# The Principle and Downhole Testing of Water Injection Exploration in Depleted Reservoirs
## 1 Introduction
### Water Injection Test Process and Water Injection Data  
This time, the water injection test used the method of simultaneous injection and reinforcement while drilling. A pneumatic grouting pump ZBQ16/12 was used in this experiment, with a maximum pressure of 12 MPa and a maximum flow rate of 2 L/min, and a minimum flow rate of 2 L/min. In the actual water injection process, water injection was first performed at the minimum flow rate while observing the pressure. If the pressure rose above 10 MPa (indicating that the seepage rate was less than 2 L/min, suggesting that this section had good resistance to water pressure), the check valve was closed, and pressure changes were observed. To ensure the reliability of the test data, two identical tests were conducted at the minimum flow rate again. If the results were the same, it indicated that this section indeed had resistance to water pressure, and the water injection \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Hole Number** & **Opening Position** & **End Hole Target Point** & **Borehole Orientation \(\angle\) (\(\lx@math@degree\))** & \
\begin{tabular}{c} **Angle of Borehole** \\ \(\angle\) (\(\lx@math@degree\)) \\ \end{tabular} &
\begin{tabular}{c} **Depth** \\ **(m)** \\ \end{tabular} \\ \hline
151 & after C\({}_{68}\) 12.5 m &
\begin{tabular}{c} Bottom pumping \\ roadway of 7\({}_{3}\)24S \\ \(7_{2}\)24S \\ \(155\) \\ \end{tabular} & N267.6 & 22.8 & 51.7 \\
153 & before C\({}_{68}\) 60 m & \(7_{2}\)24S working face goal & N267.6 & 52.5 & 96.5 \\
155 & before C\({}_{68}\) 127 m & 156 holes & N80 & 0 & 40 \\
156 & before C\({}_{68}\) 97 m & 155 holes & N50 & 0 & 47.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of drilling parameters. Figure 3: Water injection test flow chart. for this section could be terminated. Without grouting, drilling continued for another 4 m to enter the next section of water injection. If the pressure could not rise to 10 MPa during water injection at the minimum flow rate, observation was continued for 30 min. If after 30 min the pressure still could not reach 10 MPa, the flow rate was increased by one level. If the pressure rose above 10 MPa, two identical tests were conducted again as described above. If both tests reached the pressure, water injection for the next stage would begin, and post-grouting hole drilling was required. If the pressure could not rise to 10 MPa, observation continued for 30 min, and the flow rate was increased again, repeating the aforementioned test process. The water injection process is shown in Figure 3.  
(1) Hole No. 151  
The borehole underwent 4 stages of water injection tests. Injection was conducted at a depth of 31.7 m (with the test section being 20-24 m away from the roadway) using a flow rate of approximately 10 L/min. The water pressure reached around 10 MPa and remained stable, with a rock permeability coefficient of approximately 0.00275 m/d. Continuing forward, injection was carried out at a depth of 35.7 m (with the test section being 16-20 m away from the roadway). Starting with a flow rate of 10.26 L/min, the flow rate was gradually increased. When the flow rate reached 23.76 L/min, the water pressure stabilized at around 6 MPa, and the permeability coefficient reached approximately 0.01080 m/d. Proceeding further, injection was performed at a depth of 39.7 m (with the test section being 12-16 m away from the roadway). Injection started with a flow rate of 9.34 L/min and was gradually increased. When the maximum flow rate reached 27.31 L/min, the water pressure stabilized at around 5.6 MPa. At maximum flow, the permeability coefficient reached approximately 0.013202 m/d. Continuing to drill to a depth of 43.7 m (with the test section being 8-12 m before reaching the end of the borehole), injection was carried out. At a flow rate of 11.53 L/min, the water pressure stabilized at around 5.07 MPa, and at a flow rate of 20.51 L/min, the water pressure stabilized at around 4.83 MPa. The permeability coefficient reached approximately 0.01080 m/d. Hole No.