Monitoring and surveillance of subsurface multiphase flow and well integrity

Abstract

With maturing oil fields, there is an increasing focus on improving the oil recovery factor and pushing the envelope towards a 70% target. This target is indeed very challenging and can be reached by fully understanding the reservoir characteristics before using an enhanced oil recovery method. These include reservoir heterogeneities, displacement efficiency, horizontal sweep, vertical sweep due to flow behind the casing, and the presence of conductive faults or fractures. Therefore, a proper surveillance should be performed to evaluate the injectant plume front, reservoir conformance, well connectivity, and the assessment of well integrity, which can be crucial for the success of the project and its future development. This paper discusses a special downhole logging technique including a set of conventional multiphase sensors alongside high precision temperature (HPT) and high-definition spectral noise logging (SNL-HD). It was run for an injector and producer pair near the wellbore area to provide complete assessment of the integrity issues that might impair the lateral sweep of injectants into the target layer. The operation was carried out with a tool string that contained no mechanical parts and was not affected by downhole fluid properties. It was also conducted under both flowing and shut-in conditions to identify flow zones, to check fracture signatures and to provide multiphase fluid velocity profiles. The results of the survey allowed for in-depth assessment of borehole and behind casing flow, confirming lateral continuity, and allow for better well planning and anticipation of possible loss of well integrity. Combining the behind casing flow assessment with borehole multiphase flow distribution can be used for production optimization by sealing unwanted water contributing zones that might impair production in the future.