A dual-reservoir completion using Intelligent Well system together with an electrical submersible pump (ESP) in a high-rate well was recently deployed in one of the large carbonate fields in Saudi Arabia. The well was equipped with ESP to provide artificial lift to pump the oil to a centralized processing facility that is far a way from the well through a 2-zone "Smart" well completion, which remotely controls fluid inflow from each of the two laterals. This completion enables commingled production from two reservoirs while balancing flow contribution from each reservoir and avoiding cross-flow from one reservoir into the other.
Commingled production from stacked reservoirs in the same field, or a single reservoir with multiple pay intervals, has many benefits during the development of a field - higher production rates per well, cost savings from reduction in the total number of development wells, flexibility in locating surface facilities as a result of minimal footprint, etc., Wide variation in reservoir properties, coupled with existence of natural fractures within an active waterflood environment in this case, prompted adoption of Intelligent Well technology to control fluid withdrawal and enhance waterflood front conformance. Additionally, there was a need to use proven conventional ESP system to lift the expected high production rates from the two prolific reservoirs.
The new completion uses a re-designed downhole hydraulic disconnect tool with an integral anchor assembly, instead of other systems that have been used in the industry in the past, to connect the upper completion incorporating the ESP system with the lower completion that incorporates the Intelligent Well completion. Thus, ESP workover can be performed without the need to retrieve the Intelligent Well completion. This integrated system has enabled the two producing reservoirs to be commingled successfully and has provided the flexibility to control inflow from each reservoir in the future as the flow regimes change.
This paper describes the equipment selection process, completion equipment, planning and deployment procedures of the Intelligent Well completion. Economic drivers for this robust completion as well as the reservoir management implications of successful deployment in this test case well and future expansion across the entire field are also discussed.
Introduction
The dual-lateral dual-reservoir well was drilled recently and completed in one of the largest multi-pay fields in Saudi Arabia. The field has several stacked oil-bearing reservoirs, which call for commingling production from some of these reservoirs to optimize field development. Additionally, pressure maintenance strategy requires the use of water injection to supplement reservoir energy for commercial exploitation.
Fractures have been identified in many of these reservoirs from extensive resistivity and acoustic image logs ran across the field, as well as from the dynamic data gathered during past production periods. Small and large scale fractures present in these reservoirs are suspected to be conduits for the communication between the two reservoirs shown in Figure 1, which are separated by a thick section of fractured non-reservoir rock. Detailed review of historic pressure data shows synchronized pressure histories for these two reservoirs during past reservoir depletion, which was more concentrated at the crest and western parts of the field. This pressure performance suggests that the two reservoirs are connected hydrodynamically. Logs from both reservoirs also show concentration of fracture clusters at the crestal area and western parts of these reservoirs.
