# A New Algorithm Model Based on Extended Kalman Filter for Predicting Inter-Well Connectivity
## 6 Quantitative Classification of Ineffective Circulation Channels
### Rating of Ineffective Circulation Channels  
The rating of ineffective circulation channels helps to identify the pairs of wells that require optimization and improve the production efficiency of the entire oilfield. Considering the inter-well connectivity coefficient, time-lag coefficient, and connectivity volume derived from the SV-DC model, a multidimensional score for evaluating well pair performance is proposed. As this is our initial exploration in this direction, the approach is intentionally kept simple. Based on the injection and production data from the Qinhuangdao 32-6 oilfield, which has a large number of well groups and sufficient data, the inter-well connectivity coefficient ranges from 0 to 1, the time-lag coefficient ranges from 0 to 5, and the connectivity volume ranges from 0 to 600,000 cubic meters.  
\[\text{score}=\frac{mean_{\lambda}\times mean_{V}}{mean_{\tau}} \tag{29}\]  
Using Equation (29), the level of ineffective circulation channels can be graded according to the calculated score. The classification criteria are established based on the distribution of these parameters and the experience from the Qinhuangdao 32-6 oilfield data analysis. The abundant data available allow us to compute a wide range of values, providing a solid foundation for defining the four levels of classification. The larger the inter-well connectivity coefficient and connectivity volume, and the smaller the time-lag coefficient, the higher the score, indicating better connectivity between wells. This scoring system divides the ineffective circulation channels into four levels, as shown in Table 5, with Level I representing the best connectivity and Level IV representing the poorest.  
According to the proposed rating method, the development time and level of ineffective circulation channels in the entire oilfield are calculated as shown in Table 6. Well pairs of key optimization measures are selected to optimize the oilfield production strategy further. Due to the difficulty in determining the development time for ineffective circulation channels in Level III and Level IV well pairs, these cases are not displayed in Table 6. For the accuracy validation of the data in Table 6, reservoir engineering methods and tracer monitoring were considered. The development of ineffective circulation channels was determined and verified by tracer data collected in block N  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Score** & **Level** \\ \hline score \(\geq\) 20,000 & I \\
10,000 \(\leq\) score \(\leq\) 20,000 & II \\
5000 \(\leq\) score \(\leq\) 10,000 & III \\ score \(\leq\) 5000 & IV \\ \hline \hline \end{tabular}
\end{table}
Table 5: Grading of ineffective circulation channels based on SV-DC model results. Levels I, II, III and IV indicate best, good, poor, and very poor connectivity, respectively.  
with strong connectivity identified by tracer monitoring results, of which 24 are consistent with the conclusion of our proposed identification of ineffective circulation channels, with an accuracy of 96%. For instance, in well group C03, well H03H had the earliest tracer breakthrough time, while well H19H1 had the latest. Correspondingly, the development of ineffective circulation channels in well group C03 and well H03H was also observed to be the earliest.