Abstract
Kuwait Oil Company (KOC) is actively recovering hydrocarbons from Heavy-oil reservoirs located in the Northern Kuwait (NK) Fields. NK Heavy Oil (NKHO) reserves are mainly located in two major fields: Field -1 (cold well) and Field – 2 (thermal well). Currently this heavy oil field is in development phase and KOC plans to add additional wells yearly. Filed -2 is a thermal field producing with a water cut of approximately 45%. Typically, water coning is a major challenge hindering thermal recovery in a heavy oil reservoir with a bottom or boundary aquifer. This situation typically occurs when the production zone is near an aquifer or a water-bearing formation with a permeable connection, based on the ratio of horizontal to vertical permeability between the oil production zone and water formation. Coning occurs with pressure drawdown, causing water to migrate from the bottom to the wellbore. This is strictly a near-wellbore phenomenon that occurs only once the pressure forces drawing fluids toward the wellbore exceed the natural buoyancy forces that segregate gas and water from oil. Once water coning is observed, it needs to be addressed with appropriate method to restore the normal development of the reservoir. If water coning continues to expand, thermal well will reach a high water cut level within a short time. Coning is a rate- sensitive phenomenon generally associated with high production rates. Although it can be controlled by decreasing the rates of production, it is not a favorable approach because oil production is reduced and water production impacts the economic life of reservoirs and ultimate recovery. Moreover, it increases operating expenses such as pumping, water/oil separation, and equipment costs. Excess water production can induce sand production and damage down hole completion or wellbore integrity, inviting frequent well interventions or even to severe circumstances like abandoning of the well. On the other hand, produced water can causes wellbore corrosion and scaling on casing and production tubing because of polar and nonpolar ions from the aquifer.
Because of the chemical complexity of the produced water, its disposal is a major environmental concern. This also increases disposal costs. Therefore, developing a proper and economical method to shut off or lower excess water has become one of the most significant concerns of the KOC in the NKHO field. Field - 2 is a relatively new emerging field with increased intervention complexity due to an increase in water cuts.
Early remedial job trials using conventional thermal slurries were unsuccessful in Field – 2. This study illustrates the development and deployment of a novel cementing solution to address the challenges associated with conventional thermal cement for low pressure, low temperature, water shut off cement squeeze jobs. The slurry design and approach have good potential for vast applications in Kuwait and heavy oil fields worldwide.
