To improve Oil production rates and recovery factors North Kuwait shifted its exploitation strategy from vertical to horizontal completions. These horizontal ICD completions did indeed reduce the draw down pressure within the reservoir, thereby delaying water breakthrough. When water did eventually breakthrough, there was no completion mechanism to effectively control the conning effect, other than choking back/reducing the flow rate further with the consequent further loss of oil production. Additionally, water shut-off opportunities in passive ICD-completed wells were limited and marginally successful, since the water moves laterally along wellbore to adjacent compartments. The coning control completion (CCC) technology is an excellent emerging technology for improved oil recovery from water drive reservoir.
The coning control completion (CCC) technology, applicable only in vertical or moderately-deviated wellbores (< 60°), is a technology that revolutionizes the development strategy of water drive reservoirs. The fundamental principle of this technology is to create a pressure drawdown, or pressure sink (ΔP), at or just below the OWC within the water leg, equal to or marginally more than the ΔP across the perforated interval within the oil leg. This drawdown retards the progression of water cone into the oil column and can be achieved using an inverted, bottom-discharge high-volume ESP. A preferential flow of the bottomor edgewater is created, parallel to the bedding plant, just under the OWC. The disposal options for the diverted water is either to "dump" into an under lying aquifer, or to preduce to surface for processing and re-injection, if necessary.
For the interval perforated, the candidate well flowed naturally at rates six (6) times the calculated critical coning rate with a subsequent early water breakthrough resulting in a 45% loss in oil production. After commissioning the inverted ESP system water cuts have not only decreased by 50%, but also stabilized. After a planned or unplanned ESP shut down, the water cone redeveloped, but was brought under control again, and water cuts reduced and stabilized accordingly. Flowing BHP at the oil perforations, ESP intake pressure, and watercut are all monitored closely to ensure the watercut from the oil perforations are maintained at an optimum level, but not allowed to disappear. ESP rates are estimated by correlating the intake and discharge pressures from the specific pump curves.
With inverted ESP's the coning control completion technology facilitates reduced surface water production while increasing oil production from partially-perforated oil columns at much higher than critical coning rates. A direct benefit is derived from subsurface disposal of the pressure-sink water to underlying aquifers within the same wellbore, significantly reducing surface water processing, handling, disposal and associated operational cost.