One of the most important parameters of the drilling fluid is the filtration index. Under the action of pressure drop, when drilling with overbalance, the water phase penetrates into the formation. The penetration of the aqueous phase into the oil-saturated reservoir leads to a decrease in its permeability for oil, since the aqueous phase changes the wettability and effective porosity of the rock. At the same time, not the entire volume of the aqueous phase during the reverse filtration of oil is able to release pores, especially small ones. Calculation of the volume of filtrate penetrating into the formation is an urgent task, since with this data it is possible to take a number of measures to reduce filtration, select methods for intensifying production or cleaning the bottomhole formation zone. Also, these data can be useful in calculating the reservoir productivity indicators, taking into account the contamination of the bottomhole formation zone, including the skin factor.
The article presents software for calculating the volume of drilling fluid filtrate that penetrates into the reservoir during the initial opening. The author's calculation method uses analytical approaches and dependences of filtration experiments, derived using correlation and regression analysis. Laboratory data of a standard filter press test are used as input parameters: filtrate viscosity, filtration area, pressure drop, filtration process table. The necessary input parameter is the experimental dependence of the volume of the filtrate on the time of the filtration experiment, on the basis of which the parameters of instantaneous filtration are determined during the formation of the filter cake and the parameters characterizing further filtration through it. The dependence of the accumulated filtrate volume on time, determined using a filter press, is connected to the program as a separate tabular file with one of the standard extensions. The calculation for downhole conditions takes into account: filtrate viscosity at downhole temperature, repression pressure, filtration area, process time.
References
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9. Certificate of registration of the computer
