Abnormal pressure rise during the build-up on flooded horizontal wells of prirazlomnoye oilfield: benefit or harm?

Introduction. The article raises the topic of complications that arise during the recording of pressure buildup curves at some flooded wells of the Prirazlomnoye field. The complication is a sharp increase in pressure, which can occur at any time during a well test. This anomaly leads to a distortion of the pressure build-up and, accordingly, to errors in interpretation.

Goal. The purpose of this work is to analyze the mechanism and causes of anomalous pressure growth in water-flooded horizontal wells, to propose a method for restoring the true appearance of distorted pressure build-up with identifying problematic reservoir intervals.

Materials and methods. The work is based on the analysis of real readings from pressure and temperature sensors installed at various depths in the wellbore during periods of abnormal pressure growth.

Results. It is concluded that during the anomaly there is a decrease in the level of the oil-water phase interface below the pressure sensors. Reasoning about the reasons and mechanisms for reducing the phase separation level is given. A mathematical tool is also proposed for calculating the depth of phase separation reduction in the wellbore, which allows you to correctly recalculate pressures from the measurement depth to the target depth and obtain smooth pressure recovery curves without anomalies.

Conclusion. In conclusion, the conditions under which it is possible to observe similar anomalies in other wells are highlighted. It is concluded that it is important to pay attention to such effects.

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