Perforation Clustering: A Case Study

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Shale rock, is a sedimentary rock composed of mixture flakes of clay and silt sized other mineral. Process of shale formation is called compaction. Shale oil, is an unconventional is produced by various processes like thermal dissolution, hydrogenation etc. Shale gas, is natural gas that is extracted from shale formations. China is estimated to have the world's largest shale gas reserves.
Clustering: Cluster placement should be matched to reservoir quality
Single clustering: gas production is reduced significantly when the cluster spacing is single the width growth of fracture is strongly inhibited due to mechanical interaction
Multiple clustering: multiple cluster perforation are typically used to create multiple fractures in any single stage placing these perforation is critical issue cause the number of perforation cluster to be used and the space between them significantly impact how effective the fracture can be created in the formation
Production using perforation cluster:
Perforation cluster productivity is determined by running production logs into horizontal wells. If multiple fluid phases are present then more sophisticated PLs are required that can differentiate the segregated fluids flowing in the well. Fiber Optic systems can also be deployed and monitored for extended periods of time to see how production can change along the lateral with time. Productivity from each perforation cluster can also be modeled using reservoir simulators. This requires knowledge of the petro physical properties of the shale and also the effectiveness of the completion. The latter can be modeled via hydraulic fracturing simulators.

Multi-stage hydraulic fracture
In this technique the shale rock is fractured by pressuri...

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... 60 years is 41.7% for Case 3 and for Case 4 it is found to be 38.9%.

Fig. 3 Comparison of Case 3 and Case 4.
Fig. 3 Explanation:
In the above graph it can be seen that the Y-axis is over the gas production rate and is taken in Mscf/D units. On the X-axis we take the time, and the unit or scale taken is by days. The dotted line represent the gas-production rate and the non-breaking line denotes the cumulative gas production. The Purple line denotes the Case 3 and Blue line denotes the Case 4.

By the following statistics we can derive the following conclusion that increasing the number of perforation clusters in one stage does not necessarily increase the initial gas rate and the cumulative gas production because the width growth of center and sub-center fractures is inhibited under certain fracture spacing and geo-mechanical properties of the reservoir.

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