0.6 ]
k fd ⋅ W fd
(1)
——fracture conductivity, 10-3μm2·m;
t Dbs ——radial flow starting time, h. According to the empirical equation proposed in the paper: Feasibility of analysis for shortening test time of low permeability reservoirs published in Petroleum Exploration and development[7], is the starting point where radial flow is reached：
t φ ⋅ Ct ⋅ X f = Dbs [(1 − f w ) µ o + f w ⋅ µ w ] (2) 3.6k 2
t bs
Xf
——fracture half length, m；
f w ——water cut,%；
k ——permeability,10-3μm2； C t ——total compressibility,MPa-1； FIG.1 PRODUCING PERFORMANCE LU 39-17
But according to the recent dynamic response of Lu 39-17,there were effectual evidence that fluid production, oil production and working fluid level all increased and water cut decreased, the injection rate of Lu 39-16 stayed in 40m3/d and the injection rate of Lu 39-18 sharply increased from 20m3/d to 40m3/d, the cumulative injection were close to 2.0×104m3,which might be caused by Lu 39-18.It shows that although perforation section did not coincide, there were still some hydrodynamic relations because there were not stable mud layer for insulation. When the injection rate was big enough or changed, the adjacent wells could be stimulated. So the no-mobile interface might be influenced by injection front. It is necessary to have more research on this topic. Theoretical Model Radial flow must be reached to obtain formation dynamic data for fractured wells, besides, the time for pressure to reach boundary should be considered. For fractured wells, radial flow starting time correlates with fracture conductivity. According to empirical
φ ——porosity,%；
µ o , µ w ——viscosity of oil and water, mPa·s. For fractured wells, it is necessary to prolong buildup period to obtain qualified data. The buildup process was quite slow due to low pressure and low permeability. So the wellbore storage must be considered and the flowing time should be extended. According to the statistic of 54 sets of data in 42 wells, when the flowing time was three times the radial flow starting time, the error for interpreting formation parameter and pressure would be smaller, and it will be more accurate to judge boundary type. Tripled radial flow starting time:
t bs ' = 3t bs
(3)
Effective wellbore radius：
rwe = rw− s (4) In the equation: s ——skin factor；
rw ——wellbore radius, m.
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