Surface Expressions: Gamma Ray Observation of Shallow Air-Sands Enables Early-Detection and Monitoring of Fluid Breakthrough

O'Sullivan, Terence P. (Consultant, Vapor Condensation Technologies LLC) | Skinner, Tom (Consultant) | Wright, Jacob (Berry Corporation)

OnePetro 

Abstract Surface expressions occur when hot oil, water and vapor associated with steam injection in heavy oil reservoirs flows uncontrollably to surface, creating safety and environmental hazards. A new method for early-time identification of these events and monitoring of remediation efforts is proposed. Transient high gamma ray (THG) is a high-resolution, high-amplitude measurement that samples a large volume of rock when vapor containing radon condenses at a cooled well and gamma ray increases by a factor of 10 to 200. The effect is transient because gamma ray returns to normal when this transport process is reversed, as wellbore temperature equilibrates. Absence of this high-amplitude, high-resolution signal through shallow air sands above a heavy oil reservoir is confirmation that vapor breakthrough has not occurred. For wells located in an area where surface expressions have occurred, the method identified contaminated sands and detected flow-behind-casing in an uncemented well. Gamma ray transects in an area of surface expressions identified hot spots, caused by plumes of vapor that condense just below the surface. In at-risk areas, observation wells can provide assurance that injected steam is contained. When surface expressions occur, the method can be used to optimize and confirm the effectiveness of mitigation efforts.

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