Traditional Results

The gamma ray log is one of the most reliable logs. The well A, B and C have different depth ranges for the gamma ray log. Table 2 shows the depth range of the gamma ray log of these three wells. The depth origin is at surface, which is same as that for seismic data.

3cTable 2: The gamma ray log interval of the wells Well	log start	log end Well A

The gamma ray log is most frequently used to quantify shale volume along the well (). According to the consolided condition of rock property in this area, we used following empirical equation () to calculate shale volume from gamma ray value:

$$\begin{eqnarray} V_{shale}=0.33\left( 2^{2V_{shale}^* }-1 \right) \end{eqnarray}$$ (235)

Here V_shale^* is the linear function of $\gamma$:

$$\begin{eqnarray} V_{shale}^*=\frac{\gamma-\gamma_{min}}{\gamma_{max}-\gamma_{min}}\end{eqnarray}$$ (236)

The $\gamma$ here is the gamma ray value, $\gamma_{min}$ and $\gamma_{max}$ are the minum and maximum value of the gamma ray. Figure show the gamma ray log of these three wells. Figure is the shale volume calculated by using equation (6).

 

gammaray Figure 2 From left to right are the gamma ray log for the well A, B and C

 

shaleline1 Figure 3 From left to right are the shale volume for the well A, B and C. The shale volume was calculated from gamma ray value using equation (6). I selected $\gamma_{max}$ for A,B and C as 165,105 and 200 respectively by hand