Virtual Magnetic Resonance Logs, a Low Cost Reservoir Description Tool

Magnetic resonance imaging (MRI) logs are well logs that use nuclear magnetic resonance to accurately measure free fluid, irreducible water (MBVI), and effective porosity (MPHI). Permeability is then calculated using a mathematical function that incorporates these measured properties. This paper describes the methodology developed to generate synthetic magnetic resonance imaging logs using data obtained by conventional well logs such as spontaneous potential (SP), gamma-ray, caliper, and resistivity. The synthetically generated logs are named virtual magnetic resonance logs or ‘VMRL’ for short. Magnetic resonance logs provide the capability of in-situ measurement of reservoir characteristics. The study also examines and provides alternatives for situations in which all required conventional logs are unavailable for a particular well. Synthetic magnetic resonance logs for wells with an incomplete suite of conventional logs are generated and compared with actual magnetic resonance logs for the same well. In order to demonstrate the feasibility of the concept being introduced here, the methodology is applied in two different fashions. First, it is applied to four wells; each from a different part of the country. These wells are located in East Texas, Gulf of Mexico, Utah, and New Mexico. Since only one well from each region is available, the model is developed using a segment of the pay zone and consequently is applied to the rest of the pay zone. In a second approach, the technique is applied to a set of wells in a highly heterogeneous reservoir in East Texas. Here the model was developed using a set of wells and then was verified by applying it to a well away from the wells used during the development process. This technique is capable of providing a better reservoir description (effective porosity, fluid saturation, and permeability) and more realistic reserve estimation at a much lower cost.