Usefulness of well test made in different time. Monitoring injection wells hydraulic fracture dynamics in low-permeability reservoirs by PLT and PTA

Background. At the moment hard-to-recover reserves in company portfolio of Gazpromneft are about 60–80 %. The low-permeable reservoir development is produced using hydraulic fracturing. It is required to assess risks both at the beginning and in the process of reservoir development to select correct wells operation and reservoir development. This can be accomplished only by regularly well test. Well tests monitor parameters, and also their changes.

Aim. Integrated analysis of hydrodynamic characteristics (reservoir pressure, transmissivity, fracture half-length, injectivity profile) for low-permeability reservoir, which influence development field. Analysis was made using pressure transient analysis (PTA) and production logging tools (PLT) using different time studies.

Materials and methods. Initial data of PLT and PTA, daily injection rates and tubing head pressure. Tubing head pressure was calculated on the top depth of perforations intervals. In addition the authors used well log interpretation results and PVT-properties.

Interpretations PTA and PLT were carried out using standard methods and analytical models. The author gives a detailed description further in the text.

Results. Injectivity index behavior based on conducted analysis is non-typical sometimes: increase fracture halflength and injectivity index despite injection rate and bottom hole pressure (BHP) aren’t changed. The effect is related reservoir pressure and its change in the drainage area. It is may lead to water breakthrough through fractures (increasing fracture of injection well in direction to production well).

Conclusions. The authors consider complex interpretation well test at different time on the pilot project. The results can to substantial influence field development system. In this connection there is a need to create special programs of regular well tests to find correct production and injection wells operation, and as a result, increase the displacement efficiency and oil recovery factor. Significance of regularly well test increases because of their influence of reserve recovery. Due to different effects which are shown up PTA and PLT under stable well performance. This is particularly important for oil industry and Gazpromneft because hydrocarbon reserves of the low-permeable reservoir preponderate.

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