METHOD FOR INTEGRAL STATUS ASSESSMENT OF BOTTOMHOLE FORMATION ZONE Russian patent published in 2014 - IPC E21B47/00 E21B49/00 

FIELD: oil and gas industry.

SUBSTANCE: method for integral status assessment of bottomhole formation zone includes operation of the well in steady conditions before hydrodynamic research, hydrodynamic research by repressuring method, determination of bottomhole pressure and continued fluid influx to the well from formation after its shutdown and processing of measurement results. At that during processing of measurement results current formation pressure is determined by multiplication method, approximation of the measurement results is made including division of actual pressure buildup curve (APBC) into separate sections at coefficient of determination less than 0.99. Then selection of approximate equations is made for the selected sections and division of the whole research period into intervals with uniform time increments. Values of bottomhole pressure are calculated for the specified intervals. The approximated APBC is processed by determined pressure moments with determination of formation pressure and nondimensional diagnostic property. The obtained formation pressure is compared with the pressure obtained by multiplication method. When the values differ per more than 0.3 MPa, approximation procedure shall be made with use of other approximate equations. Then against results of formation pressure determination by multiplication method the degree of bottomhole pressure buildup is assessed and well production index is determined for the conditions. In order to specify position of the processed section the log-log plot is plotted. The actual and approximated APBC is processed by tangent method with determination of parameters for the remote formation section. The results of actual and approximated APBC processing by tangent method are compared. When permeability coefficients for the remote formation section are different as related to actual and approximated curves, then approximation procedure is performed with use of other approximate equations. Then skin factor is determined for APBC with almost full pressure buildup, at least equal to 99%, and for APBC without pressure buildup. Status of the bottomhole formation zone is assessed against values of diagnostic property and skin factor. When APBC cannot be processed by tangent method, processing is made by differential or integral methods considering influx after the operations, with preliminary made procedure of approximate buildup curves for equidistant time values. Parameters are determined for the remote formation zone using several methods considering influx after the operations, in case of their status deterioration dimensions and properties of the remote formation zone are determined using permeability values determiner at earlier stage for the remote formation zone. Status of the bottomhole and remote formation zones is assessed against values of diagnostic property, permeability, hydraulic conductivity, piezoconductivity and dimensions of the bottomhole formation zone.

EFFECT: improving determination accuracy for indices characterising status of the bottomhole formation zone.

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