This paper presents the use and value of information obtained from interference testing performed during the early production of Kashagan field. Numerous field examples of the interference and pulse tests are presented along with their implications for improving reservoir characterization and modeling. Design aspects of the conducted tests and an approach to address uncertainties in the pressure data are also described. A significant amount of important interference data was captured during the start-up and subsequent ramp- up of Kashagan field. This included local well to well interference and pulse testing as well as an extended test that covered a larger area of the field. However, operational activities at observer wells complicated the available data and necessitated application of a pressure correction methodology. This methodology had to account for the inherent uncertainty in the interpretation of the data. Moreover, to increase our confidence in the interpretation, a dedicated pulse test was performed in the specific part of the field. Finally, responses from all observation wells were integrated and analyzed to capture big picture learnings from the early interference testing program. When results of the interpreted interference response from all observers were combined, several groupings of wells became apparent. This helped to understand the degree of connectivity in various areas of the field. For dynamic model calibration, it was preferable to have a range of interference responses for each well to reflect uncertainty in the data. Therefore, so called "early" and "late" response curves were developed for each well. Overall, the collected and analyzed interference data was very useful in reducing uncertainty during this early period and will be used to optimize reservoir management decisions and future phases of the field development. Results presented in this paper can be used by practicing engineers as another great example for advocating the use of permanent downhole gauges (PDHGs) and importance of proper planning and execution for the interference and pulse tests.

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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.