FORMATION PRESSURE ESTIMATION FROM THE DYNAMICS OF RECOVERY RATE AND BOTTOM-HOLE PRESSURES

When interpreting pressure curves in various software packages, the initial reservoir pressure is determined before a given production history. Formation pressure dynamics can be determined only with completely closed formation boundaries. At the same time, changing the operating modes of neighboring wells leads to a change in reservoir pressure in the drainage area of the studied well for long-term pressure records. In this regard, there is a need to calculate not only the initial, but also later reservoir pressures in the absence of closed reservoir boundaries.To solve this problem, two methods have been proposed for estimating reservoir pressure from long pressure and flow rate curves for any type of boundaries and reservoir:— by dividing the curve into sections with different skin factors, further recalculating the change in skin difference to the change in reservoir pressure (does not work for closed borders);— by recalculation through the calculated well productivity.The first method is recommended to be used for unsteady modes, the second — when pseudo-steady modes are reached.Approbation for 19 wells confirmed that the main criterion for the applicability of both methods is the relative constancy of productivity and properties of the bottomhole zone of the formation, i.e. the absence of winder, pilot injection, hydraulic fracturing, etc., in the studied area of the time, the absence of a multiple change in production rate when changing operating modes, there are also another number of restrictions, such as the presence of an individual means of measuring production rate on the well (SKZ or one lug per GZU) and the use of only one measuring instrument, the duration of the time between the measured and calculated reservoir pressures is not recommended for more than six months, wells with SHSNU are not recommended for calculations, due to the long time to reach the mode, but if there are GIK records and compliance with the main criteria, formation pressure can be estimated.These methods are auxiliary and do not replace real formation pressure measurements.