Pressure build-up time upon shutting-in a well depends on filtration parameters of formation, increasing with their impairment. Therefore, incomplete pressure build-up curve for low permeability reservoirs frequently occurs. In this case the segment, offsetting by 1.5 of log cycle from derivative maximum, is not achieved. Interpretation of such pressure build-up curves, using known programs as Pansystem, Saphir, Fekete etc., leads to a significant error. This is confirmed by skin pressure drop with the absolute values considerably exceeding depression, as well as unreal flow efficiency.
In this connection, a method for interpretation of pressure build-up curve has been elaborated, allowing to increase accuracy in determination of formation and bottom-hole zone filtration parameters. This is achieved by combined consideration of wellbore storage and prehistory of filtration using numerical methods. In so doing, knowledge of initially unknown formation pressure and boundaries, on which it is maintained constant, is not required.
The method received wide practical approval for reservoirs with permeability of 0.1-300 mD. The results showed that actual value of perm thickness product, calculated by suggested method, is smaller then by well-known methods. The difference is increasing at short pressure build-up time and also for reservoirs with low perm thickness product. Therefore, the most effect from application of the suggested method is achieved while interpretation of pressure build-up curve with low perm thickness product. The method has also been used to estimate efficiency of different stimulation methods for wells, drilling-in and completion methods in Tatneft JSC fields. Results of interpretation allowed to give practical recommendations on selection of most efficient technologies.