Geostatistics: Application of kriging and conditional simulation techniques in the reservoirs cps-2 of the Carmópolis field, Sergipe, Brazil

Abstract

Five important parameters in reservoir simulation are permeability, top of reservoir height, net pay, porosity, and water saturation. Using geoestatistical techniques, these parameters, plus oil volume, are estimated for the CPS-2 reservoirs of the Carmópolis oil field. Study of the top of reservoir variable showed that, when faults are considered, the contours appearing on maps obtained by kriging are in significant agre­ement with results obtained by PETROBRÁS staff using traditional methods. Geoestatistical estimates of oi! volume are also very much in fine with those obtaíned by the company. Moreover, global precision estimates of in-situ volumes, obtained by kriging, show that the qualifier 'proven' is appropriate in describing the Car­mópolis reserves. The main advantages of reliance on geostatistical techniques are threefold: a saving intime, an objective mapping of parameters, and a measure of the precision of estimation, The study confirms that: the preferentíal directions observed in variograms correspond to the directions of the paleochannels interpre­ted by geologists; the use of faults "is importam in modeling variograms and in ascertaining top of reservoir height by kriging;and, lastly, the shifting of faulted blocks does not significantly affect other variables studied.