METHOD FOR DETERMINING HORIZONTAL SHAFT MAXIMUM LENGTH IN CONDITIONS OF CAVERN-FRACTURED CARBONATE OIL AND GAS-SATURATED FORMATION WITH ABNORMALLY LOW FORMATION PRESSURE Russian patent published in 2017 - IPC E21B43/16 E21B43/30 

FIELD: oil and gas industry.

SUBSTANCE: method comprises determining abnormality coefficients, fracturing, absorption, measured depth, vertical depth, mud density equivalent to circulating density considering distribution on the shaft. Wherein identification and analysis of cavern-fractured formation permeability gradations is carried based on previously drilled wells, then the chart of allowable depression/repression range is plotted; the range of fluctuation in equivalent circulating density of particular horizontal shaft point is additionally evaluated based on actual measurements of downhole pressure fluctuations in the well, equivalent circulating density is calculated based on bottomhole pressure fluctuations characterized by chart line thickness; then the chart of combined pressures of horizontal shaft interval is plotted and, based on the chart, horizontal shaft maximum possible length is determined at intersection of allowable repression/depression ranges and equivalent circulating density range.

EFFECT: improved accuracy of calculation of maximum horizontal barrel length for a particular type of fractured reservoir and hydrocarbon system.

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