Spectral Acoustic Logging for Well and Reservoir Performance Evaluation for Chemical EOR Project - During Water Injection Stage

Abstract The pilot Chemical EOR project in Sabriyah Field, Kuwait is implemented applying a five-spot pattern: four injectors and one producer. The results of base-line logging campaign performed in EOR area with the purpose of appraising the current state of the reservoir before EOR implementation have been addressed earlier in [1]. The objective of this paper is to demonstrate the results and value of reservoir-oriented noise and temperature logging campaign carried out during the water injection stage, before chemical injection. To investigate the reservoir and well parameters in EOR area, an integrated logging suite consisting of High Precision Temperature (HPT) and Spectral Noise Logging (SNL) tools was run. High-definition broadband SNL tool with a large scanning radius successfully located the active flow units including low-rate ones and differentiated between reservoir flows, behind-casing channelling and leaks in well completion components, even behind multiple barriers. HPT data were analysed to quantify flow/injection profiles by matching the simulated reservoir temperature logs with field measurements under flowing/injection and static conditions, riglessly. The main objectives of the extensive logging campaign during water injection phase before chemical EOR were to determine the water injection profile in pilot injectors and estimate the effective thickness of the target reservoir zones being developed. It was found out that injection/flow profiles in injectors and producers drilled in a heterogeneous formation were non-uniform: the flow from injector to producer propagated mostly through highly-permeable layers. This resulted in a rapid injection water breakthrough: in the producer, water breakthrough occurred in a highly permeable zone only several feet thick. The least effective thickness (34-38% of the entire perforation zone) was found in the injectors situated to the west of the producer, while in the eastern part of the EOR area the effective thickness of the reservoir was 56-59%. It was also discovered that the underlying formation cooled off considerably after the pilot injection had started, which might be caused by water migration to the lower reservoir zones in offset injector, because no substantial water loss to the underlying formation was detected in the logged injectors. The information obtained during the surveys will be used for updating the Chemical EOR Project to ensure injection water flow control by injecting chemicals and chart the de-risking and mitigation plan for implementing and testing during EOR pilot. The results confirmed the possibility of using polymers during development of such kind of a heterogeneous reservoir, and requirements of more due diligence prior to the implementation of EOR pilot.