Abstract

Field development of mature fields in Kuwait Oil Company have seen a paradigm shift over the past couple of years, to adopt the latest field proven technology to exploit the remaining reserves. The Mauddad formation in the Bahrah field is a low permeability with high viscosity oil which was previously developed with vertical cased and perforated wells with electrical submersible pumps (ESP). Inflow monitoring also posed a challenge to conduct production logs due to challenges with the Y-tool of the ESP.

In light of these challenges, it was decided to drill horizontal wells, installed with multi-stage frac completions with acid being the stimulant. The described solution was considered a recent success because of the 300% increased production compared to offset vertical wells over the same producing period. However, ESPs are still required to lift fluids to surface in these horizontal wells and the understanding of inflow performance of each stage remained a monitoring challenge. A solution was identified to utilise intelligent inflow tracers after the successful pilot in another field development in Kuwait, using passive inflow control devices (ICD) with ESPs. Therefore, it was decided to pilot the same technology which provided intervention free, permanent downhole monitoring. However, the additional challenge was to prove that inflow tracers could survive the harsh acid operation and continue to function as a reliable downhole sensor thereafter.

The wells installed with intelligent chemical inflow tracers are used to provide a trend assessment of the clean-up phase of production, productivity assessment information for each stage and to event monitoring such as identifying the location of water breakthrough. Fluid samples collected from the surface flow lines were analyzed for unique chemical tracer signatures and interpreted the corresponding tracer signals. The monitoring campaigns have provided an improved understanding of fracture efficiency which has translated to frac design optimsation and also reduced subsurface uncertainty.

This paper discusses the chemical sensor design, integration of the sensors, run in hole procedure, sampling, analysis and interpretations of multi-stage acid frac wells, penetrating the Mauddud reservoir. Several wells were installed with chemical sensors adjacent to the sliding sleeves compartmentalized with swell packers in horizontal producing sections of up to 3,000-ft. The post operation interpretation revealed that chemical sensors functioned after the acid jobs and revealed how each stage performed from the frac clean up operation and how productivity changed over the life of the well.

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