Unexpected Well Performance Case Study


Figure 1: A reservoir section showing the performance of clusters.

Operators implement different completion designs to maximize production throughout their field. When a well underperforms, clients begin to question what is impeding production. Using the Z-System® operators will be able to determine what is the root cause of underperforming wells. This case study will focus on a US unconventional well, where the Z-system® deployed a 0.6” OD, 20,000-foot-long carbon fiber rod to acquire DAS and DTS to evaluate well performance. The main objectives of this run were to use DFO measurement during a post-frac sensing operation to provide a clear and thorough understanding of cluster performance and to evaluate wellbore integrity.

The main objective for this analysis was to identify the number of clusters that are open and have contributing production. Using the Z-System®, DAS and DTS data was acquired to provide a cluster level understanding on the completion design.

Figures 1 and 2 below show an acoustical representation of the well’s performance over two intervals of the reservoir. Each figure shows a stage with its respective clusters. The well had an ununiform production profile throughout the lateral indicating some stages had no flow contributing to the production. No abnormal acoustic signals were present, verifying that there were no wellbore integrity issues.

Doing a qualitative analysis on acoustical measurements, Table 1 shows the cluster efficiency of the two intervals sensed. Cluster efficiency describes which stages were contributing to the flow. It can be noted that only some of the clusters showed signs of flow while most of the clusters showed no flow.Clusters that were flowing showed strong production.

IntervalClustersEfficiency (%)
Fig. 133%
Fig. 238%

When evaluating completion design techniques, using intervention based DFO technology such as the Z-system® will give a thorough diagnostic to ensure maximum recovery at minimum completion cost.


Figure 2: A reservoir section showing the performance of clusters.