Systematic Approach to Develop a Colloidal Silica Based Gel System for Water Shut-Off

Abstract

Undesirable water production can significantly affect the economic life of producing wells. Excess water production results in loss of productivity, corrosion, and scaling. Also, the need for water handling facilities and reinjection of unwanted water can further add to the total cost of the project, which consequently increases the cost of production. In offshore operations, produced water can have an adverse impact on the environment. The use of a colloidal silica based fluid system was developed for water shutoff application. A systematic experimental study was conducted to evaluate the effect of key parameters on the gelation properties of this system; that is: particle size, pH, temperature, and silica concentration. Also, the effect of different salts, as an activator agent, were tested to initiate in-situ gelation of colloidal silica. The performance of this system was evaluated by conducting static gelation tests as well as high pressure and high temperature viscosity measurements up to 150°C. Colloidal silica solutions exhibit low viscosity. Proper selection of suitable activators can lead to in-situ gelation and formation of a high viscous gel to block the pore space. The permanent sealing of formation porosity can be achieved by building the viscosity of colloidal silica. The colloidal silica gelation time can be tailored by varying the activator type and concentration to match the field operation requirements. Kinetics of colloidal silica gelation at elevated temperatures showed quicker viscosity buildup. The gelation time can be varied by controlling the initial pH of the system. A stable system and good dispersion was achieved for the colloidal silica solution without using an activator, as confirmed from the Zeta potential results. Increasing the salt concentration and temperature or lowering the pH of the system results in unstable system that triggers the gelation process. The existence of more than one of the above factors (i.e., salt, temperature, and lower pH) results in further reduction in gelation time. Colloidal silica has a low viscosity and can penetrate deeper into the formation matrix before transforming into a gel. The fluid system presented in this paper was developed to address the needs of water shutoff applications. The environmentally friendly system is comprised of two components; colloidal silica and an activator.

The long term stability of silica nanoparticle gels in waters of different ionic compositions and pH values

“…The strongest difference is observed between NaCl and Na 2 SO 4 which is in tandem with data reported by Huang et al (67). Hamer and Wu (88) and Goldberg (89).…”

“…There are two regimes by which silica particle aggregation can proceed. These are known as reaction limited cluster aggregation (RLCA) and diffusion limited cluster aggregation (DLCA) (65)(66)(67). In RLCA not all collisions lead to the formation of an aggregate.…”

Conformance Control in Oil Reservoirs by Citric Acid-Coated Magnetite Nanoparticles

“… 76 , 92 − 100 Nevertheless, few studies reported the application of NPs for shutoff purposes. 12 , 59 , 60 , 101 − 105 When a magnetic field was applied, magnetorheological smart fluids demonstrated reversible and swift liquid-to-solid-like transfiguration. 106 , 107 Accordingly, magnetic NP-based well fluids are ideal for water shutoff and conformance control, especially since external magnetic field applications to oil reservoirs have been demonstrated.…”

Cellulose Nanofibrils and Tubular Halloysite as Enhanced Strength Gelation Agents

“…Silica gel formation from silica nanoparticles is widely employed in water shutoff services in oil wells [1,2] and was recently proposed to be used in geothermal applications [3].…”