Taking Into Account The Conductivity Contribution Of Shale Laminations When Evaluating Closely Interlaminated Sand-Shale Hydrocarbon Bearing Reservoirs Available to Purchase

When shales are present under the from of thin shale streaks within hydrocarbon bearingshaly sands, the conductivity contribution of the shale content has to be substantially higher than that incoming from interstitial clay. As a consequence the bulk formation resistivity of such shaly sands appears abnormally low, resulting in serious underestimations of hydrocarbon potential when applying conventional methods of water saturation determination. A new analysis procedure has been developed in an aim to :" evaluate what proportion of the clay content is made up of shale laminations," determine the water saturation by interpreting the respective conductivity contributions of these shale laminations and of the remaining clay content. This is obtained with the help of specific algorithms that can easily be integrated in current shaly sands interpretation programmed. Examples of application are presented, where realistic water saturation values are so determined from low-resistivity formations having tested substantial hydrocarbons flows with no water-cut.