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Initial Results of Direct Multivariate Modeling of Previous HitSandstoneNext Hit Reservoir Quality Using Whole-Rock Elemental Data


Whole-rock elemental data is now routinely acquired Previous HitfromNext Hit core in the laboratory (by ICP or XRF), and Previous HitfromNext Hit Previous HitcuttingsNext Hit at wellsite (by XRF) while drilling. While primarily used for chemostratigraphic correlation and mineralogy modeling, this data may also contain stand-alone predictive information about Previous HitsandstoneNext Hit reservoir quality; specifically porosity and Previous HitpermeabilityNext Hit. The ability to predict these attributes directly Previous HitfromNext Hit elemental analysis of Previous HitcuttingsNext Hit while drilling is of great practical value. The rationale behind elemental prediction of Previous HitsandstoneNext Hit reservoir quality is based on the premise that mineralogy and flow properties of a given Previous HitsandstoneNext Hit are each related to the sum total of processes that generated and modified the sand (e.g., weathering, erosion, transport, temporary storage, final deposition, bioturbation, compaction, early diagenesis, burial diagenesis, hydrocarbon charge, etc.). Therefore, a mathematical relationship may exist between elemental composition (tied to mineralogy) and flow properties such as porosity and Previous HitpermeabilityNext Hit. An element-based predictive model for porosity and Previous HitpermeabilityNext Hit was created to test this premise using data Previous HitfromNext Hit over 1,450 core plugs, Previous HitfromNext Hit 12 wells, in two completely unrelated reservoir sequences. Specifically, one sequence was deposited in an estuarine-dominated environment, while the other was deposited in an eolian-dominated environment. While these sequences exhibited similarities in their mineralogical and lithological characteristics, their respective elemental (i.e., compositional) variations span completely separate convex hulls in the 10D compositional space. This attribute of the available dataset mandated the use of “local models” to predict the flow properties of each sequence, as opposed to a single “global model,” which could be used to predict both sequences. Training and testing of the models were accomplished using k-fold cross-validation. The elemental data was partitioned by well to emulate a real-world field-development scenario; where the data Previous HitfromNext Hit existing cored wells could be used to construct predictive models applicable to the analysis of Previous HitcuttingsNext Hit Previous HitfromNext Hit future wells. Based on the initial dataset, the resultant model accuracy was ± 2 vol% for porosity and ± 11 mD for Previous HitpermeabilityNext Hit. Additionally, it is believed that the uncertainty related to laboratory reference measurements of low-Previous HitpermeabilityTop sandstones is the limiting factor with respect to the accuracy of the current models.