METHOD FOR DETERMINING THE BOUNDARY CONDITIONS FOR THE USE OF PRIMARY TRACERS IN A SINGLE-WELL CHEMICAL TRACER TEST Russian patent published in 2022 - IPC E21C41/24 E21B47/00 G01N31/22 

FIELD: oil and gas industry.

SUBSTANCE: invention relates to a method for determining the optimal operating interval for primary (distributing) tracers used in test trials, which are aimed at obtaining information about the properties of an oil-bearing formation under field conditions. A feature of the claimed method is the development of a new model for the selection of primary tracers from a number of esters, including the analysis of a wide range of parameters that allow analytically verifying the success of their application in a single-well chemical tracer test (SWCTT). A method for determining the boundary conditions for the use of primary tracers in a single-well chemical tracer test, which consists in preparing two-phase oil-water systems with a primary tracer, for which, first, aqueous solutions of the primary tracer are prepared at a concentration of 1 wt.%, while water with different salinity is used, solutions are added to oil in a volume ratio of oil-water 1:1; the distribution coefficients of the primary tracer are determined in a two-phase oil-water system 1:1 at each temperature and water salinity. An interval of values of the distribution coefficient of the primary tracer is obtained at each temperature and salinity of the water to establish the minimum and maximum thresholds for the distribution coefficient of the primary tracer. The hydrolysis time of 50% in a two-phase oil-water system is calculated for each primary tracer, taking into account the rate constant of hydrolysis in the aqueous phase at each temperature and at each residual oil saturation S_or. An interval of values of the distribution coefficient of the primary tracer is allocated for each value of residual oil saturation, oil reservoir temperature and water salinity, assuming that the optimal process holding time is from 1 to 12 days for the hydrolysis of the primary tracer. At the same time, the obtained interval of values of the distribution coefficient of the primary tracer limits the conditions for using the primary tracer in a single-well chemical tracer test in cases where the hydrolysis time turns out to be lower than the optimal process holding time and if the value of the tracer distribution coefficient above the maximum obtained experimentally is required to increase the hydrolysis time.

EFFECT: solution of the problem with the choice of the primary tracer for the purpose of effective use in certain reservoir conditions; taking into account the influence of the kinetic and extraction properties of the primary tracer during its hydrolysis and distribution in the oil-water system in reservoir conditions.

1 cl, 9 dwg