# Investigation on Interference Test for Wells Connected by a Large Fracture
## 6 Conclusions  
To deal with the situation that there is no practical analysis model of the interference test for WsCLF, an one-dimensional governing equation is established in this study. An analytical solution is further obtained by the similarity transformation method. Using this solution, the extremum equation of the interference test for WsCLF is derived, and the type-curve of the interference test is plotted. Then, interference test data was fitted by the type-curve. It is found that the extremum equation of the interference test for WsCLF differs from that for homogeneous reservoirs by a factor 2. However, it is to be noted that the computed permeability may be quite different because their respective porosity and compressibility are quite different.  
On the interference test type-curve of the double logarithmic coordinate, the pressure and pressure derivative curves of WsCLF increase over time, and both finally become straight lines with a slope of 0.5. When the crossflow of the reservoir matrix to the large fracture cannot be ignored, the slope of these straight lines is 0.25. Considering the distinct shapes of pressure derivative curves for different connections, the connection form of wells can be diagnosed and the intensity of fractures can be qualitatively judged through the pressure derivative curves of the interference test.  
In this study, it is assumed that the two wells are connected by a large fracture. In fact, when two wells communicate through a narrow, high-permeability strip formation, the flow in the formation  
Figure 5: Interference test type-curve for wells connected by a large fracture with crossflow of the reservoir. (**a**) Different C\({}_{f}\). (**b**) Different \(F_{\rm D}\).  
is a radial flow near the well and then turns into a linear flow. If the strip is very narrow, the radial flow phase is very short and is even covered by the wellbore storage phase. At this time, the flow characteristics are similar to that of the WsCLF. Therefore, the results of this study can also be used for the analysis of such a situation.  
It is difficult to maintain the production rate of gas or oil wells constant in reality. Given that the extremum equation is independent of the production rate, it is only necessary to be able to distinguish the relationship between different active signals. However, when using the type-curve for analysis, the production rate must be considered. If the fluctuation of the production rate is not large over a long time, it can be treated as a constant production period. The average production rate is used in the analysis. Therefore, in order to use the type-curve for analysis, it is necessary to retain a substantially stable production rate over an extended period of time.  
Conceptualization, G.H. and Y.L.; methodology, G.H. and W.L.; formal analysis, G.H. and W.L.; investigation, D.G. and W.L.; writing--original draft preparation, G.H.; writing--review and editing, D.G. and Y.L.; funding acquisition, G.H.  
This research was funded by the National Natural Science Foundation of China, grant number 11602276.  
The authors declare no conflict of interest.