METHOD FOR DETERMINING COEFFICIENT OF EFFECTIVE POROSITY OF ROCKS IN WELLS Russian patent published in 2023 - IPC G01V11/00 G01V1/28 G01V1/30 

FIELD: oil and gas industry.

SUBSTANCE: invention is intended to determine the coefficient of effective porosity of rocks in productive and water-saturated intervals and can be used in calculating reserves and in the hydrodynamic model of the formation along the depth of the studied section in the well. The method for determining the coefficient of effective porosity of rocks in wells is that the coefficients of porosity and residual water saturation, the values of bulk density and the interval time of travel of a longitudinal acoustic wave are determined in conditions simulating the reservoir conditions using previously washed, non-extracted core samples with contrasting filtration-capacitive properties. Grain-size analysis of the samples is carried out and the volumetric contents of sand and silt fractions in the rock volume are determined. Then, by means of regression analysis, the parameter of the linear relationship between the volumetric contents of the sand and silt fraction of the samples is determined, by which the coefficient of maximum porosity of the formation and the volumetric content of the clay fraction of the samples are found, and the parameter of the linear relationship between the volumetric content of the clay fraction and the coefficient of residual water saturation of the samples, by which the value is determined of the coefficient of minimum residual water saturation corresponding to the coefficient of maximum porosity of the formation. Then, based on the value of the coefficient of maximum porosity of the formation and the value of the coefficient of minimum residual water saturation, the coefficient of maximum effective porosity of the formation and the coefficient of boundary porosity for each sample are determined. By analysing the data from the resulting sample, the coefficients of the minimum K_{p b min} and maximum K_{p b max} of the boundary porosity of the formation are determined and by regression analysis the parameters C1, C2, C3, C4 of linear relationships of bulk density values are determinedσ in g/cm³ and interval timeΔ T in mcs/m with porosity coefficient K_pt, %. Next, volumetric density value is measured in depth in the well with a standard quantization step σ density gamma-gamma method (GGM-P) and interval time of travel of a longitudinal acoustic wave ΔT using the acoustic method (AM) and calculate the effective porosity coefficient at each point along the depth of exploration of the formation in the well.

EFFECT: optimization of the algorithm for determining the coefficient of effective porosity of the formation based on data from two independent research methods by combining the results of laboratory studies of core material according to the model of relict residual water and geophysical studies of wells that penetrate intergranular (granular) reservoir rocks, and, as a consequence, ensuring increasing the reliability of determining the coefficient of effective porosity of the formation by increasing the volume of controlled information.

1 cl, 1 dwg