New Methods for Cutting Pressure Retained Cores from Deep Unconventional Reservoirs in West Kuwait - First Ever Successful Pressure Coring Operation in the Najmah Kerogen

Abstract

Abstract The successful recovery of pressurized core samples from an unconventional HPHT reservoir is presented. Optimized methods and technologies such as implementation of Managed Pressure Drilling (MPD) technique as well as coring technology customization and adaptation are discussed. Results from offset wells are compared and a best practice method is described how to recover pressurized cores from the organic rich Najmah Kerogen in West Kuwait. A coring BHA was configured using a modified version of the LPC Core Barrel hence allowing for the first time to consider recovering pressurized core samples from a well with a very challenging operating envelope. Furthermore, the provided methodology ensures that well conditions are maintained to allow for a pressurized core recovery in most stable wellbore environment avoiding any unwanted subsurface problems. With three consecutive runs planned on for the pressurized coring using MPD each 10 ft., the results obtained showed a successful coring operation of which typical wellbore downhole issues were avoided with no loss time due to well ballooning, mud losses and well kicks. The successful coring operations as well as all subsequent on-site analysis procedures showed possibility to recover pressurized core samples from unconventional formations with high formation pressure in a safe and effective manner. Avoiding core damage due to petal-centerline fractures and disking is fundamental in quantifying natural fractures in this unconventional reservoir. This novelty approach of core barrel system modification and using MPD technique in acquiring the pressurized cores has made it possible to obtain representative near in-situ data to better reservoir interpretation and quantification of natural fractures. The method has a great potential to ensure high core recovery in high angle wells while delivering superior reservoir fluid and rock information which is not obtainable by other means.