This paper discusses case histories, where Distributed Temperature Survey (DTS) with Fiber Optic Enabled Coiled Tubing (FOECT) was used during stimulation treatment and well testing by the Operator in Southern Iraq oilfield.
The field was discovered in 1984 with hydrocarbon accumulation in four (4) major reservoirs, first oil production was achieved from the top carbonate reservoir in 2013. The wells were drilled to penetrate a thick carbonate reservoir which ranges from 80m to 100m thickness, subsequently completed as single selective producer with cemented casing and perforated across the targeted zone. Permeability and porosity varies drastically within same carbonate reservoir thus effective treatment fluid diversion is required to ensure the largest possible surface area of the reservoir is contacted and exposed to stimulation fluid to achieve uniform stimulation and sustainable production.
Main challenge for stimulation treatment in heterogeneous carbonate reservoirs is to achieve optimum placement of the stimulation fluid without some knowledge of, and control over where the treatment fluids flow. Traditional way to record production and injection fluid profile is via running a production logs with wireline equipment, however this require additional equipment and time. This was addressed by using CT equipped with fiber-optic real-time telemetry, that offer 3D temperature profiling which significantly improved the stimulation treatment by providing downhole monitoring throughout the entire treatment and thus a new level of control of fluid placement. In addition, the FOECT allow real-time interpretation of Pressure Transient Analysis (PTA) to evaluate the well deliverability, production performance of the stimulation treatment and basic reservoir description (e.g. permeability and total skin).
This technique helped in reducing time and the number of well intervention runs, while improving fluid placement to achieve faster, more informed stimulation treatment. Lessons learned from these case histories enhanced Operator understanding of the reservoir and led to recommendations for future treatments and potential replication.
Steps and considerations in decision making, reaching the most advantageous solution for the stimulation treatment as well as the detailed engineering evaluation for the two (2) wells candidates will be addresses in this paper.