The heavy oilfield, Argonauta O-North Field, operated by Shell Brasil Petroleo in the Campos Basin, has been developed using eleven horizontal wells including four peripheral water injectors and seven producers. Production flow from this field uses one common riser. Successful development of the field requires effective wellbore clean out, as well as strict injection and produced water management. In order to achieve this, knowledge of positional oil flow from each well and source of water breakthrough was considered essential. Therefore, as part of the overall reservoir surveillance program, the application of over fifty unique specialist oil and water inflow tracers together with chemical waterflood tracers was planned and implemented.
The eleven wells were drilled and completed in 2013 with well testing and first oil production later in the same year. Each production well was initially monitored using standard ramp up tests followed by static pressure build up measurement. During this time produced oil samples were taken from the comingled production line located on the FPSO Espiritos Santo in order that tracer presence could be measured and quantitative information gained regarding positional oil inflow to each well. After five months of production, water cut started to increase. Water samples were taken on a regular basis from the common flow line. Using knowledge of where each of the unique water tracers was located in the lower completions, information was generated with respect to which well was producing water and from what position along the horizontal length it was originating. In addition to individual positional inflow, data was generated on whether the water was flowing from one of the four water injection wells or originated from the formation.
This paper provides an overview of the project objectives, discusses best practice for inflow and waterflood tracer design when used in a subsea field development, details critical pre-screening tests to ensure the use of optimal tracer types and formulations, how the tracers were integrated into sand screens, their deployment into each well, sampling strategy and presents and discusses a number of results from the beginning of production to present day.