As the operator, CNOOC completed drilling two exploratory wells in a deep-water field of the Republic of Congo from May to November of 2013, in 600 m of water depth. Indications of oil and gas- heavy oil layer, gas layer and thin oil layer were found in the E-1 well according to logging data analysis. There are many challenges for the operator and service companies to perform the appraisal of this heavy oil reserve in a deep-water offshore environment, such as operational cost control, low temperature near the seafloor/mud line, heavy oil flow assurance, sand control, etc. In order for the well test to be effective, all the above issues must be fully understood and methodology employed that will reduce the chance that operational risks will occur.

This paper presents an integrated well test program of the E-1 well developed and implemented for reservoir characterization and formation evaluation in the Congo basin. The program used a combination of various formation evaluation techniques such as wire wrapped screen sand control, PCP with electric heating rod and insulation tubing, hydrate prevention, emergency response in complex condition. The integrated well test program was designed and modified to meet the project delivery timeline and cost constraints, while responding to the challenge of properly testing the oil/gas reservoirs.

This paper also gives the data analysis results and summarizes the encountered problems and learned lessons from field operations.

The treatment practices and gained experiences from the field operation presented here provide valuable guidance for future deep-water heavy oil exploration and development operations.

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