Abstract
Kuwait Oil Company (KOC) has its biggest and the oldest field "The Greater Burgan" producing for several decades now and providing the biggest contribution to Kuwait's oil production. With continuous increase in oil demand and requirement of maximizing the production, more than one reservoir within a well are planned to be produced from. Many wells in KOC are connected to more than one heterogenous reservoir with big difference in the reservoir pressures and productivities. This made it difficult to open these reservoirs for production simultaneously as it would cause the higher pressure / productivity reservoir to over-power the lower pressure / productivity reservoir. KOC adopted a novel completion strategy for such wellbores, these wells were completed with a 9-5/8in casing and the two different reservoirs were completed with 2 tubing's in the well, with production zones hydraulically isolated. These dual string completions have the Tubing Long (TL) tapping the deeper reservoirs, which is the Burgan reservoir in most cases while the Tubing Short (TS) was tapping the shallower reservoir, which is the Wara reservoir in most cases. The tubing sizes utilized for these completions were 3.5in. An example of a typical dual completion well-schematic can be seen below in figure 1.
This dual completion design has a shortfall, in case of reservoir depletion of any of the strings; conventional ESP could not be lowered in the wells due to completion size limitations. Additionally, any workover would be planned in the well only if both strings, TL & TS ceased from production causing huge amount of deferred production for the TL commonly as the Burgan reservoir has faster increase in the water cut.
KOC pioneered a novel solution to quickly restore production and minimize deferred oil in their dual completion wells. The technique utilizes a slim ESP set inside production tubing without the need of a work over rig. The rigless wireline ESP deployment solved a major challenge of managing dual completions for KOC and the future wells planned with dual completions. Wells are put back to production with capacity of producing up to 2200 bbl/day. A detailed candidate selection is required before every job to review the well barriers and confirm the capability of the pump to perform the operation. Proactive well management and surveillance require digital solutions with seamless flow of data from downhole to the hands of engineers, edge computing enable operators to proactively manage their assets, detect and manage potential issues, and ultimately improve well performance. Additionally, this approach reduces the dependency of domain experts to frequently analyze data enabling the capability to act in real time. Once the other string has increase in the water cut and ceases to flow, the slim ESP can be easily retrieved riglessly within short span to enable well workover and plan the future of the well accordingly.
This paper will discuss the first deployment of this pump in Kuwait in a dual string well, which marks a solution for major issue that was faced for many years.
The first step of planning the slim ESP in a dual string well is to perform well simulation to ensure the pump will be capable of lifting the fluid. This is followed by a wellhead connection compatibility and a tubing integrity check to ensure that the well integrity is in a good condition and no fluid re-circulation is expected during production. During tubing integrity check, the integrity of any accessories in the well such as sliding sleeves is also evaluated to avoid leaks. The operations require setting a special packer inside the tubing to create a seat for the pump and the full Wireline stack pressure control equipment is then rigged up on the wellhead and the pump is connected to the TECline cable mounted on the wireline unit drum. The complete deployment of the pump on Wireline unit takes between 8-10 hrs and the whole operation from deployment to commissioning is done in less than 24 hours.
The first deployment of the slim ESP managed to restore a production of 2000 bbl of liquid in the TL of a dual completion well without disturbing the flow from the TS. Portable GOR measured water cut to be 70% providing oil gain of 600 bbl/day along with sustained natural production from TS the well has been producing for more than 5 months with smooth operation. This also marks the longest production from any oil well made by this slim ESP worldwide. The details of the two well candidates where deployments were done in a dual string are listed in the table below –
The first installation in a dual string paved the road for a long-term deployment of these pumps in Kuwait fields. This will enable more wells to be completed with dual string helping Kuwait maximize its production, without having to drill multiple wells for different reservoirs and avoiding surface congestions.
