Abstract
Some wells in the Kashagan field did not perform as well as expected. Despite producing virtually no water, calcite deposition was found to be the root cause of the problem. A comprehensive well surveillance program, which was proven to be very efficient for an early scaling diagnosis, was developed by the operator, North Caspian Operating Company (hereafter NCOC). As a result, well scaling is currently well managed and prevented from reoccurring. The objective of this paper is to share an early experience with well scaling in the Kashagan field, as well as to describe the developed set of well surveillance techniques.
The aim of the various well surveillance techniques discussed in this paper is to improve an Operator's ability to identify the very first signs of scale accumulation. This, in its turn, enables to introduce timely adjustments to the well operating envelope and to schedule a scale remediation / inhibition treatment with the intention to prevent any potential scaling initiation from further development. The approach is quite extensive and incorporates continuous BHP/BHT monitoring, routine well testing, PTA analysis, and fluid/water sampling.
Developed approach experienced multiple revisions and modifications. Further optimization continues, however, the described well surveillance techniques represent the latest Operator's vision on the most efficient way for well scaling monitoring and identification. In the Kashagan field, BHP/BHT readings have proved to be the most direct and instantaneous indication of any early signs of potential deterioration in well performance (qualitative analysis) while well testing and PTAs are considered as the most essential techniques in confirming and quantifying scaling severity (quantitative analysis). It is important to mention that BHT increase is explained by Joule-Thomson heating effect being specific for the Kashagan fluid (happening during increased pressure drawdown). This, in turns, enables to predict future well performance, design well operating envelop accordingly and, most importantly, develop a yearly schedule for proactive well treatments with SI.
In conclusion, it shall be highlighted that discussed complex of well surveillance techniques has been concluded to be very efficient and reliable tool in identifying any scaling tendencies at its initial stage. Due to successful implementation of this approach in the Kashagan field, scale development is now well-managed and kept under control. To mention, that utilization of well surveillance techniques and methods outlined in this paper may reduce the time required to identify and ultimately mitigate well scale accumulation in any active assets with similar operating environments.