Cut-Off Determination for Multilayer Sandstone Reservoir Based on Rock Type by Using Combination of Open Hole Log Data and Production Logging Data. SPE 182175 13 Oct 2016


Rock physical characteristics data of each reservoir layer, such as porosity, water saturation, and shale volume can be obtained from open hole log results which will bring information about the conditional limits of productive reservoir layer before being produced, meanwhile each layer productivity can be known according to production logging results. Combination of those open hole log and production logging data can be used as a reference to determine the reservoir layers which will be produced later. In order to increase accuracy and validity of the parameter, the entire reservoir layers need to be classified into several rock types based on its physical characteristics and then productive reservoir cut-off parameter is determined for each rock type.


Productivereservoir cut-off is expressed in a dimensionless parameter, α(alpha) based on a correlation result which correlates the rockphysical characteristics data (porosity, water saturation, and shalevolume). Alpha (α) is a constraint value which shows the layertendency of being productive or non-productive, so that perforationplan can be conducted. Alpha (α) is effective to be used fordetermining reservoir cut-off, because it can still be obtained whilecut-off from rock physical characteristics is indefinable. Cut-offbased on α value is accurate with average error 6.62%. Rock typingprocess clearly increases the accuracy of cut-off value, becausewithout this process, the average error of α value becomes 15.79%. 


Thenovelty of dimensionless parameter, α, to determine productivereservoir cut-off is in its ability to give a constraint whilecut-off from rock physical characteristics is indefinable.