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Low-field NMR Measurements of Sealed Core and Live Oil Samples

IP.com Disclosure Number: IPCOM000245706D
Publication Date: 2016-Mar-31
Document File: 8 page(s) / 627K

Publishing Venue

The IP.com Prior Art Database

Abstract

We describe a measurement system and method for determining live oil properties and quantification of the saturation in core plugs in its in-situ state by integrating a nuclear magnetic resonance sensor in a pressurized container where freshly collected live oil samples or harvested reservoir core plug samples are stored during downhole fluid collecting or coring process and being sealed in the condition substantially identical to that of the in situ reservoir condition. The live oil cylinder or core plugs containers can be transported to the surface and measurements of NMR being conducted at in-situ condition or at the other controllable pressure and temperature conditions. The paper describes methods of implementing a low-field NMR sensor capable of conduct measurements with samples in a metallic cylinder with a removable temperature regulator jacket. Live oil GOR and viscosity can be derived from the NMR relaxation time measurements with or without in conjunction with NMR derived diffusivity measurements. The fluid phase saturation can be determined by separately analyzing and quantifying the oil vs. non-oil fluid (such as formation water) NMR responses.

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Low-field NMR Measurements of Sealed Core and Live Oil Samples       

 

 

Abstract

We describe a measurement system and method for determining live oil properties and quantification of the saturation in core plugs in its in-situ state by integrating a nuclear magnetic resonance sensor in a pressurized container where freshly collected live oil samples or harvested reservoir core plug samples are stored during downhole fluid collecting or coring process and being sealed in the condition substantially identical to that of the in situ reservoir condition. The live oil cylinder or core plugs containers can be transported to the surface and measurements of NMR being conducted at in-situ condition or at the other controllable pressure and temperature conditions. The paper describes methods of implementing a low-field NMR sensor capable of conduct measurements with samples in a metallic cylinder with a removable temperature regulator jacket. Live oil GOR and viscosity can be derived from the NMR relaxation time measurements with or without in conjunction with NMR derived diffusivity measurements. The fluid phase saturation can be determined by separately analyzing and quantifying the oil vs. non-oil fluid (such as formation water) NMR responses.

Introduction

Measuring live oil properties and reservoir core samples with in-situ fluids at the reservoir environment conditions is the most reliable approach for determining the reservoir quality, reservoir production potential, and production strategy. The common practice of core NMR measurements can only mimic the real reservoir conditions because the core harvested from wells are normally not kept in reservoir conditions during the collection, transportation, and/or storage processes of the harvest core samples.  Live oil cylinders are routinely deployed in downhole sampling systems, which allows the core plugs to be preserved in the reservoir conditions during harvesting, transportation, storage, and measurements at surface. However, live oil cylinders are built with metallic housing to withstand the high downhole pressure and abrasive handling. Because of skin-depth in the metal cylindrical layer is short and is frequency dependent, the alternate magnetic field (B1) is substantially shielded by the metal wall of the container, which significantly weakens or effectively blocks RF pulse energy delivery to the sample chamber inside the metal cylinder. Thus, in the current practice, if one wants to maintain the in-situ conditions, the live oil and core plugs have to be transferred to another live oil cylinder or core holder built with RF transparent materials.  It is a non-trivial, time consuming and cost-ineffective process if the sample transfer occurs in the same pressure environment as that of the original cylinder. Therefore, in general practice, majority of the core sample transferring processes occur in ambient environment. Once the conditions are altered, it is not always possible to restore...