PKKR JSC operates a couple of dozens of fields with more than a thousand wells. Consequently, a massive wells' surveillance program is conducted which includes pressure transient testing (PTT) and analysis (PTA). It leads to different kinds of cases which, eventually, help us to understand challenging issues. Thus, in the paper we try to shed light on how these data are critical to make the right decision with the aim of getting economical benefits for the company.

Field operation performs PTT on 70-80 wells annually such as pressure buildup and deliverability on producers, pressure falloff on injectors and interference tests on observation wells. All the tests are interpreted by the engineers of the company refusing from service companies during oil price decline in 2015 and purchasing commercial software. Using the software interpreter builds Horner and log-log plots, IPR curve which give the quantitative and qualitative parameters of near the wellbore, undamaged zones and outer boundary conditions. This information coupled with geological and production data are analyzed to gather puzzles into one full picture.

As the result of PTA the company could make important decisions which brought to millions of dollars of savings and earnings. The paper demonstrates standard cases, e.g. a pressure buildup test on a well helped to decide to execute fracturing and multiple time increase in oil rate was obtained. Oppositely, on another well falloff test showed presence of fractures, hereby, planned stimulation measures were cancelled in spite of low injectivity. In addition, falloff tests give additional information on how waterflooding is effectively carried out. Another case which was under active discussion includes the issue of converting a well to water injection, so we conducted an interference test and it reveals no response on adjacent producers. Again the company avoided the wrong decision and waste of money. Moreover, interference tests played a vital role in an extraordinary case where it was unclear how the wells produced gas more than reserves. Unexpectedly, the reason was a communication between two lithologically different reservoirs via fractures. So, it dramatically changed the geological concept of the field. There are other situations when PTA results help to characterize geometry of the reservoirs, presence of faults, their transmissibility, fractures distribution which all are critical for static modeling and dynamic simulation.

PTA is a crucial part of geology and petroleum engineering. It essentially helps engineers and managers to make right decisions. Sometimes it leads to big savings or significant profit earnings due to conducting or avoiding the works. Also PTA can change the geological picture of the whole field if properly analyzed. Thus, it is a powerful tool in the hands of geologists, reservoir and production engineers.

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